Sex-sorted semen can increase the profitability of dairy cattle by producing offspring of the desired sex. The objective of the present study was to compare conception rate, stillbirth, calving difficulty and sex ratios from sexed and conventional semen in a commercial dairy herd in Isfahan province, Iran. Data were collected from April 2009 until December 2015 on 13,343 inseminations in 8,011 ...

An experiment was designed to determine the effects of dietary monensin on age and weight at puberty in Bos taurus crossbred beef heifers. One hundred and forty heifers were allotted to two weight classes: heavy (H) and light (L) groups, consisting of heifers above and below the average weaning weight, respectively. Heifers within each weight class were assigned to one of three diets during a 2...

Angus x crossbred heifers (270 per trial) were used in an experiment conducted over one 105-d summer and one 104-d winter feeding period. Treatments were identical for each trial and included: 1) control, 2) estrogenic implant (E), 3) trenbolone acetate implant (TBA), 4) E + TBA (ET), 5) melengestrol acetate (MGA) in the feed, and 6) ET + MGA (ETM). Each treatment was replicated in five pens, w...

Metabolic hormone profiles and their associations with measures of body fat and reproduction were evaluated among Angus, Brangus, and Brahman heifers (n = 8/breed). Heifers of similar age from breeding programs in semi-arid environments were pen-fed for 10 wk prior to 1Experimentation was supported by New Mexico Agricultural Experiment Station (Hatch project # 180674), the NIH SCORE and RISE pr...

Peripheral serum progesterone concentrations were evaluated in beef heifers following breeding collected on d 6 +/- 1, 9 +/- 1 collected on d 6 +/- 1, 9 +/- 1 and 12 +/- 1 (estrus = d 0) after the puberal estrus of all heifers and after the third estrus of E3 heifers. Progesterone concentrations were higher (P less than .05) for heifers in E1 compared with heifers in E3 on d 6, 9 and 12 after b...

The hypothesis that luteinizing hormone (LH) secretion in prepubertal females is responsive to estradiol negative feedback and that decreased feedback occurs as puberty approaches was tested in heifers. In the first experiment, seven heifers were maintained prepubertal by dietary energy restriction until 508 days of age (Day 0). All heifers were placed on a high-energy diet on Day 0 at which ti...

The aim of this study was to determine whether the decline in oestradiol inhibition of circulating luteinizing hormone (LH) and follicle-stimulating hormone (FSH) during the peripubertal period of heifers is associated with a change in opioid modulation of LH and FSH secretion. Opioid inhibition of LH secretion was determined by response to administration of the opioid antagonist naloxone. Prep...

Experiments were conducted to determine the role of estrogens on endogenous PGF2 alpha secretion and luteolysis following injection of cloprostenol in heifers. In Exp. 1, eight luteal-phase heifers were used to evaluate tamoxifen (T) as an estrogen antagonist. Heifers received T (35 mg i.v.) or ethanol:saline vehicle (ES) every 4 h for 44 h. All received cloprostenol (500 micrograms i.m.) immed...

Longevity and lifetime productivity are important factors influencing profitability for the cow-calf producer. Heifers that conceive earlier in the breeding season will calve earlier in the calving season and have a longer interval to rebreeding. Calves born earlier in the calving season will also be older and heavier at weaning. Longevity data were collected on 2,195 heifers from producers in ...

Crossbred beef heifers (n = 78) were assigned randomly to one of three treatments. Heifers received either no implant, one estradiol-releasing implant (Compudose), or two estradiol-releasing implants. Heifers were implanted at birth and then reimplanted every 150 d. Calves were maintained with the cows until weaning at approximately 200 d of age. Heifers were placed in the feedlot as one group ...