Understanding the drivers of improved pig weaning weight by investigation of colostrum intake, sow lactation feed intake, or lactation diet specification

Modern sows have low feed intake (FI) during lactation. The main aim of this study was to understand interactions between and separate effects of FI and nutrient density on litter weaning weight (WW). Key drivers of colostrum intake (CIn), piglet survival, WW, and colostrum yield (CY) were also investigated. Sows (n = 82) were offered a High (15.8 MJ/kg DE; 1.3% total lysine) or Normal (15.2 MJ/kg DE; 1.28% total lysine) specification lactation diet at either a High (feed allowance increased by 0.5 kg/d after farrowing until intake reached 10 kg/d) or Low (feed allowance was increased by 0.3 kg/d after farrowing until intake reached 7.5 kg/d) feeding level (2 x 2 factorial design). A subset of sows (n = 18) were observed during farrowing to collect data on factors affecting CIn. No interactions were found between diet specification and feeding level. Sows on the Low feeding level lost 10.6 kg more BW during lactation than those on the High feeding level (P < 0.001). Sows offered the High specification diet lost 6.4 kg more BW than those on the Normal specification diet (P = 0.018). Diet specification had no effect on ADFI. Between birth and weaning, litters of sows offered the High feeding level grew 326 g/d faster (P < 0.001) and were heavier at 28 d (114 kg; P < 0.001) compared with those of sows offered the Low feeding level (104 kg). Although litters from sows offered the High specification diet had WW similar to that of litters from sows offered the Normal specification diets, their ADG was 190 g/d greater (P = 0.018) between birth and weaning. A regression analysis was completed using data from 192 sows and indicated that FI and lysine intake throughout lactation and DE and lysine intake from 14 to 28 d of lactation were the main drivers of litter WW. Lactation efficiency was 0.65 from 0 to 7 d and decreased to 0.42 from 21 to 28 d. Variation in CIn was mainly explained by 24-h weight, birth weight, and the duration of farrowing. Colostrum yield was significantly correlated (P = 0.004; pseudo R-2 = 54.5%) with litter birth weight. Piglet WW was positively correlated with 3-wk weight (P < 0.001) but negatively correlated with sow parity (P = 0.035), number born alive (P = 0.045), and being female (P < 0001). Out of 45 variables, preweaning piglet survival was positively correlated (P = 0.008) with only 24- to 48-h weight gain. In conclusion, lactation FI and DE and lysine intake in the second half of lactation were the main drivers of litter WW.