PERFORMANCE OF GILTS AND BARROWS FROM THREE BREEDING GROUPS MARKETED AT THREE LIVEWEIGHTS WHEN OFFERED DIETS CONTAINING TWO LEVELS OF DIGESTIBLE ENERGY FOR A LIMITED PERIOD PER DAY

Abstract

The influence of high (HE) and low (LE) digestible energy diets fed for two 1-hr periods per day on the performance of Duroc × Yorkshire, Hampshire × Yorkshire, or Yorkshire × Yorkshire pigs marketed at 68, 91 or 114 kg liveweight was studied. Under the feeding system employed, daily feed intake averaged 2.01 kg and did not differ between dietary groups. The HE diet containing 3652 kcal DE/kg improved (P < 0.01) rate of gain and feed conversion compared with the LE diet containing 2757 kcal DE/kg. DE requirement averaged 9.89 Mcal/kg gain and did not differ between dietary groups. Carcasses from pigs fed the HE diet had higher dressing percentage, greater total backfat thickness, and lower ratio of loin to backfat thickness, percent lean in the ham face, ham as a percent of carcass and Canadian ROP score.Barrows had a higher daily feed consumption and average daily gain but were inferior to gilts in feed conversion. Gilts were superior to barrows in all carcass measurements except dressing percentage, where differences were nonsignificant.Breeding groups differed (P < 0.01) in rate of gain, feed conversion, and dressing percentage and their carcasses differed in loin area and length. Feed required per unit gain increased with increasing market weights but gain did not differ. With increasing market weights, dressing percentage, length, loin area and total backfat thickness increased while the ham as a percent of carcass and ROP scores decreased. Market weight did not significantly alter the ratio of loin area to total backfat, suggesting that the present Canadian carcass grading standards should be extended to cover a greater weight range without penalty.Major significant interactions for average daily gain existed between diet by sex and diet by breeding group and for feed conversion between diet by sex. The data indicate that sex and breeding background of market pigs are important considerations in formulation of energy requirements. Use of LE diets or of feeding methods that restrict DE intake may mask potential differences that exist between groups.