Four Holstein and four Brahman x Hereford heifers about 8 mo of age were used in a study to determine whether breed influences the effects of ambient temperature on concentrations' of prolactin in serum. Two heifers of each breed were stanchioned in each of two environmental chambers at 21 C for 7 d, after which chamber temperatures were changed to 7 or 31 C during 6 h. After 5 d at 7, 21 or 31...

Iso-immunization of heifers with bull semen and homogenized testis combined with Freund's complete adjuvant resulted in an induced temporary infertility. Eleven heifers injected intradermally with semen and six heifers with testis required an average of4\m=.\11 and 4\m=.\83 inseminations/conception, respectively, compared with nine control heifers which averaged 1\m=.\11services/conception. Two...

Two commercial feedlot experiments were conducted to determine the effects of feeding melengestrol acetate (MGA) or MGA plus ractopamine (MGA+OPT) on the performance and carcass characteristics of finishing heifers. In Nebraska (Exp. 1), 1,807 heifers (337.3 ± 20.0 kg) and in Texas (Exp. 2), 1,964 heifers (331.5 ± 6.1 kg) were fed 0.4 mg of MGA daily. For heifers fed MGA+OPT, 200 mg of ractopam...

Wet brewers grains (WBG) were evaluated as a feed source for growing Angus heifers (201 kg, 313 d of age) during a 112-d wintering trial. Effects on growth, feed efficiency, serum Se and first breeding performance were examined. Three replications of four heifers each were fed the following diets: (1) corn silage with no protein supplement (CSNS); (2) corn silage plus 33.8% of the diet dry matt...

Sahar, Mohammad W. M.S., Purdue University, December 2014. Growth of PostWeaned Grazing Dairy Heifers when Evaluating the Effects of Providing Shade or Parasite Control. Major Professor: Tamilee Nennich. Reduced heat stress and lower gastrointestinal parasite loads can increase growth rate in heifers, potentially reducing the age at first breeding and lowering the costs associated with raising ...

Thirteen ovariectomized heifers were randomly divided into two groups for each of three experiments. In the first experiment, 10 mg estradiol-17~ (E) was injected intramuscularly into all heifers. Seven heifers also received intramuscularly (im) 25 mg progesterone (P) at 1 2 , O, +12 and +24 hr relative to E injection. Estradiol had a biphasic effect on serum luteinizing hormone (LH) measured a...

The aim of this study was to characterize changes in serum concentrations of triiodothyronine (T(3)) and thyroxine (T(4)) in relation to growth and the onset of puberty in Carora heifers, a Venezuelan dairy breed. Heifers aged 7 to 16 months were grouped retrospectively according to puberty status into 4 groups: Pubertal (control group; n = 12) and nonpubertal (n = 8) contemporary (born during ...

Studies in numerous species provide evidence that diet during development can mediate physiological changes necessary for puberty. In cattle, several studies have reported inverse correlations between postweaning growth rate and age at puberty and heifer pregnancy rates. Thus, postweaning growth rate was determined to be an important factor affecting age of puberty, which in turn influences pre...

A severe or moderate suppression of serum insulin-like growth factor I (IGF-I) was induced in heifers, beginning at 104 days of age, by active immunization against growth hormone-releasing factor (GRFi) or by chronic feed restriction (RES), respectively. We hypothesized that reduced serum IGF-I results in decreased serum estradiol-17 beta (E2), which in turn delays onset of puberty. The objecti...

Angus and Charolais heifers (195 +/- 7 kg) were actively immunized against growth hormone-releasing factor (GRF) to evaluate the effect on concentrations of somatotropin (ST), insulin-like growth factor I (IGF-I), insulin (INS), growth, and onset of puberty. Primary immunizations were given at 184 +/- 7 d of age (d 0 of experiment) by injecting (s.c.) 1.5 mg of GRF-(1-29)-Gly-Gly-Cys-NH2 conjug...