Silanikove Nissim, Merin Uzi, Shapiro Fira, Leitner Gabriel
Biology of Lactation Laboratory, Institute of Animal Science, ARO, the Volcani Center, PO Box 6, Bet Dagan 50250, Israel.
J Dairy Sci. 2013 Oct;96(10):6400-11. doi: 10.3168/jds.2013-6740. Epub 2013 Aug 9.
The present work compared metabolic and immune responses in genetically high-producing cows that produced a low amount of milk before expected involution and in cows with the same genetic potential that produced copious amounts of milk before their scheduled drying-off. Ten multiparous lactating Israeli Holstein cows producing approximately 10,500 L in the current lactation, without bacterial infection and scheduled for drying-off approximately 60 d before their expected parturition, were studied. Five of the cows that exhibited a sharp, spontaneous reduction in milk yield at the end of their lactation and produced less than ~14L/d were defined as cows approaching natural involution (ANI), and 5 cows that produced between 25 and 35 L/d were defined as cows approaching forced involution (AFI). Three days before scheduled drying-off, milking was stopped and milk samples were collected from each quarter. After milking cessation, only modest swelling was observed in the udders of the ANI cows. In the ANI cows, lactose and fat concentrations decreased and the fat:lactose concentration ratio indicated that on d 1 and 2 fat concentrations decreased faster than lactose concentration, whereas on d 3, the rate of reduction was about the same for lactose and fat. In contrast, in AFI cows, fat concentrations increased on d 1 and the fat:lactose ratio indicated that changes in fat secretion were minor compared with those of lactose secretion. Rennet clotting time of milk after drying-off in the ANI cows increased, whereas curd firmness decreased rapidly, such that mammary secretions did not coagulate on d 3. In the AFI cows, such significant changes were observed only on d 3. The inflammatory response increased in both groups, but at each stage the increase was greater in ANI cows than in AFI cows. On d 1, the increase in leukocyte numbers in the ANI cows was made up of mononuclear cells (i.e., T lymphocytes and macrophages). In contrast, in the AFI cows, we observed a marked increase in leukocyte numbers, mainly in the form of polymorphonuclear cells. Our data indicate that the abrupt mammary involution induced in AFI cows provoked signs of distress, which were associated with neutrophilia in milk. In contrast, in the ANI cows, cessation of milking occurred without evidence of engorgement of the udder. Physiological differences in ANI and AFI cows are distinct and are reflected in the differences in the leukocyte populations in milk.
本研究比较了在预期干奶前产奶量低的遗传高产奶牛和在预定干奶前产奶量高的具有相同遗传潜力的奶牛的代谢和免疫反应。研究了10头多胎泌乳的以色列荷斯坦奶牛，它们在当前泌乳期产奶量约为10,500升，无细菌感染，且预定在预期分娩前约60天干奶。其中5头奶牛在泌乳末期产奶量急剧自发下降，产奶量低于约14升/天，被定义为接近自然干奶的奶牛（ANI），另外5头产奶量在25至35升/天之间的奶牛被定义为接近强制干奶的奶牛（AFI）。在预定干奶前3天，停止挤奶并从每个乳区采集牛奶样本。停止挤奶后，ANI奶牛的乳房仅出现轻微肿胀。在ANI奶牛中，乳糖和脂肪浓度降低，脂肪与乳糖浓度比表明，在第1天和第2天，脂肪浓度下降速度快于乳糖浓度，而在第3天，乳糖和脂肪的下降速度大致相同。相比之下，在AFI奶牛中，第1天脂肪浓度增加，脂肪与乳糖比表明，与乳糖分泌变化相比，脂肪分泌变化较小。ANI奶牛干奶后牛奶的凝乳酶凝固时间增加，而凝乳硬度迅速下降，以至于在第3天乳腺分泌物无法凝固。在AFI奶牛中，仅在第3天观察到如此显著的变化。两组的炎症反应均增加，但在每个阶段，ANI奶牛的增加幅度均大于AFI奶牛。在第1天，ANI奶牛白细胞数量的增加由单核细胞（即T淋巴细胞和巨噬细胞）组成。相比之下，在AFI奶牛中，我们观察到白细胞数量显著增加，主要以多形核细胞的形式。我们的数据表明，AFI奶牛中诱导的突然乳腺退化引发了应激迹象，这与牛奶中的中性粒细胞增多有关。相比之下，在ANI奶牛中，停止挤奶时未出现乳房充血的迹象。ANI和AFI奶牛的生理差异明显，并反映在牛奶中白细胞群体的差异上。
