烟酸对热应激条件下奶牛生产性能、血清离子浓度的影响

本试验旨在研究向日粮中添加不同水平的烟酸对热应激条件下奶牛生产性能、维持行为及血清中离子浓度的影响。试验选择健康泌乳后期中国荷斯坦奶牛3头，采用3×3拉丁方设计，在基础日粮中添加0、8、 15 g/d 烟酸，试验期63 d。结果表明：①添加8、15 g/d烟酸与对照组相比热应激奶牛的产奶量提高29.9%（P<0.05）、22.0%（P<0.05），4%标准乳含量分别提高了28.5%（P<0.05）、21.5%（P＜0.05），且不同添加水平间并无显著差异（P>0.05）。添加烟酸不影响奶牛的乳蛋白率、乳脂率和乳糖的水平;②添加8、15 g/d烟酸与对照组相比对热应激奶牛卧息和站立时间、排粪和排尿次数及饮水次数均无显著影响（P>0.05），但显著提高奶牛反刍时间（P<0.05），且不同添加水平间并无显著差异（P>0.05）；③添加烟酸8、15 g/d与对照组相比均不同程度提高奶牛血清Ca2+、K+、Na+浓度，但两添加组间无显著差异（P>0.05）；添加烟酸使奶牛血清Mg2+浓度提高，Cl-浓度降低，但未达显著水平（P>0.05）。综合分析试验奶牛生产性能、维持行为和血清离子浓度指标的变化，给热应激条件下奶牛补饲烟酸有助于缓解热应激，烟酸适宜添加量为8 g/d。

Influence of Supplemental Niacin on Performancer and Ion Chroma of Serum for Dairy Cows in the Condition of Heat-stressed

An experiment was conducted using three Chinese Holstein cows in early lactation under hot environment,in a 3×3 Latin square design,to determine the effects of the basal diets supplemented with 0，8，15 g/d niac in each cow as control group A，group B,group C on performance,maintenance behavior and ion chroma of serum．The feeding experiment had been carried out for 63 days.The results showed :① compared with control group A，milk yield of group B and C was increased by 29.9% (P<0.05)，22.0% (P<0.05),respectively，and 4% fat corrected milk yield was increased by 28.5% (P<0.05)，21.5%(P<0.05),respectively，there was no significant difference between group B and C (P>0.05)；dietary niacin had no effect on the content of milk fat, milk protein and milk sugar; ②compared with control group， there was no effect on the hours of standing and lying, the number of micturition and defecation, the number of drinking-water,but rumination time was significantly increased (P<0.05). Also, there was no significant difference between group B and group C (P>0.05); ③compared with control group A， the Ca2+,K+,Na+ chroma of serum of group B and group C was increased in diffferent extent, but there was no significant difference between group B and group C (P>0.05 ).The Mg2+ chroma of serum was increased,and the Cl- chroma of serum was decreased, but not reached significant levels (P>0.05). As performance,maintenance behavior and ion chroma of serum were concerned,niacin supplementation with 8 g/d in the ration of lactating cows had the best effect and released the effect of heat stress in hot environment．