Effects of Pre‐Weaning Energy Substitutions on Post‐Weaning Follicle Development, Steroid Hormones and Subsequent Litter Size in Primiparous Sows

Abstract

The present study investigated the effects of pre-weaning energy substitutions on follicular development, endocrine characteristics and subsequent litter size in primiparous sows. Sows were fed a standard lactation diet (14.1 DE MJ/kg) and then allocated to a Control (C, n=24), Fat (F, n=23), Sugar (S, n=23) or post-weaning Regumate (positive control; R, n=22) treatment at 9 days before weaning of the C, F and S treatments. During the treatment period (8days), 1kg of the lactation diet was substituted with 1kg of a fat-rich (F, 23.85 DE MJ/kg) or sugar-rich (S, 15.75 DE MJ/kg) substitution for F and S sows, respectively. For the R treatment, sows were weaned 8 days earlier than other treatments and fed a lactation diet at 3.5kg with two doses of altrenogest as topdressing from 1 day before weaning until the day on which the other sows were weaned. The F treatment aimed to increase energy intake, and the S treatment aimed to elevate post-prandial glucose and insulin concentrations. Weaning-to-ovulation interval tended to be reduced in the S treatment compared with C (p=0.06) and F (p=0.08) treatments. Body weight (BW) loss during the treatment period, post-weaning follicle development, plasma oestradiol and pre-weaning leptin did not differ among C, F and S sows, although BW loss was lower and leptin was higher in the R treatment. Post-ovulatory progesterone concentration in the S treatment was higher (p<0.05). Sows in the S and R treatments had a greater proportion of litters with larger litter sizes (p<0.05). The outcome suggests that increasing circulating insulin and glucose concentrations during late lactation or a week of metabolic recovery positively improves subsequent litter size in primiparous sows.