Effect of controlled feeding on growth, efficiency and carcass composition of grower pigs from a selected breeding line

Abstract

Commercial pig production makes use of pigs produced by breeding companies through deliberate breeding plans and selection strategies. This leads to ongoing improvement in growth performance and efficiency of pigs. In order to take full advantage of these genetic improvements the environmental management and nutrition should meet the requirements of the improved pig genotypes. The objective of this study was to determine the growth performances and carcass characteristics of entire male grower – finisher pigs from a specific boar subjected to different feed level allocations and housing systems under South African circumstances. The terminal sire used to produce this male offspring was bred by Topigs Norsvin South Africa and exhibited superior growth performance. This boar achieved an average test gain of 1.740 kg per day. The pigs were randomly allocated to a feeding treatment from an age of 15 weeks. They were either fed on an ad libitum basis or a daily controlled amount. This controlled amount of feed was calculated to match their growth potential to produce optimal growth. Furthermore the animals were randomly allocated to one of the two housing systems. The feeding treatments were tested under individual and group housing systems. Controlled feeding led to significantly lower growth rates. This can be seen in the significantly (P< 0.01) higher average daily gains (ADG) and 21 week empty bodyweights. The difference in growth rates was due to the difference in nutrient intakes. A strong linear relationship was found between the available lysine and metabolisable energy intake and the ADG achieved. The efficiency with which growth took place was significantly (P< 0.01) higher under the controlled feeding treatment in the individual housing system. The feeding treatment applied had no significant effect on the feed efficiency in the group housing system. The difference in efficiency between the two feeding treatments was ascribed to the difference in adipose tissue deposition. A significantly (P< 0.01) lower P2 backfat thickness was recorded under the controlled feeding treatment. Carcass parameters were significantly affected by the feeding treatments. Control fed pigs produced carcasses with significantly (P< 0.01) higher lean meat percentage and significantly (P< 0.01) lower fat percentage, warm carcass mass, cold carcass mass and carcass compactness. The housing system in which pigs were kept, significantly affected their feed intakes when ad libitum feeding was applied. The lower (P< 0.01) feed intakes achieved in the group housing system led to the difference between the feeding treatments being smaller than that of the individual housing system. This explains why the difference in performance between feeding treatments in the group housing system was smaller than in the individual housing system. Growth rates and empty bodyweights were only affected when the pigs were fed ad libitum. This is demonstrated in the higher (P< 0.01) ADGs and empty body weights achieved in the individual housing system. Individual housing led to significantly higher P2 backfat thickness levels (P< 0.01) throughout the experiment when data from the two feeding treatments were pooled. Pigs exposed to the group housing system produced lighter carcasses than those kept in the individual housing system. In conclusion the offspring exhibited a higher growth rate and higher slaughter weight when fed on an ad libitum basis. Ad libitum feeding led to heavier and leaner carcasses and a higher income in the individual housing system. Although ad libitum feeding led to a higher growth rate and heavier carcasses in group housing no significant difference was found in the net income. When the offspring was tested in the individual housing system, controlled feeding led to a slower but more efficient growth than achieved with an ad libitum feeding regime. Feeding regime had no effect on the efficiency of growth of pigs in the group housing system. The level of feed allowance in commercial situations should match the growth potential of the pigs being used. Furthermore the best feed allowance should be calculated by taking into account effects on growth rate, feed efficiency and carcass composition. Based on these the best economical level should be determined and accurately applied.