Influence of food intake on plasma LH concentrations in multiparous sows

Abstract

Nutrition may influence reproductive processes by a number of mechanisms including a direct effect on gonadotrophin secretion. The level of energy intake during lactation in multiparous sows may therefore have important consequences for luteinising hormone (LH) secretion after weaning. An experiment was carried out with 19 crossbred sows to investigate the effect of food intake in lactation and from weaning to day 6 post coitum on the pulsatile characteristics of LH on days 2 and 4 after weaning and on the preovulatory LH surge characteristics. During a 28 day lactation, sows were either offered 1.8 kg day −1 plus 0.55 kg per piglet suckled day −1 (H-high) of a commercial sow diet or 1.8 kg day −1 plus 0.25 kg per piglet suckled day −1 (L-low). After weaning, the sows from each lactation feeding regime were given either 1.5 kg day −1 (L-low) or 3.5 kg day −1 (H-high) until day 6 post weaning. The four treatment groups that comprised the 2 × 2 factorial design were thus HH, HL, LH and LL. Sows were mated at the appearance of oestrus. There were no significant differences between any of the treatment groups in episodic release of LH at either day 2 or day 4 post weaning. Also, there were no apparent effects of either food intake in lactation or between weaning and service on the timing and characteristics of the preovulatory surge of LH. The time intervals from the onset of the LH surge to peak LH concentrations for treatments LL, LH, HL and HH were 8.3 h, 8.7 h, 12.7 h and 11.3 h respectively and these differences approached significance ( P ⇒ 0.05). There were no significant correlations between liveweight loss during lactation and either the time to the onset of the LH surge or the time at which peak LH concentrations were observed.