CARCASS CHARACTERISTICS OF BROILER CHICKEN STRAINS FED DIFFERENT LEVELS OF FEED RESTRICTION DURING ELEVEN TO SEVENTEEN DAYS OF AGE.

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1 CARCASS CHARACTERISTICS OF BROILER CHICKEN STRAINS FED DIFFERENT LEVELS OF FEED RESTRICTION DURING ELEVEN TO SEVENTEEN DAYS OF AGE Olawumi Simeon Animal Breeding and Genetics Unit, Department of Animal Production and Health Sciences Ekiti State University, P. M. B. 5363, Ado-Ekiti, Nigeria Abstract The effect of short-term feed restriction during starter phase on the carcass characteristics of Anak Titan and Arbor Acre broiler chickens were studied during a 49d production period. Ninety day-old broiler (45 chicks each of Arbor Acre and Anak Titan) chicks were purchased from local hatcheries and were reared in groups on strain basis for 10 days to acclimatize. At 11 th day, all the chicks on strain basis were randomly distributed into nine experimental units under three treatments having five chicks each. Analyzed data showed that both strains had similar mean values in live weight and other carcass yields regardless of the treatment applied. Neither of the strains recorded mortality during the experiment meaning that the two strains demonstrated some level of tolerance to feed restriction on a short-term. However, there was significant effect of strain on abdominal fat with Anak Titan broilers having more fat pad than Arbor Acre when exposed to similar feed restriction treatment. With regards to the three levels of feeding regimens applied, full-feeding and 85% full-feeding recorded similar mean values, but, higher and superior to 75% full-feeding regimen. That is, birds placed on 85% feed restriction gained as much weight as their fully fed mates following refeeding. Strain x treatment interaction significantly affected live weight at maturity and all the carcass yields measured. It is suggested that for maximization of feed utilization and profitable broiler meat production in the humid tropics, Arbor Acre and 85% ad libitum for short-term during starter phase could be considered. Key words: strain, feed restriction, carcass, Arbor Acre, Anak Titan, broiler chickens INTRODUCTION The recent research efforts to improve genetic potentials of broilers for increased growth rate has led to increased body fat deposition, high mortality and high incidence of metabolic diseases and skeletal disorders (Zubair and Leeson, 1996). To minimize these negative effects of genetic selection associated with fast growing broilers that consume feed ad libitum, the concept of feed restriction becomes imperative in order to grow the industry and satisfy the animal protein requirements of the citizenry. Some investigators observed that feed restriction has significant effect on body fat of broilers (Yu et al., 1990). Also, broilers fed diluted diets were found to be significantly affected in performance (Sahreel and Shariatmadari, 2007). In addition, feed restriction in Ross 308 broilers in terms of diet dilution was found to have significant effect on body weight, body weight gain, feed conversion ratio, gizzard, fat pad and spleen (Fanooci and Torki, 2010). With regard to visceral organs, the authors reported that diet dilution had no significant effect on breast, thigh and drumstick, liver, lung, pancreas and bursa weights. Similarly, previous researchers observed significant effect of diet dilution on live weight, carcass weight, abdominal fat percent, breast and thigh percentages (Sahreel and Shariatmadari, 2007). In agreement with previous study, Azarnik et al. (2010) also found significant effect of feed restriction on body weight gain, feed consumption and feed conversion ratio. In addition, the researchers reported positive effect of feed restriction on carcass, breast and abdominal fat weights. 261

2 However, previous study found that prolonged feed restriction depressed relative weight of breast muscle (Acar et al., 1995). In addition, other authors found a negative effect of prolonged feed restriction on thyroid gland activity and plasma triiodothyronine concentration, respectively (McMurtry et al., 1988; Yahav and Plavnik, 1999). There are many options of feed restriction available to farmers and these include intermittent feeding, skip-a-day feeding, diet dilution, time of restriction and quantitative feed restriction (Samara et al., 1996; Lee and Leeson, 2007; Sahreel and Shariatmadari, 2007; Benyi et al., 2011). It was noted that all these different ways are meant to improve efficiency of feed utilization and weight gain and reduction in mortality rate. Feed constituted 70-75% of the total cost of production in a broiler enterprise (Mahmood et al., 2005), and whatever method to reduce this high input component should be considered for the good of the farmers and overall interest of the industry. It had been reported in literature that feed restriction in broilers can help improve feed efficiency, reduce feed cost and mortality in addition to producing chicken meat at affordable price (Zubair and Leeson, 1996). On the negative side, feed restricted birds are hyperactive; exhibit increased pacing before the expected feeding time and increased drinking and pecking at non-food objects when compared with ad libitum fed birds (Kostal et al., 1992; Savory et al., 1992). In view of the contrasting reports on effect of feed restriction on broiler carcass characteristics, the present study was undertaken to examine the effect of quantitative feed restriction at starter phase on live weight and carcass traits of two strains of broiler chickens reared in the derived savannah zone of Nigeria. MATERIALS AND METHODS The study was carried out at the Teaching and Research Farm, Ekiti State University, Ado-Ekiti from September - November, Ado-Ekiti is situated along latitude and North of the Equator and longitude and East of the Greenwich meridian. The city falls under Derived Savannah zone. The city enjoys two separate seasonal periods namely, Rainy (May-October) and Dry (November- April) seasons. Ninety, one-day old broiler (45 chicks each of Arbor Acre and Anak Titan) chicks were purchased from local hatcheries and were reared in groups on strain basis for 10 days (acclimatization period). The chicks were kept under the same management conditions such as light, space, temperature, ventilation and relative humidity. They were brooded on the floor bedded with dry wood shavings, and the temperature of the house was controlled to meet the chicks requirements. On arrival, multivitamins were added to water together with prophylactic dosage of antibacterial drug. Fresh and clean water was available ad libitum. The chicks were vaccinated against Newcastle and infectious bursa diseases at recommended dose, and at specified ages. At 11 th day of age, all the chicks on strain basis were randomly distributed into nine experimental units (replicates) under three treatments having five chicks each. These experimental units were allotted to three treatments per strain (three replicates/treatment), that is, T 1 (ad libitum), T 2 (85% ad libitum) and T 3 (75% ad libitum). The restricted feeding lasted 7 days, that is, 11 th -17 th day. Thereafter, the birds were restored to full feeding till the end of the experiment (49 days). During the adaptation period all the chicks were fed ad libitum, but from 11 th to 17 th day, T 1 (T 1 R 1, T 1 R 2, T 1 R 3 ) birds alone were given full feed, while T 2 (T 2 R 1, T 2 R 2, T 2 R 3 ) and T 3 (T 3 R 1, T 3 R 2, T 3 R 3 ) birds were given 85% and 75% ad libitum, respectively. The birds were fed starter mash (1-4 weeks) containing 22%CP and 3000Kcal/KgME, while between 4-7 weeks they were given finisher feed containing 20%CP and 3100Kcal/KgME. 262

3 At 49 th day of age, one bird per replicate, that is, three birds per treatment on strain basis were randomly selected after starving them overnight for carcass evaluation. The birds were numbered and weighed individually to obtain live body weight and thereafter, slaughtered, bled, scalded and plucked. After the removal of feathers, the carcasses were eviscerated and dissected manually into various parts such as breast muscle, back muscle, drumstick, thigh muscle, wings, legs and giblets (heart, liver and gizzard). The different parts were weighed using sensitive scale and were expressed in grammes. Data collected at 49 th day of age include live body weight, slaughter weight, dressing weight, eviscerated weight, carcass weight, breast weight, back muscle weight, drumstick and thigh weights, neck and head weights, wing and leg weights, leg length, intestinal length, liver, lung, heart, gizzard and abdominal fat weights. Statistical Analysis The data collected were analyzed by the analysis of variance technique in completely randomized design, while the differences between means were separated by Duncan New Multiple Range Test as per SAS(2001). The appropriate statistical model used was: Y ijk = µ + G i + R j + ɛ ijk Y ijk = observation on k th population, of i th strain and j th feed restriction µ = common mean G i = fixed effect of strain (i=2) R j = fixed effect of feed restriction (j=3) ɛ ijk = error term Results and Discussion Effect of feed restriction intake on live weight and carcass characteristics of broiler chicken strains regardless of treatment applied was presented in Table 1. There was no significant (P>0.05) effect of strain on all the carcass traits with the exception of except abdominal fat where Anak Titan recorded higher mean values than Arbor Acre. But, in live weight, slaughter, dressed weight and other visceral organs, the two strains had similar mean values. The pooled data for each strain, full-fed and feed restricted birds inclusive showed that short-term feed restriction had little effect on final body weight of broilers. It can be inferred from the result of this study that feed restricted birds of the two strains regained their growth potentials following refeeding, attained market weight at the same physiological age like their mates which were full-fed. This insignificant difference in mature live weight of both fullfed and feed restricted birds reported between strains could be attributed to a phenomenon of catch-up growth upon refeeding, and this corroborates the findings of previous authors (McMurtry et al., 1988). It could also be deduced from the study that the two strains showed some level of tolerance to feed restriction based on the fact that no mortality was recorded in all the groups as a result of treatment applied. Also, there was no incidence of skeletal or metabolic diseases during the observed period. This means that none of the strains was negatively affected by the feed restriction programme. In effect therefore, the potential of short-term feed restriction as management tool aimed at reducing mortality rate, fat deposition, leg disorders and other problems associated with full feeding is very promising and rewarding. Though, Anak broilers had more fat pad than Arbor Acre at 49 th day of age following 263

4 refeeding, the quantity was much less than the amount reported with broilers fed ad libitum throughout in a previous study (Olawumi and Fagbuaro, 2011). The performances of birds under different feed restriction programme regardless of genotype were shown in Table 2. There was significant (P<0.01) effect of treatment on almost all the carcass characteristics evaluated. Live weight of birds under unrestricted and 85% feed restricted intake recorded similar mean values, but superior to their 75% feed restricted mates. Similar trend was recorded for all other traits measured except liver, heart, intestine, lung, gizzard and proventriculus where no significant (P>0.05) effect was found among the different treatments. Also insignificant among the treatments was the abdominal fat deposition. Interaction effect between strain and treatment was given in Table 3. There was significant (p<0.01) strain x treatment interaction effect on live weight, slaughter weight, dressing weight, eviscerated and carcass weights and other lean cuts. The obtained result of feed restriction on broiler performance was consistent with the findings of early studies which noted that carcass yield and breast muscle were significantly lower in feed restricted broilers (Azarnik et al., 2010). Also in agreement with this study were the findings of some authors who reported that the performance of broilers fed diluted feeds was significantly lower than the control(sahreel and Shariatmadari, 2007). The results of this study indicate that short-term feed restriction intake during starter phase up to 85% full feed is economical, practicable and has no negative consequences on broiler performance. Both full-fed and 85% full-fed birds were similar in live body weight, carcass weight and other lean cuts, and superior to 75% full-fed birds. The latter treatment adversely affected broiler growth, carcass cuts and visceral organs, and therefore, should not be considered in any feed restriction programme. The birds of the latter could not catch up even after returning the birds to normal, unrestricted feeding. In the current study, there was significant strain x feed restriction effect on broiler chicken performance. This implies that growth rate and carcass traits of birds under feed restriction depend on strain of the birds and treatment applied. In this study, Anak Titan broilers recorded higher and superior mean values at full-feed than Arbor Acre in all the traits considered at 49 th day of age upon refeeding. On the other hand, Arbor Acre had higher and superior mean values at 85% full-feed in all the traits than Anak Titan. The study reveals that the former tolerated feed restriction intake better than the latter. However, at 75% full-feed, both strains were at par, that is, recorded similar mean values. It is indicated in this study that 85% feed restriction could be practiced to maximize profit, reduce feed wastage, prevent excessive fat deposition and minimize cost of production without any adverse effect on broiler performance. In addition, Arbor Acre broilers seemed to be better and superior in carcass yields at 85% feed restriction than Anak Titan, and therefore, could be recommended for commercial production under quantitative feed restriction programme. CONCLUSION Evidence from this study indicate that substantial catch-up growth was recorded when birds were subjected to feed restriction at 85% ad libitum than 75% ad libitum feed regimen on short-term during starter phase. This implies that the phenomenon of catch-up growth depends on the extent or degree of feed restriction applied. With regards to the three levels of feeding regimens applied, full-feeding and 85% full-feeding recorded similar mean values, but, higher and superior to 75% full-feeding regimen. In addition, birds performances in this study depend on strain and treatment given. There was also reduced body fat deposition as a result of feed restriction 264

5 ACKNOWLEDGMENTS The author is indebted to the staff and workers of Teaching and Research farm, Ekiti State University, Ado-Ekiti for their support and assistance towards the successful completion of this study. REFERENCES 1. Zubair, A.K, Leeson, S Compensatory growth in broiler chickens: a review. World s Poult. Sci., 52: Yu, M.W., Robinson, F.E., Clandinin, M.T, Bodnar L Growth and body composition of broiler chickens in response to different regimens of feed restriction. Poult. Sci., 69: Sahrael, M., Shariatmadari, F Effect of different levels of diet dilution during finisher period on broiler chickens performance and carcass characteristics. Int. J. Poult. Sci., 6: Fanooci, M., Torki, M Effects of dietary restriction on performance, carcass characteristics, white blood cell count and humoral immune response of broiler chicks. Global Veterinaria, 4(3): Azarnik, A., Bojarpour, M., Eslami, M., Ghorbani, M.R., Mirzadeh, K The effect of different levels of diet protein on broilers performance in ad libitum and feed restriction methods. J. Anim. and Vet. Advances, 9(3): Acar, N., Sizemore, F.G., Leach, G.R., Wideman, R.F., Owen, R.I., Barbato, G Growth of broilers in response to feed restriction regimens to reduce ascites. Poult. Sci., 74: McMurtry, J.P., Plavnik, I., Rosebrough, R.W., Steel, N.C., Proudman, J.A Effect of early feed restriction in male broilers on plasma metabolic hormones during feed restriction and accelerated growth. Comparative Biochemistry and Physiol., 91: Yahav, S., Plavnik, I Effect of early-age thermal conditioning and food restriction on performance and thermo-tolerance of male broiler chickens. Br. Poult. Sci., 40: Samara, M.H., Robinson, K.R., Smith, M.O Interaction of feeding time and temperature and their relationship to performance of broiler breeder hens. Poult. Sci., 75: Lee, K.H., Leeson, S Performance of broilers fed limited quantities of feed or nutrients during seven to fourteen days of age. Poult. Sci., 82: Benyi, K., Acheampong-Boateng, O., Norris, D Effects of strain and different skip-a-day feed restriction periods on the growth performance of broiler chickens. Tropical Anim. Health and Prod., 43 (4) Mahmood, S., Hasan, S., Ahmad, F., Ashraf, M., Alam, M., Muzaffar, A Influence of feed withdrawals for different durations on the performance of broilers in summer. Int. J. Agric and Biol. 7(6): Kostal, L., Savory, C.J., Hughes, B.O Diurnal and individual variation in behaviour of restricted-fed broiler breeders. Appl. Anim. Behaviour Sci., 32: Savory, C.J., Seawright, E., Watson, A Stereotyped behaviour in broiler breeders in relation to husbandry and opioid receptor blockade. Appl. Anim. Behaviour Sci., 32: Statistical Analysis System SAS SAS Users Guide. Statistics, 8 th edition 2001, SAS Institute Cary, NC, USA. 16. Olawumi, S.O., Fagbuaro, S.S Productive performance of three commercial broiler genotypes reared in the Derived savannah zone of Nigeria. Int. J. Agric. Res., 6(11):

6 Table 1. Least square means showing the effect of strain on carcass traits of feed restricted broiler chickens Strains Traits Arbor Acre Anak Titan Live Slaughter Dressed Eviscerated Carcass Breast Back Thigh Drumstick Wing+leg Head+neck Leg length (cm) Liver (g) Heart (g) Intestine (g) Lung (g) Abdominal fat (g) b a Gizzard+proventriculus (g) Gizzard only (g) Bursa (g) ab :means along rows with different superscripts are significantly different (p<0.01) 266

7 Table 2. Least square means showing the effect of feed restriction intake on carcass characteristics of broiler chickens Feed Restriction Intake Traits 100% 85% 75% Live a a b Slaughter a a b Dressed a a b Eviscerated a a b Carcass a a b Breast a ab b Back a ab b Thigh a a b Drumstick a ab b Wing+leg Head+neck Leg length (cm) 6.73 a b a Liver (g) Heart (g) Intesting (cm) Lung (g) Abdominal fat (g) Gizzard+proventriculus (g) Gizzard only (g) Bursa (g) 3.33 a b b ab :means along rows with different superscripts are significantly different (p<0.01) 267

8 Table 3. Strain x feed restriction interaction effects on carcass traits of broiler chickens Strains ANAK TITAN ARBOR ACRE Traits Live weight (g) Slaughter Dressing Eviscerated Carcass Breast Back weight (g) Thigh Drumstick 100% 85% 75% 100% 85% 75% 2300 a 2100 ab 1920 b ab ab 1900 b a ab b ab 2050 ab 1810 b 2070 a ab b ab ab 1700 b 1797 a ab b 1700 ab 1686 ab b a abc 1195 c ab ab bc a ab 326 b a 480 a 410 ab 438 a ab b 383 ab 351 ab 367 ab 219 a a ab a 213 a b 260 a 223 ab 204 b ab ab b abc: means along rows with different superscripts are significantly different (p<0.01) 268