Response of lactating cows to supplemental rumen protected methionine and niacin
会议名称：《第七届草食动物营养国际学术研讨会》
会议日期：2007年
学科分类：090502[农学-动物营养与饲料科学] 0905[农学-畜牧学] 09[农学]
基 金：Supported by the National Key Technology R&D Program of China (2002BA518A10) Hebei provincial Committee for Scientific Research Program (06547004D-6)
关 键 词：lactating cows RPMet niacin milk yield milk composition
摘 要：正The objective of this study was to determine the effects of supplementing rumen protected methionine and niacin in the basal diet on milk yield,milk composition and blood metabolic parameters in lactating dairy *** Holstein cows（3.1±1.4 lactation period,23.2±4.2 kg/d milk）were used in a duplicate 4×4 Latin square design with 14-d adaptation and 6-d sampling *** designed as follows:1) the basal diet,control（C）;2)the basal diet plus RPMet（6 g/d）;3)the basal diet plus Niacin（25 g/d）;4)the basal diet plus RPMet（6 g/d ）and Niacin（25 g/d）.The basal diet consists of corn silage,brewer’s grain,chopped alfalfa hay,corn meal, soybean meal,cottonseed meal,wheat bran,vitamin and mineral supplements. Cows were individually fed and milked twice *** the last 10d of each experimental period,milk yield was recorded daily,milk samples were collected at the last 3d and proportionally mixed daily to analyze milk *** sample were collected before feeding in the morning and serum was obtained by *** results showed that:RPMet supplementation in the diet increased 4% FCM（P0.05）and the percentages of milk fat（P0.05）and protein （P0.05）,but had no effects on the SNF（P0.05）and lactose percentage （P0.05）.Dietary niacin supplementation increased milk yield（P0.05）,4% FCM （P0.05）,milk protein percentage（P0.05）and lactose percentage（P0.05）,but had no influence on milk fat percentage（P0.05）and SNF（P0.05）.Serum urea nitrogen content（P0.01）and serum glucose content（P0.05）were significantly decreased with RPMet supplementation in the diet of lactating cows,but the concentrations of NEFA,total cholesterol and triglyceride（P0.05）in the serum were not *** dietary niacin supplementation ,the contents of NEFA （P0.01）and total cholesterol（P0.01）in serum were significantly decreased 7.74% and 4.32% separately comparing with the control *** were no changes of serum urea nitrogen content（P0.05）,but serum glucose content