Abstract
Reducing the inclusion of expensive feed ingredients in weaned-pig diets decreases feed costs, but compromises growth performance of pigs. Inducing compensatory growth can improve ADG and potentially increase profits. A serial slaughter study was conducted to determine the effect of reducing standardized ileal digestible (SID)-Lys content of newly-weaned pig diets on growth performance and carcass quality at slaughter. In total, 240 newly-weaned pigs (7.2 ± 0.1 kg BW) were randomly allocated to 1 of 3 experimental diets with 8 replicated pens (4 barrow-pens and 4 gilt-pens with 10 pigs/pen). Pigs were fed diets containing 110% (Control), 80% (-20Lys), and 60% (-40Lys) of NRC (2012) SID-Lys recommendations with 15.6, 11.3, and 8.5 g/kg SID-Lys, respectively, for 3 consecutive weeks (restriction phase). During the following 6 weeks, pigs were fed a common diet [14.6 g/kg SID-Lys, 20% above NRC (2012) recommendation; recovery phase]. To assess carcass quality, all pigs were phase-fed commercial diets until market weight (130 kg). During the restriction phase, BW, ADG, and G:F decreased linearly with dietary Lys content (BW: 14.4, 13.9, and 12.9 ± 0.2 kg for Control, -20Lys, and -40Lys, respectively; P < 0.01). At the end of the recovery phase, BW was similar amongst treatments (50.7 ± 0.7 kg). From weaning to attaining 50 kg BW, ADG was not different (706, 683, and 682 ± 10 g/d; P > 0.05), but G:F was greater for Control than pigs fed reduced-Lys diets (0.612, 0.597, and 0.541 ± 0.011 for Control, -20Lys, and -40 Lys, respectively; P < 0.05). There were no differences in carcass quality traits amongst treatment groups (P > 0.05) for pigs slaughtered at 130 kg BW. In conclusion, newly-weaned pigs fed low-Lys diets for 3 weeks achieved compensatory growth after a 6-week recovery period, with no effects on carcass quality at market weight.