Amino acid imbalance with excess methionine in late-finishing pigs: effects on performance and carcass quality

Limitations in harvest facility capacity can necessitate feeding strategies to slow growth rate in late-finishing pigs. In Experiment 1, six dietary treatments were used with 423 late-finishing pigs (initial weight of 109.5 kg) randomly allotted (mixed-sex) across 24 pens in a 35 d study. The treatments consisted of: 1) Positive Control (PC, 11.7% CP [Crude Protein] diet with added amino acids (AAs), 2) Methionine (Met) 0% (8.8% CP with added AA), 3) Met 1% (8.8% CP with added AA plus 1% added Met for 35 d), 4) Met 1%-1.8% (8.8% CP with added AA plus 1%, 1.2%, 1.4%, 1.6%, and 1.8% added Met for d 0-7, 7-14, 14-21, 21-28, and 28-35 d, respectively), 5) Met 2% (8.8% CP with added AA plus 2% added Met for 35 d), and 6) Met 1.5%-2.3% (8.8% CP with added AA plus 1.5%, 1.7%, 1.9%, 2.1%, and 2.3% added Met for d 0-7, 7-14, 14-21, 21-28, and 28-35 d, respectively). Overall, pigs on the PC had improved average daily gain (ADG) and gain to feed ratio (G:F; P < 0.05) compared to the other five treatments. Pigs on Met 1% had reduced overall ADG and average daily feed intake (ADFI; P < 0.05) with similar G:F compared to pigs on Met 0%. Compared to pigs on Met 1%, pigs on Met 1%-1.8%, Met 2%, and Met 1.5%-2.3% had reduced (P < 0.05) ADG of 28%, 54%, and 53%, respectively; and decreased (P < 0.05) ADFI of 12%, 26%, and 26%, respectively. Dressing percent was similar among all six treatments. In Experiment 2, three dietary treatments were used with 393 late-finishing pigs (average initial weight was 108.8 kg) randomly allotted (mixed-sex) across 24 pens in a 35-d study. The treatments consisted of 1) Met 2%, 2) Met 1.5%-2.3%, and 3) Met 2.0%-2.8% (8.8% CP with added AA plus 2.0%, 2.2%, 2.4%, 2.6%, and 2.8% added Met for d 0-7, 7-14, 14-21, 21-28, and 28-35 d, respectively). Treatments 1 and 2 were identical to Experiment 1. Overall, pigs on Met 1.5%-2.3% had ADG of 241 g and ADFI of 2,040 g which were greater (P < 0.001) compared to pigs on Met 2% with ADG of 57 g and ADFI of 1,515 g. Furthermore, pigs on Met 2%-2.8% had an overall ADG of -62 g and ADFI of 1,254 g which were less (P < 0.05) than those pigs on Met 2%. Percent lean and dressing percent were similar among the three treatments. These data suggest that late-finishing growth can be manipulated in a concise and effective manner by creating AA imbalances with varying levels of excess Met.