Effect of natural betaine and ractopamine HCl on whole-body and carcass growth in pigs housed under high ambient temperatures1

Abstract

Betaine is an osmolyte that helps to maintain water homeostasis and cell integrity, which is essential during heat stress. We hypothesized that supplemental betaine can improve growth during heat stress and may further improve the response to ractopamine. Two studies were conducted to determine: 1) the effects of betaine in combination with ractopamine; and 2) the optimum betaine level for late finishing pigs during heat stress. Heat stress was imposed by gradually increasing temperatures over 10 d to the target high temperature of 32°C. In Exp. 1, pigs ( = 1477, BW = 91.6 ± 3 kg) were assigned within BW blocks and sex to 1 of 4 diets arranged in a 2 × 2 factorial RCB design (68 pens; 20 to 23 pigs/pen). Treatments consisted of diets without or with ractopamine (5 mg/kg for 21 d followed by 8.8 mg/kg to market) and each were supplemented with either 0 or 0.2% of betaine. Betaine reduced ( ≤ 0.05) BW (123.1 vs. 124.3 kg), ADG (0.780 vs. 0.833 kg/d), and ADFI (2.800 vs. 2.918 kg/d), but did not impact carcass characteristics. Ractopamine increased ( < 0.01) BW (125.5 vs. 121.9 kg), ADG (0.833 vs. 0.769 kg/d), G:F (0.295 vs. 0.265), HCW (94.1 vs. 90.0 kg), carcass yield (74.8 vs. 73.8%), loin depth (63.6 vs. 60.0 mm), and predicted lean percentage (53.2 vs. 51.7%) and reduced ADFI (2.822 vs. 2.896 kg/d, = 0.033) and backfat depth ( < 0.001; 20.2 vs. 22.5 mm). In Exp. 2, pigs ( = 2193, BW = 95.5 ± 3.5 kg) were allocated within BW blocks and sex to 1 of 5 treatments in a RCB design (100 pens; 20 to 24 pigs/pen). Treatments consisted of diets with 0, 0.0625, 0.125, 0.1875% of betaine, and a positive control diet with ractopamine, but not betaine. Betaine tended to decrease carcass yield quadratically ( = 0.076; 74.1, 73.5, 73.8, and 73.9 for 0, 0.0625, 0.125, 0.1875% of betaine, respectively), but did not impact other responses. Ractopamine improved ( < 0.001) BW (121.6 vs. 118.5 kg), G:F (0.334 vs. 0.295), carcass yield (74.7 vs. 73.8%), loin depth (61.7 vs. 59.0 mm), and predicted lean percentage (53.2 vs. 52.6%), and reduced backfat (18.7 vs. 20.4 mm). Collectively, data indicate that under commercial conditions, betaine did not improve performance of pigs housed under high ambient temperatures, regardless of ractopamine inclusion. Ractopamine improved whole-body growth and especially carcass growth of pigs raised under high ambient temperatures. The ability of ractopamine to stimulate growth during heat stress makes it an important production technology.