PERFORMANCE OF SELF-FED PIGS, FROM TWO BREED POPULATIONS DIFFERING IN GROWTH RATE, FROM 18 TO 90 kg LIVEWEIGHT WHEN FINISHER DIETS CONTAINED 0 OR 2.2 ppm BAMBERMYCINS

Abstract

Seventy-two Lacombe and 72 Yorkshire pigs were separately assigned, at 18-kg average liveweight, to three replicates, each consising of three pens containing eight male castrates, eight gilts or four of each sex. A 16% protein, barley-wheat-soybean meal, diet was fed ad libitum until the pen weight averaged 34 kg. Subsequently, the eight pigs were divided between two adjacent pens and received a 14.5% protein, barley-soybean meal, diet supplemented with 0 or 2.2 ppm bambermycins (Flavomycin) up to 90-kg market weight. Growth rate in the Lacombe population was faster (P < 0.01) in both the growing (730 g/day) and finishing (906 g/day) periods than in the Yorkshires (547 and 767 g/day, respectively). Daily feed intakes were higher (P < 0.01) for the Lacombes (1727 and 3174 vs. 1392 and 2659 g/day, respectively) but gain:feed ratios and carcass measurements were similar in both breeds. Differences between castrates and gilts, for performance and carcass data, were relatively greater in the Yorkshires and appeared to be a result of the breed differences in feed intake. Results from mixed-sex pens were within the range of values obtained from unisex pens. Inclusion of bambermycins did not affect (P > 0.05) live performance or carcass measurements of pigs in either population, perhaps because the experimental conditions allowed a level of growth, in unsupplemented pigs, superior to those typical of commercial production. Key words: Market pigs, sex differences, live performance, carcass measurements, bambermycins, feed intake