Reducing variation in finisher growth performance through early post-weaning dietary intervention

It is well established that pigs with low weaning weights have compromised performance throughout the grower-finisher phase (Gondret et al. 2005). There will always be a percentage of pigs that fall below target weaning weights, if steps are not taken to address this poorer performance it will continue into the grower-finisher phase and variation will increase, adding costs to the supply chain (Douglas et al. 2014a). It was hypothesised that a nutritional intervention in early growth (prior to 35 kg) would enhance the performance of light-weight weaner pigs and result in reduced overall variation in weight at slaughter.

A total of 420 male pigs (Large White, Landrace, Duroc terminal cross) weighing 4.5 ± 0.67 kg (mean ± SD) were received at weaning (19 days of age). Eight pens (14 pigs/pen) were randomly filled with pigs to create the Control group, representing a normal population of pigs of varied weight. The remaining pigs were allocated on weight, to create eight pens (14 pigs/pen) of Low weaning weight pigs, and eight pens (14 pigs/pen) of High weaning weight pigs. Intermediate-weight pigs were removed from the experiment such that the Low and High weight groups were discrete. A starter diet [15.0 MJ digestible energy (DE)/kg, 0.8 g standardised ileal digestible lysine (SID L)/MJ DE] was fed to all groups for the first 4 weeks after weaning. Control and High groups were fed to a program matched to average group weight, as per industry practice. After the starter diet, a series of diets were fed: pigs to 25 kg live weight (14.5 MJ DE/kg, 0.8 g SID L/MJ DE); from 25–50 kg (14.0 MJ DE/kg, 0.7 g SID L/MJ DE); from 50–70 kg (13.8 MJ DE/kg, 0.65 g SID L/MJ DE); from 70–90 kg (12.8 MJ DE/kg, 0.55 g SID L/MJ DE); and from 90 kg (12.6 MJ DE/kg, 0.55 g SID L/MJ DE). The Low group remained on the starter diet until they reached 35 kg live weight, before transitioning into the normal feeding program. Pigs were weighed weekly in the starter phase, before being weighed at diet transitions. Feed disappearance was measured by hand in the starter phase and delivered by a FeedPRO^™ system (FeedLogic Corp., Wilmar, MN USA) in subsequent phases. As variation was the main measure of the intervention, all pens ended the experimental period at the same time, when first pigs reached market specifications (95–105 kg live weight), however all pigs were grown out to market weight. Data were analysed via a GLM ANOVA (Genstat, 16th Edition; UK), with differences determined by least significant difference (P < 0.05).

Low-weight weaners remained compromised compared to both the High and Control groups, despite the dietary intervention. The Low group ate less feed than the High and Control groups (P < 0.001), converted feed to gain at the same rate and thus grew slower (P < 0.001), taking 14 days longer to reach market weight (Table 1). Despite reduction in variation due to selection at entry, there was no difference in exit weight CV. These results reflected Douglas et al. (2014a) in that the Low group were ‘too late to catch up’, however, the results of Douglas et al. (2014b) suggested that without our intervention performance may have been poorer. This study showed that producers should reduce impediments that require them to wean pigs at a lighter than optimum weight, as these compromises are conserved throughout the growth phase.

Table 1.  Growth performance and coefficient of variation (CV) of a Control population of pigs compared with pigs of Low and High weaning weights across the whole experimental period