Department of Animal Sciences, University of Florida, Gainesville 32611.
Phibro Animal Health Corporation, Teaneck, NJ 07666-6712.
J Dairy Sci. 2017 Sep;100(9):7659-7668. doi: 10.3168/jds.2017-12619. Epub 2017 Jun 21.
Heat stress during late gestation negatively affects the physiology, health, and productivity of dairy cows as well as the calves developing in utero. Providing cows with active cooling devices, such as fans and soakers, and supplementing cows with an immunomodulating feed additive, OmniGen-AF (OG; Phibro Animal Health Corporation), improves immune function and milk yield of cows. It is unknown if maternal supplementation of OG combined with active cooling during late gestation might benefit the developing calf as well. Herein we evaluated markers of innate immune function, including immune cell counts, acute phase proteins, and neutrophil function, of calves born to multiparous dams in a 2 × 2 factorial design. Dams were supplemented with OG or a bentonite control (NO) beginning at 60 d before dry off and exposed to heat stress with cooling (CL) or without active cooling (HT) during the dry period (∼46 d). At birth, calves were separated from their dams and fed 6.6 L of their dams' colostrum in 2 meals. Calf body weight and rectal temperature were recorded, and blood samples were collected at birth (before colostrum feeding) and at 10, 28, and 49 d of age. Calves born to either CL dams or OG dams were heavier at birth than calves born to HT or NO dams, respectively. Concentrations of serum amyloid A were higher in the blood of calves born to OG dams relative to NO and for HT calves relative to CL calves. In addition, calves born to cooled OG dams had greater concentrations of plasma haptoglobin than calves born to cooled control dams. Neutrophil function at 10 d of age was enhanced in calves born to cooled OG dams and lymphocyte counts were higher in calves born to OG dams. Together these results suggest that adding OG to maternal feed in combination with active cooling of cows during late gestation is effective in mitigating the negative effects of in utero heat stress on postnatal calf growth and immune competence.
妊娠后期的热应激会对奶牛的生理、健康和生产性能以及子宫内发育的小牛产生负面影响。为奶牛提供主动冷却设备，如风扇和浸湿器，并为奶牛补充免疫调节饲料添加剂 OmniGen-AF（OG；Phibro Animal Health Corporation），可以改善奶牛的免疫功能和产奶量。目前尚不清楚在妊娠后期为奶牛补充 OG 并结合主动冷却是否也会使正在发育的小牛受益。在此，我们评估了在一项 2×2 析因设计中，多胎奶牛所产小牛的先天免疫功能标志物，包括免疫细胞计数、急性期蛋白和中性粒细胞功能。奶牛从干奶前 60 天开始用 OG 或膨润土对照（NO）补充，在干奶期（约 46 天）期间暴露于热应激下，要么进行冷却（CL），要么不进行主动冷却（HT）。小牛出生时与母亲分开，分两次喂食 6.6 升母亲的初乳。记录小牛的体重和直肠温度，并在出生时（在初乳喂养前）以及 10、28 和 49 日龄时采集血液样本。出生时，CL 组和 OG 组的小牛体重均大于 HT 组和 NO 组，OG 组的小牛体重均大于 HT 组。此外，与 HT 组相比，出生于 OG 组的小牛血清淀粉样蛋白 A 浓度更高，与出生于对照组的小牛相比，出生于冷却 OG 组的小牛血浆结合珠蛋白浓度更高。10 日龄时，出生于冷却 OG 组的小牛中性粒细胞功能增强，出生于 OG 组的小牛淋巴细胞计数更高。这些结果表明，在妊娠后期，将 OG 添加到奶牛的饲料中并结合主动冷却奶牛，可以有效减轻子宫内热应激对产后小牛生长和免疫能力的负面影响。
