Lammoglia M A, Bellows R A, Grings E E, Bergman J W, Short R E, MacNeil M D
Fort Keogh Livestock and Range Research Laboratory, ARS, USDA, Miles City, MT 59301, USA.
J Anim Sci. 1999 Apr;77(4):824-34. doi: 10.2527/1999.774824x.
Effects of prepartum fat supplementation of the dam on cold tolerance of calves were determined in two studies. In Exp. 1, 22 F1, crossbred heifers gestating F2 calves received diets containing either 1.7 or 4.7% dietary fat starting at d 230+/-2d of gestation. Safflower seeds (Carthamus tinctorius) containing 37% oil with 79% linoleic acid were the supplemental fat source in isocaloric-isonitrogenous diets. Calves were separated from their dams at birth, fed pooled dairy-cow colostrum, muzzled to prevent sucking, and returned to their dams in a heated (22 degrees C) barn for 3.5 h. At 4 h of age, a jugular catheter was inserted. At 5 h of age, calves were placed in a 0 degrees C room for 140 min and rectal temperatures and blood samples were obtained at 10- and 20-min intervals. Blood was assayed for glucose, cortisol, and cholesterol. In Exp. 2, 18 multiparous, crossbred beef cows bred to Murray Grey sires were randomly assigned to receive diets containing either 1.7 or 3.1% dietary fat starting at 235+/-2 d gestation. Safflower seeds were used as the supplemental fat source in isocaloric-isonitrogenous diets. At d 260 of gestation, premature parturition was induced in one-half of the cows from each diet group by feeding Ponderosa pine (Pinus ponderosa) needles. Experimental protocols were the same as in Exp. 1, except that cold exposure was at 9 degrees C for 200 min. Rectal temperatures were affected in Exp. 1 by time and diet x time (both P < .01) and diet x calf sex (P < .05) and in Exp. 2 by calf age (P < .05), time, and calf age x time (both P < .01). Plasma cortisol concentrations were affected by time (P < .01) and calf sex x time (P < .05) in Exp. 1 and by time ( P < .01) in Exp. 2. Cholesterol concentrations in Exp. 1 were affected by diet x time (P < .05) and in Exp. 2 by time (P < .05). Plasma glucose concentrations were affected in Exp. 1 by diet (P < .05) and in Exp. 2 by calf age, time, and calf age x time (all P < .01). We conclude from Exp. 1 that feeding heifers supplemental fat during late gestation increased glucose concentrations in the newborn calf, resulting in favorable responses in body temperature in the cold-stressed newborns. This increase in substrate availability suggests a potential positive effect on heat generation in newborns during sustained periods of cold stress. In Exp. 2, premature calves had compromised cold tolerance possibly due to impaired shivering or brown adipose tissue thermogenesis.
两项研究确定了产前给母牛补充脂肪对犊牛耐寒性的影响。在实验1中，22头怀有F2犊牛的F1杂交小母牛从妊娠230±2天开始，分别采食含1.7%或4.7%日粮脂肪的日粮。含37%油脂且79%为亚油酸的红花籽（Carthamus tinctorius）作为等热量、等氮日粮中的补充脂肪来源。犊牛出生后即与母牛分开，饲喂混合的奶牛初乳，并戴上口套以防吮乳，然后在温度为22℃的暖棚中与母牛待在一起3.5小时。4小时龄时，插入颈静脉导管。5小时龄时，将犊牛置于0℃的房间中140分钟，并每隔10分钟和20分钟采集直肠温度和血样。检测血液中的葡萄糖、皮质醇和胆固醇含量。在实验2中，18头与墨累灰牛种公牛配种的经产杂交肉牛母牛，从妊娠235±2天开始随机分配，分别采食含1.7%或3.1%日粮脂肪的日粮。红花籽作为等热量、等氮日粮中的补充脂肪来源。在妊娠260天时，每组日粮中的一半母牛通过饲喂黄松（Pinus ponderosa）针叶诱导早产。实验方案与实验1相同，只是冷暴露温度为9℃，持续200分钟。实验1中，直肠温度受时间、日粮×时间（P均<0.01）和日粮×犊牛性别（P<0.05）的影响；实验2中，直肠温度受犊牛年龄（P<0.05）、时间以及犊牛年龄×时间（P均<0.01）的影响。实验1中，血浆皮质醇浓度受时间（P<0.01）和犊牛性别×时间（P<0.05）的影响；实验2中，血浆皮质醇浓度受时间（P<0.01）的影响。实验1中，胆固醇浓度受日粮×时间（P<0.05）的影响；实验2中，胆固醇浓度受时间（P<0.05）的影响。实验1中，血浆葡萄糖浓度受日粮（P<0.05）的影响；实验2中，血浆葡萄糖浓度受犊牛年龄、时间以及犊牛年龄×时间（P均<0.01）的影响。我们从实验1得出结论，妊娠后期给小母牛补充脂肪可提高新生犊牛的葡萄糖浓度，使冷应激状态下的新生犊牛体温产生良好反应。底物可用性的这种增加表明，在持续的冷应激期间，对新生犊牛产热可能有积极影响。在实验2中，早产犊牛的耐寒性受损，可能是由于颤抖或棕色脂肪组织产热受损所致。
