Effects of Monosodium Glutamate on Nursery Pig Performance

Two experiments were conducted to evaluate the effects of monosodium glutamate (MSG) on nursery pig performance. In Exp. 1, 1,134 nursery pigs (PIC 280×1050, initially 5.1 kg BW) were allotted to 6 treatments fed for 48 d. There were 27 pigs/pen and 7 pens/treatment. Dietary treatments contained 0, 0.5, 1.0, 1.5, and 2.0% MSG, or a high salt diet, formulated to an equal Na content as the 1.0% MSG diet. Experimental diets were fed in 3 phases from d 0 to 12, d 12 to 26, and d 26 to 48. During phase 1, no evidence for differences was detected among MSG treatments. In phase 2, increasing MSG decreased (linear, P<0.045) ADG, ADFI, and G:F while pigs fed the high salt diet (0.84% added salt) had decreased (P<0.001) ADG (254 vs. 317 g; SEM=11.3) and G:F (0.572 vs. 0.674; SEM=0.0154) compared with pigs fed the 1% MSG diet. In phase 3, pigs fed the high salt diet had decreased (P<0.028) ADG (528 vs. 561 g; SEM=10.1) and ADFI (797 vs. 851 g; SEM=17.3) compared with those fed the 1% MSG diet. For the overall nursery period, increasing MSG decreased (linear, P=0.033) ADG (388, 372, 378, 369, and 370 g for 0 to 2% MSG, respectively; SEM=7.9). Pigs fed the high salt diet had decreased (P<0.009) ADG (341 vs. 378 g; SEM=7.9), ADFI (546 vs. 578 g; SEM=12.2), and G:F (0.625 vs. 0.654; SEM=0.0044) compared to those fed 1% MSG. In Exp. 2, 700 nursery pigs (PIC C-29×1050, initially 6.2 kg BW) were allotted to 5 treatments fed for 42 d. There were 10 pigs/pen and 14 pens/treatment. Dietary treatments contained 0, 0.5, 1.0, 1.5, and 2.0% MSG and were balanced for Na and Cl using sodium bicarbonate and potassium chloride. Experimental diets were fed in 3 phases from d 0 to 14, d 14 to 28, and d 28 to 42. For ADG and ADFI, there was no evidence for differences within any phase or overall (ADG overall: linear, P=0.538; 464, 462, 458, 457, and 461 g, respectively; SEM=5.3). Increasing MSG resulted in poorer G:F (linear, P=0.003; 0.670, 0.660, 0.654, 0.654, and 0.645, respectively; SEM=0.0057) for phase 3. Thus, for the overall nursery period, G:F tended (quadratic, P=0.080) to be poorer with increasing MSG. In conclusion, MSG did not improve nursery pig performance and MSG may reduce intake and gain when dietary Na is not balanced.