No abstract

An experiment was designed to test whether pigs can differentiate between two foods differing in their protein content. A control food (160 g protein per kg food) and six choice-feeding treatments, in which the diets differed only in their protein concentrations, were used in the experiment. Pigs were given the following choices of protein: 220 v. 180; 220 v. 140; 220 v. 100; 180 v. 140; 180 v. 100 and 140 v. 100 g protein per kg food. Group data were collected on 240 Landrace x Large White pigs during the growing phase (30 to 90 kg), all pigs used being of similar genetic background. A 2 x 7 factorial design was replicated twice, with 10 pigs per pen, and with barrows and gilts being penned separately. Food bins for the choice-feeding treatments were placed side-by-side and an 8-day training period, in which the pigs were allowed access to only one of the two foods on alternate days, was used at the beginning of the trial to allow them to learn the position, taste and physiological effect of each of the two foods. All pigs were weighed weekly, as was the amount of food consumed in each pen. The conclusion reached was that growing pigs were able to differentiate successfully between two foods on the basis of their protein content and to change the selected diet to match their changing requirement for dietary protein. As a result, there was a significant reduction in food intake (P < 0-001) and in the P2 backfat thickness (P < 0-01) and the food conversion ratio was significantly improved (P < 0-001) compared with the control treatment.

Link to this article: http://journals.cambridge.org/abstract_S0003356100037491How to cite this article: M. M. V. Bradford and R. M. Gous (1992). The response of weaner pigs to a choice of foods differing in protein content. AbstractTwo experiments were designed to test the hypothesis that young growing pigs between 7 and 25 kg live weight are capable of selecting a diet which closely matches their changing requirement for amino acids, when offered a choke between two balanced foods differing only in their protein content. In the first experiment, three single-food treatments (8-6,11-7 and 17-4 g lysine per kg food) and one choice-feeding treatment (8-6 v. 17-4 g lysine per kg food), were used. In the second experiment, three foods of similar nutrient composition (approx. 14-7 g lysine per kg food) were formulated using different ingredients (fish meal, soya-bean oilcake meal and a combination of sunflower-, cottonseed-and groundnut-oilcake meals). These were fed either alone or as a choice with each other or with a low protein food (8-3 g lysine per kg food) to test whether palatability or anti-nutritional factors would override the selection based on protein alone. In both experiments, 10 pigs were housed per pen, with males and females being penned separately. One food bin with a central partition was supplied per pen, and an initial 6-day training period was used, in which pigs experienced each of the two foods on offer, separately, at daily intervals. All pigs were weighed weekly, as was the amount of food consumed in each pen. The conclusions reached were that growing pigs are able to differentiate successfully between two foods on the basis of their amino acid contents, and of changing the selected diet to match their changing requirement for dietary amino acids. However, one of the foods on offer appeared to contain either anti-nutritive factors or unpalatable components, and whereas the piglets performed as well on this as on the other foods of similar nutrient content when these foods were offered as the sole source of food, they actively selected against this food when it was offered as a choice, even if this meant their growing at a significantly slower rate than that of which they were capable.

Two experiments were conducted to test whether young pigs are capable of discriminating against a feed based on its nutrient balance (or protein value) and/or the presence or absence of anti-nutritional factors, and whether there is an order of preference. In each experiment 48 Large White x Landrace female pigs weighing 16.5±1.50 kg were randomly allocated to one of either 12 dietary treatments (Experiment 1) or 14 dietary treatments (Experiment 2) and kept on the treatment diets for four weeks. In Experiment 1 there were four single feed control treatments, four two-feed choice treatments and four three-feed treatments. The choices were between soyabean oilcake vs. cottonseed oilcake as the main dietary protein source, and between diets that have a higher (balanced) versus lower (unbalanced) proportion of amino acids compared with the balance of amino acids in ideal protein. Experiment 2 had similar choices to Experiment 1, but also included treatments with 1% added tannin. The results showed that when young pigs were given a choice of diets their preference was firstly against potentially harmful substances in the feed (e.g. tannin) or an anti-nutritive factor (e.g. cottonseed oilcake), and then for better-balanced or higher protein-value feeds.

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.