Lack of Growth Response of Eight-week-old Broilers to Certain Antibiotics

Abstract

Two experiments with day-old broiler chicks designed to study the efficacy of chlortetracycline, bacitracin, oxytetracycline and penicillin in growth promotion were conducted. The first experiment included five consecutive trials. In two trials, duplicate pens of 50 males per treatment were used, and in the other three trials, duplicate pens of 50 straight-run chicks were used. A typical broiler ration was used as a control. The four dietary treatments (mg./kg.) were: chlortetracycline, 25; bacitracin, 5; oxytetracycline, 25; penicillin, 5. The second experiment consisted of two trials with ten groups of 50 straight-run chicks per treatment. Five of these groups were fed a diet containing animal protein (as in the first experiment) and the other five groups were given a diet containing all-plant protein. The antibiotic levels were 0 and 50 mg. of chlortetracycline, bacitracin, oxytetracycline, or penicillin per kilogram of diet. All trials in both experiments were terminated after 8 weeks of dietary treatments. In the first experiment and in the second experiment with diets containing animal protein, antibiotics had no growth stimulatory effect. Chlortetracycline and penicillin did, however, stimulate a significant growth response when added to an all-plant protein diet. In general, heavier body weights were obtained from antibiotics with diets containing animal protein than with all-plant protein diets.

Broiler Chick Growth Response to Antibiotics, 1981–1982

“…This agrees with the observation of other investigators who have reported that antibiotics promote growth only when incorporated into nutritionally adequate diets (Hays, 1976). Our results are contrary to the results of Menge et al (1973) who found that growth stimulation by antibiotics increased with increasing levels of soybean meal. This may have been due to a nutrient sparing effect by antibiotics (Jukes, 1977).…”

“…Jukes (1977) cited several investigators on the sparing effects of some antibiotics on the requirement for a number of vitamins (thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, folic acid, B 12 , biotin, and vitamins A and D), calcium, and protein. Menge (1973) observed an increase in response to antibiotics with increased soybean meal in the diet. Menge (1973) observed an increase in response to antibiotics with increased soybean meal in the diet.…”

Effects of route and level of administration of procaine penicillin on the performance of broiler chickens

“…The experiments being reported were done to re-evaluate the effrcacy of penicillin as a growth promoter. In the initial two experiments, a level of penicillin (27.5 mg kg-') similar to levels used in some previously published studies (Menge 1973) (Blair 1990) (Tables 2 and 3). These results agree with those of Schaible (1966) and Dafwang et al (1987).…”

“…Le rendement 6conomique moins bon (6,6-15,6Vo de moins que dans le traitement t6moin) obtenu pour les poulets trait6s ir Ia p6nicilline 6tait attribu6 en grande partie au co0t de I'antibiotique. Dans l'expdrience 3, les r6gimes avec pdnicilline ont produit des poids corporels de 3,6 d 5,4% plus 6lev6s (P < 0,05) d 21 j que le r6gime t6moin, mais il n'y avait plus d'effet significatif sur le poids ir 42 j. Aucun niveau mesurable de r6sidus (limite de d6tection 100 pg kg-') n'a pu 6tre observ6 dans le foie, dans le rein et dans le muscle (poitrine et cuisse) des poulets du groupe 2 qui avaient reEt 27 ,5 mg de p6nicilline par kg durant les 42 (Menge 1973;Marusich et al 1978;Patel and McGinnis 1980). There is considerable controversy, however, about the biological mechanism(s) by which antibiotics improve the growth of poultry (Sunde et al 1990).…”