Effects of protein levels on feedlot performance and carcass characteristics of meat type swine

Data collected on 68 hogs at the Knoxville Experiment Station, Knoxville, Tennessee, were used to determine the effect of varying protein levels on feedlot performance and carcass characteristics in swine. The protein level sequences were: (1) 12-12-12 percent, (2) 14-14-12 percent, (3) 16-14-13 percent, (4) 16-16-16 percent, (5) 18-16-14 percent and (6) 20-18-16 percent. The levels in each sequence were reduced at 75 pounds and again at 130 pounds. In the period from weaning to 75 pounds, the 18 percent and 20 percent protein levels showed significantly (P < .01) greater gains when compared with the 12 percent and 14 percent protein levels. There were significant differences (P < .01 and P < 05) in feed conversion when 20 percent and 18 percent were compared to 12 percent and 14 percent protein and when 20 percent and 12 percent were compared to 12 percent, 16 percent and 18 percent protein, respectively. In the period from 40 to 130 pounds, there were significant differences (P < .01) for ADG when comparisons of 12-12 percent and 14-14 percent versus 18-16 percent and 20-18 percent and 12-12 percent versus 14-14 percent were made. There was also a significant difference (P < .05) when 16-14 percent and 16-16 percent were compared to 12-12 percent, 14-14 percent, 18-16 percent and 20-18 percent protein in favor of the previous. In the feed conversion for this period, there were significant differences (P < .05 and P < .01) respectively when 20-18 percent and 18-16 percent protein were compared to 12-12 percent and 14-14 percent protein and when 14-14 percent was compared to 12-12 percent protein in favor of the higher levels in both cases. In the period from 40 pounds to market weight, there was a significant difference (P < .01) when 12-12-12 percent and 14-14-12 per cent and 14-14-12 percent protein were compared with 18-16-14 percent and 20-18-16 percent protein in favor of the higher sequence levels. When compared with 12-12-12 percent protein, 14-14-12 percent protein was significantly (P < .05) greater. There was also a significant difference (P < .05) when 16-14-13 percent and 16-16-16 percent was compared to 12-12-12 percent, 14-14-12 percent, 18-16-14 percent and 20-18-16 percent protein. There were no significant differences in feed efficiency among any of the comparisons made. When the pigs were somascoped at 75 pounds, 20 percent and 18 percent protein was significantly greater (P < .05) than 14 percent and 12 percent protein for backfat thickness. Fourteen percent protein was also significantly greater than 12 percent protein for the same trait. When the pigs were somascoped at 130 pounds, 20-18 percent and 18-16 percent protein was significantly lower (P < .05) than 14-14 per cent and 12-12 percent protein. At the end of the test, there were no significant differences in backfat thickness (somascope or carcass backfat) for any of the comparisons made. In the analysis for percent ham and loin, 20-18-16 percent and 18-16-14 percent protein was significantly greater (P < .01) than 14-14-12 percent and 12-12-12 percent protein. Percent lean cuts also showed significant differences (P < .01) in the above rations in favor of the higher levels 16-16-16 percent was significantly greater (P < .05) than 16-14-13 percent protein for percent lean cuts. In the analysis for loin eye area, 20-18-16 percent and 18-16-14 percent was significantly greater (P < .01) than 14-14-12 percent and 12-12-12 percent protein. There were no significant differences for any of the comparisons for carcass length, ham quality scores, loin quality scores or loin marbling scores.