Effect of Piglet Weaning Weight on Wean-to-Finish Growth Performance and Ultrasound Carcass Measures

Nicole K Moest, Naomi C Willard, Caleb M Shull, Denny McKilligan, Mike Ellis

The objective of this study was to evaluate the impact of variation in piglet weaning weight (WW) resulting from interventions during lactation on post-weaning performance. A split-split plot design was used with a 2 x 2 x 2 factorial arrangement of treatments: 1) Liquid milk replacer [MR; main plot; No Supplement (NS) vs. Supplement (SU)]; 2) Litter size [LS; sub-plot; LOW (4 pigs less than functional teat number) vs. HIGH (2 pigs greater than functional teat number)]; 3) WW [sub-sub-plot; LIGHT (2 lightest barrows and 2 lightest gilts within each litter) vs. HEAVY (2 heaviest barrows and 2 heaviest gilts within each litter)]. Each MR feeder was available to 2 litters, one on the LOW and one on the HIGH LS treatment. Cross-fostering was carried out at 24 h after birth to create LS treatment litters; MR treatment was applied from 24 h after birth until weaning (20 days of age). The study involved 256 pigs housed in mixed-sex pens of 4 pigs (2 barrows; 2 gilts) and was carried out from weaning to a fixed pen weight (130.0 ± 2.27 kg). Pigs were weighed at start and end of the study when ultrasound scans were collected (at the 10th rib) to measure backfat depth (BF) and Longissimus muscle area (LMA). Data were analyzed using PROC MIXED of SAS; the model accounted for fixed effects of MR, LS, WW, and all interactions, and random effects of replicate, replicate by MR interaction and replicate by MR by LS interaction. There were no treatment interactions (P > 0.05) for any measurements (Table 1). The MR treatment had no effect (P > 0.05) on WW; the SU treatment had greater (P ≤ 0.05) ADFI but had no effect (P > 0.05) on other measurements compared with the NS treatment (Table 1). Compared with the LOW LS treatment, the HIGH LS treatment had lighter WW (1.7 kg; P ≤ 0.05), and greater days on test (4 days; P ≤ 0.05); however, there were no differences (P > 0.05) for other measurements. Compared with the LIGHT WW treatment, HEAVY pigs had greater WW (1.7 kg; P ≤ 0.05), fewer days on test (7.9 days; P ≤ 0.05), greater (P ≤ 0.05) overall ADG (38 g) and ADFI (78 g), less BF (0.17 cm; P ≤ 0.05) and greater LMA (1.37 cm²; P ≤ 0.05). In conclusion, providing MR during lactation had little effect on post-weaning performance. However, increasing LS above sow functional teat number reduced WW and increased the time to reach harvest weight with no effect on post-weaning growth performance. In addition, HEAVY WW piglets had improved post-weaning growth performance and carcass lean measurements compared with LIGHT WW piglets.