Akhlaghi Behzad, Ghorbani Gholam Reza, Alikhani Masoud, Kargar Shahryar, Sadeghi-Sefidmazgi Ali, Rafiee-Yarandi Hassan, Rezamand Pedram
Department of Animal Sciences, College of Agriculture, Isfahan University of Technology, Isfahan 4156-83111, Iran.
Department of Animal Sciences, College of Agriculture, Shiraz University, Shiraz 71441-65186, Iran.
J Anim Sci Technol. 2019 Nov;61(6):313-323. doi: 10.5187/jast.2019.61.6.313. Epub 2019 Nov 30.
The interactive effect of dietary fat supplementation and milk yield level on dairy cows performance under heat stress has not been thoroughly investigated. The purpose of this study was to evaluate the effect of production level, the source of fat supplements and their interaction on dairy cows performance under heat stress. In this study, 64 Holstein multiparous cows were divided into 2 groups and received one of two rations having either calcium salts of fatty acids (Ca-FA) or high-palmitic acid (PA) supplements (2.8% of DM; dry matter). After completing the experiment and based on maturity-equivalent milk, cows were divided into two groups of high-yielding (14,633 kg) and medium-yielding (11,616 kg). Average temperature humidity index (THI) was 71 during the trial period. Apparent digestibility of dry matter ( = 0.04), organic matter ( = 0.05), and neutral detergent fiber (NDF; = 0.04) for cows fed Ca-FA were greater than cows fed PA. The milk fat content in high-producing cows was 0.3% greater than medium-producing cows ( = 0.03). The milk protein content in cows fed Ca-FA was greater than cows fed PA ( < 0.01). High-producing cows had greater serum cholesterol ( = 0.02) than medium-producing cows. The cows fed PA tended to have a greater BUN than cows fed Ca-FA ( = 0.06). Alanine aminotransferase and aspartate aminotransferase tended to be increased by PA, which indicates that cows in PA treatment may have experienced more adverse effect on the liver function than cows on Ca-FA. Therefore, under heat stress and in 90 d trial, milk production level does not affect the cows' response to PA or Ca-FA. Although cows fed Ca-FA received lower energy than those fed PA, they compensated for this shortage likely with increasing the digestibility and produced a similar amount of milk.
在热应激条件下，日粮脂肪补充剂与产奶量水平对奶牛生产性能的交互作用尚未得到充分研究。本研究的目的是评估生产水平、脂肪补充剂来源及其交互作用对热应激条件下奶牛生产性能的影响。在本研究中，64头荷斯坦经产奶牛被分为2组，分别采食两种日粮之一，其中一种日粮含有脂肪酸钙盐（Ca-FA），另一种日粮含有高棕榈酸（PA）补充剂（占干物质的2.8%）。实验结束后，根据成熟当量奶量，奶牛被分为高产（14,633千克）和中产（11,616千克）两组。试验期间平均温度湿度指数（THI）为71。采食Ca-FA的奶牛干物质（P = 0.04）、有机物（P = 0.05）和中性洗涤纤维（NDF；P = 0.04）的表观消化率高于采食PA的奶牛。高产奶牛的乳脂含量比中产奶牛高0.3%（P = 0.03）。采食Ca-FA的奶牛乳蛋白含量高于采食PA的奶牛（P < 0.01）。高产奶牛的血清胆固醇含量高于中产奶牛（P = 0.02）。采食PA的奶牛血尿素氮（BUN）含量有高于采食Ca-FA的奶牛的趋势（P = 0.06）。PA有使丙氨酸氨基转移酶和天冬氨酸氨基转移酶升高的趋势，这表明PA处理组奶牛的肝功能可能比Ca-FA处理组奶牛受到了更严重的不良影响。因此，在热应激条件下且为期90天的试验中，产奶水平不影响奶牛对PA或Ca-FA的反应。尽管采食Ca-FA的奶牛摄入的能量低于采食PA的奶牛，但它们可能通过提高消化率来弥补这一不足，并产出了相似数量的牛奶。
