Variables associated with peripartum traits in dairy cows. IX. Relationship of season and other factors to blood plasma concentrations of progesterone and the estrogens

Factors affecting postpartum ovarian activity in crossbred primiparous tropical heifers

The relationship between postpartum ovarian activity and a total of 9 variables was studied in a dry tropical environment. Primiparous cows (n=61) that had shown no peripartum abnormalities, and were not suckled but milked twice daily, were used in the study. Independent variables included crossbreeding, sex of the calf, season, body condition, weight of cow at calving, age of dam at calving, uterine involution, calf weight and accumulated milk yield. Diet was a controlled variable. Dependent variables were first estrus postpartum and/or first milk progesterone elevation prior to first estrus. A bull fitted with a chin ball marker was used to detect first estrus postpartum, while ovarian structures were palpated per rectum once a week. Progesterone was measured by RIA in milk samples collected twice weekly. First postpartum estrus was detected at 56 +/- 32 days postpartum, a first milk progesterone elevation was observed in 50.8% of cows at 42 +/- 27 days. Cows calving in the dry season had longer intervals and those who calved males had shorter postpartum intervals. Accumulated milk yield affected both intervals significatly (p < 0.01). Weight, age and uterine involution were asociated with first milk progesterone elevation, while crossbreeding, weight at calving and weight postpartum change were associated with the dependent variables.

Factors associated with edema of the mammary gland in primigravid dairy heifers

The severity and anatomical extent of mammary edema (edema) of 73 primigravid Holstein heifers was scored, and certain hormones in peripheral blood plasma were quantified. The objective was to obtain by least-squares analysis of covariance independent estimates of the association of each hormone and other factors with edema scores around first calving. Mammary edema prepartum increased with age of heifer and gestation length, decreased as calf birthweight increased, but was unrelated to seasonal fluctuations in temperature and photoperiod. The increase in edema during the last week of pregnancy was accounted for by associations with prepartum concentrations of hormones in plasma. The independent estimates of hormonal relationships to edema score prepartum were positive for plasma estrone and estradiol-17 alpha and were negative for plasma estradiol-17 beta and progesterone. Plasma prolactin was not related to edema score. After parturition, estradiol-17 beta was the only independent variable associated (negatively) with edema. The results indicate a complicated interaction among the sex steroids of late pregnancy wherein some steroids may promote edema and other steroids may inhibit edema in heifers.

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). Intake was lowest on prepartum day 1. Main effects of diet-group, health status, and month were not related significantly to intake when covariates were included in the statistical model. Intake decreased with increasing age of cows, but it was not related independently to body condition score. There were seasonal variations in intake which could be accounted for statistically by either month as a main effect or by quantitative indices of seasonality (temperature, photoperiod, plasma prolactin). Intake was lowest in February, June, and July and highest in October. Calf birthweight was related to intake in an unexpected manner. Intake was lowest in dams carrying either small or large calves. Prolactin of plasma was associated independently with intake, but this hormone may be just another measure of seasonal variation. All variables accounted for 58% of the total variance in intake. When seasonal variations in intake were accounted for statistically by other variables, none of the steroid hormones (progesterone, estrone, estradiol-17 beta, and estradiol-17 alpha) were associated independently with variation in voluntary intake. Associations of cow age and of climatic indices with intake were greater during days 7, 4, and 1 prepartum as compared to day 250 of gestation, days .5 to 2.5 postpartum, and days 3 to 30 of lactation.