The early weaning of pigs IV. Comparisons of levels of antibiotic and sources of protein in diets for pigs weaned at 9 lb. live weight

Abstract

In Exp. 1 groups of piglets weaned at about 9 lb. live weight were fed one of three 29% protein diets up to 26 lb. live weight. These diets A, B and C contained 42, 20 and 0% dried skim milk, 15, 25 and 32% white fish meal and 22, 34 and 47% rolled oat groats, respectively. At 26 lb. all pigs were changed over to a standard 17% protein diet.The replacement of about one-half of the dried skim milk in diet A with white fish meal and rolled oat groats caused 4% faster growth from 9 to 26 lb. live weight, but the replacement of all the dried skim milk caused growth over the same weight range to be slower by 6%. The quadratic component of these treatment effects was significant at P < 0·0·25. The slower growth with the diet containing no dried skim milk was associated with a lower daily consumption of feed, and the improved growth rate with the intermediate skim milk level was probably associated with an improvement in food conversion efficiency. Treatment differences in food conversion efficiency before 26 lb. live weight, however, were not statistically significant. There were no significant carry-over effects of treatments upon performance from 26 to 50 lb. live weight.In Exp. 2 piglets weaned at about 9 lb. live weight were fed individually up to 40 lb. live weight. From 9 to 26 lb. antibiotic levels of 22, 45, 67 and 90 mg./lb. feed were compared, but from 26 to 40 lb. all pigs were fed a standard diet containing 18 mg. antibiotic/lb. In diets fed before 26 lb. the antibiotic was a mixture of 3 parts by weight chlortetracycline: 1 part by weight procaine penicillin. From 26 to 40 lb. live weight the antibiotic fed was chlortetracycline.Before 26 lb. live weight increases in antibiotic level caused average increases of up to 5% in growth rate and 4% in food conversion efficiency. Taken in conjunction with previous results the improvement in growth rate in favour of the highest antibiotic level was significant at P < 0·05.There were no carry-over effects of antibiotic level on growth rate from 26 to 40 lb., but there was the suggestion of a linear trend whereby each increase in antibiotic level fed before 26 lb. caused a decrease in food conversion efficiency between 26 and 401b. (P = 0·10).The results are discussed in relation to financial economies which may be made in diets for early weaned pigs.