Interaction of dietary protein, fiber, and energy on growth performance in finishing barrows
Cline, Paul Martin
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The objective of these studies was to determine the performance response to changes in dietary fat, protein, and fiber content in finishing barrows. Previous work has shown that increases in dietary energy density result in decreased feed intake. Experiment 1 was conducted in 3 trials of 18 pens each (4 pigs/pen, total n=216). Within each trial, barrows (PIC C42 x 280, initial wt. = 84 kg) were blocked by weight and assigned to one of 9 experimental diets in a 3 x 3 factorial arrangement, with main effects of crude protein (12, 16, 20%, lysine: 0.60, 0.80, 1.00%) and added Fat (1, 6, 11%). The lowest protein diet with 1% added fat, met the NRC recommendations for pigs in this weight range. Body weight, intake and efficiency were determined initially and on d 14 and 28. There were no significant interactions of dietary protein and fat. There was a main effect of dietary protein on gain (P < 0.03). Average daily gain increased as dietary protein increased from 12 (1.08 kg/d) to 16% CP (1.16 kg/d), but no further increase was observed at 20% CP (1.16 kg/d). There were no effects of protein level on feed or caloric intake or on gain:feed ratio (P > 0.10). There was no main effect of dietary fat on gain (P > 0.05). There were main effects of dietary fat on caloric intake (P< 0.01) and efficiency (P < 0.01). Gain was not different in pigs fed 1 (1.10 kg/d), 6% added fat (1.12 kg/d) or 11% fat (1.15 kg/d). Daily caloric intake was increased as dietary fat level increased from 1 to 11% (10.5, 10.8 and 11.8 Mcal/d). Gain:feed ratio improved linearly with fat addition (0.34, 0.36 and 0.38). Serum urea, determined at the end of the feeding period, increased as dietary protein increased (P < 0.01), but was not affected by dietary fat. Experiment 2 was conducted in 2 trials of 25 individually penned pigs each (1 pig/pen, total 50 pigs). In each trial barrows (initial wt=85.3kg) were blocked by weight and assigned one of five experimental diets (0.50, 0.55, 0.60, 0.65, and 0.70 % lysine) with a constant lysine: ME ratio (1.833). The lowest diet, 0.50% lysine did not meet NRC requirements however all other diets met NRC requirements. There was main effect of dietary lysine on final body weight, gain, intake, feed efficiency, caloric intake, and lysine intake. All parameters measured increased linearly as %lysine was increased in the diet. Experiment 2 showed that even at a constant lysine: ME ratio swine performance characteristics can vary.