Influences of month of birth and age on patterns of luteinizing hormone secretion in prepubertal heifers.
An experiment was done to determine if month of birth and age influenced patterns of luteinizing hormone (LH) secretion in prepubertal heifers. Mean concentrations of LH increased linearly (P<.05) in March-born heifers between one and seven months of age. This was partially due to an increase in number of LH pulses. The prepubertal pattern of LH concentrations was quadratic (P<.05) for heifers born in September because concentrations were slightly higher (P=.15) than those in March-born heifers at one month of age. There were no differences between groups during the remainder of the prepubertal period (3 to 7 months). There was a tendency (P=.18) for September-born animals to reach puberty at younger ages than those born in March. September-born heifers also had greater (P=.06) average daily gains, but body weights at puberty were similar for the two groups. These results show that season of birth influenced LH concentrations at one month of age, but did not significantly affect the increase between three and seven months of age.
Schillo
K K
KK
Department of Meat and Animal Sciences, University of Wisconsin, and Regional Primate Research Center, Madison, WI 53706, USA.
Dierschke
D J
DJ
Hauser
E R
ER