Department of Veterinary Medicine, University of Sassari, via Vienna 2, 07100 Sassari, Italy.
Department of Agronomy, Food, Natural resources, Animals and Environment (DAFNAE), University of Padova, viale dell'Università 16, 35020 Legnaro (PD), Italy.
J Dairy Sci. 2022 Aug;105(8):6724-6738. doi: 10.3168/jds.2022-22098. Epub 2022 Jul 2.
At the global level, the quantity of goat milk produced and its gross production value have increased considerably over the last 2 decades. Although many scientific papers on this topic have been published, few studies have been carried out on bulk goat milk samples. The aim of the present study was to investigate in the field the effects of farming system, breed type, individual flock, and stage of production on the composition, coagulation properties (MCP), curd firming over time parameters (CF), predicted cheese yield (CY%), and nutrient recovery traits (REC) of 432 bulk milk samples from 161 commercial goat farms in Sardinia, Italy. We found that the variance due to individual flock was of the same order as the residual variance for almost all composition and cheesemaking traits. With regard to the fixed effects, the effect of farming system on bulk milk variability was not highly significant for the majority of traits (it was lower than individual flock), whereas the effects of breed type and stage of production were much higher. More specifically, the intensive farms produced milk with the best concentrations of almost all constituents, whereas extensive farms exhibited faster rennet coagulation times, a slower rate of curd firming, lower potential curd firmness, and lower percentages of fat and energy recoveries in the fresh curd. Farms rearing the local breed, Sarda, alone or together with the Maltese breed, produced milk with the best concentrations of fat and protein, superior curd firmness, and better predicted percentage of fresh curd (CY) and recovery traits. The results show the potential of both types of breed, either for their quantitative (specialized breeds) or their qualitative (local breeds) attributes. As expected, the concentrations of fat, protein fractions, and lactose were influenced by the stage of production, with samples collected in the early stage of production (in February and March) having a greater quantity of the main constituents. Somatic cells reached the highest levels in the late stage of production, which corresponds to the goats' advanced stage of lactation (June-July), although no differences were present in the logarithmic bacterial counts between the early and late stages. Regarding cheesemaking potential, bulk milk samples of the late stage were characterized by delayed rennet coagulation and curd firming times, the lowest values of curd firmness, and a general reduction in CY%, and REC traits. In conclusion, we highlight several issues regarding the effects of the most important sources of variation on bulk goat milk, and point to some critical factors relevant for improving dairy goat farming and milk production.
在全球范围内，过去 20 年来，山羊奶的产量和总产值都有了显著增长。尽管已经发表了许多关于这个主题的科学论文，但对大量羊奶样本的研究却很少。本研究旨在实地调查养殖系统、品种类型、个体羊群和生产阶段对意大利撒丁岛 161 个商业山羊场的 432 个羊奶样本的组成、凝乳特性（MCP）、凝乳时间参数（CF）、预测奶酪产量（CY%）和营养回收特性（REC）的影响。我们发现，对于几乎所有的组成和干酪制作特性来说，个体羊群的方差与残差方差处于同一数量级。就固定效应而言，对于大多数特性来说，养殖系统对羊奶变异性的影响并不显著（低于个体羊群），而品种类型和生产阶段的影响则要高得多。具体来说，集约化养殖场生产的羊奶几乎所有成分的浓度都最好，而粗放养殖场的凝乳时间更快，凝乳速度更慢，潜在凝乳强度更低，新鲜凝乳中的脂肪和能量回收率也更低。单独或与马耳他品种一起饲养撒丁岛本地品种的农场生产的羊奶脂肪和蛋白质浓度最高，凝乳强度最好，新鲜凝乳（CY）和回收特性的预测百分比更好。结果表明，这两种类型的品种都有潜力，无论是其数量（专门品种）还是质量（本地品种）属性。正如预期的那样，脂肪、蛋白质分数和乳糖的浓度受生产阶段的影响，在生产初期（二月和三月）采集的样本中主要成分的含量更大。体细胞在生产后期（六月至七月，即母羊泌乳后期）达到最高水平，尽管在早期和后期阶段之间，对数细菌计数没有差异。关于干酪制作潜力，后期的羊奶样本具有凝乳时间和凝乳时间延迟、凝乳强度最低以及一般的 CY%和 REC 特性降低的特点。总之，我们强调了羊奶大量样本中最重要的变异源的影响，并指出了一些对提高奶山羊养殖和牛奶生产有重要意义的关键因素。
