attributable to degenerative changes produced by the treatment, in laying hens

Transcription

1 Quarterly Journal of Experimental Physiology (1979) 64, Effect of Protamine Zinc Insulin on Feed Intake and Weight Gain in Broiler Chicks M. M. SHANAWANY,* A. K. AL-KHAZRAJI,. HAMED AND P. EDELSTEN From the Department of Animal Production, University of Alfateh, Tripoli, Libya (RECEIVED FOR PUBLICATION 1 MAY 1979) Ten-day old Robro broiler chicks were used to test the effect of daily subcutaneous injections of two insulin levels (5- and 1-IU. kg- 1 BW) administered for two different periods (5 and 21 days). Birds which received either 5- or 19-IU insulin significantly increased their feed intake over those of the controls (P < 5). However, the lower insulin dose was found to be more effective in increasing both the feed consumption and weight gain of the birds, especially if administered for a long period. Between the injection periods, the high insulin dose seemed to have a greater carry-over effect. On the other hand, the administration of 5- or 1-IU insulin for either 5 or 21 days had no effect on efficiency. Protamine zinc insulin has been shown to cause hyperphagia and weight gain in the rat and rabbit [MacKay, Calloway and Barnes, 194). Insulin-induced hyperphagia is believed to be due primarily to hypoglycaemia or increased glucose utilization [Anand, 1967]. In the domestic fowl, protamine zinc insulin produces hypoglycaemia, but this is normally associated with a depression of feeding activity and a subsequent fall in body weight [Lepkovsky, Len, Koike and Bouthilet, 1965]. The reduction in feed consumption caused by protamine zinc insulin may be attributable to degenerative changes produced by the treatment, in laying hens [Lepkovsky et al., 1965] and in 1-day old ducks [Evans, 1972]. Matei- Vladescu [1971] reported that the minimal insulin dose capable of inducing anorexia in chickens is 3IU. kg-1 body weight and that smaller doses ( 1-1. IU. kg-1 BW) induce a decrease of feed intake if repeatedly administered. This experiment was designed, therefore, to determine the effect of insulin level and the length of the administration period on the performance of growing broiler chicks. Methods One hundred one-day old Robro broiler chicks, obtained from the Ministry of Agriculture, were housed in wire floored electrically heated brooders. All birds were fed a starter commercial diet containing 23% crude protein and then a grower diet containing 17% crude protein. Feed and water were provided ad libitum and 16 h of light were provided daily. When 1 days old, the birds were divided into 3 groups. Groups A and B *Present address: Department of Agriculture, University of Reading, RG6 2AT, Berks, England. 291

2 292 SHANAWANY, AL-KHAZRAJI, HAMED AND EDELSTEN were of 4 chicks each, while group C was of 2 chicks. Five and 1 IU protamine zinc insulin/kg-1 body weight (Bovine, 4 IU/ml, Swiss Serum and Vaccine Berne) were daily administered subcutaneously to birds in groups A and B respectively. Birds in group C, acting as controls, were given similar volumes of physiological saline via the same route. After 5 days of daily injections, groups A and B were each divided into two subgroups (Al, A2, Bi and B2). Birds in Al and Bi ceased receiving injections whereas they were continued with those in subgroups A2 and B2 for a further 16 days. Feed intake and body weights were recorded at different periods as shown in Table I. Statistical examinations of the data were performed using the analysis of variance described by Snedecor and Cochran [1967]. Duncan's new multiple range test [1955] was used to separate significant differences between means. The experiment was terminated after 42 days when the birds reached the marketing age (52 days old). Results and Discussion Feed intake Feed intake data (g/day) are presented in Table I. During the first five days, when insulin was not administered there were no differences in the amount of food consumed by the different groups of birds. The effect, however, became pronounced after the 5th day of the injections. Birds which received either 5- or 1-IU insulin significantly increased their feeding activity over those of the controls. Birds in subgroups Al and A2 (5-IU for 5 days and for 21 days respectively) consumed approximately 356 g and 651 g more than the controls, during the 42 days of the experiment. Birds in subgroups Bi and B2 (1-IU for 5 days and for 21 days respectively) consumed about 496 g and 361 g more than the controls, during the same period. It is clear, therefore, that the low insulin dose was more effective in increasing the feeding activity of the birds than the high dose, especially if administered for a long period. Between insulin levels, those birds that received 5-IU insulin for 21 days had significantly eaten more than those which received 1-IU for the same period (P < 5). No significant differences were found between birds receiving 5- or 1- IU for 5 days. It seems reasonable to assume that the high insulin dose, used in this experiment, had a greater carry-over effect than did the low dose. This is partly supported by the fact that, between the injection periods, birds which received the high dose for either 5 or 21 days did not differ significantly in their feeding activity as shown in Fig. 2 (P< 5). On the other hand, those that received the low insulin dose for 21 days ate significantly more than those which received the same dose but for only 5 days (Fig. 1). The fact that 1-day old broiler chicks were used in this study could probably explain the discrepancy between the results obtained in the present experiment and those obtained and reported by Lepkovsky et al. [1965].

3 PZI EFFECTS ON CHICKS 293 'I : * * - * oooo Oc olo r- cni ice ri * * oo N r) m C _ot rw c... cn C1 ONrt 4t cn C'N o ~~r-c~ r1e~ooc~ C1~1r- n _ - _~ N CZ -o O C b t C clr"t Oc r e _~O O c enc en C.) Ct m o~~~) _- en m -o mx mx^ - cn ** "t e Z ~~C~~~~~Or._ *xd tn > N N ^ ^ n O r_ ON * n *too> a 1) = t _ m N m o ^ t en *> r - - CvC1NNC m -C4' -W cl C enc It "CCZC m o - ~~~C-) - C4 C~l -c~ c~ - -D O) O' 6 CDCl ~~~~~~~~~~~~~~~~j.-~ ~~~~~~~ $C)C)C)O* >N = <D - ~~~ ~ ~ ~ ~ ~ ~~~~~ClCC~~~~~~~ ~~~~w-', CZ)~ r.^ _ E U3 1)~~~14 C) C) 3 ~~~~~~~~ OL)== uo >,,=

4 294 SHANAWANY, AL-KHAZRAJI, HAMED AND EDELSTEN t / // 6( 4( EXPERIMENTAL PERIOD (days FIG. 1. The effect of daily subcutaneous injections of 5 IU protamine zinc insulin/kg-1 BW on average feed intake, (. S-IU insulin for 5 days, ( ) 5-IU insulin for 21 days, control (1( / /~~ (1 s1 ' I EXPERIMFN ITAL PERIOD idaysl FIG. 2. The effect of daily subcutaneous injections of 1-IU protamine zinc insulin/kg-' BW on average feed intake. (. ) 1-IU insulin for 5 days, (-- ) 1-IU insulin for 21 days, (_) control.

5 PZI EFFECTS ON CHICKS 295 Body weight gain Only in the overall experimental period was the weight gain significantly different amongst treatments as shown in Table I. Birds that received 5-IU insulin for 21 days were those to gain the most. Between the injection periods, birds in subgroup A2 (5-IU for 21 days) gained approximately 14g more than those in subgroup Al (5-IU) for 5 days). The difference in weight gain could primarily be due to the difference in feeding activity observed. These results are in complete agreement with those obtained in mammals. Feed efficiency Feed efficiency data, expressed as kg food/kg-' weight gain, are shown in Table I. The administration of insulin whether 5- or 1-IU for either 5 or 21 days had no effect on feed efficiency. References ANAND, B. K. (1967). Central chemosensitive mechanisms related to feeding. In: Handbook of Physiology, vol. 1, Ed. Charles F. Code, American Physiological Society, Washington, 459. DUNCAN, D. B. (1955). Multiple range and multiple F test., Biometrics, 11, EVANS, A. J. (1972). The effect of protamine zinc insulin on weight gain and fat deposition in the juvenile domestic duck. Quarterly J. Experimental Physiology, 57, LEPKOVSKY, S., LEN, R., KOIKE, T. and BOUTHILET, R. (1965). Effects of protamine zinc insulin on chickens. American J. Physiology, 28, MACKAY, E. M., CALLAWAY, J. W. and BARNES, R. H. (194). Hyperalimentation in normal animals produced by protamine insulin. J. Nutrition, 2, MATEI-VLADESCU, C. (1971). Insulin anorexia in chickens. Revue Roumaine de Biologie, Serie de Zoologie, 16, SNEDER, G. W. and CHRAN, W. G. (1967). Statistical Methods, The Iowa State University Press, Ames, Iowa, USA.