Enhancement of Ovulation Rate in Gilts by Increasing Dietary Energy and Administering Insulin during Follicular Growth

Abstract

Two experiments were conducted to examine influences of dietary energy and insulin on ovulation rate and patterns of luteinizing hormone (LH), follicle stimulating hormone (FSH), glucose, insulin and estradiol in gilts during 6 d before estrus. In Exp. 1, 36 gilts were given altrenogest for 14 d to synchronize estrus. In a factorial arrangement, gilts were fed one of two levels of dietary energy (5,771 or 9,960 kcal metabolizable energy (ME)/d), and given one of two levels of porcine insulin (0 or .1 IU/kg body weight iv every 6 h). Dietary treatments began 4 d before and insulin treatments began 1 d after the last day of altrenogest, respectively, and lasted until 24 h after estrus. Main effect means for number of corpora lutea were 14.0 +/- 1.3 and 17.6 +/- .9 for 5,771 and 9,960 kcal ME (P less than .05), and 14.6 +/- 1.0 and 17.0 +/- .9 for 0 and .1 IU insulin (P less than .05). Number of LH peaks on d 3 was greater for gilts that received 9,960 kcal than 5,771 kcal (3.3 +/- .2 vs 2.7 +/- .2; P less than .05), and for .1 than 0 IU insulin (3.2 +/- .2 vs 2.7 +/- .2; P less than .05). During the first 24 h of sampling, concentrations of LH and FSH were greater (P less than .05) in gilts receiving 9,960 kcal ME plus insulin than for other treatment combinations. Concentrations of estradiol were not affected by treatments. In Exp. 2, two formulations of insulin were evaluated for influence on ovulation rate. All gilts received altrenogest and 9,960 kcal ME/d as in Exp. 1. Then on the first day after altrenogest, seven gilts each received short-acting insulin (as in Exp. 1), long-acting insulin (zinc suspension, 1.0 IU/kg body weight every 18 to 24 h), or served as controls. Ovulation rates were increased (P less than .05) by both insulin preparations (15.6, control; 19.1, short-acting; 18.5, long-acting; SE = 1.2). Concentrations of LH tended to be greater after short-acting insulin, but differences were not significant (P = .13). We conclude that increases in ovulation rate produced by dietary energy and insulin are not necessarily accompanied by changes in gonadotropins or estradiol.

Endocrine bases of lactational anoestrus in the sow

“…In underfed prepubertal gilts, refeeding increases follicular fluid IGF-I concentrations (Charlton et al, 1993). In cyclic gilts, insulin treatment increases ovulation rate even without a concomitant rise in LH secretion (Cox et al, 1987b (Kirkwood et al, 1988). In cultured porcine granulosa cells, GH enhances the stimulatory effects of oestradiol-17P and FSH on progesterone secretion (Hsu and Hammond, 1987).…”

Within-litter variation in birth weight: impact of nutritional status in the sow

“…Development of follicles and oocytes is improved owing to higher concentrations of insulin (Matamoros et al, 1990;Tokach et al, 1992;van den Brand et al, 1998;Ziecik et al, 2002) or IGF-1 in plasma (Ferguson et al, 2003). The underlying mechanism by which insulin increases follicular development is possibly due to an increase in luteinizing hormone (LH) pulsatility (Cox et al, 1987) or LH production (Adashi et al, 1981), and a higher LH pulse frequency (van den Brand et al, 2000).…”

Factors Influencing Sexual Maturation, Puberty and Reproductive Efficiency in the Gilt

“…Recently, Cox et al (1987) reported that insulin injections during the follicular phase increase ovulation rate, either by a direct effect on ovarian follicle recruitment, or by an effect on the hypothalamo-hypophyseal-ovarian axis. In their reviews, Hughes and Varley (1980) and Aherne and Kirkwood (1985), suggest that the effect of flushing is only in increase ovulation rate to the level that would be obtained if the gilt was maintained on a high level of diet intake.…”