Effects of pre- and postpubertal feeding on production traits at first and second estrus in gilts.

Abstract

The effects of feeding level on body weight (BW), lifetime growth rate, backfat thickness (BF), fatness (BF/BW) and ovulation rate at first (puberty) and second estrus were examined in 145 gilts. From 47.2 kg until puberty, gilts were fed 2.0 kg/d (L) or had ad libitum access to feed (H). From puberty to second estrus, the feed allowance of one-half of the L gilts was increased to 2.8 kg/d. Flush-feeding only normalized ovulation rate (OR) to that observed in gilts with ad libitum access to feed. At puberty, a quadratic negative relationship between lifetime growth rate and age indicated that age at puberty was minimum at a growth rate of less than or equal to .60 kg/d. Thereafter, age at puberty became independent of, or possibly positively related to, lifetime growth rate. Gilts with higher lifetime growth rate also were heavier and fatter at puberty. It was concluded that puberty may have been attained when a certain BF or fatness was achieved, because growth rate of restricted-fed gilts and quickly growing gilts with ad libitum access to feed may have been associated with reduced fat deposition. Hence, maximizing growth rate in replacement gilts does not hasten the attainment of puberty. Growth rate may be manipulated by feed restriction, in order to attain a target BW at boar stimulation (approximately 90 kg), which would coincide with a minimum age (approximately 155 d) and BW at puberty (approximately 97 kg). Nutritional flushing during the first estrous cycle then could be used to normalize OR at mating at second estrus of gilts that were restricted-fed when prepubertal.

Endocrinology of nutritional flushing in gilts

“…Nevertheless, shorr-term improvements in nutritional state preceding mating increase twinning rates in ewes (Nichols 1924), and similarly, short-term, high-level feeding during the estrous cycle lncreases ovulation rate in gilts (Robertson et al 1951 (Beltranena et al 1991) have recently corroborated the results of Self et al (1955) rhat nutrirional flushing merely restores ovulation rate of feed-restricted silts to that of contemporaries fed ad libitum.…”

Lysine and metabolyzable energy requirements of lactating sows for subsequent reproductive performance

“…However, this effect may be reduced due to weaning-to-estrus interval feed intake, especially in wide intervals. In part, this improvement is related to insulin, IGF-I (insulin growth-like factor), and LH plasma levels, because these hormones show a positive response to increasing feed intake (Zak et al, 1997;Beltranena et al, 1991). When there is a high post-weaning feed intake, the liver blood flow may be enhanced, which provide an increased progesterone clearance rate .…”

Feed restriction in cyclic gilts: gonadotrophin-independent effects on follicular growth

“…In cyclic gilts, flushing increases ovulation rate [2,8] and, in underfed prepubertal gilts, refeeding stimulates follicular development [7], possibly without altering plasma gonadotrophins. In reproductive sows, a reduced feed supply during lactation delays ovarian development and oestrus after weaning, through inhibition of LH secretion [28,31], and increases the number of small follicles (< 1 mm) [28], whose growth may be independent of gonadotrophin levels.…”