全混合日粮营养水平对热应激肉牛生长性能、瘤胃形态学及肉质的影响

Effects of total mixed ration nutrient levels on growth performance,rumen morphology and meat quality of heat-stressed beef cattle

文章旨在评估热应激条件下通过调整全混合日粮营养水平来改善肉牛生长性能、瘤胃形态学及肉品质。试验将6月龄大、平均体重为(85.08±2.31)kg的64头荷斯坦肉牛随机分为2组,每组8个重复,每组32头。从6月龄开始试验,两组肉牛分别饲喂粗蛋白质水平为16.0%和12.0%的全混合日粮,持续到15月龄。整个试验期间外界环境温度为(36±2.5)℃,相对湿度为65%~70%。结果:不同营养水平全混合日粮对肉牛整个试验期的日增重和料重比无显著影响(P>0.05)。高营养组10和15月龄肉牛的体重、6~10月龄平均日增重和采食量及11~15月龄的料重比显著高于低营养组(P<0.05),但6~10月龄料重比显著低于低营养组(P<0.05)。高营养组肉牛瘤胃乳头长度和角质层厚度较低营养组显著提高38.53%和43.98%(P<0.05),但瘤胃pH、乳头宽度、结缔组织宽度和非角化上皮厚度分别显著降低2.89%、37.78%、42.08%和34.99%(P<0.05)。高营养组肉牛肌肉的屠宰率、热胴体重及肌肉粗脂肪含量较低营养组分别显著提高10.21%、21.87%和25.20%(P<0.05),而低营养组肉牛肌肉粗灰分含量比高营养组显著提高27.17%(P<0.05)。结论:在本研究条件下,通过改变全混合日粮配方可提高高温环境下肉牛的采食量和饲料效率,其中高营养水平日粮组可提高肉牛日增重,改善热应激环境条件下肉牛的瘤胃形态学指标。

The purpose of this study was to evaluate the improvement of growth performance,rumen morphology and meat quality of beef cattle under heat stress by adjusting nutrient level of total mixed diet.Sixty-four 6-month-old Holstein beef cattle with an average body weight of(85.08±2.31)kg were randomly divided into 2 groups with 8 replicates per group and 32 cattle per group(4 head/replicate).Starting from 6 months of age,beef cattle in both groups were fed a total mixed diet with crude protein level of 16.0%and 12.0%,respectively,and continued to 15 months of age.During the whole experiment,the ambient temperature was(36±2.5)℃and the relative humidity was 65%~70%.Results:There were no significant differences in the effects of different nutrient levels on daily gain and feed/gain of beef cattle during the whole experiment period(P>0.05).The body weight,average daily gain and feed intake of beef cattle at 10 and 15 months of age,6~10 months of age and feed/gain of beef cattle at 11~15 months of age in high nutrition group were significantly higher than those in low nutrition group(P<0.05),but the feed/gain of beef cattle at 11~15 months of age was significantly lower than that in low nutrition group(P<0.05).The length of rumen nipple and cuticle thickness of beef cattle in high nutrition group were significantly increased by 38.53%and 43.98%compared with low nutrition group(P<0.05).However,rumen pH value,papillary width,connective tissue width and non~keratinized epithelial thickness were significantly decreased by 2.89%,37.78%,42.08%and 34.99%(P<0.05),respectively.Slaughter rate,hot carcass weight and crude fat content in muscle of beef cattle in high nutrition group were significantly increased by 10.21%,21.87%and 25.20%(P<0.05),respectively,while ash content in muscle of beef cattle in low nutrition group was significantly increased by 27.17%(P<0.05)compared with that in high nutrition group.Conclusion:Under the conditions of this study,the feed intake and feed efficiency of beef cattle under high temperature environment can be improved by changing the total mixed diet formula,and the daily gain of beef cattle under high nutrient level diet group can be improved,and rumen morphological indexes of beef cattle under heat stress environment can be improved.