A comparison of phase feeding and choice feeding as methods of meeting the amino acid requirements of growing pigs

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Abstract
Two experiments are reported in which a comparison was made of phase feeding and choice feeding as methods of meeting the changing amino acid requirements of growing pigs. In the first experiment, three feeding strategies were used: a system in which a single food (165 g protein per kg food) was offered throughout the growth period; a phase-feeding system, using five different treatments; and three choice-feeding treatments, in which the two diets offered differed only in their protein concentrations. The second experiment consisted of six treatments, three of which constituted a single feeding system, being a high, a medium, (the control) and a low protein food (240, 165 and 100 g protein per kg); there were two phase-feeding treatments, of three and five phases; and one treatment in which a choice was offered of the high and the low protein foods. In both experiments, group data were collected on Landrace × Large White pigs, sexes separate, during the growing period (30 to 90 kg). All pigs were weighed weekly, as was the amount of food consumed in each pen of 10 animals. Phase feeding improved food conversion efficiency (+4·4 g/kg) and caused a decline in both food intake (−45·3 g) and P2 backfat thickness (−0·4 mm) with each increment in the number of phases used. Results of the choice feeding treatments were not statistically significantly different from either the control or the phase feeding treatments. The intake of dietary protein was higher in the choice treatments than in the control (420 v. 370 g in experiment 1 and 345 v. 334 g in experiment 2). Where the two foods on offer differed only in protein content, pigs reduced the proportion of high protein food in the combination chosen by 0037 and 0·059 per week in the two experiments respectively, these linear trends being statistically highly significant. They were less successful in differentiating between the high protein food and maize, the proportion of high protein food chosen decreasing at a statistically significant rate of 0018 per week, but where the maize had not been supplemented with vitamins and minerals there was no significant trend in the way in which the pigs selected their diet, demonstrating the importance of the correct design of the two foods on offer in a choice-feeding programme.