C.J. Callahan

Profiles of reproductive hormones associated with fertile and nonfertile inseminations of dairy cows

Differences in plasma levels of estrogen, progesterone, luteinizing hormone (LH), and urinary estrogens between fertile and nonfertile matings in dairy cows were studied. Samples were collected at 8-hour intervals prior to ovulation (Day 0), every day through Day 8, and on alternate days during Days 10-18. Every nonfertile case had hormonal levels outside the limits found in 10 of 11 fertile cases. Of 27 cases, 30 which involved lactating cows, 32 had a palpable corpus luteum following insemination, and 11 were fertile. Delayed estrus and a delayed preovulatory increase in LH following a decrease in progesterone to less than .75 ng/ml were consistently observed in nonfertile matings. These cases represented 75% of those with subnormal postovulatory levels of progesterone. Asynchronies among nonfertile cases compared with fertile cases involved progesterone, LH, estrogens, and urinary estradiol-17beta prior to ovulation. Examples illustrative of abnormal hormonal profiles included ovarian cysts and early and late regression of the corpus luteum.

Variables associated with peripartum traits in dairy cows. I. Effect of dietary forages and disorders on voluntary intake of feed, body weight and milk yield☆

Daily voluntary intakes of feed by each of 89 Holstein cows were compared between day 220 of gestation and day 30 postpartum over a 21-month period. Diets designed to meet NRC requirements and which contained either chopped hay (29 cows), hay crop silage (HCS; 30 cows) or corn silage (CS; 30 cows) were compared prepartum (27 to 0 days), peripartum (1 day before to 3 days after calving) and postpartum (days 4 to 30 postpartum). Mixed rations, fed during lactation, were 60% forage and 40% concentrate dry matter (DM). Cow management was similar to commercial operations. The experimental hypothesis was that pre-disposition for partum and postpartum disorders (abnormal) could be related either to voluntary intake of different diets or to physical traits. Intakes (DM or estimated net energy) across diets decreased 30% between days 7 and 1 prepartum and averaged 18% and 20% lower peripartum and postpartum, respectively, in abnormal cows than in control cows. Seasonal effects on intakes were significant. In general, changes in body weight and condition and differences in udder edema and milk yield reflected intakes. The results support the original hypothesis.

Variables associated with peripartum traits in dairy cows. II. Interrelationships among disorders and their effects on intake of feed and on reproductive efficiency

Daily individual voluntary intakes of dry matter (DM % of body weight) and estimated net energy (ENE, Mcal/100 kg) by 89 Holstein cows were compared between day 220 of gestation and day 30 postpartum over a 21-month period. The purpose was to compare effects of diet and health status (control vs. abnormal) on intakes of DM and ENE. The cows were fed either chopped hay, hay crop silage (HCS) or corn silage (CS). Compared to controls, voluntary intakes of DM and ENE were decreased (most to least) in cows with fat cow syndrome (FCS), parturient paresis (PP), mastitis (MST), retained fetal membranes-metritis (RFM-M), and displaced abomasum (DA) prepartum and FCS, DA, PP, RFM-M and MST peripartum. Cows fed hay had a lower incidence of RFM-M (28%) than cows fed HCS (57%) and CS (47%) as well as superior reproductive efficiency subsequently (89% conceived vs. 72% and 78%, respectively).

Ovariectomy as a means of abortion and control of estrus in feedlot heifers

Three hundred and six heifers were randomly assigned to treatment groups in a three by six factorial design. Treatments were ovariectomy, melengestrol acetate (MGA), manual abortion, intramuscular estradiol cypionate (ECP) or Prostaglandin F2alpha and untreated controls. The Average Daily Gain (ADG) of the Ovariectomized Group was less (p < .01) during the first 24 days and not different (p > .05) for the total feeding period. Feed intake of the Ovariectomized Group was less (p < .05) than Manual Abortion, Prostaglandin or Control Groups during the first 24 days but essentially the same (p > .05) for the total period. The Prostaglandin Group required fewer days to reach slaughter condition than the Ovariectomy or MGA Groups (p < .05). The only difference in the cost/benefit analysis was in the direct cost of the treatments. Factors other than the various treatments interrupted many pregnancies. The effects of treatments varied with 100% of pregnancies terminated only in the Prostaglandin F2alpha Group.

Artificial induction of lactation in cattle: Effect of modified treatments on milk yield, fertility, and hormones in blood plasma and milk.

Holsteins were divided into groups CON and IL, each with six dry cows and six heifers. Group CON calved in mid-summer when group IL was treated (kg body weight per day) with (a) progesterone (P; .25 mg) and estradiol-17beta (Ebeta), either .05 mg or .10 mg, for 7 days; (b) continued Ebeta at one-third the initial rate until udders were engorged; (c) then 12 injections (8-hr intervals) of TRH (each 200 mug) or saline; and (d) GnRH during lactation. Milk yield was not affected by Ebeta dose rate, TRH or GnRH. GnRH luteinized the persistent ovarian follicles in group IL, and pregnancy rates were 80% and 83% in groups IL and CON, respectively. Large differences (P < .01) between groups IL and CON were observed in plasma prolactin (IL-low), insulin (IL-high) and growth hormone (IL-low) wherein insulin was correlated (P < .01) negatively with milk yield between days 7 to 49 of lactation. Milk concentrations of P, Ebeta, estrone and estradiol-17alpha in group IL were no higher (P > .10) 14 days after the last injection of P or Ebeta than in group CON or in milk from the herds bulk tank. The steroids were lowest in milk and plasma from ovariectomized cows. It was hypothesized that high insulin, as well as low prolactin and growth hormone, may contribute to inferior induced lactations.

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. The blood traits evaluated were concentrations of plasma total protein, whole blood hemoglobin, packed cell volume, and white blood cells, and serum glutamic oxalacetic transaminase (SGOT), glucose, urea nitrogen, calcium, inorganic phosphorus, magnesium, potassium and sodium. No blood trait was useful to predict a disorder prior to its visual signs with one possible exception. Serum glucose and calcium were lower and SGOT and magnesium were higher peripartum which was prior to death of three cows from fat cow syndrome.

Dietary urea for dairy cattle IV. effect on reproductive hormones

Abstract Effects of continuous free-choice feeding of urea in blended rations on reproductive hormones were compared during three consecutive reproductive periods. Urea nitrogen replaced plant nitrogen as follows for Groups 1, 2 and 3, respectively: 0, 22 and 45% from insemination to mid pregnancy, 0, 8 and 16% thereafter until 2 weeks before first calving, and 0, 18 and 36% precalving and during lactations. Dietary urea was consistently associated with significantly increased progesterone in blood plasma at all periods. In contrast, estrogen was significantly lower in urine of Group 3 during Days 1 to 18 after first insemination as heifers, but not at second calving or during Days 1 to 18 after insemination for third pregnancy. Plasma estrogen was significantly lower in Group 3 than Group 1 only during the first pregnancy. Group 2 was intermediate. Length of first gestation was subnormal in Groups 1 and 2. It was concluded that dietary urea caused differences in reproductive hormones which were improtant only during the first pregnancy as heifers.

Dietary urea for dairy cattle III. Effect on ovarian activity

Abstract Holstein heifers were divided into three groups of 27 at least 60 days before any were inseminated to evaluate gross effects on ovarian activity when urea was fed continuously for more than 2 years. Groups were reduced to 21 heifers each before calving. In Groups 1, 2 and 3, respectively, urea nitrogen replaced 0, 22 and 45% of plant nitrogen in heifer rations from insemination to mid pregnancy, 0, 8 and 16% there-after until 2 weeks before calving, and 0, 18 and 36% precalving and during lactation. The rations were blended and fed free-choice. Dry matter in the lactation ration was 44% corn silage, 10% alfalfa bromegrass silage and 46% concentrate. Body weight increases were similar on each ration through second calving. Likewise, estrous cycles and intervals between inseminations were similar. After the second calving, groups were not different for time to first ovulation or for intervals between ovulations. In general, urea did not affect gross measures of ovarian activity. Effects of urea on abortion, retained fetal membranes, and conception efficiency were reviewed.