Nutritional anestrus in beef cows: effects of body condition and ovariectomy on serum luteinizing hormone and insulin-like growth factor-I.
The objectives of this experiment were to determine if a postcastration increase in concentrations of LH occurs in nutritionally anestrous beef cows and to examine the relationship between body energy reserves and secretion of LH and insulin-like growth factor-I (IGF-I). Nonpregnant, nonlactating, Hereford cows were fed to maintain (M) body weight (BW), body condition score (BCS), and normal estrous cycles (n = 5) or were fed a restricted (R) diet for 26 wk to lose BW and BCS and to become anestrus (n = 10). At 5-7 wk after the initiation of anestrus, R cows were randomly allotted to be ovariectomized (OVX) via flank incision (n = 5) or to remain intact (INT, n = 5). OVX was performed when R cows became anestrous. All M cows were OVX. Serum was collected frequently the day before and during the first 10 days after OVX, and concentrations of progesterone, estradiol, LH and IGF-I were quantified. On Day 10 after OVX, 1 mg of estradiol was injected into 3 cows from each group and serum was collected for 30 h. After OVX, there was a treatment-by-day effect for mean serum LH and IGF-I concentrations. Concentrations of LH increased (p less than 0.01) and concentrations of IGF-I decreased (p less than 0.05) in M-OVX cows when compared with R-OVX and R-INT cows. Concentrations of LH and IGF-I were similar for R-OVX and R-INT cows. The number of LH pulses was similar for M and R cows.(ABSTRACT TRUNCATED AT 250 WORDS)
Richards
M W
MW
Department of Animal Science, Oklahoma State University, Stillwater 74078.
Wettemann
R P
RP
Spicer
L J
LJ
Morgan
G L
GL
D000780:Anestrus / Q000502:physiology*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight; D002417:Cattle; D004734:Energy Metabolism; D004958:Estradiol / Q000494:pharmacology / Q000502:physiology; D005260:Female; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood* / Q000378:metabolism; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology
D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone