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《Animal Husbandry & Veterinary Medicine》 2019-01
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Effects of different crude protein levels in diet on milk production performance,nitrogen digestion and biochemical indexes of blood in Holstein cows

CHENG Guangmin;CHEN Fengmei;FU Guihua;XU Xiangting;HU Shilin;LIU Jiansheng;Shandong Vocational College of Animal Science and Veterinary Medicine;  
This experiment was conducted to investigate the effects of dietary crude protein level on milk urea nitrogen ( MUN),nitrogen digestion and blood urea nitrogen ( BUN) of Chinese Holstein dairy cows. Sixteen multiparous cows were used in a replicated 4 × 4 Latin square design and the crude protein levels of the four diets were 12. 72%,13. 52%,14. 43% and 15. 37% respectively. Each lactating cow underwent four experimental periods and each period had a 10 adaptation,followed by a 5 day period of total fecal and milk collection. Milk yield,milk composition and dry matter intake ( DMI) of the cows were measured in the last 5 day period. Blood samples were taken in the last day of the sample collection period. The results showed that there was no significant difference between DMI and milk yield in the four treatment groups ( P0. 05),but the MUN increased with higher dietary CP levels. Furthermore,the MUN of the high protein level group was significantly higher than the low protein group ( P0. 05). With the increase of dietary CP level,the intake of nitrogen,fecal nitrogen and the digestibility of nitrogen increased,too ( P 0. 05). The BUN in the high protein group was higher than that in the low protein group ( P0. 05),which was consistent with the change in MUN. In conclusion,under the experimental conditions,different protein levels influenced the changes in MUN and BUN but had no effect on milk yield and nitrogen digestion; and MUN might replace BUN as an indicator in detecting the protein nutrition status in dairy cows.
【Fund】: 山东省高等学校科技发展计划(J14LF54)
【CateGory Index】: S823.5
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