Effect of restricted food intake, before and/or after mating, on the reproductive performance of Greyface ewes

Abstract

The effect on the reproductive performance of Greyface (Border Leicester x Scottish Blackface) ewes of a low level food intake and associated loss of live weight from either 14 days before mating, or from the time of mating, until 11 to 26 days after mating, was investigated. Ewes (252) were allocated to one of three treatments with ewes within each treatment divided into two flocks (flock A: 16 ewes per treatment; flock B: 68 ewes per treatment). Ewes of treatment LL were given a ration providing proportionately 0-5 estimated metabolizable energy (ME) requirements for maintenance from 2 weeks before mating. Those of treatment HL were given a daily ration providing 1-5 estimated ME requirements for maintenance until mating and the restricted ration thereafter. Ewes of treatment HH were given the higher ration throughout the experimental period. Flock A ewes were slaughtered at 11 days post mating and flock B ewes at between 18 and 26 days post mating. Treatment differences in the ovulation rates of flock A ewes were not statistically significant but in flock B, ewes of treatment LL had a lower mean ovulation rate (1-81) than those of treatments HL (2-23) and HH (2-09) (P < 0-001). The lower ovulation rate of LL ewes relative to HL ewes in flock B was reflected in a lower mean potential lambing rate per ewe pregnant than in the HL treatment (1-58 v. 1-79; P < 0-01) and per ewe put to the ram (1-37 v. 1-65; P < 0-01). HL ewes had a slightly lower mean potential lambing rate per ewe pregnant (1-79 v. 1-97; P < 01) and per ewe put to the ram (1-65 v. 1-82; P < 0-05) than HH ewes. Ova wastage rates of LL + HL and HH ewes were 0-26 and 014 (P < 001) respectively at 24 days post mating. Values for LL and HL ewes (0-27 and 0-25 respectively) were not significantly different.Estimated mean conceptus lengths were 370, 500 and 1400 u,m for LL, HL and HH ewes respectively (P < 0-05).It is concluded that low food intake before mating reduced the mean ovulation rate and low intakes after mating compromised embryo growth rate and induced a higher rate of ova wastage; this increase in the incidence of ova wastage was not significantly exacerbated by the low levels of intake prior to mating.

Plasma urea nitrogen and progesterone concentrations and follicular dynamics in ewes fed proteins of different degradability

“…Opposite to the observations of this experiment, Rhind et al (1989), Lozano et al (1998) and O'Callanghan et al (2000) observed difference in the blood progesterone concentration in ewes subjected to different feeding programs. However, in these studies, ewes presenting lower blood progesterone concentration ingested twice to four times more ME than those with higher concentration of this hormone.…”

“…A nutritional strategy that may be used to enhance ovulation rate and, consequently, prolificacy, is overfeeding or flushing, which consists in increasing nutrition levels in ewes before mating. The effects of overfeeding with high-energy diets are well known (Rhind et al, 1989;Viñoles et al, 2008); however, few studies have verified this with protein-rich feeds. Some authors have demonstrated that overfeeding with protein feeds increased ovulation rate (Molle et al, , 1997, while the same variable was unaltered by overfeeding with proteins of different degradability (Branca et al, 2000;Saunders et al, 2010).…”

Efeito da sobrealimentação com fontes de proteína de diferentes degradabilidades sobre a ovulação em ovelhas Santa Inês

“…Embora os efeitos da sobrealimentação com dietas ricas em energia sejam bem documentados (Rhind et al, 1989;Vinõles et al, 2008), as informações relativas à sobrealimentação com alimentos proteicos são escassas. Molle et al (1997) observaram maior número de ovulações em ovelhas da raça Sarda sob sobrealimentação com 270 g de farelo de soja/dia a partir de 14 dias antes até dois dias após a monta, do que em ovelhas não suplementadas (1,8 vs 1,3 corpos lúteos, respectivamente).…”

The effect of maternal nutrition level during the periconception period on fetal muscle development and plasma hormone concentrations in sheep

“…It is known that nutritional status of ewes around the mating period alters ovarian activity and lambing rates after mating in many sheep breeds (Lassoued et al, 2004). Low feed intake before mating reduces the mean ovulation rate and inadequate nutrition after mating induces a higher rate of ova wastage (Rhind et al, 1989). Moreover, over-feeding during early gestation reduces pregnancy rate and reproductive performance (Parr et al, 1987).…”