EFFECTS OF DIETARY VITAMIN C AND VITAMIN E ON THE PERFORMANCE OF LAYING HENS IN THE HUMID TROPICS
This study which lasted for 52 weeks investigated the effects of dietary Vitamin C (L-ascorbic acid) and Vitamin E (dl- alpha tocopheryl acetate) on the performance of laying hens in the humid tropics. A total of 240 twenty-four week old Golden Neslink pullets were randomly selected from a flock of 550 birds and randomly divided into sixteen treatments of 15 pullets. The birds were initially vent examined to ensure that they were at point of lay before commencing the study. Each pullet was randomly assigned to a previously cleaned and disinfected cage measuring 49 x 35 x 42cm at a stocking density of one bird per cage. Four dietary levels of Vitamin C: 0, 200, 400, and 600mg Kg-1 basal diet were combined with four dietary levels of Vitamin E: 0, 125, 250 and 375mg Kg-1 basal diet in a 4 x 4 factorial arrangement in a Completely Randomized Design. All management principles were observed. Dead birds were promptly removed for autopsy when the need arose. At the end of the study, three birds were selected per treatment for haematological investigation. Blood samples were collected from the wing vein of the birds using a 3ml syringe and a 23-gauge needle and placed in micro tubes with Ethlene diamine tetra acetic acid (EDTA) as anti-coagulant for determining the haematological values. The samples were cooled to 4 oC, using icepacks and transferred to the laboratory within 12h of blood collection. The economic implication of the study was then calculated. Data obtained were subjected to analysis of variance (ANOVA) using SPSS. The mean minimum and maximum indoor temperatures recorded during the study ranged between 18.3-25.0 oC and 27. 15-34 oC respectively while the RH values lay between 53.0 and 88.9%. These were well outside the zone of thermo neutrality for laying hens.
Results obtained indicated that, there were highly statistical differences (P < 0.01) between Vitamin C and Vitamin E treated birds for hen day production (HDP), feed intake (FI), feed conversion ratio (FCR), Haugh unit score (HUS), , egg weight (EWT) and incidence of cracked eggs. The treatment, T7 (400mg vitamin C + 125 mg vitamin E Kg-1 basal diet) was superior to all the other treatments and had the highest values for HDP (85.45±1.15), FI (113.15±0.56), HUS (96.27±0.47), and EWT (69.11±1.52). These values were however, statistically similar (P > 0.05) to T8 (600mg Vitamin C + 125 mg Vitamin E Kg-1 basal diet). The lowest values for HDP (42.33±1.43), FI (65.42±0.61), HUS (75.50±2.10) and EWT (54.50±1.15) were observed in T1 (Controls). The synergism between Vitamin C and E is different from the sum of the two vitamins applied separately. Loss in body weight, incidence of cracked eggs and mortality were statistically higher (P < 0.01) in T1 (controls) than vitamin treated birds which showed no significant (P > 0.05) differences. With Vitamin C supplementation, birds on T3 (400 mg Vitamin C kg-1 basal diet) were superior to T2 (200 mg Vitamin C kg-1 basal diet) and T4 (600 mg Vitamin C kg-1 basal diet). Similarly, for Vitamin E supplementation, birds on T9 (250 mg Vitamin E kg-1 basal diet) were statistically different (P < 0.01) from T5 (125 mg Vitamin E kg-1 basal diet) and T13 (375 mg Vitamin E kg-1 basal diet). For haematological values investigated T7 recorded the highest values for RBC (4.11±0.15×106), Hb (8.80±0.31g/dl), and WBC (18300±519.62/mm3) and these were statistically similar (P > 0.05) to T8 but highly statistically different (P < 0.01) from the rest of the treatments. There was highly significant interaction (P < 0.01) in the net income/dozen of eggs that accrued from the study. T7 had the highest net income/dozen egg of N1, 627.11±28.68 while the least net income (N560.50±32.12) was generated from T1. This work therefore upholds that vitamins C and E act in synergy, and that the combined effects of the two antioxidants are additive, immunomodulatory, anti-parasitic and economical.
Human diets in tropical countries such as Nigeria are most often protein-poor, both quantitatively and qualitatively (Okeke et al., 1985; Ojewola, et al., 2004). For instance, the contemporary average per capita protein consumption in Nigeria is estimated at 7-10g (Oluremi et al., 2008; Okuneye, 2002). This estimate falls far below the FAO (1997) recommendation of 35g/caput/day. Meanwhile, it should be borne in mind that the Nigerian population on the other hand, continues to rise. Current demographic figures show that the total head count overshoots 140 million at a 3.0% annual growth rate (BBC News, 2006; Nigerian News, 2006), without a corresponding livestock population to match (FAO, 2005). To stabilize this situation, no improvement could be made in this country without an increase in food crops, livestock and fish farming. Even then, from the point of view of quality protein consumed, animal proteins by far outweigh proteins from crop sources (Obioha, 1992). Regrettably, there is a perennial low intake of animal products such as meat, milk and eggs in Nigeria (Onyimonyi, 2002). Unfortunately, these animal products are the major sources of high quality proteins. The implication is that, the nutritional status of the Nigerian population and economic development are inextricably linked. This is a clear indication of the inability of the traditional system of animal agriculture to meet the protein needs of Nigerians creating an avenue for protein malnutrition to persist!
The immediate remedy would thus, involve the massive production of animals with short reproductive cycles such as poultry, pigs and rabbits. But when a quick means of significantly increasing turnover rate thereby modifying farm income and improving animal protein in the human diet is the objective, then poultry becomes the animal of choice (Emeruwah, 1999; Ojewola, et al., 2004).
Apart from these dimensions, Obioha (1992) has earlier demonstrated that poultry are excellent feed converters. Carew et al. (2007) have also shown that, poultry do not suffer social infringement on consumer acceptability like other livestock species such as pigs. The foregoing has triggered the rising demand for poultry products like eggs and meat given their palatability and high nutritional value (CTA, 1987; Ojewola, et al., 2005). These attributes among others, make the poultry industry stand tall amidst rival livestock producing ventures.
However, for poultry to perform its ascribed roles, it is necessary to closely scrutinize the environmental factors that have the capability of frustrating their genetic potentials. Nigeria being a humid tropical country is associated with a myriad of these environmental factors. Sinkalu et al. (2008) have listed these environmental stressors as: deprivation of food and water, high ambient temperatures (AT), relative humidity (RH), high velocity, noise, motion, overcrowding, vibration and mishandling. Among these factors, high AT and RH are the most important meteorological stress factors adversely affecting poultry in general, and laying hens in particular (Asli et al., 2007; Ayo and Sinkalu, 2007; Ayo et al., 2005a; Ramnath et al., 2008).
The ideal temperature (conventionally referred to as the zone of thermo neutrality) under which the performance of laying hens is not adversely affected by temperature has been earlier identified by Oluyemi and Roberts (2000) as 12.8-26.00C. CTA (1987) has however given the thermo neutral zone to be 16 -200C. Anderson and Carter (2007) on the other hand identified the range of thermo neutrality as 12.8 – 23.9 0C. Recent field work by Imik et al. (2009) has narrowed the thermo neutral zone of laying hens to 18- 220C.
Temperatures outside the critical limits of the thermo neutral zone such as those obtained in most humid tropical regions of the World like Nigeria have been reported to constitute heat stress (CTA, 1987; Ensminger et al., 1990; Holik, 2009; Kucuk et al., 2003; Oguz et al., 2010). Under heat stress conditions, poultry perform sub-optimally owing to a reduction in feed intake, egg production, egg weight, Haugh units and yolk index (Asli et al., 2007; CTA, 1987; Freeman and Crapo, 1982; Oguz et al., 2010; Smith, 2006; Smith and Oliver, 1972; Vathana et al,. 2002).
Similarly, some authorities Sahin et al. (2002a, b) and Sinkalu et al. (2008) have demonstrated that metabolic (anabolic) activities of tissue building such as transcription, RNA processes and translation are impaired as a result of heat stress.
Earlier reports point that temperatures exceeding 200C enhance heat production by the birds and this supersedes that dissipated through the various processes of elimination (Lewis and Thomas, 1985). Bains (1996) further reported that heat stress could stimulate the increase in corticosterone and catecholamine secretions. Collaborating the work of Freeman and Crepo (1982), Altan et al. (2003), Gous and Morris (2005), Halliwell and Gutteridge (1989), Klasing (1998), Minka and Ayo(2007), and Seifulla and Borisova(1990) have severally demonstrated that, this biochemical activity elicits the generation of free radicals, which cause lipid per oxidation of cytomembranes. Consequently, the natural antioxidant defense systems of the body are overwhelmed (Altan et al., 2003; Sahota and Gillani, 1996; Shini, 2003; Tauler et al., 2003) due to alterations in haematological values (Dawson and Bortolotti, 1997). Apart from stimulating hypothalamo – hypophyseal adrenocortical axis, high and low temperatures alter the susceptibility of animals including laying hens to infectious diseases (Dohms and Metz, 1991; Ramnath et al., 2008; Siegel, 1985). Holik (2009) reported that the electrolytes balance of the fowl become altered due to panting and mineral excretion increases.
With the prospective climate change predisposed by global warming, the magnitude of the low performance may be worsened (IPCC, 2007; Spore, 2008) especially where no adaptation and mitigation strategies are employed to exempt laying birds from these environmental adversaries (Nombor and Okeke, 2009). Affluence poultry farmers could build poultry houses with open – sides or fit ceiling/asbestos sheets or hang ceiling fans in poultry house roofs as ameliorative measures, these strategies are rather very expensive. The next option therefore, would be the manipulation of layer nutrition to intercept the adverse effects of heat stress.
In this wise, the use of antioxidants especially Vitamin C (L-ascorbic acid) and Vitamin E (dl-α-tocopheryl acetate) as dietary supplements in the nutrition of laying hens under humid tropical regions of the world have been demonstrated to be beneficial and economical (Asli et al., 2007; Balnave and Brake, 2005; Ciftci et al., 2005; Oguz et al., 2010; Panda et al., 2008). Even though birds can synthesis Vitamin C endogenously (Daghir, 1995a; McCuskey, 1985; Wikipedia, 2010), under stress conditions such as low or high environmental temperatures, it becomes inadequate (Kucuk et al., 2003; Oguz et al., 2010; Puthpongsiriporn et al., 2001; Ramnath and Rekha, 2010; Ramnath et al., 2008). As for Vitamin E, Biswas et al. (2010), Bolukbasi et al. (2007), Chan and Decker (1994), and Wikipedia (2008) have emphasized its inability for endogenous synthesis in the fowl hence its requirements must be met from exogenous dietary sources.
The climatic conditions of the South – Eastern Nigeria as depicted in Nsukka and its environs reflect a typical tropical climate. Work by Okonkwo and Akubuo (2007) has revealed an average annual minimum and maximum temperature ranges of 22.00C – 24.70C and 33.00C – 37.00C respectively.
These ranges appear to fall outside the zone of thermo neutrality of laying hens which is 18- 220C as recently defined by Imik et al. (2009). As such, adverse effects of heat stress are suspected to clasp egg production parameters of laying hens in this region.
Given the above therefore, the general objective of this study was to investigate the effects of dietary Vitamins C and E used either singly or in combination on egg production parameters under Nsukka humid tropical conditions.
1.1 SPECIFIC OBJECTIVES
- determine the levels at which Vitamin C supplementation will optimally improve production in laying hens under heat stress.
- determine the dietary levels of Vitamin E that will enhance layer performance under humid tropical conditions.
- establish any synergetic relationship that may arise between Vitamin C and Vitamin E used in combination to improve the performance of laying hens in the humid tropics
- investigate the effect of Vitamins C and E as antioxidants on hematological values of laying hens.
(e) determine the economic benefits of dietary Vitamins C and E fed to laying birds under heat stress.
Among the topical issues on the “Yar Adua’s” 7 point – agenda is food security reforms primarily geared towards revolutionizing the agricultural sector leading to a 5 – 10 fold increase in yield and production (Aluko, 2007). Given Nsukka’s tropical conditions, research in this zone directed towards increasing egg production is worthwhile in the realization of the goals of the 7 point – agenda as far as food security is concerned.
Secondly, University of Nigeria, Nsukka has made previous attempts towards environmentally modifying the poultry Unit (by building open – sided houses) so as to record commercial benefits. This attempt may direct air movement onto the floor. And even if ceiling/asbestos sheets together with fans were to be fitted in the roofs, much still remain on the manipulation of the nutritional requirements of the birds if optimum performance is to be achieved.
Thirdly, Okonkwo and Akubuo (2007) have given the average annual minimum and maximum temperature ranges in Nsukka as 22.00C – 24.70C and 33.00C – 37.00C respectively. (Note sharp changes in corresponding figures of 200C-230C and 270C -320C as earlier reported by Breinholt et al. (1981). This increase in air temperatures might probably be as a consequent of global warming. These temperature ranges indicate that laying hens at Nsukka are experiencing temperatures above the comfort zone most of the time unnoticed. In the present face of climate change, this research is worth undertaking.
More so, dietary Vitamins C and E have not been shown to have residual but beneficial effects on treated animals unlike antibiotics, hormones and other growth promotants whose use in livestock nutrition is at present discouraged (Schell, 1984).
Lastly, since this work is a maiden attempt in this location, data generated from the study will provide baseline information upon which subsequent investigation will be based.
EFFECTS OF DIETARY VITAMIN C AND VITAMIN E ON THE PERFORMANCE OF LAYING HENS IN THE HUMID TROPICS