Calory-Protein Restriction -The Most Promising Economic Feeding Method for Commercial Broilers
S.Venkata Rama Rao, Ravindra Reddy, M.V.L.N. Raju and Ch.Sridhar
The success of commercial broiler production mainly depends upon offering exact and optimum declares levels of protein and energy. Since they represent about 95% of the cost of the principle input, the broiler ration IS1 (1092) hits recommended 23% CP and 2800 Kcal ME/kg for broiler finisher. So any attempt to reduce the levels protein and energy in broiler diet without sacrificing or lowering broiler performance will in turn reduce the cost or broiler production considerably. Further, it makes possible in production or lean meat which is very much desirable for the present day health conscious human population. By avoiding excess dietary in take of caloric and protein, wasteful conversion of these nutrients into invisible fat and the resultant deter mental effect on kidney and liver can be minimized. Restricted feeding though is normal feeding practice in broiler breeder production during their growing period (from X to 20 works of age), it can also be practiced in commercial broilers feeding programme in order lo achieve subsequent compensatory growth with maximum feed efficiency besides production of lean meat with less fat content.
Restricted feeding can be practiced in several ways i.e. quantitative feed restriction where measured amount of feed is offered and qualitative feed restriction in which certain nutrient or diet is diluted. Certain non-toxic and inert materials like sand, rice hulls, oat hulls, etc. Which contain no nutritive value will be used in dilution of diet.
Qualitative Feed Restriction:
Qualitative feed restriction has been tried for protein or energy or for both simultaneously.
Protein restriction can be practiced in two ways:
a) Restriction of dietary protein (8 to 16% CP) at an early age i.e. up to 2 to 3 weeks of age (Barnes and Miller. iy76; Marks. 1979: Barnes a nd Miller. 19X1.. Choudhary and Aggarwala.198 6 Rama Rao 1991) and provision of suggested optimum level subsequently
b) Restriction of dietary protein (7 to 14%) from I day to 56 days of age (Twining 1978; Kulkarni. 1979).
By feeding broilers with low protein (< 16%) starter diet and finisher diet having optimum levels, several workers (Barnes and Miller. 1976: Marks. 1979: Barnes and Miller. 1981: Rama Rao.. 1991) obtained compensatory growth in broilers which early protein restriction was followed by offering normal protein allowances. However, feeding lower levels (19 to 20%) of dietary protein during both growing (8-6 wks.) find finishing (7-8 wks.) periods has resulted in production of boilers with optimum body weight (Moran Jr. 1979; Diambra and Mc carteny 19894). Where as boilers subjected to protein restriction throughout the period ( I day - 56 days) showed poor growth rates (Twining Jr. el al.. 1978; Kulkarni. 1979).
Whenever nutrient restrictions followed in terms of low protein diets, it is essential to use anticoccidials like nicarbazin, but not inophores. Which can depress growth and cause poor or uneven rufncd featuring (Parsons and Baker. 19K2)?
Compensatory growth also resulted due to restriction of energy during early stage and provision of normal levels of energy during later part of growth (Deaton ct ;il.. 1973; Diambra and Me Cartency. 1984). Energy restriction during early life of broilers also resulted in reduction in abdominal fat deposition (Plavnik and Hurwilz 1990.91). Energy restriction during last 10 days of finishing period also resulted in reduced fat pad weight with no change in carcass characteristics.
A model for determining level of energy restriction, based on (he body wciglil of broiler was developed by Plavnik and Hurwitz (19K5) where the daily energy allowance during restriction period was calculated as 1.6 Kcal x body weight
Combined Calorie and Protein restriction:
Broiler chicks subjected to severe mil nail restriction (18% CP and 27()() Kcal ME/kg during initial 3-4 weeks) were able to compensate their growth depression subsequently when offered normal broiler finisher diet (Rama Rao el al.. 1991).
Quantitative Feed Restriction:
Studies of Teeter and Smith (19S5) indicated that a 25% reduction in feed intake in broilers from 28 to 39 days of age resulted in 30% reduction in weight gain and almost a 50% reduction in abdominal fat. Feeding of 50% ad lib intake from I day to 49 days li;is resulted in approximately 50% reduction in weight gain with an improved feed conversion efficiency (Washburn 1990). This improved feed utilization may be related to the reduced fat anabolism and improved energy utilization during restriction period.
Broilers were able lo adopt for quantitative feed restriction (50% of ad lib) during finishing period, particularly during 7th week (Leeson. 1992).
Feed restriction can also be practiced by fasting the broilers for 2 to 6 days during early stages of growth (I to 10 days of age) to reduce abdominal fat deposition (March and Hansen. 1977: Cabel and Waldroup. 1990).
Quantitative feed restriction and fasting method should be carried out only on wire flooring as birds that are reared on litter floor if subjected to diet restriction or deprivation would consume litter material, which may reduce or nullify the effects of restricted feeding programme and also increase the incidence of certain diseases like Coccidiosis. Colibacillosis etc,
Dilution of normal broiler diet with nutritionally inert Nontoxic, and bulky materials like sanJ . Oat hulls. Cellulose etc to reduce nutrient intake by the bird while maintaining on ad labium feeding is valid when the broiler chicken were eating to near physical capacity (Newcomb and Summers. 19K4),
Reduced abdominal fill deposition and body weight gain were observed when broilers were fed the normal did diluted (3:1 or 1:1) with pulverized oal hulls (March and Hansen. 1977). Whereas significant increase in the abdominal fat were however observed at 7lh week of age in broilers fed die! Containing Cellulose and Sand ( 1:2 ratio) during first week (Jensen ct al, 1987).
Deposition of abdominal fat was linear to (lie level of finisher did dilution (from 10 to 50%) with a mixture of sand and oal hulls where as the body weight gain was not reduced by (lie level of did dilution (Leeson 1992).Leeson; md co workers further noticed a 70% increase in feed intake in broilers when they arc offered diluted did during finisher period (36 to 49 days). So it is imperative to consider the increased feed in lake by the broilers on diluted diet while practicing this programme.
Physiological basis for compensatory Growth:
The ability of the caloric and protein restricted broilers lo compensate the early growth depression was attributed to the higher protein and energy contents of did fed subsequently. It is also quite possible that underfed broilers have lower maintenance requirement for protein and energy due to lower body weight (Mitchell. 1962;
Apfelbaum, 1978; Forsumclal.. 1981)and these birds therefore recover faster when given optimum level of nutrients. Another possible reason is (lie better utilization of these two nutrients at low dietary concentration than at higher levels (Diambra and McCartney. 1980). Feed restriction will lower the maintenance requirements by reducing the energy loss (total heal production) and the basal metabolic rate and the specific dynamic action of feed (Mitchell. 1962; Apfelbaum. 1978; Forsumclal. 1981).
Nutrient restriction and carcass quality:
Dietary treatment had no significant effect on meal to bone ratio, eviscerated carcass weight and giblet weight (Kondra el al.. 1962, Mahaplra et al.. 1984), Whereas Shyam Sunder ct al. (1988) found inverse relation between giblet weight and dietary density of protein and energy. Higher dietary energy produced birds with minimum abdominal fat (Deatonet ill. 1972: Kubenuet il.. 1974; Coon c al., 1981; Trindade ct al.. 1981 and Bahgel and Pradhan. 1988).
Decreasing dietary caloric protein ratio (either by decreasing energy content or by increasing crude protein level) caused significant reduction in abdominal fat deposition (Griffiths el ill.. 1977 and Rama Rao, 1989). The reason for this has been attributed to depressed hepatic lip genesis (Yeh and Leveillc. 1969) and an increased synthesis of uric acid (Buttery and Boorman 1976). Nutrient restriction (Protein and/or energy) during early stages of life has been shown to reduce the abdominal fat deposition by delaying adipoeyte hyperplasia, hypertrophy or both (March and Hansen. 1977; Plavnik and Hurwitz 1985; Plarnikctal. 1986),
In general. Carcass fat decreased in a linear manner with increasing levels of dietary protein. Where as increased levels of dietary energy resulted in increased carcass fat (Summers el ill.. 1965), However, early protein and / or energy restriction has resulted in decreased total carcass fat (Pesti and FIeleher. 1984; Rama Rao el al.1989).Increasing the level of dietary protein and fat has been reported to depress fatly acid synthesis in liver of chicks (Nishida et al.. 1960. Hill et al. 1960; Weise et al., 1967). Hepatic lipogenesis was reduced / altered by the level of dietary protein regardless of its quality. The rate of fatty acid synthesis was however same for all groups despite the fact that body weight gain and feed efficiency were improved by increasing the level of effective protein.
Serum cholesterol level was inversely related to dietary protein level. This has attributed to the cholesterogenes depressing effect or cliolesteral catabolism stimulatory effect or both (Nashida el al.. 1960) of high protein diet. Reduction in availability of Cytoplasmic reducing powers (NADH and NADPH) is the main reason for depressed fatty acid synthesis in birds fed high protein diet
Broilers should be reared lo a minimum period of 49 days when subjected to feed restriction to obtain compansatory growth (Plarnik and Hurwilz. 1988)
Post restriction performance (Compensatory growth and decrease fat deposition) of broilers appears to be influenced by a number of factors. The nature, severity and duration of the restriction the pattern of re feeding the stage of growth potential of bird (Wilson and Osbourn. 1960; (Herry el ill. 197H ; Plavnik and Cornejo. 1982 .Plavnik and Hurwilz 1985). and certain environmental factors like temperature and season of the year (Kubena et al,. 1972) were attributed.
Importance of Calorie and Protein Restriction:The growth rate of commercial broilers is being continuously increased each year by intensive continuous and rigorous selection for higher body weight and meal to bone ratio. This is predisposing the commercial broilers to several metabolic disorders of skeletal and cardiac systems which hamper their growth performance. This diet restriction offers a great scope to tamper or postpones growth during early age till the boiler develop skeleton to sustain this weight a nd there by to reduce Lamness and other disorders (Leeson and summers. 1988).