Endocrine changes and management factors affecting puberty in gilts

Puberty in gilts is the occurrence of first oestrus and the onset of reprod uctive capability (usually at between 200 and 120 days of age). It is the c ombined effect of genetic factors and management factors (including nutriti on, boar exposure and season) that contribute to the age at puberty. Consum er demands for leaner pork have lead to genetic selection for increased lea n tissue growth rate and reduced body fat. This has resulted in a delay in the age at puberty and a decrease in energy stores for subsequent growth, p regnancy and lactation. Restriction of dietary protein during the prepubert al period is a way to enhance body-fat reserves; however, this has detrimen tal affects on the age at puberty and ovulation rates, but can be overcome by restoring dietary protein in the weeks before the induction of puberty. Luteinizing hormone (LH) is a key hormone in regulating ovarian follicular growth and, hence, the age at which puberty occurs. Concentrations of LH in the blood fluctuate during the prepubertal period in association with ovar ian development. The nutritional modulation of hormone secretion is not cle ar. Future management strategies to enhance both reproductive performance a nd to satisfy consumer demands need to consider hypothalamo-pituitary matur ation in association with body weight and body-composition parameters. (C) 2001 Elsevier Science B.V. All rights reserved.