Effect of increasing levels of undegradable intake protein on metabolic and endocrine factors in estrous cycling beef heifers1,2

Abstract

To determine the influence of three levels of undegradable intake protein (UIP) supplementation on metabolic and endocrine factors that influence reproduction, 23 yearling crossbred heifers (body condition score = 4.5 +/- 0.5; initial BW = 362 +/- 12 kg) were stratified by BW and assigned randomly to one of three supplements: 1) low UIP (1,135 g x heifer(-1) x d(-1); 30% CP, 115 g UIP, n = 7); 2) mid UIP (1,135 g x heifer(-1) x d(-1); 38% CP, 216 g UIP, n = 8); or 3) high UIP (1,135 g x heifer(-1) x d(-1); 46% CP, 321 g UIP, n = 8). Heifers were estrually synchronized before initiation of supplementation. Supplement was individually fed daily for 30 to 32 d, at which time heifers were slaughtered (d 12 to 14 of the estrous cycle) and tissues collected. Heifers were fed a basal diet of sudan grass hay (6.0% CP) ad libitum. On d 28 of supplementation (d 10 of the estrous cycle), no differences were observed (P > 0.10) in serum insulin or IGF-I among treatments. At slaughter (d 10 to 12 of the estrous cycle), treatments did not influence corpus luteum weight, cerebral spinal fluid leptin, or IGFBP; serum estradiol-17beta, progesterone, leptin, IGF-I, and IGFBP; or anterior pituitary content of IGFBP (P > 0.10). Follicular fluid IGFBP-2 and IGFBP-4 were greater in high-UIP heifers than low- or mid-UIP heifers on d 12 to 14 of the estrous cycle (P < 0.05). Basal serum LH concentrations and LH area under the curve (every 15 min for 240 min) did not differ (P > 0.10) following 28 d of supplementation (d 10 of the estrous cycle); however, basal serum FSH concentrations were greater (P = 0.06) in low- and mid- vs. high-UIP heifers (5.2 and 5.2 vs. 4.6 ng/mL, respectively), and FSH area under the curve was greater (P = 0.03) in low- vs. high-UIP heifers. At slaughter (d 12 to 14 of the estrous cycle), anterior pituitary LH and FSH content and steady-state mRNA encoding alpha, LHbeta, and GnRH receptor did not differ (P > 0.10) among treatments. However, FSHbeta mRNA was increased approximately twofold (P = 0.03) in mid vs. low UIP. In summary, low and mid levels of UIP supplements fed to estrous cycling beef heifers seemed to enhance pituitary expression and/or secretion of FSH relative to high levels of UIP. Moreover, high-UIP supplementation was associated with increased low-molecular-weight IGFBP compared with supplementation of low and mid levels of UIP. These data suggest that differing levels of UIP supplementation may alter pituitary and ovarian function, thereby influencing reproductive performance in beef heifers.

Homocysteine Increases the Expression of Vascular Endothelial Growth Factor by a Mechanism Involving Endoplasmic Reticulum Stress and Transcription Factor ATF4

“…1 g of each template DNA was then used to synthesize unlabeled antisense RNA probes using MAXIscript™ in vitro transcription kit (Ambion, Austin, TX). RNA was then blotted onto nylon membrane as described previously (35). Mem-branes were blocked for 30 min in 5 ml of ULTRAhyb® (Ambion) at 68°C.…”

Early weaning in Northern Great Plains beef cattle production systems: II. Development of replacement heifers weaned at 80 or 215d of age

“…However, the response to insulin was not observed for heifers at the JG location. Kane et al (2004) reports that insulin response to rumen undegradable protein may be influenced by environment and duration that rumen undegradable protein is offered. In addition, the responses of serum NEFA concentrations at the end of the 133-d period ending at normal weaning differed between heifers at LARRL and JG.…”

Utilization of dried distillers grains for developing beef heifers1,2,3

“…Lalman et al (1993) reported similar pregnancy rates for heifers fed a high UIP supplement vs. those fed a supplement balanced for protein degradability. Kane et al (2004) supplied postpubertal heifers 321, 216, or 115 g/d of UIP, mainly from feather meal and fishmeal. Heifers supplemented with 321 g of UIP/d had increased follicular fluid IGFBP-2 and IGFBP-4 on d 12 to 14 of the estrous cycle, lower basal serum FSH, and reduced FSH area under the curve compared with heifers fed 115 g of supplemental UIP/d, indicating high UIP intake may impair gonadotropin secretion and follicle development.…”

“…In the same study, fewer heifers fed high UIP supplements were detected in estrus during the first 21 d of the breeding season, but pregnancy rates did not differ. Additionally, supplementing postpubertal heifers with high UIP (321 g/d), mainly from feathermeal and fishmeal, decreased serum concentrations of FSH compared with heifers consuming 115 g/d UIP (Kane et al, 2004).…”