Relationships of hormones, temperature, photoperiod, and other factors to voluntary intake of dry matter in pregnant dairy cows prior to parturition.

Voluntary intake of dry matter per 100 kg body weight (defined as intake) was quantified in 86 pluriparous Holstein cows which calved during 19 consecutive mo. Least squares techniques were used to examine the association of intake during the last 8 days before calving with numerous independent variables representing seasonal and physiological factors. The data were summarized as prepartum days 7, 4, and 1 (means of days 8 to 6, 5 to 3, and 2 to 0, respectively).

Variables associated with peripartum traits in dairy cows. VII. Hormones, calf traits and subsequent milk yield.

Independent effects of certain partum and peripartum traits on subsequent milk yields (Y) during days 1 to 27 (Y27), 28 to 60 (Y60) and 1 to 200 (Y200) of lactation were estimated from data on 167 Holstein cows and first-calf heifers. The variables were health status, calf sex and covariates (linear, quadratic and cubic) of calf birth weight (CBW), cow age (CA), month of calving code (season) and the peripartum blood plasma concentrations (means of three samples taken from 48 hr prepartum to within 2 hr postpartum) of prolactin (PRL), progesterone (P4), estrone (E1), estradiol-17 beta (E beta) and estradiol-17 alpha (E alpha). Except for Y200 values, the measures of milk yield were positively correlated (P < .

Variables associated with peripartum traits in dairy cows. IV. Seasonal relationships among temperature, photoperiod, and blood plasma prolactin.

Concentrations of prolactin in plasma were measured in 176 dairy cows and heifers from 13 days before calving to 2.5 days after calving over 21 mo. Prolactin averaged 35.

Variables associated with peripartum traits in dairy cows. III. Effect of diets and disorders on certain blood traits.

BLood samples were collected from 89 Holstein cows on days 220 and 250 of gestation, within 24 hr prepartum and postpartum and on day 30 postpartum. Balanced diets which contained either chopped hay (29 cows), hay crop silage (HCS; 30 cows) or corn silage (CS; 30 cows) were fed from day 220 of gestation to day 30 postpartum. The purpose was to determine if variations in certain blood traits were indicative of peripartum and postpartum disorders.