Effects of dietary fat on growth performance and carcass characteristics of growing-finishing pigs reared in a commercial environment

We conducted two experiments to evaluate the effects of added choice white grease on performance and carcass merit of barrows and gilts reared under c ommercial conditions. Pigs were housed either 20 (Exp. 1) or 25 (Exp. 2) pe r pen and were provided 0.67 m(2) of pen space per pig. Diets were based on corn and soybean meal and fed in a meal form. The proportion of soybean me al was increased in diets with added fat to maintain the same calorie:lysin e ratio in all diets within a weight phase. In Exp. 1, 480 pigs were fed di ets with 0, 2, 4, or 6% fat. Total lysine contents of the control diets wer e 1.21, 0.88, and 0.66% during the weight phases 36 to 59, 59 to 93, and 93 to 120 kg, respectively. Gain:feed was increased linearly (P < 0. 0 1) due to fat addition in all weight intervals and over the total experiment. The effect of added fat on ADG was not consistent among the weight phases; a l inear (P < 0.01) improvement was found from 36 to 59 kg, but no effect was found during the heavier weight phases. Over the total experiment, however, ADG was improved (P < 0.01) linearly. Carcass traits were not affected by treatment. Experiment 2 used 900 pigs to evaluate possible carryover effect s on performance and carcass merit from feeding 6% fat. The experiment was divided into four, phases: 25 to 45, 45 to 70, 70 to 90, and 90 to 115 kg; lysine contents of the control diets fed in each phase were 1.23, 1.05, 0.8 1, and 0.63%, respectively. The six treatments consisted of no added fat th roughout the experiment or 6% added fat fed from 25 to 45 kg, 25 to 70 kg, 25 to 90 kg, 25 to 1.15 kg, or 45 to 70 and 90 to 115 kg. Carryover effects for ADG and GY (P < 0.07) were found for the 90- to 115-kg interval and fo r ADFI and ME intake (P < 0.05) for the 45- to 70- and 70- to 90-kg interva ls. When fat was added in the previous weight interval, ADG and GY were imp roved and ADFI and ME intake were decreased in the subsequent weight interv al. Pigs fed fat from 25 to 115 kg had more (P < 0.05) backfat and lower (P < 0.05) carcass leanness than pigs on the other treatments. These data sug gest that fat can be added or removed from diets of growing-finishing pigs without any detrimental carryover effects. In fact, the positive carryover effect on ADG and G:F from 95 to 115 kg suggests that feeding fat from 25 t o 95 kg will maximize performance over the total growing-finishing period b ut minimize any detrimental effects of added fat on carcass leanness.