Compensatory Body Protein Gain in Newly Weaned Pigs

The concept of compensatory growth (CG) represents a means to improve nutrient utilization and decrease costs in pork production. While CG can occur following a period of amino acid intake restriction, there is limited work examining CG in newly weaned pigs. A serial slaughter study was conducted to determine effects of Lys restriction immediately following weaning on growth performance and carcass composition. 144 Duroc x Yorkshire x Landrace pigs (initial BW of 6.9 ± 0.21 kg) were randomly allocated to one of three dietary treatments (6 pens/treatment with 8 pigs/pen; 4 barrows, 4 gilts). For three weeks (restriction phase), pigs were fed starter diets containing 110% (Control: 15.6 g/kg), 80% (Lys80: 11.3 g/kg), or 60% (Lys60: 8.5 g/kg) of NRC (2012) requirements for Lys. After the restriction phase, all pigs were fed a common grower diet containing 120% of NRC (2012) requirements for Lys (14.6 g/kg) for 6 weeks (recovery phase). During the restriction phase, pig BW gain (P<0.01; 411, 373, and 319 ± 7.5 g/d, respectively for Control, Lys80, Lys60) and G:F (P<0.01; 0.807, 0.716, and 0.631 ± 0.0123, respectively) decreased linearly with decreasing dietary Lys levels. At end of the restriction phase, there was a significant linear decrease in BW with decreasing dietary Lys levels (P<0.01; 15.5, 14.8, and 13.6 ± 0.37 kg, respectively). In addition, there was a linear decrease in carcass weight (P<0.01; 11.6, 10.9, and 10.3 ± 0.30 kg, respectively) and carcass CP content (P<0.01; 16.5, 16.1, and 15.3 ± 0.19 %, respectively) with decreasing dietary Lys levels in pigs slaughtered at end of restriction phase. Following completion of the recovery phase there was a trend for a linear increase in BW gain (P=0.06; 844, 862, and 905 ± 19.9 g/d, respectively) and a linear increase in G:F (P<0.01; 0.529, 0.552, and 0.569 ± 0.0101, respectively) with decreasing dietary Lys levels. Carcass weight (P>0.10; 40.5, 40.3, and 39.6 ± 0.80 kg, respectively) and carcass CP content (P>0.10; 16.8, 17.4, and 17.1 ± 0.18 %, respectively) were similar across dietary treatments in pigs slaughtered at end of recovery phase. At the end of the study, BW (average of 50.5 ± 0.63 kg) was similar (P>0.10) across dietary treatments. In conclusion, newly weaned pigs previously fed a diet restricted in Lys for 3 weeks, achieved full CG after a 6 week recovery period.