Effect of Lysine, Crude Fiber and Free Gossypol in Cottonseed Meal on the Performance of Growing Pigs

Abstract

Two factorial designed individual pig feeding trials and a digestion trial were conducted to delineate the effect of lysine, crude fiber and free gossypol in cottonseed meal (CSM) on the performance of growing pigs fed sorghum-CSM diets. Trial 1 examined three levels of lysine (.60, .70, .80%), two levels of fiber (3.0, 4.5%) and three levels of free gossypol (90, 300, 500 ppm) using specially processed CSM's while Trial II examined the same levels of dietary lysine and two levels of fiber (2.58, 3.54%) using a commercial direct solvent cottonseed meal. Supplemental iron was added to all CSM diets to give a 1:1 weight ratio of iron:free gossypol. The effect of dietary fiber levels in Trial II on energy and protein digestibility was investigated in Trial III. In Trial I, increasing the dietary lysine level gave a quadratic improvement in gains (P<.05) and feed intake (P<.10) and a linear improvement in feed efficiency (P<.05). Crude fiber level had minimal effect on feed intake and gain, but pigs fed the low fiber diet had more desirable feed to gain ratios (P<.05). Dietary free gossypol level did not significantly affect any production trait (P>.10). Increasing dietary lysine levels in Trial II caused a linear increase in feed intake (P<.05), gains and feed efficiency (P<.01). Performance indicated that lysine availability was much lower in the commercial direct solvent than the special processed cottonseed meals. Crude fiber level had little effect (P>.10) on pig performance. In Trial III, the low fiber diet exhibited higher dry matter and gross energy digestibilities (P<.05) than the high fiber diet. These data suggest that the lowered performance of growing pigs fed sorghum-CSM diets is due primarily to low dietary lysine. Dietary crude fiber affected only feed utilization while dietary free gossypol had no effect on pig performance when iron was included in the diets on a 1:1 weight ratio to free gossypol.