Paape M J, Capuco A V
Immunology and Disease Resistance Laboratory, USDA-ARS, Beltsville, MD 20705, USA.
J Anim Sci. 1997 Feb;75(2):556-65. doi: 10.2527/1997.752556x.
Migration of neutrophils into mammary tissue provides the first immunological line of defense against bacteria that penetrate the physical barrier of the teat canal. Evasion of neutrophil defenses provides an opportunity for invading bacteria to become established. Depletion of neutrophils results in a dramatic increase in susceptibility to intramammary infection. Numerous cytoplasmic particles are shed from the apical surface of mammary secretory cells during milk secretion in goats. Only those counting methods that are specific for deoxyribonucleic acid can distinguish cell-like particles from somatic cells and thereby give reliable estimates of somatic cell numbers in goat milk. Unlike in milk from dairy cows, the somatic cell count in goat milk is influenced by the presence of nucleated cytoplasmic particles, stage of lactation, parity, and caprine arthritis-encephalitis. Investigations indicate that a dry period is necessary for optimal milk production in dairy cows but may not be necessary in goats. However, in many other respects regulation of bovine and caprine lactation seems to be quite similar. Studies have demonstrated additive galactopoietic effects of growth hormone and frequent milking in both species and a recently isolated chemical feedback inhibitor of lactation seems effective across both species. Increasing lactational performance has the potential for decreasing milk somatic cell counts in late lactation.
中性粒细胞迁移至乳腺组织，为抵御穿透乳头管物理屏障的细菌提供了第一道免疫防线。逃避中性粒细胞的防御为入侵细菌的定植提供了机会。中性粒细胞的耗竭会导致乳腺内感染易感性急剧增加。在山羊产奶期间，乳腺分泌细胞的顶端表面会脱落大量细胞质颗粒。只有那些针对脱氧核糖核酸的计数方法才能将类细胞颗粒与体细胞区分开来，从而可靠地估计山羊奶中的体细胞数量。与奶牛的奶不同，山羊奶中的体细胞计数受有核细胞质颗粒的存在、泌乳阶段、胎次和山羊关节炎-脑炎的影响。调查表明，干奶期对奶牛的最佳产奶量是必要的，但对山羊可能并非必要。然而，在许多其他方面，牛和山羊泌乳的调节似乎非常相似。研究表明，生长激素和频繁挤奶对这两个物种都有累加的促泌乳作用，最近分离出的一种泌乳化学反馈抑制剂似乎对这两个物种都有效。提高泌乳性能有可能降低泌乳后期奶中的体细胞计数。
