Effects of varying levels of undegradable intake protein on endocrine and metabolic function of young post-partum beef cows.
Twelve Hereford x Angus heifers, 2.5 year, 492 +/- 17 kg (BCS = 5 +/- 0.5), were randomly assigned to one of three supplements, stratified by calving date and calf sex. Treatments consisted of a daily equivalent of: (1) low undegradable intake protein (UIP) (L: 908 g per cow per day; 36% CP, 108 g UIP), (2) middle UIP (M: 908 g per cow per day; 36% CP, 165 g UIP), and (3) high UIP (H: 908 g M + 243 g feather meal per cow per day; 46% CP, 335 g UIP). Cows were fed sudan grass hay (7.3% CP, as fed) daily at 2% BW (as fed). Supplement was individually fed twice weekly from Week 2 to Week 11 post-partum. Cow body weight (BW), backfat (BF) and rumpfat (RF) thicknesses decreased in all cows, (P < 0.05) yet did not differ among treatments (P > 0.10). There were no differences among treatments in calf BW (P > 0.10). Serum insulin, blood urea nitrogen (BUN), milk components and yield did not differ among treatments (P > 0.10). Area under the curve (AUC) for serum LH was greater (P = 0.07) in H versus L and M (809 versus 599 and 607 +/- 69 U, respectively). No differences were observed in FSH AUC or mean serum concentrations (P > 0.10). Uterine pH did not differ among treatments or between supplement versus non-supplement days (P > 0.10). Serum progesterone remained below I ng/ml for all cows indicating absence of return to estrus. Under the conditions of this study, BW, BF, RF, serum insulin, BUN, milk components, and yield, uterine pH and serum FSH were not affected by level of UIP. However, supplement containing high levels of UIP enhanced GnRH-induced LH release.
Kane
K K
KK
Department of Animal and Range Sciences, New Mexico State University, Las Cruces 88003-8003, USA.
Creighton
K W
KW
Petersen
M K
MK
Hallford
D M
DM
Remmenga
M D
MD
Hawkins
D E
DE
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001806:Blood Urea Nitrogen; D001823:Body Composition; D001835:Body Weight; D002417:Cattle / Q000502:physiology*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006728:Hormones / Q000097:blood*; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000097:blood; D007774:Lactation; D007986:Luteinizing Hormone / Q000097:blood; D011374:Progesterone / Q000097:blood
D004044:Dietary Proteins; D006728:Hormones; D007328:Insulin; D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone