Effect of dietary energy, body condition and calf removal on pituitary gonadotropins, gonadotropin-releasing hormone (GnRH) and hypothalamic opioids in beef cows.
Beef cows (n = 64) were slaughtered to evaluate effects of dietary energy and calf removal (CR) on hypothalamic and adenohypophysial endocrine characteristics. From d 190 of gestation until parturition, cows received maintenance (ME; n = 32) or low (LE; n = 32) energy diets (ME = 100%, LE = 70% NRC recommendations). After parturition, half (n = 16) of each prepartum diet group received low (LE; n = 32) or high (HE = 130% NRC; n = 32) energy diets. At 30 d postpartum, cows were slaughtered 0 or 48 hr after CR. Hypothalami [preoptic area (POA), hypothalamus (HYP), stalk-median eminence (SME)] and pituitaries were collected. Basal and K(+)-induced release of GnRH from SME, and pituitary luteinizing hormone (LH) and follicle stimulating hormone (FSH) did not differ among groups (P greater than .05). Hypophyseal LH was correlated (P less than .01) with body condition score (BCS) at parturition and slaughter (r = .36 and .47, respectively). Prepartum LE diet increased (P less than .05) met-enkephalin in POA compared to prepartum ME (.59 +/- .05 vs. .44 +/- .04 pmol/mg) regardless of postpartum diet or suckling status. Concentrations of beta-endorphin in combined HYP + POA were decreased (P less than .05) by 48 hr CR (15.1 +/- 1.1 vs. 18.1 +/- 0.7 fmol/mg).(ABSTRACT TRUNCATED AT 250 WORDS)
Connor
H C
HC
Department of Animal Science, University of Wyoming, Laramie 82071.
Houghton
P L
PL
Lemenager
R P
RP
Malven
P V
PV
Parfet
J R
JR
Moss
G E
GE
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004032:Diet; D004723:Endorphins / Q000032:analysis*; D002149:Energy Intake; D004744:Enkephalin, Methionine / Q000032:analysis; D005260:Female; D005640:Follicle Stimulating Hormone / Q000032:analysis; D006065:Gonadotropins, Pituitary / Q000032:analysis*; D007031:Hypothalamus / Q000032:analysis; D007774:Lactation; D007986:Luteinizing Hormone / Q000032:analysis; D010902:Pituitary Gland / Q000032:analysis; D010906:Pituitary Hormone-Releasing Hormones / Q000032:analysis*; D001615:beta-Endorphin / Q000032:analysis
D004723:Endorphins; D006065:Gonadotropins, Pituitary; D010906:Pituitary Hormone-Releasing Hormones; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone