Glufosinate herbicide-tolerant (LibertyLink) rice vs. conventional rice in diets for growing-finishing swine

Genetically modified (GM) rice (LibertyLink, event LLRICE62) that is tolerant to glufosinate ammonium (Liberty) herbicide was compared with a near-isogenic (NI) conventional medium-grain brown rice (cultivar, Bengal) and a commercially milled long-grain brown rice in diets for growing-finishing pigs. The GM and NI rice were grown in 2000. The GM rice was from fields treated (GM+) or not treated (GM-) with glufosinate herbicide. The GM- and NI rice were grown using herbicide regimens typical of southern United States rice production practices. The four rice grains were similar in composition. Growing-finishing pigs (n = 96) were fed fortified rice-soybean meal diets containing the four different rice grains from 25 to 106 kg BW. Diets contained 0.99% lysine initially (growing phase), with lysine decreased to 0.80% (early finishing phase) and 0.65% (late finishing phase), when pigs reached 51 and 77 kg, respectively. The percentage of rice in the four diets was constant during each of the three phases (72.8, 80.0, and 85.8% for the growing, early-finishing, and late-finishing phases, respectively). There were six pen replicates (three pens of barrows and three pens of gilts) and four pigs per pen for each dietary treatment. All pigs were slaughtered at the termination of the study to collect carcass data. At the end of the 98-d experiment, BW gain, feed intake (as-fed basis), and feed:gain ratio did not differ (P > 0.05) for pigs fed the GM+ vs. conventional rice diets, but growth performance traits of pigs fed the GM+ rice diets were superior (P < 0.05) to those of pigs fed the GM- rice diet (ADG = 0.86, 0.79, 0.81, and 0.85 kg/d; ADFI = 2.41, 2.49, 2.37, and 2.45 kg/d; feed:gain = 2.80, 3.17, 2.95, and 2.89 for GM+, GM-, NI, and commercially milled rice, respectively). Carcass traits (adjusted for final BW) did not differ (P = 0.10) among treatments (hot carcass yield = 73.5, 72.6, 72.6, and 73.2%; 10th-rib backfat = 23.0, 22.7, 21.3, and 23.8 mm; LM area = 38.6, 38.0, 38.2, and 38.1 cm(2); carcass fat-free lean = 50.5, 50.5, 51.2, and 50.0%). Gilts grew slower (P < 0.05) and were leaner (P < 0.05) than barrows. Responses to type of rice did not differ between barrows and gilts, with no evidence of a diet x gender interaction (P = 0.50) for any trait. The results indicate that the glufosinate herbicide-tolerant rice was similar in composition and nutritional value to conventional rice for growing-finishing pigs.