Introduction
⌅Soybean meal (SBM) is one of the most common protein supplements used in livestock diets. It contains high level of lysine, but low in methionine, valine, and isoleucine, which are the first, second, and third limiting amino acids (AA), respectively in dairy cows (Schingoethe, 1996Schingoethe DJ, 1996. Balancing the amino acid needs of dairy cows. Anim Feed Sci Technol 60: 153-160. https://doi.org/10.1016/0377-8401(96)00976-5). Also, the use of SBM in animal diets increases the cost of livestock production because it is considered as an imported product in most countries and is expensive. Sesame meal (SM), a by-product of sesame oil extraction, can replace SBM at a lower cost with a positive effect on milk production and nutrient digestibility (Abo Omar, 2002Abo Omar JM, 2002. Effect of feeding different level of sesame oil cake on performance and digestibility of Awassi lambs. Small Rumin Res 46: 187-190. https://doi.org/10.1016/S0921-4488(02)00173-6; Obeidat et al., 2019Obeidat BS, Kridli RT, Mahmoud KZ, Obeidat MD, Haddad SG, Subih HS, et al., 2019. Replacing soybean meal with sesame meal in the diets of lactating Awassi ewes suckling single lambs: Nutrient digestibility, milk production, and lamb growth. Animals 9: 157. https://doi.org/10.3390/ani9040157). The amounts of dry matter (DM), crude protein (CP), ash, ether extract (EE), nitrogen free extract and crude fiber in SM are about 83-96%, 23-46%, 7.5-17%, 1.4-27%, 25-32% and 5-12%, respectively (FAO, 1990FAO, 1990. Production Year Book. Guide to Food and Agriculture Organization, Rome, Italy. 52 pp.). As a fat source, SM is valued for its high levels of unsaturated fatty acids (UFA), especially linolenic acid and linoleic acid, which can modify some bioactive components in milk, such as conjugated linoleic acid and omega-3 fatty acids (Medeiros et al., 2014Medeiros E, Queiroga R, Oliveira M, Medeiros A, Sabedot M, Bomfim M, et al., 2014. Fatty acid profile of cheese from dairy goats fed a diet enriched with castor, sesame and faveleira vegetable oils. Molecules 19(1): 992-1003. https://doi.org/10.3390/molecules19010992).
Decreasing the degradability of protein in the rumen has the potential to improve milk production by providing more AAs for absorption in the small intestine. Many measures are taken to protect feed against degradation in the rumen (Haryanto, 2014Haryanto B, 2014. Manipulating protein degradability in the rumen to support higher ruminant production. Wartazoa 24(3): 131-138. https://doi.org/10.14334/wartazoa.v24i3.1070). Among these, treatment with formaldehyde is the most common, efficient and least expensive method (Walli, 2005Walli TK, 2005. Bypass protein technology and the impact of feeding bypass protein to dairy animals in tropics: A review. Ind J Anim Sci 75: 135-142.). Formaldehyde toxicity has been studied in rats, rabbits, and dogs after oral feeding, and the LD50 was 800, 270, and 550 mg/kg of body weight (BW), respectively (NCBI, 2023NCBI, 2023. PubChem compound summary for CID 712 formaldehyde. National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/Formaldehyde [Jan 21, 2023].), indicating the low toxicity of formaldehyde. Wales et al. (2010)Wales AD, Allen VM, Davies RH, 2010. Chemical treatment of animal feed and water for the control of Salmonella. Foodborne Pathog Dis 7: 1-15. https://doi.org/10.1089/fpd.2009.0373 concluded that formaldehyde, when applied as an antimicrobial feed additive, has not been generally shown as a cause of adverse responses in animals. Formaldehyde significantly reduces the solubility of protein and makes it very resistant to microbial attack in the rumen without affecting its digestibility in the small intestine (Sanjukta & Rai, 2016Sanjukta S, Rai AK, 2016. Production of bioactive peptides during soybean fermentation and their potential health benefits. Trends Food Sci Technol 50: 1-10. https://doi.org/10.1016/j.tifs.2016.01.010). There are few reports on the effects of formaldehyde-treated SM on dairy. However, a positive effect of feeding formaldehyde-treated SBM or canola meal on nutrient intake, milk production and composition was observed in cattle, goats and sheep (Tajaddini et al., 2021Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519). Thus, the objective of current study was to evaluate the effect of substitution of SBM by treated or untreated SM in the diet of Murciano-Granadina dairy goats on feed intake, nutrient digestibility, milk yield, milk fatty acid (FA) profile, blood metabolites, and rumen fermentation characteristics.
Material and methods
⌅Sesame meal processing
⌅The formaldehyde was diluted with water (37%) and sprayed on SM samples (resulting in a final concentration of 0.8 and 1.2 g formaldehyde/100 g CP of SM), mixed homogenously for 15 minutes, and kept in nylon bags for 48 h. Then, the bags were opened and the SM was allowed to dry in the shade for three days before being introduced into the experimental diets (Hadjipanayiotou, 1992Hadjipanayiotou M, 1992. Effect of protein source and formaldehyde treatment on lactation performance of Chios ewes and Damascus goats. Small Rum Res 8: 185-197. https://doi.org/10.1016/0921-4488(92)90039-7).
Animals and experimental diets
⌅The Animal Care and Use Committee of Shahid Bahonar University of Kerman approved all animal handling protocols in compliance with EU standards (EC, 2010EC, 2010. Directive 2010/63/EU of the European Parliament and of the Council of 22 September 2010 on the Protection of Animals Used for Scientific Purposes. Off. J. Eur. Union 2010, 276, 33-79. https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:276:0033:0079:en :PDF [30 June 2023].). This experiment was carried out on a herd of Murciano-Granadina dairy goats in Kerman, Iran (30º 150 N latitude and 57º 010 E longitude). At the 16th week of lactation, forty multiparous Murciano-Granadina dairy goats (42.8 ± 3.3 kg of BW and 1.95 ± 0.31 kg/d average milk yield) were allocated to four groups (n = 10 per group) as a completely randomized design. They were fed with diets containing: 1) SBM (control), 2) untreated SM, 3) treated SM with 0.8 g formaldehyde/100 g CP and 4) treated SM with 1.2 g formaldehyde/100g CP (Table 1). The level of SM in diets 2, 3 and 4 was 12.5%. During a 56-d experimental period (including 14 d for animal’s adaptation to the experimental diet and 42 d for data collection), goats were housed individually in pens (1.5 × 1.5 m). The experimental diets were formulated to be iso-energetic and iso-nitrogenous based on nutrient requirements of dairy goats according to NRC (2007)NRC, 2007. Sheep, goats, cervids, and new world camelids. In: Nutrient requirements of small ruminants, Acad Press, Washington D.C.. The diets had a forage-to-concentrate ratio 62:38 (on DM basis) and animals were fed a total mixed ration twice daily ad libitum at 08:00 and 16:00. Fresh water was provided freely throughout the experiment.
| Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g Formaldehyde treated SM | |
|---|---|---|---|---|
| Ingredients (% dry matter) | ||||
| Alfalfa hay, chopped | 16.0 | 16.0 | 16.0 | 16.0 |
| Corn silage | 16.3 | 16.3 | 16.3 | 16.3 |
| Wheat straw, chopped | 2.00 | 2.00 | 2.00 | 2.00 |
| Corn grain, ground | 16.0 | 16.0 | 16.0 | 16.0 |
| Barley grain, ground | 11.0 | 11.0 | 11.0 | 11.0 |
| Soybean meal | 18.8 | 7.50 | 7.50 | 7.50 |
| Sesame meal | 0.00 | 12.5 | 12.5 | 12.5 |
| Beet pulp | 4.00 | 4.00 | 4.00 | 4.00 |
| Wheat bran | 12.7 | 11.5 | 11.5 | 11.5 |
| Sodium bicarbonate | 1.40 | 1.40 | 1.40 | 1.40 |
| Calcium carbonate | 0.30 | 0.30 | 0.30 | 0.30 |
| Mineral-vitamin premix2 | 1.20 | 1.20 | 1.20 | 1.20 |
| Salt | 0.30 | 0.30 | 0.30 | 0.30 |
| Chemical composition (g/kg dry matter) | ||||
| Dry matter | 615 | 616 | 613 | 613 |
| Organic matter | 921 | 919 | 918 | 918 |
| Metabolizable energy (Mcal/kg) | 2.61 | 2.61 | 2.61 | 2.61 |
| Crude protein (CP) | 166 | 167 | 167 | 167 |
| Rumen undegradable protein (% CP) | 48.0 | 48.0 | 36.2 | 66.0 |
| Rumen degradable protein (% CP) | 118 | 119 | 63.8 | 101 |
| Ether extract (EE) | 26.4 | 27.2 | 27.2 | 27.2 |
| Neutral detergent fiber | 280 | 280 | 280 | 280 |
| Acid detergent fiber | 200 | 200 | 200 | 200 |
| Non-fiber carbohydrates3 | 408 | 407 | 407 | 407 |
1 Sesame meal. 2 Each kg of the premix contained (DM basis): 500000 IU vitamin A, 100000 IU vitamin D, 2000 IU vitamin E, 190000 mg Ca, 25000 mg P, 40000 mg Na, 30000 mg Mg, 5000 mg Zn, 3500 mg Mn, 2500 mg Fe, 400 mg Cu, 35 mg Co, 90 mg I, 40 mg Se. 3 NFC = 1000 - (NDF + CP + EE + Ash).
Milk yield and composition
⌅Daily milk yield of goats during the experiment was recorded twice a day through an automatic device. On the last five day of the experiment, approximately 50-mL milk samples were collected in tubes containing potassium dichromate (as a preservative) and stored at 4°C until analysis for milk composition, including fat, protein, lactose, total solids and solids-not-fat contents using a Milko scan apparatus (FOSS Electric, Hillerod, Denmark).
The production of 4% fat-corrected milk (FCM), energy-corrected milk (ECM), and total solids-corrected milk (TSCM) were calculated according to NRC (2001)NRC, 2001. Nutrient requirements of dairy cattle, 7th ed. Subcommittee on dairy cattle nutrition, Acad Press, Washington D.C., Sjaunja et al. (1991)Sjaunja LO, Baevre L, Junkkarinen L, Pedersen J, Setala J, 1991. A nordic proposal for an energy corrected milk (ECM) formula. Performance recording of animals: State of the art EAAP Publication, 50: 156-157. https://www.researchgate.net/publication/284193091, and Tyrrell & Reid (1965)Tyrrell HF, Reid JT, 1965. Prediction of the energy value of cow’s milk. J Dairy Sci 48: 1215-1223. https://doi.org/10.3168/jds.S0022-0302(65)88430-2, respectively.
Another milk subsample was used for determining FA profile using fat extracts generated by trans-esterification to form methyl esters as described by Bouattour et al. (2008)Bouattour M, Casals R, Albanell E, Such X, Caja G, 2008. Feeding soybean oil to dairy goats increases conjugated linoleic acid in milk. J Dairy Sci 91: 2399-2407. https://doi.org/10.3168/jds.2007-0753. The FA in the milk sample extracts were then measured using a gas chromatography (GC; 3400 Varian Star; Varian Inc., Palo Alto, CA, USA) and a fused silica capillary column (CP-SIL-88- 0.25 mm × 60 m). The column temperature used for the fatty acid quantification ranged from 50 to 190 °C (hold 1 min at 50 °C; increase 4 °C/min to 190 °C; hold 10 min). Helium gas was used as the carrier gas.
Digestibility
⌅Daily samples of feed offered and refused were collected and after grounding through a 1-mm screen Wiley mill were kept at -20°C for subsequent analysis. In order to determine nutrient digestibility, individual faecal samples (50 g) were collected for all goats at last five experimental days. Acid-insoluble ash was used as an internal indicator (Liu, 2022Liu K, 2022. New and improved methods for measuring acid insoluble ash. Anim Feed Sci Technol 288: 115282. https://doi.org/10.1016/j.anifeedsci.2022.115282). The samples of SM, treated SM, feed, and feces were analyzed for DM (method 930.15), organic matter (OM; method 942.05), CP (method 990.03), and EE (method 920.39) according to AOAC (2000)AOAC, 2000. Official methods of analysis, 17th ed. The Association of Official Analytical Chemists, Gaithersburg, MD, USA.. Neutral detergent fiber (NDF) was determined according to Van Soest et al. (1991)Van Soest PV, Robertson J, Lewis B, 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. J Dairy Sci 74: 3583-3597. https://doi.org/10.3168/jds.S0022-0302(91)78551-2.
Rumen fermentation variables
⌅On last day of the experiment, about 40-50 mL of rumen content was collected via a stomach tube 3 h post-feeding. The rumen fluid was filtered through four layers of cheesecloth. The pH was determined immediately using a pH meter (Sentron, model A102-003). For determination of NH3-N, about 5 mL of filtered rumen fluid was acidified with 1 mL of 0.2 N HCl to stop fermentation and frozen at -20oC. For volatile fatty acids (VFA) analysis, 1 mL of strained rumen fluid was mixed with 0.25 mL of an acid solution containing 200 mL/L of orthophosphoric acid and 20 mmol 2-ethyl-butyric acid and frozen at -20oC. The total VFA and its components (acetic, propionic, isobutyric, butyric, isovaleric and valeric acids) were determined by GC using ethyl butyric acid as an internal standard. Total numbers and generic composition of rumen protozoa were determined according to the method of Dehority (2003)Dehority B, 2003. Rumen microbiology, 1st published. British Library Cataloguing in Publication Data..
Blood variables
⌅On the last day of the experiment, blood samples were collected via jugular venipuncture through vacuumed tubes containing lithium heparin at 3 h after feeding. Plasma was harvested after centrifuging at 3000 rpm for 15 min, partitioned into aliquots and stored at -20°C until further analysis. Plasma glucose, cholesterol, triglyceride, blood urea nitrogen (BUN), albumin, total protein, high-density lipoprotein (HDL), low-density lipoprotein (LDL), very-low-density lipoprotein (VLDL), aspartate transaminase (AST) and alanine transaminase (ALT) were determined with a spectrophotometer using commercial kits (Pars Azmoon Diagnostics, Tehran, Iran).
In order to assess the total antioxidant capacity (AC) and malondialdehyde (MDA) in plasma and milk, samples were stored at -70°C until the analysis. The thiobarbituric acid technique was used to measure the amount of MDA in plasma and milk (Moore & Roberts, 1998Moore K, Roberts LJ, 1998. Measurement of lipid peroxidation. Free Radic Res 28: 659-671. https://doi.org/10.3109/10715769809065821). Milk and blood AC were determined using the ferric reduction in antioxidant power technique (Benzie & Strain, 1996Benzie IF, Strain JJ, 1996. The ferric reducing ability of plasma (FRAP) as a measure of “antioxidant power”: the FRAP assay. Anal Biochem 239: 70-76. https://doi.org/10.1006/abio.1996.0292). All measurements were conducted in five replicates and in compliance with the manufacturer’s recommendations.
Statistical analysis
⌅All data were analyzed as a completely randomized design using GLM procedure (except for the milk yield data which was analyzed by MIXED procedure) of SAS (version 9.1.3, SAS Institute, Cary, NC, USA). All data were analyzed by the model: Yij = µ + ai + eij , where Yij, µ, ai, and eij represent the dependent variable, the overall mean, the fixed effect of dietary treatment, and the experimental error, respectively. The Tukey test was used to examine the differences among treatments mean. The results were considered significantly different when p ≤ 0.05 or p ≤ 0.01.
Results
⌅Nutrients intake and digestibility
⌅The experimental diets had no effect (p > 0.05) on DM or nutrient digestibility (Table 2). Goats fed diet containing formaldehyde-treated SM had greater (p < 0.01) DM, OM, CP, and ME intakes than those fed untreated SM and SBM. Feeding formaldehyde-treated SM diets resulted in greater (p < 0.01) NDF intake compared to diets containing SBM. The apparent digestibility of any of the nutrients was not affected by the experimental diets.
| Item | Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g formaldehyde treated SM | SEM2 | p-value |
|---|---|---|---|---|---|---|
| Intake (g/d) | ||||||
| Dry matter | 1629c | 1683bc | 1748ab | 1777a | 23 | 0.004 |
| Organic matter | 1514c | 1565bc | 1625ab | 1662a | 22 | 0.004 |
| Crude protein | 270c | 278bc | 289ab | 294a | 3.62 | 0.003 |
| Neutral detergent fiber | 458b | 469ab | 486a | 489a | 6.42 | 0.006 |
| Metabolizable energy (Mcal/kg) | 4.19b | 4.36b | 4.54a | 4.59a | 0.06 | 0.003 |
| Digestibility (%) | ||||||
| Dry matter | 68.4 | 68.5 | 71.2 | 70.8 | 0.95 | 0.090 |
| Organic matter | 69.4 | 69.9 | 72.3 | 71.8 | 0.87 | 0.070 |
| Crude protein | 73.5 | 74.1 | 74.6 | 76.8 | 1.07 | 0.100 |
| Neutral detergent fiber | 53.8 | 54.1 | 55.2 | 55.4 | 0.64 | 0.210 |
1 Sesame meal. 2 SEM: Standard error of mean. a,b Means within row with different superscripts differ (p < 0.05).
Milk yield, milk composition and fatty acids
⌅The diet containing 1.2 g formaldehyde-treated SM resulted in a greater (p < 0.01) milk yield than diet containing untreated SM or SBM (Table 3). The lowest amount of FCM, ECM and TSCM was observed in goats fed with diet containing SBM (p < 0.01), while there was no difference between treatments containing treated and untreated SM. Milk yield efficiency (g milk yield/g DM intake) in goats fed with formaldehyde-treated SM was greater than that in other groups (p < 0.05), but efficiency of FCM was not affected by experimental treatments. Furthermore, milk contents of fat, lactose, total solids and solids not fat were not affected by experimental treatments, but milk protein was higher (p < 0.05) in goats fed diet containing 1.2 g formaldehyde-treated SM than the other groups.
| Item | Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g formaldehyde treated SM | SEM2 | p-value |
|---|---|---|---|---|---|---|
| Yield (g/day) | ||||||
| Milk | 1922c | 2152b | 2288ab | 2358a | 57 | <0.001 |
| FCM 4%3 | 2139b | 2429a | 2523a | 2588a | 49 | 0.003 |
| ECM4 | 2034b | 2298a | 2409a | 2473a | 61 | 0.001> |
| TSCM5 | 1921b | 2171a | 2273a | 2328a | 58 | 0.007 |
| Efficiency | ||||||
| Milk yield/DMI6 | 1.18c | 1.28b | 1.31a | 1.32a | 0.03 | 0.036 |
| FCM 4%/DMI | 1.31 | 1.44 | 1.45 | 1.46 | 0.03 | 0.063 |
| Milk composition (%) | ||||||
| Fat | 4.75 | 4.87 | 4.68 | 4.65 | 0.09 | 0.350 |
| Protein | 3.21b | 3.20b | 3.26ab | 3.32a | 0.03 | 0.048 |
| Lactose | 4.27 | 4.22 | 4.24 | 4.16 | 0.04 | 0.070 |
| Total solids | 12.3 | 12.2 | 12.2 | 12.1 | 0.11 | 0.750 |
| Solids-not-fat | 7.48 | 7.42 | 7.51 | 7.48 | 0.04 | 0.520 |
1 Sesame meal. 2 SEM: Standard error of mean. 3 Fat corrected milk (g/day) = 0.4 Milk yield (kg/d) + 15 Fat yield (kg/d). 4 Energy corrected milk (g/day) = milk production (g/day) × [38.3×fat (g/kg) + 24.2×protein (g/kg) + 16.54×lactose (g/kg) + 20.7] /3140. 5 Total solid corrected milk (g/day) = (12.3×g of fat) + (6.56×g of nonfat solids) - (0.0752×g of milk). 6 DMI: Dry matter intake. a,b Means within row with different superscripts differ (p < 0.05).
The concentrations of C18:1-cis and C18:3-cis in the milk of goats fed SBM diet were lower (p < 0.01) than those in goats fed formaldehyde-treated SM diets (Table 4). The saturated FA (SFA), short-chain FA (SCFA), and medium-chain FA (MCFA) were higher and unsaturated FA (UFA), UFA/SFA, monounsaturated FA (MUFA), poly unsaturated FA (PUFA), and long-chain FA (LCFA) were lower in the milk of goats fed a diet containing SBM compared to other groups (p < 0.01).
| Fatty acids | Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g formaldehyde treated SM | SEM2 | p-value |
|---|---|---|---|---|---|---|
| C16:0 | 30.7 | 27.3 | 28.5 | 27.5 | 1.19 | 0.190 |
| C16:1-cis | 1.29 | 1.41 | 1.47 | 1.43 | 0.05 | 0.120 |
| C16:1-trans | 0.43 | 0.44 | 0.45 | 0.46 | 0.03 | 0.910 |
| C18:0 | 9.33 | 10.3 | 9.71 | 9.90 | 0.46 | 0.480 |
| C18:1-cis | 15.2b | 19.1a | 19.7a | 19.8a | 0.51 | 0.001 |
| C18:1-trans | 2.52 | 2.41 | 2.41 | 2.29 | 0.06 | 0.110 |
| C18:2-cis | 3.14 | 3.28 | 3.41 | 3.38 | 0.09 | 0.180 |
| C18:2-trans | 0.31 | 0.35 | 0.29 | 0.28 | 0.02 | 0.110 |
| C18:3-cis | 0.85b | 0.93b | 1.21a | 1.15a | 0.04 | 0.001 |
| C18:3-trans | 0.02 | 0.02 | 0.01 | 0.01 | 0.002 | 0.190 |
| SFA3 | 72.6a | 68.3b | 67.3b | 67.5b | 0.66 | 0.001 |
| UFA4 | 27.4b | 31.7a | 32.7a | 32.5a | 0.66 | 0.001 |
| UFA/SFA | 0.38b | 0.47a | 0.49a | 0.48a | 0.01 | 0.001 |
| MUFA5 | 23.1b | 27.1a | 27.8a | 27.7a | 0.62 | 0.001 |
| PUFA6 | 4.32c | 4.58bc | 4.92a | 4.82ab | 0.11 | 0.001 |
| SCFA 7 | 14.5a | 13.7b | 12.8b | 13.2b | 0.35 | 0.010 |
| MCFA8 | 52.9a | 48.7b | 49.2b | 48.8b | 0.95 | 0.010 |
| LCFA9 | 32.6b | 37.6a | 37.9a | 38.0a | 1.03 | 0.002 |
1 Sesame meal. 2 Standard error of mean. 3 Saturated fatty acids. 4 Unsaturated fatty acids. 5 Monounsaturated fatty acids. 6 Polyunsaturated fatty acids. 7 Short-chain fatty acids (sum of C4:0 - C10:1 fatty acids). 8 Medium-chain fatty acids (sum of C12:0 - C17:1 fatty acids). 9 Long-chain fatty acids (sum of C ≥ 18 fatty acids). a,b Means within row with different superscripts differ (p < 0.05).
Rumen fermentation variables
⌅As shown in Table 5, the lowest pH values and NH3-N concentration and the highest total VFA concentration were observed in the rumen fluid of goats fed formaldehyde-treated SM diet than others (p < 0.01). Additionally, the concentration of acetate was lowest and propionate was highest in these goats (p < 0.01). The acetate/propionate ratio in the rumen fluid of goats fed formaldehyde-treated SM diet was also lower than that in other groups (p < 0.01). The protozoa population was not affected by the experimental treatments at 3 h after feeding.
| Item | Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g formaldehyde treated SM | SEM2 | p-value |
|---|---|---|---|---|---|---|
| pH | 6.42a | 6.38a | 6.19b | 6.17b | 0.03 | <0.001 |
| NH3-N (mg/dL) | 28.30a | 27.50a | 25.40b | 25.10b | 0.36 | <0.001 |
| Total VFA3 (mmol/L) | 71.30b | 73.50b | 76.50a | 77.80a | 0.95 | 0.002 |
| Individual VFA (mol/100 mol) | ||||||
| Acetate | 62.50a | 63.10a | 59.10b | 59.90b | 0.47 | 0.001 |
| Propionate | 20.90b | 20.50b | 23.90a | 23.60a | 0.44 | 0.002 |
| Butyrate | 8.03 | 8.15 | 8.27 | 8.11 | 0.19 | 0.840 |
| Isobutyrate | 5.49 | 5.36 | 5.42 | 5.24 | 0.16 | 0.750 |
| Valerate | 1.25 | 1.14 | 1.35 | 1.21 | 0.11 | 0.580 |
| Isovalerate | 1.81 | 1.76 | 1.88 | 1.85 | 0.14 | 0.940 |
| Acetate/propionate | 2.99a | 3.07a | 2.48b | 2.55b | 0.07 | 0.001> |
| Protozoa population (× 10 5 /mL) | ||||||
| Total protozoa | 6.23 | 6.04 | 6.22 | 6.27 | 0.15 | 0.740 |
| Entodiniinae | 3.81 | 3.49 | 3.91 | 3.87 | 0.14 | 0.190 |
| Diplodiniinae | 0.72 | 0.76 | 0.67 | 0.74 | 0.03 | 0.170 |
| Isotrichiae | 0.72 | 0.76 | 0.74 | 0.69 | 0.03 | 0.330 |
| Epidiniumae | 0.96 | 1.02 | 0.89 | 0.97 | 0.04 | 0.260 |
1 Sesame meal. 2 Standard error of mean. 3 Volatile fatty acids. a,b Means within row with different superscripts differ (p < 0.05).
Blood parameters
⌅The results of the present study showed that the concentration of hemato-chemical parameters including glucose, triglyceride, cholesterol, HDL, LDL, VLDL, total protein, albumin, BUN, AST, and ALT, was not affected by the experimental treatments (Table 6).
| Item | Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g formaldehyde treated SM | SEM2 | p-value |
|---|---|---|---|---|---|---|
| Glucose (mg/dL) | 53.90 | 55.60 | 54.00 | 52.90 | 2.77 | 0.920 |
| Triglyceride (mg/dL) | 16.80 | 20.60 | 17.10 | 21.60 | 1.48 | 0.070 |
| Cholesterol (mg/dL) | 84.90 | 88.30 | 85.00 | 90.40 | 7.55 | 0.940 |
| HDL3 (mg/dL) | 41.10 | 40.30 | 41.10 | 45.00 | 4.29 | 0.860 |
| LDL4 (mg/dL) | 40.50 | 43.90 | 40.50 | 41.10 | 9.35 | 0.990 |
| VLDL5 (mg/dL) | 3.36 | 4.12 | 3.42 | 4.32 | 0.31 | 0.070 |
| Total protein (g/dL) | 7.36 | 6.87 | 7.89 | 7.35 | 0.27 | 0.100 |
| Albumin (g/dL) | 4.06 | 3.81 | 4.15 | 4.01 | 0.16 | 0.520 |
| BUN6 (mg/dL) | 47.60 | 41.10 | 43.30 | 42.30 | 2.82 | 0.410 |
| AST7 (U/L) | 116 | 111 | 108 | 97 | 7.22 | 0.320 |
| ALT8 (U/L) | 20.20 | 18.10 | 17.60 | 16.90 | 1.26 | 0.310 |
1 Sesame meal. 2 Standard error of mean. 3 High-density lipoprotein. 4 Low-density lipoprotein. 5 Very-low-density lipoprotein. 6 Blood urea nitrogen. 7 Aspartate transaminase. 8 Alanine transaminase. a,b Means within row with different superscripts differ (p < 0.05).
Antioxidant indices in blood and milk
⌅Experimental treatments did not affect any of the antioxidant indices including superoxide dismutase, glutathione peroxidase in blood, MDA and AC in blood and milk of goats (Table 7).
| Item | Control | Untreated SM1 | 0.8 g formaldehyde treated SM | 1.2 g formaldehyde treated SM | SEM2 | p-value |
|---|---|---|---|---|---|---|
| Blood | ||||||
| SOD3 (U/gHb) | 1547 | 1476 | 1494 | 1475 | 89.90 | 0.930 |
| GPX4 (U/gHb) | 69.70 | 60.60 | 68.30 | 69.10 | 3.04 | 0.080 |
| MDA5 (nmol/mL) | 2.24 | 2.11 | 1.89 | 1.93 | 0.18 | 0.490 |
| AC6 (mmol Fe2+/L) | 0.40 | 0.46 | 0.43 | 0.40 | 0.02 | 0.230 |
| Milk | ||||||
| MDA (nmol/mL) | 0.78 | 0.74 | 0.75 | 0.74 | 0.03 | 0.790 |
| AC (mmol Fe2+/L) | 1.45 | 1.61 | 1.55 | 1.57 | 0.05 | 0.150 |
1 Sesame meal. 2 Standard error of mean. 3 Superoxide dismutase. 4 Glutathione peroxidase. 5 Malone dialdehyde. 6 Antioxidant capacity. a,b Means within row with different superscripts differ (p < 0.05).
Discussion
⌅Today’s ongoing global challenge is to optimize the use of protein and fat supplements in various production systems, which is mostly focused on the quality of produced milk/meat in developed countries, rather than raising the quantity of production in developing countries (Gulati et al., 2005Gulati SK, Garg MR, Scott TW, 2005. Rumen protected protein and fat produced from oilseeds and/or meals by formaldehyde treatment; their role in ruminant production and product quality: a review Aust J Exp Agric 45: 1189-1203. https://doi.org/10.1071/EA04131). The results of the current study demonstrated that goats fed diets containing formaldehyde-treated SM, especially those with higher levels of formaldehyde, had grater DM, OM, CP, and ME intakes than those fed diets containing untreated SM or SBM. This may be due to the processing with formaldehyde since this processing decreases protein solubility in the rumen and enhances the number of peptides and essential AAs available in the intestine and increases animal feed intake (Sanjukta & Rai, 2016Sanjukta S, Rai AK, 2016. Production of bioactive peptides during soybean fermentation and their potential health benefits. Trends Food Sci Technol 50: 1-10. https://doi.org/10.1016/j.tifs.2016.01.010). In other words, preventing the degradation of dietary CP by rumen microorganisms, increases the flow of by-pass protein and AAs to the small intestine, which helps balance of absorbed AAs and thus stimulates feed intake (Baker et al., 1996Baker M, Amos H, Nelson A, Williams C, Froetschel M, 1996. Undegraded intake protein: Effects on milk production and amino acid utilization by cows fed wheat silage. Can J Anim Sci 76: 367-376. https://doi.org/10.4141/cjas96-054). Similar to our results, Tajaddini et al. (2021)Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519 reported that DMI increases when goats are fed with formaldehyde-treated canola meal, which can be mainly attributed to higher dietary rumen undegradable protein (RUP) content of diets by using formaldehyde-treated canola meal, leading to an improved balance of amino acids post-ruminally (Forbes, 1995Forbes JM, 1995. Voluntary food intake and diet selection in farm animals. CAB Int., Oxford, UK, pp: 226-234.). Furthermore, increased milk production in goats fed a diet containing treated SM (Table 3) leads to a rise in nutrient requirements, especially energy, requiring higher nutrient consumption (Baker et al., 1996Baker M, Amos H, Nelson A, Williams C, Froetschel M, 1996. Undegraded intake protein: Effects on milk production and amino acid utilization by cows fed wheat silage. Can J Anim Sci 76: 367-376. https://doi.org/10.4141/cjas96-054). It is evident that the goats with higher milk production will consume more DM and ME. Furthermore, substitution of SBM with formaldehyde-treated SM increased RUP content of diet and RUP intake of the goats compared to control. Our results agree with previous researchers’ findings who fed formaldehyde-treated canola meal or SBM to dairy goats and cows (Baker et al., 1996Baker M, Amos H, Nelson A, Williams C, Froetschel M, 1996. Undegraded intake protein: Effects on milk production and amino acid utilization by cows fed wheat silage. Can J Anim Sci 76: 367-376. https://doi.org/10.4141/cjas96-054; Tajaddini et al., 2021Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519). However, Sirohi et al. (2013)Sirohi SK, Walli TK, Garg MR, Kumar B, 2013. Effect of formaldehyde treated mustard cake on nutrient utilization and milk production performance in crossbred cows fed wheat straw based diet. Ind J Anim Nutr 30: 5-11. reported no effect on feeding formaldehyde-treated mustard cake to lactating crossbred cows.
Partial substitution of SBM with either untreated or treated SM with different levels of formaldehyde had no effect on nutrient digestibility. These findings might be attributed to the similarities in chemical composition of four dietary groups as mentioned by Mahmoud & Bendary (2014)Mahmoud AEM, Ghoneem WM, 2014. Effect of partial substitution of dietary protein by Nigella sativa meal and sesame seed meal on performance of Egyptian lactating buffaloes. Asian J Anim Vet Adv 9(8): 489-498. https://doi.org/10.3923/ajava.2014.489.498. This result support those obtained by Obeidat et al.’s study (2009)Obeidat B, Abdullah A, Mahmoud K, Awawdeh M, Al-Beitawi N, Al-Lataifeh F, 2009. Effects of feeding sesame meal on growth performance, nutrient digestibility, and carcass characteristics of Awassi lambs. Small Rum Res 82: 13-17. https://doi.org/10.1016/j.smallrumres.2009.01.002 in which addition of different levels of SM (0, 8, and 16%) to the diet of fattening lambs have no significant effect on nutrient digestibility. Furthermore, our results are consistent with findings of Mahmoud & Ghoneem (2014)Mahmoud AEM, Bendary MM, 2014. Effect of whole substitution of protein source by Nigella sativa meal and sesame seed meal in ration on performance of growing lambs and calves. Global Vet 13(3): 391-396. http://dx.doi.org/10.5829/idosi.gv.2014.13.03.8461. Throat et al. (2016)Throat S, Gupta R, Shankhpal S, Parnerkar S, 2016. Effect of supplementing formaldehyde treated rape seed meal on milk production, gross milk composition, digestibility of nutrients and feed conversion efficiency in high producing crossbred cows. Int J Livest Res 4: 68-74. http://www.jakraya.com/journal/pdf/12-lriArticle_2.pdf also reported that the formaldehyde-treated rapeseed meal do not affect feed digestibility in high-yielding dairy cows. Furthermore, Obeidat et al. (2019)Obeidat BS, Kridli RT, Mahmoud KZ, Obeidat MD, Haddad SG, Subih HS, et al., 2019. Replacing soybean meal with sesame meal in the diets of lactating Awassi ewes suckling single lambs: Nutrient digestibility, milk production, and lamb growth. Animals 9: 157. https://doi.org/10.3390/ani9040157 reported that there is no significant difference in nutrient digestibility when SBM was replaced by SM in the diet of Awassi sheep.
Goats fed diets containing formaldehyde-treated SM had higher milk production than other groups. This may be due to the fact that when dietary protein is treated with formaldehyde, it leads to increased absorption of essential AAs and metabolizable proteins from the duodenum (Yörük et al., 2006Yörük MA, Aksu T, Gül M, Bolat D, 2006. The effect of soybean meal treated with formaldehyde on amount of protected protein in the rumen and absorption of amino acid from small intestines. Turk J Vet Anim Sci 30: 457-463. https://journals.tubitak.gov.tr/veterinary/vol30/iss5/5), and hence providing the limiting AAs for milk synthesis to the mammary gland. Increased milk production in goats fed with formaldehyde-treated SM, which were fed diets with higher contents of protected protein, may be a direct result of more postruminal supply of those amino acids involved in limiting milk production (Tajaddini et al., 2021Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519). In addition, increased milk production in response to formaldehyde-treated SM might be attributed to an increase in protein available for digestion in the intestines increasing milk precursors (Mishra et al., 2006Mishra BB, Swain RK, Sahu BK, Sawantaray DP, 2006. Effect of bypass protein supplementation on nutrient utilization, milk production and its composition in crossbred cows on paddy straw based ration. Anim Nutr Feed Technol 6(1): 123-133.). As previously stated, an increase in DM, CP and ME intake in goats fed the formaldehyde-treated SM diets could explain their increased milk production because higher ME intake is responsible for higher milk production (Tajaddini et al., 2021Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519). In accordance with our findings, Petit (2003)Petit H, 2003. Digestion, milk production, milk composition, and blood composition of dairy cows fed formaldehyde treated flaxseed or sunflower seed. J Dairy Sci 86: 2637-2646. https://doi.org/10.3168/jds.S0022-0302(03)73859-4 demonstrated that adding formaldehyde-treated flaxseed and sunflower seeds to the diet of dairy cows increases milk production up to 2.7 kg/day when compared to untreated flaxseed and sunflower seeds. Tajaddini et al. (2021)Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519 also reported that giving 1.2% formaldehyde-treated canola meal to lactating goats increased their milk, FCM, ECM and TSCM production. Similar findings were also obtained in cows, buffalos, and goats by feeding rapeseed meal treated with formaldehyde (Sherasia et al., 2010Sherasia PL, Garg MR, Bhanderi BM (2010). Study on the effect of incorporating rumen protected de-oiled rice bran on milk production in the ration of crossbred cows. Ind J Dairy Sci 63: 205-208.), formaldehyde-treated mustard and groundnut cakes (Shelke et al., 2012bShelke SK, Thakur SS, Shete SM (2012b). Protected nutrient technology and the impact of feeding protected nutrients to dairy animals: A review. Int J Dairy Sci 7: 51-62. https://doi.org/10.3923/ijds.2012.51.62), formaldehyde-treated SBM (Dosky et al., 2012Dosky KNS, Jaaf SSA, Mohammed LT, 2012. Effect of protected soybean meal on milk yield and composition in local Meriz goats. Mesop J Agric 40: 1-8. https://doi.org/10.33899/magrj.2012.32593), and formaldehyde-treated sesame cake (Bugalia & Chaudhary, 2010Bugalia HL, Chaudhary JL, 2010. Effect of feeding different levels of formaldehyde treated sesame cake on nutrients intake, milk production and economic returns in lactating crossbred cows. Ind J Anim Sci 80: 152-155.). Throat et al. (2016)Throat S, Gupta R, Shankhpal S, Parnerkar S, 2016. Effect of supplementing formaldehyde treated rape seed meal on milk production, gross milk composition, digestibility of nutrients and feed conversion efficiency in high producing crossbred cows. Int J Livest Res 4: 68-74. http://www.jakraya.com/journal/pdf/12-lriArticle_2.pdf reported that lactating cows supplemented with formaldehyde-treated rapeseed meal on iso-nitrogenous rations have higher daily milk yield and FCM, and improved production efficiency. However, our findings are inconsistent with those of Ashes et al. (1992)Ashes J, Welch PSV, Gulati S, Scott T, Brown G, Blakeley S, 1992. Manipulation of the fatty acid composition of milk by feeding protected canola seeds. J Dairy Sci 75: 1090-1096. https://doi.org/10.3168/jds.S0022-0302(92)77853-9, who found no change in milk production in response to formaldehyde-treated canola seeds. Substitution of 15% SM in the diets of lactating dairy cows decreases milk yield and feed efficiency than control diet (Shirzadegan & Jafari, 2014Shirzadegan K, Jafari M (2014). The effect of different levels of sesame wastes on performance, milk composition and blood metabolites in Holstein lactating dairy cows. J Adv Biol Biomed Res 2: 1296-1303. https://www.magiran.com/paper/2092555). Variations in the type and quantity of protein, as well as the animals’ stage of lactation, may cause different outcomes.
Goats fed diets containing SM (either treated or untreated) had higher milk fat content than those fed control diet. The results of present study agree with Hejazi & Abo Omar (2009)Hejazi A, Abo Omar JM, 2009. Effect of feeding sesame oil cake on performance, milk and cheese quality of Anglo-Nubian goats. Hebron Univ Res J 4: 81-91., who found that Anglo-Nubian goats fed diets containing 10 and 15% sesame oil cake have significantly higher milk fat than goats fed basal ration. The increasing in milk protein content in goats fed diets containing formaldehyde-treated SM may be due to increased RUP levels through treatment with formaldehyde, which is then optimally utilized in milk protein synthesis. In line with the results of the present study, Ababakri et al. (2021b)Ababakri R, Dayani O, Khezri A, Naserian A, 2021b. Influence of flaxseed with rumen undegradable protein level on milk yield, milk fatty acids and blood metabolites in transition ewes. J Anim Sci Technol 63(3): 475-490. https://doi.org/10.5187/jast.2021.e50 indicated that higher levels of dietary RUP (40%) has beneficial effects on ewes’ milk protein contents, but did not affect milk production.
Addition of untreated and formaldehyde-treated SM to the diet of lactating goats decreased SFA, SCFA and MCFA in milk, while UFA, MUFA, LCFA, and PUFA contents as well as UFA/SFA ratio significantly increased. Since the mammary gland’s epithelial cells primarily produce SCFA from de novo, their synthesis can be prevented by raising the concentration of specific LCFA (Grummer, 1991Grummer RR, 1991. Effect of feed on the composition of milk fat. J Dairy Sci 74: 3244-3257. https://doi.org/10.3168/jds.S0022-0302(91)78510-X). Indeed, the high amount of C18:1 (oleic acid) and C18:2 (linoleic acid) in SM causes an inhibition in the expression of genes involved in the de novo synthesis of milk SCFA and MCFA (acetyl-Co A carboxylase alpha and fatty acid synthase) (Thakur et al., 2018Thakur V, Paroha S, Mishra RP, 2018. Free fatty acid profile of seven sesame (Sesamum indicum L.) varieties. Int J Curr Microbiol App Sci 7: 3439-3453. https://doi.org/10.20546/ijcmas.2018.707.399) and reduces milk SCFA and MCFA contents. On the other hand, it is possible that due to the high concentration of PUFA in SM, these FAs escape rumen degradation and enter the blood and increase the milk UFA content. It is also possible that the decrease in ruminal degradation in goats fed formaldehyde-treated SM diet, led to the escape of fatty acids from rumen biohydrogenation and absorbed in the small intestine and entered the milk, and as a result, LCFA is higher in the milk of these goats. Similar to our results, Kim et al. (2013)Kim SI, Cho, BR, Choi CB, 2013. Effects of sesame meal on growth performances and fatty acid composition, free amino acid contents, and panel tests of loin of Hanwoo steers. J Anim Sci Technol 55: 451-460. https://doi.org/10.5187/JAST.2013.55.5.451 found that the ratio of UFA/SFA is higher in steers fed the diet containing SM. Also, Liu et al. (2008)Liu ZL, Yang DP, Chen P, Dong WX, Wang DM, 2008. Supplementation with selenium and vitamin E improves milk fat depression and fatty acid composition in dairy cows fed fat diet. As-Aust J Anim Sci 21(6): 838-844. https://doi.org/10.5713/ajas.2008.70618 also showed a reduction in SCFA and MCFA concentrations in milk when cows are fed diets containing SM. Given that MCFA constitutes the hypercholesterolemic component of milk fat; therefore, reducing MCFA may be recommended as a potential to improve milk’s FAs profile from the perspective of human health (Shingfield et al., 2013Shingfield KJ, Bonnet M, Scollan ND (2013). Recent developments in altering the fatty acid composition of ruminant derived foods. Animal 7: 132-162. https://doi.org/10.1017/S1751731112001681).
Replacement of formaldehyde-treated SM in the dairy goats’ diet reduced ruminal pH, NH3-N concentration, acetate production as well as acetate/propionate ratio while increasing total VFA and propionate production as compared with SBM and untreated SM. The decrease in rumen pH in goats fed formaldehyde-treated SM is influenced by the increase in total VFAs and especially the increase in propionate production in the rumen. Previous studies showed that formaldehyde-treated SBM (Yörük et al., 2006Yörük MA, Aksu T, Gül M, Bolat D, 2006. The effect of soybean meal treated with formaldehyde on amount of protected protein in the rumen and absorption of amino acid from small intestines. Turk J Vet Anim Sci 30: 457-463. https://journals.tubitak.gov.tr/veterinary/vol30/iss5/5) and formaldehyde-treated canola meal (Tajaddini et al., 2021Tajaddini MA, Dayani O, Khezri A, Tahmasbi R, Sharifi-Hoseini MM, 2021. Production efficiency, milk yield, and milk composition and fatty acids profile of lactating goats feeding formaldehyde-treated canola meal in two levels of dietary crude protein. Small Rum Res 204: 1-7. https://doi.org/10.1016/j.smallrumres.2021.106519) have no effect on sheep’s ruminal pH, but significantly decrease rumen NH3-N concentration. The reduction of ruminal NH3-N in goats fed formaldehyde-treated SM diets was predictable because treating with formaldehyde protects the protein from microbial degradation. Previous results on feeding formaldehyde-treated oilseed protein meals were reported by Shelke et al. (2012a)Shelke SK, Thakur SS, Amrutkar SA (2012a). Effect of feeding protected fat and proteins on milk production, composition and nutrient utilization in Murrah buffaloes (Bubalus bubalis). Anim Feed Sci Technol 171: 98-107. https://doi.org/10.1016/j.anifeedsci.2011.10.003 who indicated that rumen protected protein supplements save more energy, which could be wasted through urea synthesis in the liver. Similar to our findings, Wright et al. (2005)Wright C, Von Keyserlingk M, Swift M, Fisher L, Shelford J, Dinn N, 2005. Heat and lignosulfonate-treated canola meal as a source of ruminal undegradable protein for lactating dairy cows. J Dairy Sci 88: 238-243. https://doi.org/10.3168/jds.S0022-0302(05)72681-3 found a decrease in ruminal NH3-N production when lactating cows were provided heat and lignosulfonate-treated canola meal.
Increased production of VFA in goats fed formaldehyde-treated SM diets could be attributed to higher DM intake (McDonald et al., 2011McDonald P, Edwards RA, Greenhalgh JF, Morgan CA, Sinclair LA, Wilkinson RG, 2011. Animal nutrition, 7th ed. Prentice Hall, Essex, UK.). Our findings are consistent with those of Bhatt & Sahoo (2019)Bhatt RS, Sahoo A, 2019. Effect of adding formaldehyde treated protein alone and with Saccharomyces cerevisiae in diet on plane of nutrition, growth performance, rumen fermentation and microbial protein synthesis of finisher lambs. Small Rumin Res 171: 42-48. https://doi.org/10.1016/j.smallrumres.2018.12.005, reporting that feeding formaldehyde-treated SBM to lambs increases the production of rumen VFAs and propionate. On the other hand, reduced acetate production in rumen of goats fed formaldehyde-treated SM is mainly due to lower ruminal pH which in turn diminishes rumen cellulolytic activity and lowers ruminal acetate concentration (Purdie et al., 2008Purdie N, Trout D, Poppi D, Cant J, 2008. Milk synthetic response of the bovine mammary gland to an increase in the local concentration of amino acids and acetate. J Dairy Sci 91: 218-228. https://doi.org/10.3168/jds.2007-0492). Moreover, an increase in ruminal acetate production of goats fed untreated-SM and SBM diets may be due to the fact that feeding more rumen degradable protein (RDP) may enhance the deamination of AA in the rumen and the supply of branched-chain VFAs, which may promote fiber digestion and lead to an increase in ruminal acetate production in these goats (Misra & Thakur, 2001Misra AK, Thakur SS, 2001. Effect of dietary supplementation of sodium salt of isobutyric acid on ruminal fermentation and nutrient utilization in a wheat straw based low protein diet fed to crossbred cattle. As-Aust J Anim Sci 14: 479-484. https://doi.org/10.5713/ajas.2001.479).
In the present study, experimental diets had no significant effect on hemato-chemical parameters of lactating goats. The concentration of blood triglyceride and cholesterol is an indicator of an animal’s energy state and equivalent amounts of these two parameters among different dietary groups suggest animals with comparable energy status. Our results agree with those reported by previous studies (Shirzadegan & Jafari, 2014Shirzadegan K, Jafari M (2014). The effect of different levels of sesame wastes on performance, milk composition and blood metabolites in Holstein lactating dairy cows. J Adv Biol Biomed Res 2: 1296-1303. https://www.magiran.com/paper/2092555; Ashjae et al., 2021Ashjae V, Taghizadeh A, Mehmannavaz Y, Nobakht A, 2021. The effects of replacement of soybean meal by mechanically-processed sesame meal on performance and milk fatty acids profile in lactating Holstein dairy cows. Iran J Appl Anim Sci 11: 477-484.) in which the substituting SM with SBM in the diet of dairy cows have no significant effect on blood glucose, cholesterol, or calcium levels. However, our findings contradicted those of Ababakri et al. (2021a)Ababakri R, Dayani O, Khezri A, Naserian A, 2021a. Effects of extruded flaxseed and dietary rumen undegradable protein on reproductive traits and the blood metabolites in Baluchi ewes. J Anim Feed Sci 30: 1-9. https://doi.org/10.22358/jafs/139153/2021, who found that sheep given extruded flaxseed containing high levels of RUP have higher blood glucose and cholesterol concentrations.
Similar to our results, Mahima et al. (2017)Mahima M, Santosh KT, Vinod KS, Debashis R, Anu R, Rajesh M, 2017. Effect of supplementation of formaldehyde treated Mustard oil cake on feed intake, growth rate, blood biochemical and mineral constituents in Hariana heifers. Int J Livest Res 7: 82-92. https://doi.org/10.5455/ijlr.20170130024515 found no significant changes in serum creatinine, total protein, albumin, and globulin levels among heifers fed different levels of formaldehyde-treated mustard oil cake. Estimation of blood AST and ALT activity is an important factor for evaluating liver health. When the liver is damaged, these enzymes are released in high proportions into the blood, resulting in hepatopathy (Venukumar & Latha, 2004Venukumar M, Latha M, 2004. Effect of Coscinium fenestratum on hepatotoxicity in rats. Ind J Exp Biol 42: 792-797.). The ineffectiveness of the experimental treatments on liver enzymes (ALT and AST) suggested that either formaldehyde-treated or untreated SM consumption had no adverse effects on the liver.
The BUN content is commonly used to assess nitrogen balance in ruminants. High BUN levels are associated with increased dietary RDP, which is degraded into NH3-N and absorbed from the rumen to the blood (Wanapat & Pimpa, 1999Wanapat M, Pimpa O, 1999. Effect of ruminal NH3-N levels on ruminal fermentation, purine derivatives, digestibility and rice straw intake in swamp buffaloes. As-Aust J Anim Sci 12: 904-907. https://doi.org/10.5713/ajas.1999.904). In the present study, goats fed formaldehyde-treated SM showed lower ruminal NH3-N concentration, but their BUN concentration was similar to other groups. Perhaps the reason for this difference is related to other factors such as the energy in the rumen that affected the BUN concentration. Our findings contradicted the study of Shelke et al. (2012b)Shelke SK, Thakur SS, Shete SM (2012b). Protected nutrient technology and the impact of feeding protected nutrients to dairy animals: A review. Int J Dairy Sci 7: 51-62. https://doi.org/10.3923/ijds.2012.51.62, in which BUN content is reduced in buffalos fed diets containing formaldehyde-protected mustard and peanut meals.
Experimental treatments did not influence antioxidant activity of milk and blood in lactating dairy goats. Sesamin is one of the most important lignan furfuran compounds, which has various vital roles and is found in sesame seeds, oil, and meal. Some properties of sesamin include its antioxidant capacity (Jin et al., 2005Jin U, Chun J, Han M, Lee J, Yi Y, Lee S, et al., 2005. Sesame hairy root cultures for extra-cellular production of a recombinant fungal phytase. Process Biochem 40: 3754-3762. https://doi.org/10.1016/j.procbio.2005.05.008) improving immune system function and anticancer activity (Hristov & Giallongo, 2014Hristov AN, Giallongo F, 2014. Feeding protein to dairy cows-what should be our target? Proc 23rd Tri-State Dairy Nutr Conf, Fort Wayne, IN, USA, 14-16 April 2014. Ohio State University, pp: 75-84.) as well as reducing blood pressure and serum lipid content (Ordway et al., 2009Ordway R, Boucher S, Whitehouse NL, Schwab CG, Sloan B, 2009. Effects of providing two forms of supplemental methionine to periparturient Holstein dairy cows on feed intake and lactational performance. J Dairy Sci 92: 5154-5166. https://doi.org/10.3168/jds.2009-2259). Tsiplakou et al. (2021)Tsiplakou E, Mitsiopoulou C, Karaiskou C, Simoni M, Pappas AC, Righi F, et al., 2021. Sesame meal, vitamin E and selenium influence goats’ antioxidant status. Antioxidants 10(3): 392. https://doi.org/10.3390/antiox10030392 reported that feeding goats a diet rich in SM, selenium and vitamin E improves their health and their milk oxidative status. Additionally, Mitsiopoulou et al. (2021)Mitsiopoulou C, Sotirakoglou K, Labrou NE, Tsiplakou E, 2021. The effect of whole sesame seeds on milk chemical composition, fatty acid profile and antioxidant status in goats. Livest Sci 245 (74): 104452. https://doi.org/10.1016/j.livsci.2021.104452 found that supplementing the diet with a high level of sesame seed (10% vs. 5%) increased blood antioxidant activity and milk oxidative stability in goats.
In conclusion, partial substitution of costly conventional protein sources like SBM with less expensive ones like formaldehyde-treated SM in the diet of lactating Murciano-Granadina goats improved their nutrients intake, milk yield and composition, and rumen fermentation characteristics. Furthermore, the addition of formaldehyde-treated SM (1.2 g formaldehyde/ 100 g CP) to the diet of dairy goats led to an increase in PUFA and a decrease in milk SFA, which could be beneficial to human health.