Compensatory growth response and carcass quality after a period of lysine restriction in lean meat type barrows

Because research indicates that responses on dietary restrictions may depend on the gender of pigs, we examined the interaction between the lysine level in different feeding periods and the performance and carcass quality of barrows in a 2 × 2 factorial trial. In total 192 barrows were divided over 32 pens of six animals, and each pen was assigned to one of four dietary treatments: (1) high lysine levels in the growing (25-42 kg body weight [BW]), early finishing (42-73 kg BW) and in the late finishing period (73-110 kg BW) (Group HH); (2) high lysine levels in the growing and early finishing period, and low lysine level in the late finishing period (Group HL); (3) low lysine levels in the growing and early finishing period, and high lysine level in the late finishing period (Group LH); and (4) low lysine levels in all periods (Group LL). To obtain the high lysine diets, L-lysine, as well as L-threonine, DL-methionine and L-tryptophan, were added to the low-lysine diets. The low-lysine diets contained 20% (in growing) or 30% (in finishing) lysine less than the high-lysine diets. Feeding Diet LH increased the daily gain and decreased the feed-to-gain ratio in the subsequent late finishing phase (p < 0.05). Between start and slaughter, Group LL showed lower daily gain and a higher feed-to-gain ratio than the three other groups (p < 0.05). Carcass yield and lean meat percentage depended on sufficient amino acid (AA) provision in the late finishing feed (p < 0.05). Lowering the AA concentrations in the diet decreased the amount of lysine needed per kg gain and per kg lean gain (p < 0.05). An interaction between AA levels in the different phases and lean gain was observed, with Group LL showing lower lean gain than the other three groups (p < 0.05). This study shows that strategic provision of a sufficient amount of AAs either in the growing and early finishing period or in the late finishing period largely counteracts the negative effects of AA restriction in other feeding phases. Barrows can show compensatory growth after a period of AA restriction. The results of the present study show that a sufficient level of lysine in the late finishing feed rather than in the growing and early finishing feed is important for obtaining good carcass quality.