Relationship between fertility and blood glucose and cholesterol concentrations in Holstein cows.

Jugular blood samples were collected prepartum and postpartum from 97 Holstein cows and heifers. Samples were analyzed for total serum cholesterol and plasma glucose. Plasma samples taken 4, 11, 18, and 25 days postpartum were also analyzed for progesterone. Concentrations of cholesterol, glucose, and progesterone were evaluated in relation to summer- and winter-calving seasons, milk production, lactation number, days-to-conception, number of postcalving uterine infusions given, and time relative to calving. A temperature-humidity index was used as a covariate in the analysis to adjust the data for climatic effects so that seasonal effects other than temperature and humidity could be determined. Average plasma glucose was within the normal range (62 +/- 8 mg/dl). It increased before calving and then declined to a minimum value between 11 and 25 days postpartum. Glucose then increased after 25 days for the summer-calving group and remained relatively stable for the winter-calving cows. Blood glucose concentrations were inversely related to milk production. Negative correlations existed between milk production and plasma glucose at days 4, 11, 18, 25, and 39 postpartum. First-lactation heifers had higher blood glucose levels than cows in their second or later lactation. Blood glucose concentrations were not related to days-to-conception over both seasons. Average serum cholesterol was within the normal range (125 +/- 29 mg/dl). It decreased before calving and then increased for 88 days after calving. Summer-calving cows had higher serum cholesterol concentrations prepartum and winter-calving cows had higher concentrations from 39 through 88 days postpartum. Cholesterol concentrations were directly related to milk production from 25 through 88 days postpartum.(ABSTRACT TRUNCATED AT 250 WORDS)