DWBin (2022-07-31 23:53):
#paper DOI: 10.3168/jds.2021-21747 Effect of different dietary regimens at dry-off on performance, metabolism, and immune system in dairy cows. 2022年发表于《Journal of Dairy Science》。这篇文章研究发现限饲会导致奶牛产奶量减少,这可能与血糖浓度降低有关;该文研究了不同营养水平的日粮配合限饲对生产性能、内分泌和代谢反应的影响,比如在奶牛哺乳期的中期,补充含氮、产糖或者产脂的精料不会改变血浆中葡萄糖的浓度;相反血糖浓度升高后,葡萄糖转运蛋白(GLUT1、GLUT3)mRNA表达量在白细胞中被检测到,这可能与白细胞激活有关。饲料限制导致的短期能量负平衡是暂时的,而且白细胞的功能受限饲的影响不大。
IF:3.700Q2 Journal of dairy science, 2022-May. DOI: 10.3168/jds.2021-21747 PMID: 35307177
Effect of different dietary regimens at dry-off on performance, metabolism, and immune system in dairy cows
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Abstract:
Concentrate withdrawal and feed restriction are commonly used to reduce milk production and to facilitate dry-off, but may impair immune function in dairy cows. We investigated the effect of feed rations providing different amounts of nutrients in combination with feed restriction on performance, endocrine, and metabolic responses, as well as on leukocyte function before and after abrupt dry-off. Forty-three cows were studied from d 12 before until d 6 after dry-off (56 d before scheduled calving). Cows were fed experimental concentrates rich in crude protein (nitrogenic, n = 14), glucogenic precursors (glucogenic, n = 14), or lipids (lipogenic, n = 15). On d 3 before dry-off, total feed allowance was restricted to 50% in half of the animals of each dietary group, whereas feed allowance remained unchanged in the other animals. Performance parameters (milk yield, milk composition, and dry matter intake) were recorded, and daily blood and milk samples were taken and analyzed for various metabolic and endocrine parameters. Additionally, activity and mRNA abundance of several genes in leukocytes were measured at selected time points before and after feed restriction and dry-off, respectively. Feed restriction immediately resulted in a negative energy balance and decreased milk production. Concomitantly, concentrations of nonesterified fatty acids increased, whereas insulin, insulin-like growth factor-1, and glucagon decreased. After dry-off, energy balance turned positive and plasma nonesterified fatty acids decreased. Plasma glucose, insulin, and insulin-like growth factor-1 concentrations increased in all groups after dry-off. Glucose, insulin, and glucagon concentrations in plasma were higher in nonrestricted compared with restricted animals after dry-off. The experimental concentrate types marginally affected the investigated metabolic and endocrine factors, with the exception of elevated milk and plasma urea concentrations in cows fed the nitrogenic concentrate. Chemotactic and phagocytic activity of leukocytes were not affected by diets, feed restriction, or dry-off. Likewise, blood leukocyte mRNA abundance encoding for tumor necrosis factor α (TNF), heat shock protein family A (HSP70), and the glucose transporters (GLUT) 1 and 3 remained unchanged throughout the study period. Overall, the short-term negative energy balance induced by feed restriction was temporarily accompanied by metabolic adaptations, but did not alter the studied factors related to the immune system. Metabolic and endocrine adaptations supporting milk synthesis were continued during the first days after dry-off despite cessation of milking. Thus, the abrupt dry-off resulted in a short-term increase of glucose and triglyceride concentrations, with a delayed endocrine response to re-establish nutrient homeostasis in blood.
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