Introduction

Dairy goats in Europe are most common around the Mediterranean basin, and the main use of the milk is for cheese making (Ruiz-Morales et al., 2019Ruiz-Morales FA, Castel-Genís JM, Mena-Guerrero Y, 2019. Current status, challenges and the way forward for dairy goat production in Europe. Asian-Australas J Anim Sci, 32: 1256-1265. 10.5713/ajas.19.0327.). The quality of the milk required for cheese making depends on its physical, proximate chemical, and hygienic-sanitary characteristics; for example, total bacterial count (BC) and somatic cell count (SCC) Pirisi et al., 2007). Traditionally, quality assessment systems consider several parameters, such as cheese extract (protein and fat percentages) and hygienic and bacteriological quality (Pirisi et al., 2007Pirisi A, Lauret A, Dubeuf JP, 2007. Basic and incentive payments for goat and sheep milk in relation to quality. Small Rumin Res, 68: 167-178. 10.1016/j.smallrumres.2006.09.009).

In recent years, foods containing natural antioxidants in general, and milk and dairy products in particular, have been demanded by consumers for their beneficial health effects in both humans and animals (McGrath et al., 2018McGrath J, Duval SM, Tamassia LFM, Kindermann M, Stemmler RT, de Gouvea VN, Acedo TS, Immig I, Williams SN, Celi P, 2018. Nutritional strategies in ruminants: a lifetime approach. Res Vet Sci, 116: 28-39. 10.1016/j.rvsc.2017.09.011; Khan et al., 2019Khan IT, Nadeem M, Imran M, Ullah R, Ajmal M, Jaspal MH, 2019. Antioxidant properties of Milk and dairy products: A comprehensive review of the current knowledge. Lipids Health Dis, 18: 1-13. 10.1186/s12944-019-0969-8). In animals, important roles for antioxidant compounds in maintaining optimum udder health have been identified (O`Rourke, 2009O`Rourke D, 2009. Nutrition and udder health in dairy cows: a review. Ir Vet J, 62 (Suppl 4): S15-S20. 10.1186/2046-0481-62-S4-S15; McGrath et al., 2018McGrath J, Duval SM, Tamassia LFM, Kindermann M, Stemmler RT, de Gouvea VN, Acedo TS, Immig I, Williams SN, Celi P, 2018. Nutritional strategies in ruminants: a lifetime approach. Res Vet Sci, 116: 28-39. 10.1016/j.rvsc.2017.09.011). In this regard, the total antioxidant status in milk has been correlated with udder health, as reflected by the number of somatic cells present in milk. The total antioxidant capacity (TAC) is lower in mastitis milk samples compared with normal milk in cows (Atakisi et al., 2010Atakisi O, Oral H, Atakisi E, Merhan O, Metin Pancarci S, Ozcan A, Marasli S, Polat B, Colak A, Kaya S, 2010. Subclinical mastitis causes alteration in nitric oxide, total oxidant and antioxidant capacity in cow milk. Res Vet Sci, 89: 10-13. 10.1016/j.rvsc.2010.01.008) and in goats (Silanikove et al., 2014Silanikove N, Merin U, Shapiro F, Leitner G, 2014. Sub-clinical mastitis in goats is associated with upregulation of nitric oxide-derived oxidative stress that causes reduction of milk antioxidative properties and impairment of its quality. J Dairy Sci, 97: 3449-3455. 10.3168/jds.2013-7334). However, studies on milk production, commercial traits, and total antioxidant status in dairy goat farms are scarce and incomplete (Delgado-Pertíñez et al., 2013Delgado-Pertíñez M, Gutiérrez-Peña R, Mena Y, Fernández-Cabanás VM, Laberye D, 2013. Milk production, fatty acid composition and vitamin E content of Payoya goats according to grazing level in summer on Mediterranean shrublands. Small Rumin Res, 114: 167-175. 10.1016/j.smallrumres.2013.06.001). Thus, the applicability of the results obtained from commercial flocks to modify milk composition and quality is not well established.

The autochthonous Payoya breed is a dairy goat raised in pastoral systems. At the time of the study, 28 flocks, and 8,178 Payoya goats were registered in the correspondent herd-book (Association of Payoya breeders; unpublished data). The average milk production of the breed is 440 kg in 219-days lactation (ARCA, 2011ARCA, 2011. Sistema Nacional de Información de Razas. Available online: https://servicio.mapa.gob.es/arca/flujos.html (accessed on May, 18 2024).). Produced milk is mainly oriented towards the production of pure goat cheeses. As in other small ruminant farming, their economic efficiency is mainly conditioned by productivity and feeding management (Milan et al., 2003Milan MJ, Arnalte E, Caja G, 2003. Economic profitability and typology of Ripollesa breed sheep farms in Spain. Small Rumin Res, 49: 97-105. 10.1016/S0921-4488(03)00058-0; Ripoll-Bosh et al., 2012Ripoll-Bosch R, Díez-Unquera B, Ruiz R, Villalba D, Molina E, Joy M, Olaizola A, Bernués A, 2012. An integrated sustainability assessment of Mediterranean sheep farms with different degrees of intensification. Agric Syst, 105: 46-56. 10.1016/j.agsy.2011.10.003¸ Mena et al., 2017Mena Y, Gutiérrez-Peña R, Ruiz FA, Delgado Pertíñez M, 2017. Can Dairy Goat Farms in Mountain Areas Reach a Satisfactory Level of Profitability without Intensification? A Case Study in Andalusia (Spain). Agroecol Sustain Food Syst, 41: 614-634. 10.1080/21683565.2017.1320620). The researchers’ previous work (Gutiérrez-Peña et al., 2016Gutierrez-Peña R, Mena Y, Ruiz FA, Delgado Pertíñez M, 2016. Strengths and weaknesses of traditional feeding management of dairy goat farms in mountain areas. Agroecol Sustain Food Syst, 40: 736-756. 10.1080/21683565.2016.1178202; Mena et al., 2017Mena Y, Gutiérrez-Peña R, Ruiz FA, Delgado Pertíñez M, 2017. Can Dairy Goat Farms in Mountain Areas Reach a Satisfactory Level of Profitability without Intensification? A Case Study in Andalusia (Spain). Agroecol Sustain Food Syst, 41: 614-634. 10.1080/21683565.2017.1320620), in which the profitability and social data of Payoya goat systems have studied, has suggested actions to enhance the viability of farms, such as commercial strategies to improve the sales of their products, for example, through specific certification. In this regard, a national regulation for commercializing native-bred animal products (Royal Decree-Law RD 505/2013) with a logo (“100% Raza Autóctona”) has been published. This logo affects many products, including those fresh or processed from animals of autochthonous breeds (meat, milk, eggs, derivatives, and even non-food products such as wool).

Currently, consumers demand more information about the quality and origin of the products they purchase, making it necessary to establish specific identification by labeling products from autochthonous breeds. Therefore, using the above-mentioned national regulation will require assessing the quality of a farm’s products. Based on previous work, milk samples from three grazing-based management groups were analyzed for fatty acid profile and vitamin A and E contents. There were few differences between groups, but important differences were found according to the season (Gutiérrez-Peña et al., 2018Gutiérrez-Peña R, Fernández-Cabanás VM, Mena Y, Delgado-Pertíñez M, 2018. Fatty acid profile and vitamins A and E contents of milk in goat farms under Mediterranean wood pastures as affected by grazing conditions and seasons. J Food Compos Anal, 72: 122-131. 10.1016/j.jfca.2018.07.003). However, there is a lack of information comparing the effect of Payoya management systems on commercial milk quality parameters.

Mena et al. (2017Mena Y, Gutiérrez-Peña R, Ruiz FA, Delgado Pertíñez M, 2017. Can Dairy Goat Farms in Mountain Areas Reach a Satisfactory Level of Profitability without Intensification? A Case Study in Andalusia (Spain). Agroecol Sustain Food Syst, 41: 614-634. 10.1080/21683565.2017.1320620) conducted a multivariate analysis of the economic and social parameters of sixteen Payoya goat farms under conventional grazing-based management systems in southwestern Spain and identified three clusters. The primary aim of the present work was to provide an overview of the commercial traits and antioxidant composition of milk produced on those farms. These results would contribute significantly to the national regulation for the commercialization of native-bred animal products. A second aim of the current work was to assess the relationships between the antioxidant content and the hygiene-sanitary parameters in milk.

Material and Methods

Results

The indicators of feeding management are shown in Figure 1. The NERG was not statistically different between the more pastoral farms (LPG and HPG clusters; average 47%), but these values were higher (p<0.001) than that obtained for the MIG farms (19%; Figure 1a). Moreover, the MIG farms showed a higher (p<0.001) goat feed supply based mainly on concentrates (1.3 and 0.4 kg d⁻¹ for concentrate and forage supply, respectively), and no differences were found between the LPG and HPG farms (averages of 0.8 and 0.1 kg d⁻¹ for concentrate and forage supply, respectively). The amount of feed provided also changed with the month (Figure 1b). In winter (December, January, and February) and autumn (September, October, and November) months, goats received the highest amounts of concentrate (average of 1.2 kg d⁻¹; p<0.05) because the intensity of grazing was lower, and births were concentrated in those seasons of the year. The forage contribution followed an analogous pattern, supplying maximum amounts when the animals grazed less.

  

a)  

  

b)  

Figure 1 Indicators (mean values) related to feeding management (Feed supply, bars; Net Energy Requirements obtained from Grazing (NERG), line) of Mediterranean pastoral goat farms according to (a) cluster group and (b) sampling month. The feed supply per milking goat is the sum of the concentrate and fodder supplied in the manger by the farmers. The mean values for each parameter and factor levels were compared, and those with the same letter (a, b, c) do not differ (p>0.05). 

The yield, chemical and hygiene-sanitary compositions, and economic parameters of the milk according to the goat grazing group are shown in Table 1. No statistical differences in the percentages of chemical parameters were observed between the groups studied. Nevertheless, daily yields of milk and milk components were not different (p>0.05) between the MIG and HPG groups (averages of 1.34 L d⁻¹ and 65.5, 49.8, and 61.8 g d⁻¹ of fat, protein, and lactose, respectively), but were higher (p<0.05) than those obtained in the LPG group (0.77 L d⁻¹ and 39.5, 28.7, and 37.1 g d⁻¹ of fat, protein, and lactose, respectively). Consequently, and although the price of milk was similar for all farms (0.52€ L⁻¹), the final milk income was higher (p<0.01) for MIG and HPG farms (average of 0.70€ per goat d⁻¹) than for LPG farms (0.40€ goat d⁻¹) (Table 1).

The yield, chemical composition, and economic parameters of the milk were affected by the sampling month (Tables 1 and 2; Figure 2). The highest milk yield was obtained in the spring (March, April, May) months, followed by the winter months of January and February, and the lowest values were found in autumn and at the end of summer. The patterns throughout the lactation months of the lactose percentage and yield were similar, while the fat and protein percentages had an inverse relationship (higher during the autumn and, secondarily, in winter), to milk yield. The price of goat milk behaves seasonally, reaching a maximum at the end of summer and during the autumn, when there is a production deficit on farms (Figure 2). Considering the price and yields of milk (Figure 2 and Table 2), the lowest milk income was obtained in the summer months and in November (Figure 2).

  

Figure 2 Mean values of economic parameters of the goat milk in Mediterranean pastoral farms according to sampling month. The mean values for each parameter were compared, and those with the same letter (a, b, c, d) did not differ (p>0.05). 

The BC and SCC of the milk showed no significant differences (p>0.05) with respect to the groups studied (Table 1) but were affected by the sampling month (p<0.001, Table 2). The highest SCC and BC were obtained at the end of summer and autumn, while the remaining months had the lowest counts.

Regarding the relationship of milk yield and chemical parameters with the hygiene-sanitary composition, as the SCC increased, milk yield (r = −0.23, p<0.01) and lactose (r = −0.40, p<0.001) decreased, whereas fat (r = 0.29, p<0.001) and protein (r = 0.50, p<0.001) contents increased. A positive correlation was obtained between SCC and BC (r = 0.26, p<0.001).

The TAC did not vary significantly (p>0.05) between the groups studied (Table 1). Nevertheless, it was significantly higher (p<0.001) in winter and spring milk than in milk samples taken during other seasons (Table 2). Regarding the relationship between the hygiene-sanitary parameters and the TAC, a negative correlation (r = −0.30, p<0.001) between TAC and SCC was found.

Discussion

Although all animals in the study were fed by grazing, the contribution of grass differs between groups. Mena et al. (2017Mena Y, Gutiérrez-Peña R, Ruiz FA, Delgado Pertíñez M, 2017. Can Dairy Goat Farms in Mountain Areas Reach a Satisfactory Level of Profitability without Intensification? A Case Study in Andalusia (Spain). Agroecol Sustain Food Syst, 41: 614-634. 10.1080/21683565.2017.1320620) have observed that the HPG farms have similar milk production per goat to the MIG farms and greater productivity than the LPG farms, with similar NERG and concentrate and forage inputs. According to milk production and chemical composition, the levels of energy and protein provided by grazing and supplemental feeds would be similar in the HPG and MIG groups and higher than in the LPG group (Morand-Fehr et al., 2007Morand-Fehr P, Fedele V, Decandia M, Le Frileux Y, 2007. Influence offarming and feeding systems on composition and quality of goat and sheep milk. Small Rumin Res, 68: 20-34. 10.1016/j.smallrumres.2006.09.019). In the present study, milk sales are the main income (Mena et al., 2017Mena Y, Gutiérrez-Peña R, Ruiz FA, Delgado Pertíñez M, 2017. Can Dairy Goat Farms in Mountain Areas Reach a Satisfactory Level of Profitability without Intensification? A Case Study in Andalusia (Spain). Agroecol Sustain Food Syst, 41: 614-634. 10.1080/21683565.2017.1320620), and according to the current pricing system (including prevailing penalties), the differences between the groups are due to the milk productivity (L d⁻¹) because there were no differences in either the cheese extract (protein and fat percentages) or in the SCC and BC (Table 1).

Milk yield (1.20 L d⁻¹) was smaller, and the percentages of basic chemical components (5.00%, 3.69%, and 4.44% for fat, protein, and lactose, respectively) were within the range of individual test-day data from Murciano–Granadina goats (Pleguezuelos et al., 2015Pleguezuelos FJ, De La Fuente LF, Gonzalo C, 2015. Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population. Adv Dairy Res, 3: 1000145. 10.4172/2329-888X.1000145), the most important Spanish dairy goat breed, reared under a semi-intensive system, and of the bulk tank milk from dairy goat farms (de la Vara-Martínez et al., 2018de la Vara-Martínez JA, García-Higuera A, Román-Esteban M, Romero-Asensio J, Carmona-Delgado M, Berruga I., Molina A, 2018. Monitoring bulk milk quality by an integral traceability system of milk. J Appl Anim Res, 46: 784-790. 10.1080/09712119.2017.1403327). The reduced yield in the study area may be due to the characteristics of the farming systems, specifically to the autochthonous Payoya breed, which are well adapted to grazing but farmed less intensively and, consequently, have lower milk productivity. Stage of lactation and feeding (mainly due to ingestion and nutritive value of the feedstuff) differences can explain the milk yield and composition results in the months analyzed (Delgado-Pertíñez et al., 2013Delgado-Pertíñez M, Gutiérrez-Peña R, Mena Y, Fernández-Cabanás VM, Laberye D, 2013. Milk production, fatty acid composition and vitamin E content of Payoya goats according to grazing level in summer on Mediterranean shrublands. Small Rumin Res, 114: 167-175. 10.1016/j.smallrumres.2013.06.001). Regarding the physiological factor of lactation, in the farms of this study, lactation finished toward summer, and the main kidding period was in autumn. Together with the lower temperatures, this would partially explain the reduced milk production and enriched chemical composition at the end of summer and autumn. The reproduction pattern of those farming systems (births are concentrated in October–November and January–February) is made to graze the most in spring and reduce the number of lactating animals in summer, when pasturage is scarce in the Mediterranean region (Mena et al., 2017Mena Y, Gutiérrez-Peña R, Ruiz FA, Delgado Pertíñez M, 2017. Can Dairy Goat Farms in Mountain Areas Reach a Satisfactory Level of Profitability without Intensification? A Case Study in Andalusia (Spain). Agroecol Sustain Food Syst, 41: 614-634. 10.1080/21683565.2017.1320620).

Bulk tank SCC and BC have been used as indicators to evaluate udder health, as well as the efficiency of production processes and cleaning and hygiene-sanitary practices (Delgado-Pertíñez et al., 2003Delgado-Pertíñez M, Alcalde MJ, Guzmán JL, Castel JM, Mena Y, Caravaca F, 2003. Effect of hygiene-sanitary management on goat milk quality in semi extensive systems in Spain. Small Rumin Res, 47: 51-61. 10.1016/S0921-4488(02)00239-0; Gonzalo et al., 2010Gonzalo C, Carriedo JA, García-Jimeno MC, Pérez-Bilbao M, De La Fuente LF, 2010. Factors influencing variation of bulk milk antibiotic residue occurrence, somatic cell count, and total bacterial count in dairy sheep flocks. J Dairy Sci, 93: 1587-1595. 10.3168/jds.2009-2838; de la Vara-Martínez et al., 2018de la Vara-Martínez JA, García-Higuera A, Román-Esteban M, Romero-Asensio J, Carmona-Delgado M, Berruga I., Molina A, 2018. Monitoring bulk milk quality by an integral traceability system of milk. J Appl Anim Res, 46: 784-790. 10.1080/09712119.2017.1403327). In this study, geometric means for SCC (1950 × 10³ cells/mL) and BC (77 × 10³ cfu/mL) were similar to values reported for bulk tank milk from the same breed (Delgado-Pertíñez et al., 2003Delgado-Pertíñez M, Alcalde MJ, Guzmán JL, Castel JM, Mena Y, Caravaca F, 2003. Effect of hygiene-sanitary management on goat milk quality in semi extensive systems in Spain. Small Rumin Res, 47: 51-61. 10.1016/S0921-4488(02)00239-0) and other Spanish breeds (de la Vara-Martínez et al., 2018de la Vara-Martínez JA, García-Higuera A, Román-Esteban M, Romero-Asensio J, Carmona-Delgado M, Berruga I., Molina A, 2018. Monitoring bulk milk quality by an integral traceability system of milk. J Appl Anim Res, 46: 784-790. 10.1080/09712119.2017.1403327). Significant differences in the hygiene-sanitary quality of the milk were observed for different months, in agreement with a previous study of the same breed (Delgado-Pertíñez et al., 2003Delgado-Pertíñez M, Alcalde MJ, Guzmán JL, Castel JM, Mena Y, Caravaca F, 2003. Effect of hygiene-sanitary management on goat milk quality in semi extensive systems in Spain. Small Rumin Res, 47: 51-61. 10.1016/S0921-4488(02)00239-0). However, no significant differences were found by de la Vara-Martínez et al. (2018de la Vara-Martínez JA, García-Higuera A, Román-Esteban M, Romero-Asensio J, Carmona-Delgado M, Berruga I., Molina A, 2018. Monitoring bulk milk quality by an integral traceability system of milk. J Appl Anim Res, 46: 784-790. 10.1080/09712119.2017.1403327) in other Spanish breeds, indicating that the results are more related to good farming practices.

The seasonal variation of the SCC in our study could be related to the lactation phase, increasing toward the end of lactation (Zeng et al., 1997Zeng SS, Escobar EN, Popham T, 1997. Daily variations in somatic cell count, composition, and production of Alpine goat milk. Small Rumin Res, 26: 253-260. 10.1016/S0921-4488(96)01002-4; Raynal-Ljutovac et al., 2007Raynal-Ljutovac K, Pirisi A, de Crémoux R, Gonzalo C, 2007. Somatic cells of goat and sheep milk: analytical, sanitary, productive and technological aspects. Small Rumin Res, 68: 126-144. 10.1016/j.smallrumres.2006.09.012), and other non-infectious factors (Raynal-Ljutovac et al. 2007Raynal-Ljutovac K, Pirisi A, de Crémoux R, Gonzalo C, 2007. Somatic cells of goat and sheep milk: analytical, sanitary, productive and technological aspects. Small Rumin Res, 68: 126-144. 10.1016/j.smallrumres.2006.09.012). Higher counts due to physiological causes are common because several breeding females are present in the goat herds throughout the year, and postpartum and lactation periods occur successively (Raynal-Ljutovac et al., 2007Raynal-Ljutovac K, Pirisi A, de Crémoux R, Gonzalo C, 2007. Somatic cells of goat and sheep milk: analytical, sanitary, productive and technological aspects. Small Rumin Res, 68: 126-144. 10.1016/j.smallrumres.2006.09.012; Gutiérrez-Peña et al., 2016Gutierrez-Peña R, Mena Y, Ruiz FA, Delgado Pertíñez M, 2016. Strengths and weaknesses of traditional feeding management of dairy goat farms in mountain areas. Agroecol Sustain Food Syst, 40: 736-756. 10.1080/21683565.2016.1178202). Furthermore, this indicator has been associated with intra-mammary infections and milk yield losses in dairy goats (Baudry et al., 1997Baudry C, de Cremoux R, Chartier C, Perrin G, 1997. Impact of the cellular concentration of milk in goats on its production and its composition. Vet Res, 28: 277-286.; Pleguezuelos et al., 2015Pleguezuelos FJ, De La Fuente LF, Gonzalo C, 2015. Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population. Adv Dairy Res, 3: 1000145. 10.4172/2329-888X.1000145). Nevertheless, SCC levels in small ruminants have still not been included in European legislation (EC No. 853/2004) because their significance is still debatable. Unlike the milk yield in the present study, fat and protein percentages have been shown to rise as SCC increases, in agreement with previous studies in the same breeds (Delgado-Pertíñez et al., 2003Delgado-Pertíñez M, Alcalde MJ, Guzmán JL, Castel JM, Mena Y, Caravaca F, 2003. Effect of hygiene-sanitary management on goat milk quality in semi extensive systems in Spain. Small Rumin Res, 47: 51-61. 10.1016/S0921-4488(02)00239-0) and other Spanish breeds (Pleguezuelos et al., 2015Pleguezuelos FJ, De La Fuente LF, Gonzalo C, 2015. Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population. Adv Dairy Res, 3: 1000145. 10.4172/2329-888X.1000145). Although a decrease in fat and protein is expected during intramammary infection due to the reduced synthetic and secretory capacity of the mammary glands (Raynal-Ljutovac et al., 2007Raynal-Ljutovac K, Pirisi A, de Crémoux R, Gonzalo C, 2007. Somatic cells of goat and sheep milk: analytical, sanitary, productive and technological aspects. Small Rumin Res, 68: 126-144. 10.1016/j.smallrumres.2006.09.012), no studies have rigorously evidenced this phenomenon in goats (Pleguezuelos et al., 2015Pleguezuelos FJ, De La Fuente LF, Gonzalo C, 2015. Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population. Adv Dairy Res, 3: 1000145. 10.4172/2329-888X.1000145). The increases in these parameters observed in our study have also been reported by other authors (Barrón-Bravo et al., 2013Barrón-Bravo OG, Gutiérrez-Chávez AJ, Ángel-Sahagún CA, Montaldo HH, Shepard L, Valencia-Posadas M, 2013. Losses in milk yield, fat and protein contents acccording to different levels of somatic cell count in dairy goats. Small Rumin Res, 113: 421-431. 10.1016/j.smallrumres.2013.04.003; Pleguezuelos et al., 2015Pleguezuelos FJ, De La Fuente LF, Gonzalo C, 2015. Variation in Milk Yield, Contents and Incomes According to Somatic Cell Count in a Large Dairy Goat Population. Adv Dairy Res, 3: 1000145. 10.4172/2329-888X.1000145), who attributed it to a concentration effect associated with the reduction in milk yield in infected goats as inflammatory response increased. In the case of protein, a higher soluble protein concentration in milk from blood associated with a mammary infection or SCC (Leitner et al., 2004aLeitner G, Merin U, Silanikove N, 2004a. Changes in milk composition as affected by subclinical mastitis in goats. J Dairy Sci, 87: 1719-1726. 10.3168/jds.S0022-0302(04)73325-1,b) together with a concentration effect (due to decreased milk yield) could explain the higher correlation found for protein content compared to that for fat content as SCC increases.

Unlike SCC, BC is covered by EU legislation (EC No. 853/2004), with different thresholds set according to the species and the intended use of the milk. The limits for milk from species other than cow are ≤500×10³ cfu/mL when the destination of milk does not include heat treatment or ≤1500×10³ cfu/mL for heat-treated milk before processing. In our study, the BC was lower in the months with the highest environmental temperatures; this requires the implementation of good hygiene-sanitary practices on farms, including maintaining the refrigeration tank at the correct temperature. The higher counts in some months (mostly autumn) may be associated with rainfall and, consequently, dirtier animals (Delgado-Pertíñez et al., 2003Delgado-Pertíñez M, Alcalde MJ, Guzmán JL, Castel JM, Mena Y, Caravaca F, 2003. Effect of hygiene-sanitary management on goat milk quality in semi extensive systems in Spain. Small Rumin Res, 47: 51-61. 10.1016/S0921-4488(02)00239-0). The mean bacteriological values obtained in this study were lower than the maximum levels permitted by EC Regulation for products made with raw milk, which shows that the appropriate conditions of hygiene-sanitary management are being maintained at the study farms.

Dairy products contain natural antioxidants, such as vitamins, oligosaccharides, peptides, and minerals (Khan et al., 2019Khan IT, Nadeem M, Imran M, Ullah R, Ajmal M, Jaspal MH, 2019. Antioxidant properties of Milk and dairy products: A comprehensive review of the current knowledge. Lipids Health Dis, 18: 1-13. 10.1186/s12944-019-0969-8) and appreciable amounts of phenolic compounds (Di Trana et al., 2015Di Trana A, Bonanno A, Cecchini S, Giorgio D, Di Grigoli A, Claps S, 2015. Effects of Sulla forage (Sulla coronarium L.) on the oxidative status and milk polyphenol content in goats. J Dairy Sci, 98: 37-46. 10.3168/jds.2014-8414; Chávez-Servín et al., 2018Chávez-Servín JL, Andrade-Montemayor HM, Vázquez CV, Barreyro AA, García-Gasca T, Martínez RAF, Ramírez AMO, de la Torre-Carbot K, 2018. Effects of feeding system, heat treatment and season on phenolic compounds and antioxidant capacity in goat milk, whey and cheese. Small Rumin Res, 160: 54-58. 10.1016/j.smallrumres.2018.01.011; Delgado-Pertíñez et al., 2021Delgado-Pertíñez M, Martín-García I, Mena Y, Zarazaga LA, Guzmán JL, 2021. Supplementing the Diet of Dairy Goats with Dried Orange Pulp throughout Lactation: II Effect on Milk Fatty Acids Profile, Phenolic Compounds, Fat-Soluble Vitamins and Antioxidant Capacity. Animals, 11: 2421. 10.3390/ani11082421). The TAC did not vary significantly between the groups studied, in agreement with previous work (Delgado-Pertíñez et al., 2013Delgado-Pertíñez M, Gutiérrez-Peña R, Mena Y, Fernández-Cabanás VM, Laberye D, 2013. Milk production, fatty acid composition and vitamin E content of Payoya goats according to grazing level in summer on Mediterranean shrublands. Small Rumin Res, 114: 167-175. 10.1016/j.smallrumres.2013.06.001), probably due to the similar management of animals on all farms based on the use of pastures. According to several studies in cows (Clausen et al., 2009Clausen MR, Huvaere K, Skibsted LH, Stagsted J, 2009. Characterization of peroxides formed by riboflavin and light exposure of milk. Detection of urate hydroperoxide as a novel oxidation product. J Agric Food Chem, 58: 481-487. 10.1021/jf903470p) and sheep (Virto et al., 2012Virto M, Bustamante M, Ruiz de Gordoa JC, Amores G, Fernández-Caballero PN, Mandaluniz N, Arranz J, Nájera AI, Albisu M, Pérez-Elortondo FJ, Barron LJR, de Renobales M, 2012. Interannual and geographical reproducibility of the nutritional quality of milk fat from commercial grazing flocks. J Dairy Res, 79: 485-494. 10.1017/S0022029912000490), the main water-soluble antioxidants of milk are derived from the caseins and other low molecular weight compounds, which could explain the differences between results obtained in different months in this study (i.e., higher values in winter and spring milk than in the other milk samples). With respect to the latter compounds, a positive correlation (r = 0.31, p<0.001) was observed between the TAC and retinol in our previous study (Gutiérrez-Peña et al., 2018Gutiérrez-Peña R, Fernández-Cabanás VM, Mena Y, Delgado-Pertíñez M, 2018. Fatty acid profile and vitamins A and E contents of milk in goat farms under Mediterranean wood pastures as affected by grazing conditions and seasons. J Food Compos Anal, 72: 122-131. 10.1016/j.jfca.2018.07.003), in agreement with the higher content of vitamin A in winter milk in our work and the findings of Revilla et al. (2016Revilla I, González-Martín, MI, Vivar-Quintana AM, Blanco-López MA, Lobos-Ortega IA, Hernández-Hierro JM, 2016. Antioxidant capacity of different cheeses: Affecting factors and prediction by near infrared spectroscopy. J Dairy Sci, 99: 5074-5082. 10.3168/jds.2015-10564) in cheeses. However, no significant correlations have been found by other authors (Lucas et al., 2008Lucas A, Andueza D, Rock E, Martin B, 2008. Prediction of dry matter, fat, pH, vitamins, minerals, carotenoids, total antioxidant capacity and color in fresh and freeze-dried cheeses by Visible-Near-Infrared reflectance spectroscopy. J Agric Food Chem, 56: 6801-6808. 10.1021/jf800615a). Some vitamins, such as vitamin A, play an important role in supporting the immune system (Spears and Weiss, 2008Spears JW, Weiss WP, 2008. Role of antioxidants and trace elements in health and immunity of transition dairy cows. Vet J, 176: 70-76. 10.1016/j.tvjl.2007.12.015), and this could be associated, at least partially, with the lower SCC observed in the present study, in which a negative correlation (r = −0.22, p<0.01) between SCC and retinol was also observed. Indeed, vitamin A content in blood has been associated with the udder health of dairy cows (Chew et al., 1982Chew BP, Hollen LL, Hillers JK, Herlugson ML, 1982. Relationship between vitamin A and -carotene in blood plasma and milk and mastitis in Holsteins. J Dairy Sci, 65: 2111-2118.; LeBlanc et al., 2004LeBlanc SJ, Herdt TH, Seymour WM, Duffield TF, Leslie KE, 2004. Peripartum serum vitamin E, retinol, and beta-carotene in dairy cattle and their associations with disease. J Dairy Sci, 87: 609-619. 10.3168/jds.S0022-0302(04)73203-8), and dairy cows supplemented with that vitamin at the end of the prepartum period had lower SCC in postpartum milk (Agustinho et al., 2021Agustinho BC, Ramsey KC, Moore C, Tsai CY, Scholte CM, McGuire MA, Rezamand P, 2021. Effect of Different Combinations of Dietary Vitamin A, Protein Levels, and Monensin on Inflammatory Markers and Metabolites, Retinol-Binding Protein, and Retinoid Status in Periparturient Dairy Cows. Animals, 11: 2605. 10.3390/ani11092605). There are few studies in goats; therefore, further research is necessary to better understand how these parameters are affected by the hygiene-sanitary components and affect inflammatory markers, especially in individual animals.

Conclusion

No significant differences were found between clusters in the composition, hygiene-sanitary parameters, and antioxidant capacity of the milk studied, as the animals in all farms were similarly managed based on the use of natural pastures. However, significant changes were observed in the milk composition by calendar month because of lactation effects and differences in feeding regimens. The percentage of lactose and the milk component yields (g d⁻¹) patterns throughout the lactation months were similar, while the relationship between the fat and protein percentages was inverse to milk yield. During the end of summer and autumn months, the highest number of bacteria and somatic cells in the milk were observed, but the bacteriological count levels were below the legal limit set by EC regulations. The TAC was significantly higher in winter and spring milks than in the other milk samples.

The negative correlation between the antioxidant capacity and the somatic cells shows the important role of antioxidants in maintaining optimal udder health. One of the compounds involved in this antioxidant mechanism could be vitamin A due to the positive correlation between the antioxidant capacity and retinol determined in a previous study.

Finally, the information generated in this and previous studies on the quality of goat milk from the autochthonous Payoya breed will contribute to establishing the records of the traceability system to guarantee that the animal products obtained are of the native breed. All of this will help the consumer to easily identify these products and increase their demand, which will result in the conservation and promotion of the genetic heritage of these breeds and the foods derived from them.