#07-139

Complete

Date Full Report Received

09/18/2009

Date Abstract Report Received

09/18/2009

Investigation

Institution:
Primary Investigator:

Feed for the growing phase is the largest variable cost in pork production and these costs are on the rise. Thus, research that reduces feed required for pork production can result in substantial economic benefits to pork producers. It is well known that fast-growing lean pigs require less feed to reach market weight. However, ~34% of differences in feed intake between pigs are not related to growth. Thus, although past selection for lean growth has substantially increased feed efficiency, further increases are limited by differences in feed intake that are unrelated to growth and backfat. This feed intake net of growth and backfat is called residual feed intake (RFI). RFI is a unique measure of feed efficiency because it represents true differences in the ability of pigs to use feed energy for the metabolic processes of maintenance and growth. Factors that contribute to RFI have not been quantified for the pig but can include activity, behavior, digestion, heat production, maintenance requirements, immune-response, and protein and tissue turn-over rates, some of which can be related to meat quality. Current selection for feed efficiency cannot capitalize on differences that are unrelated to growth and backfat without the expense of recording feed intake. Thus, with the ultimate aim to develop genetic tests or indicator traits to select for feed efficiency without the expense of feed intake recording, the objective of this research project was to identify the main biological factors that contribute to differences in RFI. This research capitalized on a unique line of Yorkshire pigs that has been selected for reduced RFI for 5 generations and requires 7% less feed for the same rate of growth and backfat than its randomly bred control line. Results from the experiments that were conducted demonstrated that, compared to the control line, pigs from the efficient line: 1) had different feeding behavior as the Select pigs ate faster and less often, 2) tended to be slightly less active, 3) did not differ much in other behaviors that were studied, 4) were more efficient under both ad libitum and restricted feeding, 5) required less feed to maintain a constant weight, 6) tended to have lower internal organ weights, 7) had a lower fat content of the carcass, 8) had greater dressing percentage, 9) had better carcass composition with limited effects on selected measures of meat quality such as pH and water holding capacity, 10) had decreased carcass lipid content and postmortem protein degradation, 11) had physiological parameters that indicated less protein turnover and energy expenditure in muscle. In conclusion, although a substantial part of differences in feed efficiency as measured by RFI are related to differences in body composition, part of the differences appear related to pen and feeding behavior and to lower maintenance requirements and energy expenditures. Selection for RFI does not have major negative effects on meat quality.