Effect of nutrition and environmental variations on choice feeding of broilers.

Abstract

EFFECT OF NUTRITION AND ENVIRONMENTAL VARIATIONS ON CHOICE FEEDING OF BROILERS I.M. MASTIKA and R.B. CUMMING* Summary Two experiments were carried out to determine the possibility of alleviating heat stress on broilers performance by offering the chickens co+lete dietsor free choice of diets with extra illumination. Three xeek old broiler cockerels were divided into groups and randorrily assigned in two co~ltrol tetiperature rooms. In one room, the temperature was held at a constant 20+l�C dur,ing the cool period (4 pm - 9 am) and 33+l�C during the ~'lot pried (9 am - 4 pu). I each room, ten groups of chickens were randotilly distri.SuLed to each of two nutritional treatments, either a complete finisher diet or a choice of whole sorghum and protein concentrate. Feed and water xerre offered ad libitum, and light was provided for 24 hours in the first exgerir~nt and for 16 hours in the second. When light was provided for 24 ilourrs the cocxerels in the hot cyclical temperature regimen were able to fully cml;>ensate for their reduced feed intake of the complete diet and body weight and feed efficiency were not adversely affected. However, when 16 hours ii& was provided a 3% depression on body weight was recorded. In both exgerL3entsr the choice fed chickens housed in the cyclical tesperature regii;len consuned significantly (P < 0.05) less energy but maintained their proteiil iiltake when compared to the chickens fed either the conplete diet or 0 free choice at the constant 20 C temperature. Body weight of the choice fed chicxens were not affected by heat stress although light was provided only 16 hours. Feed efficiency of the choice fed chickens was consistently better than those fed a complete diet when the chickens were exposed to heat stress. I INTRODUCTION l The deleterious effect of high environmental temperatures on broilers pcrfornance have been reported widely (Adam and Rogler, 1368; El-Zusseiny, 1979; Deaton et al. 198% Generally, as ambient temperature increases, growth rate decreases and this is due largely to reduced feed consusption. Xany atteiilpts have been made to overcome this problem by reduciu the heat increnent of the diet with fat supplementation (Dale and Fuller, 1979), i;;lprovins the aaino acid balance (Waldroup et al. 1976)) improving mine acid:IE ratios (Sinurat and Balnave, 19851, increasing the protein content of `the diets (Cowan and Xichie, 1978, cycled the temperatures (Deaton et al. 1984); Dale and Fuller, 1980) and chan@g light intensity (Savory, 1973). All the above reports deal with conventional complete diets and the results are controversial. Aastika and Cum.ming (198?a, 1981b) reported that broiler chickens, inoused in experimental cages, could adequately balance their diets when they xere offered a choice of whole sorghum and protein concentrate and grew as well as broilers offered complete diets. However, there are several reports to the contrary in this area (Maurice et al. 1979; Scholtyssek, 1982) and these differences uay be due to the different approach used in the experiment. Cowan and Echie (1977) reported that choice fed broilers kept at constant tenperatures of 16, 22, 26 and 31�C grew at significantly slower 3 Department of Biochemistry, Microbiology and PJutrition, University of New En&and, Armidale, New South Wales 2351 m-&s thaa broilerq fed conplete diets in the sme environmed. Agal;? to tile contrary, Xastika and Cumming (1981b) reported that t>roiler chickens fed free chgice g--e:;5 as well as the complete fed birds when they were kept at eit,?ler 29 Z or 30 C constant temperature. They further noted that the choice feel ;~irds acre signifigantly more efficient in food conversion than tile co@.ete fed Sroiler-s at 30 C constant temperature. 'JnOer natural conditions9 ambient temperature is not consLant WA IIucWates considerably and consequently the energy requiremnt of tize cUc&n throughout the day fluctuates. Theoretically, by offering the chickens a c:qoice of grain as source cf energy along with protein concentrate, Uickens should have ar;lple opportunity to adjust their energy in varying environnental conditions. Ti?e current experiments aimed to investigate further tne possisiiity of alleviating the growth depressing effects of heat stress by offering chickem a Moice of whole grain and protein concentrate in different enviroments. II. HATERIALS AlUD METHODS (a) Chickens and management Coi:Xilercial nale broiler chicks (Hyline) were used in botn experi:llcnLs airti XW~ vaccinated by the eye drop method at one day old with A3 infectious tii~0nchiti.s vaccine and by the same uethod with Vic-s infectious DroncXtis vaccine at 14 days of age (Cuming, 1983). The chickens were reared ii? cxetric brooder and during the first ten days of age were fed a co;;mercial c:iici;en star&l- cmmble diet. Fro;;l 11 to 21 days of age, hi,-ds were %r'aiiledl' on c;loice feedins by offering them whole sorghum along witi? protein mxxntrate (Table 1)'. _ -.w~,-r...----^ --- - ._ .Table 1 Diet composition In experiment 1, a total of one hundred three week old birds were selected from 200, wingbanded and divided into twenty groups of five birds which vere then placed in wire cages (75 cm x 75 cm x 38 cd. Ten such groups iqere assigned to each controlled temperature room. In experiment 2, one hundred and twenty 3 week old birds were sisiiarly selected from 200, wingbanded and divided into 20 groups of 6 birds. Ten such groups were randomly distributed to each controlled temperature room. In each room, ten or' the two treatments Moice of whole sorghum and gater were provided groups of chickens were randomly distributed to each a complete crumble finisher diet (treatment 1) and a and crumble protein concentrate (treatnent 2). Feed ad libitum throughout. A C an (4 (b) Experimental rooms Two controlled temperature rooms measuring 5 x 6 m wide were used. cyclical tenperature regimen was employed in one room, ranging from 2041 0 during the cool period (4 pm - 8 am) and 33kl'C during the hot period (8 4 pm) and the cool room was held at a constant 20+l�C throughout the exyeriaent. Light was provided for 24 hours in e:periment 1 and 15;hours aiil - 8 pm> in experiment 2. (c) Diets Composition and calculated chemica=position of the diets use3 in these expertients are presented in Table 1. The complete finisher diet and protein concentrate were in crumble form and sorghum was offered8whole. (d) Observations Feed intake was measured twice a day, between 8.30-9.00 aril in the ldornins and 3.30-4.00 pn in the afternoon. Chickens were individually wei&hed at :Jeekly intervals. Experiment 1 was run for four weeks and experirsent 2 for three week. At the end of each experiment, two representative birds (nearest to the mean weight from each group were killed and dressed for carcass and organ weight evaluation. (e) Statistical analysis Ali data were subjected to analysis of variance (Snedecor and Cochran, 1957) and when significant treatment effects were found, Duncan's multiple ran&e test was used for comparison (Steel and Torrie, 1960). III. RESULTS (a) Exneriment 1 Uhen light was provided for 24 hours, neither feeding system nor room terqerature had any effect on body weight, feed consumption or feed conversion ratio of the chickens (Tables 2 and 3). Broilers fed the complete diet and dept at 20�C roord temperature consumed 20% more feed than those kept in the cyclical temperature regimen during the hot period (9 am - 4 pm) (Fiii;. 1). However this depression of feed intake was compensated for by the chickens during the cool period (4 pm - 9 am) (Fig. 11, when they consumed more feed. Table 2 Performance of choice fed broilers kept in different environments with 24 hotits.illuminat$on Table 3 Feed, protein and calorie intake of choice fed broilers kept in different environments with 24 hours illumination *. . . % . - . Choice fed broilers kept at 20 C consumed 30% more grain than Ixose kept in the cyclical temperature regimen duriw the hot period (9 u - 4 pis) @`is. 2)) but during the cool period (4 peal - 9 ain) the sorghun iAxkeowas relatively constant (Fig. 3). The choice fed broilers kept at constant 20 C consuxd sigificantly (P < 0.05) more calories than those kept in the cyclical teqerature regtien. Overall, the choice fed broilers kept at either a constant 20 0 or in the cyclical temperature regimen consumed as much protein as their complete diet counterparts (Table 3). Carcass, pad fat or abdo:;linal fat xere not affected by either feeding system or rooa temperature (Table 4). 0 Table 4 Carcass, fat and organ weight (%) of the choice fed broilers kept 'in.differen~`environments with 24 'hour&`iJ.lum$Q&tion The hearts of the chickens kept at the constant 20 C room temperature I-JW~ significantly (P < 0.05) heavier than those kept in the cyclical tenperature regiaen, irrespective of dietary treatment. The livers and gizzards of the choice fed birds were significantly (P < 0.05) heavier than those fed a complete diet, irrespective of room temperature. (b) Experiment 2 Total feed intake of the birds fed either the complete diet or free-choice and kept in the cyclical temperature regimen were reduced `Py 7.5% . coLApared to those held at constant 20�C (Table 6). Body weights of the c,iicxens fed the complete diets and housed in the cyclical tenperatuge regitien kjeye reduced 3% compared with those similarly fed in the constant 20 C, zlt'~ou-h this reduction was not significant (Table 5). :. 0 Table 5 Performance of choice fed broilers kept in different environments with 16 hours illumination 0 Table 6 Feed, protein and calorie intake of the choice fed broilers kept in different environtients'tjith 16 hour&,iIlumination ... the hot period (9 am - 4 prd), broilers kept in the cyclical reCaen and fed the col;lplete diet consumed 29% iess feed ii?an z:&e kept at constant 20�C (Fig. 4). Siniilarly, the choice feel birds, iturin& tm hot period, consmed 34% and 8% less sorghum and protein concentrate +zsdectively than those kept at a constant 20�C (Fig. 5). During the cool ;Zl*iod (4 pz - 9 m) the choice fed birds consuned as nuch SO~$UU as, and 7% :;lore protein concentrate than, those kept in a constant temperature (6X;. 6>, ilUl9.Q 't~L.ji~;3ratul--e 0 The uirds kept at the constant 20 C (and fed either a coLiplete diet or I'xe &mice) consuned significantly (P < 0.05) xaore calories than those housed ii2 tfze cyclical tenperature regimen of both the cmplete and choice diets. The protein consunption in all treatment s was sirrlilar CP > 0.05) (TabEe 5) excer>i for those kept in the cyclical temperature regimen and fed a coxplete A diet when it xas significantly (P < 0.05) lower. Overall, the choice r'ed oir~ds iloused in the cyclical temperature resiiilen converted feed significantly (P <SE) 1;3orc efficiently (Table 5) than those housed at a constant kqerature and fed either a conplete diet or free choice. Carcass, pad fat or abdominal fat weight and sinali intestine len&tins were not affected by either feeding systelsl or rooril tmperature (T&Ce 7). Table 7 Carcass, fat and organ weight (%) of the choice fed broilers kept in different environments with 16 hours illumination Gizzards of the choice fed birds were significantly (P < LO5) heavier than those fed a cotiplete diet. The hearts of the birds kept in the cyclizzl &ilgerature re;iaen were significantly (P < 0.05) lighter than those xepi; at cmstant ZOOC. IV . I)ISCUSSION In broiler chickens fed conventional diets the depression of feed iEtaLe ciurins ilot xeather is associated with a depression of body weigrlt (Adam and 2oL$ler, 1gis8). The results of these experiments suggest that the depression of feed i:ncl, &<e which caused loss of weight due to heat stress (33 0 C from 9 ai;1 - 3 PA) :~ay be overcoiae 'by providing the c'nickens with continuous li$l-L and .. 3rx9;lnj; the rooti temperature down to 20+l�C for the rest of the 24 houi-s (1 1). 0 Xlen 16 hours light was provided only from 4 ati to 8 p;;lr al iA0ugi-i colz+xlsation of feed intake did occur (Fig. 41, it was not sufficient to coLAigeixsate toi;ally for the depression of feed intake wilich occurred during t,'re :lo-t Geriod (Fig. 4), resulting in a 3% depression in body weight of broilers fz,A tile co;;;plete diet (Table 5). 1 +i A ' I* c* In 30th experiments, the choice fed broilers in the cyclical &dperature x~L.~en convu~;zed significantly less sorghum (30-34s) during the hot period ('j CiLi - 4 pa) than those kept at a constant 20�C (Figs. 2 and 5). Hoaver (Figs. 3 and 6) the birds ir;, ti?e syclical e,;;?erature reginen consumed as much sorghum as those in the cooler 2D'C for t tile sale period. An interesting finding is that the choice fed chickens in the cjrciical .i;el.l~~~rz.~ureore~~~en consumed as much protein as the broilers ;:ept at a CUi+:StZlt 20 C. This pattern of feed intake clearly shows that choice i'ed iJ;a()-i1 fx/ chici;ens have&he ability to regulate their feed intaLe firstly to ;;;si;isfy 'clleir energy requirement9 as reported by Llastika (1981); Szstika and Cuzin~ (lNla,b), but further to regulate their protein requiredents. This Leas aost clearly demonstrated in the second experiment Wire tile cp1.0 jJJ .e fed broilers reduced their protein concentrate intake'by 8% cJuri:l;; 'the il0-L period, w;len cotipared with choice fed birds kept at constant 2i) C. Durin; L;E cool period these birds in the cyclical temperature re;:i:i:en consu;~$ 7% ;;;();-e protei n concentrate than their counterparts kept; at a constant 23 C. rl'tie otiler interestin; point is that in the cyclical temperature re&en t*f TX choice fed clrickens converted feed more efficiently than those fel;f. tile co;l?iete diet (Tables 2 and 5). This is in agreement with the work of SiastL<a (1931) Wo showed that broiler cockerels housed at a constant 30�C converted ?ced i-nope efficiently if choice fed than if offered complete diets. l'kis increased efficiency may be due in part to the fact t:lat the ccxxlete diet erJpties much faster from the gizzard and intestines than choice h fed birds eating whole grain (Xastika, 1981). This may result in some put-ien'c- 'De-jnT incompletely absorbed by the chickens, Further Wtniosh et il. 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