Studies on health management and nutritional evaluation by milk components analysis in dairy cows. III. Relationship between conception rates, and milk urea nitrogen and milk protein concentration in a large dairy herd of high yielding cows
Moon JinSan; Joo YiSeok; Jang GumChan; Yoon YongDhuk; Lee BoKyeun; Park YoungHo; Son ChangHo
Korean Journal of Veterinary Research 40(2): 383-391
2000
ISSN/ISBN: 2466-1384 Accession: 003569473
The response of milk composition to feeding, by regular feeding analysis was studied and the relationship between milk urea N (MUN) and milk protein (MP) and fertility at the insemination period in Holstein dairy cows was determined. 355 artificial inseminations (AI) for 150 Holstein cows in the herd were used to examine the relationship between MUN and MP content and conception rate. The AI occurred for the cows 50 to 150 days in milk, and MUN and MP concentration were determined using automated infrared procedures. The mean+or-s.d. of MUN and MP concentration in the herd were 15.6+or-2.1 mg/dl and 3.23+or-0.38%, respectively. MUN contents of bulk milk were increased by increased crude protein intake. The conception rate was lower in cows in which the level of MUN was lower than 8.0 mg/dl (10.0%) or higher than 25 mg/dl (15.4%) relative to the cows in MUN content of 12.0-17.9 mg/dl (36.7%) at the time of insemination. In addition, an MP lower than 3.0% or higher than 3.25% were associated with lower conception rates. Consequently, MUN and MP analyses may be used as a monitoring tool for protein and energy nutritional balance to improve reproduction efficiency in Holstein dairy cows.