Concentrations of progesterone have been reported to influence GnRH-induced LH surges. At the beginning of many synchronization protocols, GnRH is used to synchronize follicular growth. Therefore, the objective of this study was to determine the effect of elevated concentrations of progesterone from a controlled internal drug-releasing device (CIDR) on the GnRH-induced LH surge and ovulatory re...

UNLABELLED To study the effects of an extract of plant flavonoids [Bioflavex (FL)] in cattle fed high-concentrate diets, 2 experiments were designed. In the first experiment, the effects of Bioflavex on the development of rumen acidosis was evaluated in 8 Holstein-Friesian crossbreed heifers (451 kg; SEM 14.3 kg of BW) using a crossover design. Each experimental period lasted 22 d; from d 1 to ...

We determined the effects of hCG on ovarian response, concentration of progesterone, and fertility in a fixed-time AI (TAI) protocol. Four hundred forty-four crossbred beef heifers were synchronized with the CO-Synch + CIDR (controlled internal drug-releasing insert) protocol. In addition, heifers were randomly assigned to 1 of 4 treatments in a 2 × 2 factorial arrangement of treatments with ma...

Heifer development depends on nutritional management decisions throughout all growing phases. Optimizing costs to raise heifers improves profitability of dairy farms. Feed costs for heifers make up 50% of heifer costs. Required growth rates depend on the desired age at first calving and estimated mature body weight. Intensive milk feeding improves calf growth and subsequent milk production. Pre...

Intramammary infections (IMIs) in unbred and pregnant dairy heifers were once thought to be very infrequent. However, during the last 2 decades, several studies have shown that IMIs in heifers occur frequently during the prepartum and peripartum periods. Many of these infections can persist for long periods of time, may be associated with elevated somatic cell counts (SCC), and may impair mamma...

The aim of the present study was to develop a treatment protocol for the precise synchronization of oestrus that would avoid the development of persistent dominant ovarian follicles. Bos indicus heifers, in which oestrous cycles had been presynchronized, were allocated randomly, according to the day of their oestrous cycle, to one of five treatment groups. All heifers received a subcutaneous ea...

Three experiments were conducted to evaluate plasma concentrations of glucose, insulin, IGF-I, and progesterone (P4) in pubertal beef heifers receiving exogenous glucose, insulin, or sometribove zinc. All heifers used had no luteal P4 synthesis but received a controlled internal drug-releasing device containing 1.38 g of P4 to estimate treatment effects on hepatic P4 degradation. In Exp. 1, 8 p...

The objective of this study was to determine primiparous heifer performance following three different heifer development strategies that were the result of timed nutrient limitation. Two hundred eighty-two spring-born MARC III heifers were weaned at 203+/-1 d of age and 205+/-1 kg BW. The experiment was conducted on two calf crops with 120 heifers born in 1996 and 162 heifers born in 1997. Trea...

Three experiments were conducted to evaluate plasma concentrations of glucose, insulin, IGF-I, and progesterone (P4) in pubertal beef heifers receiving exogenous glucose, insulin, or sometribove zinc. All heifers used had no luteal P4 synthesis but received a controlled internal drug-releasing device containing 1.38 g of P4 to estimate treatment effects on hepatic P4 degradation. In Exp. 1, 8 p...

Angus × Gelbvieh rotationally crossbred yearling heifers (n = 99, yr 1; n = 105, yr 2) were used in a 2-yr randomized complete block design experiment with repeated measures to determine the effect of feeding camelina biodiesel coproducts (meal and crude glycerin) on serum concentrations of triiodothyronine, thyroxine, insulin, β-hydroxybutyrate, and glucose, as well as on growth and reproducti...