Food ingredient selection by growing and finishing pigs: effects on performance and carcass quality

Various levels of rapeseed meal in weaning pig diets from weaning to finishing periods

OBJECTIVE

This experiment was conducted to investigate the influence of rapeseed meal (RSM) supplementation in weaning pig diet on growth performance, blood profile, carcass characteristics and economic analysis on weaning to finishing pigs.

METHODS

A total of 120 cross bred ([Yorkshire×Landrace]×Duroc) weaning pigs were allotted to 5 treatments in a randomized complete block design. Each treatment had 4 replications with 6 pigs per pen. Five different levels of RSM (0%, 2%, 4%, 6%, and 8%) were used as dietary treatments.

RESULTS

Overall, no treatment showed significant differences in growth performance with increased dietary RSM levels. The concentration of blood urea nitrogen (BUN) decreased as dietary RSM levels increased in 6 weeks (linear response, p<0.01). Total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triiodothyronine, and thyroxine showed no significant differences, neither were there any significant differences in the immune response (IgG and IgA). As the dietary RSM levels of weaning pig diet were increased, no differences were found among dietary treatments upon performing proximate analyses of the pork after finishing. The influence of RSM supplementation on nutrient digestibility and nitrogen retention were not affected by dietary RSM levels either. With increased dietary RSM levels in the weaning pig diet, no differences among dietary treatments were found after performing proximate analyses of the pork's physiochemical properties. In addition, there were no significant differences observed in pork colors, pH levels, and economic benefits.

CONCLUSION

Consequently, this experiment demonstrated that weaning pig's diet containing RSM influenced BUN concentration, but there were no detrimental effects on the growth performance of weaning pigs with up to 8% RSM in the diet.

Diet selection in pigs: choices made by growing pigs when given foods differing in nutrient density

Two experiments were conducted to corroborate or refute the theory that animals will choose a food that will allow them to use it with maximum efficiency. Pigs have been shown to utilize foods of high nutrient density more efficiently than those of low density, so the choices made by pigs when offered such foods could be used to test the above optimization theory. In experiment 1, 48 Large White × Landrace gilts were used, for an 8-week period starting at 22 kg live weight, while in experiment 2, 48 boars of the same cross but of a genetically improved strain were used from 24 to 60 kg live weight. In both experiments use was made of high nutrient density summit foods which were used alone, or diluted in the ratio 80 summit: 20 milled sunflower husk to provide the low density foods. In experiment 1, the high density diet (HI) contained 7·5 g lysine per kg and 13·20 MJ digestible energy (DE) per kg, whereas in experiment 2 two summit foods were formulated, the first diet (H2) was offered for 3 weeks from 24 kg live weight and the second (H3) followed until 60 kg live weight. Foods H2 and H3 contained 11·0 and 8·40 g lysine per kg respectively and 15·0 and 14·0 MJ DE per kg, respectively. Both experiments made use of a high (H1 and H2, respectively) and a low nutrient density (L1 and L2, respectively) control treatment in which pigs were given ad libitum access to H1 and H2/H3, and L1 and L2/L3 in experiments 1 and 2 respectively (no. =4). In addition, a medium density treatment (Ml) consisting of a 50: 50 mixture of H1 and L1 (no. = 4) was given in experiment 1. Two choice-feeding treatments where used in both experiments, the first in which H1 and H2IH3 were placed in the left bin (CL1 (no. =18) and CL2 (no. = 20), respectively) and the appropriate dilution diet in the right bin, and the second in which H1 and H2/H3 were placed in the right bin (CR1 (no. = 18) and CR2 (no = 20)). There were no differences in average daily growth rates between treatments within experiments but there were significant differences (P < 0·05) in food intakes and efficiency of food utilization (FCE) between treatments. The highest intakes and lowest FCE were obtained on the L1 and L2 treatments while the lowest intakes were recorded on the choice-feeding treatments. There were no significant differences in FCE neither between H1, CL1 and CR1 nor between H2, CL2 and CR2. Only in experiment 1 were there significant differences (P < 0·05) between choice-feeding treatments on the basis of the position of the food bin but there was no preference for a particular position. The results indicated that pigs were able to differentiate successfully between two foods on the basis of their nutrient density, that bin position was not used as a cue in the choice made, that a small amount of the ‘unwanted’ food was consumed throughout the experiment and that the diet selected maximized FCE.

Diet selection by groups of pigs: effect of a trained individual on the rate of learning about novel foods differing in protein content

Choice feeding could be more widely applied with pigs if the initial variability between individuals in diet selection was overcome and there was a better understanding of the factors affecting the learning process in groups. In six replicates, two groups of four pigs (live weight 35·5±0·95 kg) were formed containing either an individual trained to select between two foods or an untrained control animal. The groups were offered food L (130 g crude protein (CP) and 5·6 g lysine per kg) and food H (260 g CP and 15·5 g lysine per kg) in two troughs as a choice for a period of 14 days. Food intake was measured twice daily for the first 3 days and then daily. The pigs were weighed three times per week and feeding behaviour was video recorded on the 1st and 3rd days of grouping. There was no effect of the trained pig on the performance of the group over the 2-week period (daily live-weight gain: 1·19 kg and 1·21 kg for the pigs in control or trained groups; s.e.d. 0·057). Within the first 8-h period of food recording pigs in groups with a trained pig selected a diet similar to that of the trained pig, whereas those with a control pig showed initial variation in selection before adopting a pattern in favour of one food, usually after about 3 days. In the first 24 h the pattern of visits to the troughs by the naïve pigs followed that of the trained pig whereas the pigs in the control groups initially visited the troughs at random. After 3 days the difference between the groups was small and largely non-significant. In five of the six replicates the groups selected a diet comprising 0·65H: 0·35L, which was similar to that expected from their lysine requirements. The two groups in the other replicate selected more of food L and this and the other findings are discussed in relation to the influence of social learning, previous nutritional experience and food composition on diet selection by pigs.