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Effect of dietary betaine and ractopamine on growth and carcass characteristics in finishing pigs housed under high ambient temperatures
Betaine is an osmolyte that helps to maintain water homeostasis and cell integrity, which is essential during heat stress. We hypothesized that supplemental betaine would improve growth that is depressed during heat stress, and possibly has a greater outcome combine with ractopamine. Two studies were conducted to determine 1) the effects of betaine in combination with ractopamine, and 2) the optimal betaine level for late finishing pigs. High environmental temperatures were imposed by gradually increasing temperatures over 10 d to the target high temperature of 32°C. In Exp. 1, pigs (n=1,477, BW=91.6 ± 3.1 kg) were assigned within weight blocks and sex to 1 of 4 dietary treatments arranged in a 2 x 2 factorial RCB design. Treatments consisted of diets without or with ractopamine (5 ppm for 21 d followed by 8.8 ppm to market) and each of these diets were supplemented with either 0 or 0.2% of betaine. Pigs were housed approximately 22 pigs per pen using a total of 68 pens. Betaine reduced ADFI (P=0.001; 2.80 vs. 2.92 kg/d) and ADG (P=0.05; 0.78 vs. 0.83 kg/d), but did not impact carcass characteristics. Ractopamine reduced (P=0.04) ADFI, improved (P<0.001) gain:feed (0.295 vs. 0.265), market weight (125.8 vs. 122.1 kg), carcass yield (74.9 vs. 73.8%), loin depth (63.6 vs. 60.0 mm), and lean percentage (53.1 vs. 51.7%), and reduced backfat (20.7 vs. 22.0 mm). In Exp. 2, pigs (n=2,193, BW=95.6 ± 3.5 kg) were assigned within weight blocks and sex to 1 of 5 dietary treatments in a RCB design. Pigs were housed in pens with approximately 22 pigs each; using a total of 100 pens. Treatments consisted of diets supplemented with 0, 0.0625, 0.125, 0.1875% of betaine, and the 0% betaine diet supplemented with ractopamine as in Exp. 1. Betaine decreased carcass yield in a quadratic manner (P=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 (P<0.001) gain:feed (0.334 vs. 0.295), market weight (121.6 vs. 118.5 kg), carcass yield (74.7 vs. 73.8%), loin depth (61.7 vs. 59.0 mm), and lean percentage (53.5 vs. 52.5%), and reduced backfat (18.8 vs. 20.4 mm). Collectively, data indicate that under commercial conditions, betaine did not improve pig performance housed under high ambient temperatures, regardless of ractopamine inclusion. Ractopamine improved pig growth and carcass characteristics under high ambient temperatures.
Keywords: betaine, ractopamine, finishing pigs.