Effects of dietary energy density and lysine : calorie ratio on growth performance and carcass characteristics of growing-finishing pigs

We conducted two experiments to evaluate the effects of dietary energy dens ity and lysine: calorie ratio on the growth performance and carcass charact eristics of growing and finishing pigs. In Exp; 1, 80 crossbred barrows (in itially 44.5 kg) were fed a control diet or diets containing 1.5, 3.0, 4.5, or 6.0% choice white grease (CWG). All diets contained 3.2 and 2.47 g of l ysine/Mcal ME during growing (44.5 to 73 kg) and finishing (73 to 104 kg), respectively. Increasing energy density did not affect overall ADG; however , ADFI decreased and feed efficiency (Gain:feed ratio; G:F) increased (line ar, P < .01). Increasing energy density decreased and then increased (quadr atic, P < .06) skinned fat depth and lean percentage. In Exp. 2, 120 crossb red gilts (initially 29.2 kg) were used to determine the effects of increas ing levels of CWG and lysine:calorie ratio fed during the growing phase on growth performance and subsequent finishing growth. Pigs were fed increasin g energy density(3.31, 3.44, or 3.57 Meal ME/kg) and lysine:calorie ratio ( 2.75, 3.10, 3.45, or 3.80 g lysine/Mcal ME). No energy density x lysine:cal orie ratio interactions were observed (P > .10). Increasing energy density increased ADG and G:F and decreased ADFI of pigs from 29.5 to 72.6 kg (line ar, P < .05). Increasing lysine:calorie ratio increased ADG and ADFI (linea r, P < .01 and .07, respectively) but had no effect on G:F. From 72.6 to 90 .7 kg, all pigs were fed the same diet containing .90% lysine and 2.72 g ly sine/Mcal ME. Pigs previously fed with increasing lysine:calorie ratio had decreased (linear, P < .02) ADG and G:F. Also, pigs previously fed increasi ng CWG had decreased (linear, P < .03) ADG and ADFI. From 90.7 to 107 kg wh en all pigs were fed a diet containing .70% lysine and 2.1 g lysine/Mcal ME , growth performance was not affected by previous dietary treatment. Carcas s characteristics were not affected by CWG or lysine:calorie ratio fed from 29.5 to 72.6 kg. Increasing the dietary energy density and lysine:calorie ratio improved ADG and G:F of growing pigs; however, pigs fed a low-energy diet or a low lysine:calorie ratio from 29 to 72 kg had compensatory growth from 72 to 90 kg.