BREED AND SEX-DIFFERENCES IN FAT DISTRIBUTION AND MOBILIZATION IN GROWING PIGS FED AT MAINTENANCE

To study breed and sex differences in fat distribution and fat mobiliz ation in growing pigs during maintenance feeding, pigs of Norwegian La ndrace and Duroc of Canadian origin were compared. A total of 92 anima ls were fed to maintain constant body weight of around 58 kg over an e ight weeks period of maintenance feeding. Computed tomography was used for measuring body composition at weeks zero, four and eight. Landrac e pigs contained more internal fat (2.58 versus 2.20 kg) and less inte r/intramuscular fat (1.90 versus 2.26 kg) at start of the maintenance feeding period than the Duroc pigs (p < 0.01). Castrates contained mor e inter/intramuscular fat (2.15 versus 2.01 kg) and less subcutaneous fat (5.30 versus 5.58 kg) than gilts (p < 0.01). Fat was mobilized as feed was restricted to maintenance level. A greater proportion of fat from subcutaneous and inter/intramuscular fat depots was mobilized com pared to internal fat in both breeds and sexes (p < 0.001). Correlatio ns between subcutaneous and inter/intramuscular fat were higher (0.61- 0.90) than those between these depots and internal fat depots (0.26-0. 70). Reasons for breed and sex differences in fat distribution, and di fferences in availability between the fat depots during the maintenanc e period are discussed.