Objective: This study aimed to evaluate feeding strategies to increase broiler growth rate, reduce heat stress and improve welfare. Materials and Methods: A total of 240 Cobb 500 day-old chicks were distributed in a completely randomized design in a factorial arrangement (3×2) forming 3 treatments: T1 (control-ad libitum feeding), T2 (feed withdrawn between 11 am to 4 pm daily) and T3 (ad libitum feed +1% palm oil) and (2 levels of water treatments: P1 (plain portable water) and P2 (Tetrapluera tetraptera powder dissolved in water, as organic anti-heat stressor). Data on growth rate, carcass analysis and blood biochemical parameters were collected. Data were analyzed using the generalized linear model (GLM) procedure of SAS. The level of statistical significance was set at p<0.05. Results: The results showed that the total feed consumption, final body weight and weight gain were higher in T3 than that of T1. Both the major and full breast muscle weights for T3 was higher than those of T1 and T2. The carcass parameters were not affected by feeding strategy, water treatment, or their interactions, except for head and full gizzard weights. Platelet counts for T3 was higher but mean platelet volume (MVP) and platelet large cell ratio (PLCR) was higher for T1 than that of T3. The MVP was also higher for P1 than that of P2. Conclusion: The results showed that feeding strategies influenced broiler growth more than water treatment. Prekese had phytochemicals that have inhibitory effects on respiratory illnesses and coccidiosis, such as saponins, flavonoids, polyphenols and tannins.
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Poultry production has been severely hampered by climate change, effects of heat stress and poor feeding strategies which negatively affect the sustainability of production1,2. Several studies on feeding strategies and management of heat stress especially in the tropics have been carried out in broilers3-5. Research has shown that, within 16-26°C, which is called the thermoneutral zone, poultry can maintain a constant body temperature with the least effort6. Under high ambient temperatures, poultry birds try to regulate their body temperature by modifying their behavior and physiological homeostasis in order to decrease the temperature of their body. Some nutritional manipulations and combinations have been shown to reduce stress in broilers3,7.
Fasting during warmer time of the day minimizes heat burden and increases survival chances of broilers8. Birds become heat-stressed when their body temperature becomes higher than the optimal range for basic daily activities. All classes and ages of birds exhibit similar behavioral characteristics when exposed to heat. However, meat-type birds are more susceptible to heat stress6. The effects are also more prominent in older birds as they have a larger body size, higher metabolism and less surface area for dissipating excess heat than young birds. Heat stress decreases feed intake, weight gain and meat quality in broilers3,9.
During the growing phase, high temperatures deteriorate broiler’s meat quality characteristics. In order to minimize heat increment, feeding time should be reduced or birds should be fed during cool hours of the day9. Studies have shown that heat stress has negative effects on the production performance and meat characteristics of broiler8. A decline in feed consumption during high temperature results in poor broiler performance, which reduces growth rate and meat quality as well as feed utilization efficiency4,6,9. Therefore, broiler feeding strategies should be developed to minimize the impact of heat stress on growth and welfare.
Globally, climate change has impacted poultry and livestock production1. The purpose of this research was to explore the best strategies for reducing heat stress, increasing animal welfare, meat yield and quality through feeding during hot weather conditions in broiler production.
MATERIALS AND METHODS
Location and period of study: The study was conducted at the Department of Animal Science, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi, Ghana located at a latitude of 06°41’N and a longitude of 01°33’W with an altitude of 261.4MSL, above sea level10,11. All experiments were conducted according to the Procedure for Animal Research Ethics Committee (AREC) of the Kwame Nkrumah University of Science and Technology, Kumasi-Ghana, Q and Planning Unit12.
Experimental animals: A total of 240 day-old Cobb 500 broiler chicks were obtained from Topman Farms, Ntinsere in the Atwima Nwabiagya North District, Ashanti Region. On arrival, birds were weighed and randomly assigned to one of the research pens labelled according to feeding and water treatments. The initial weight of birds were ranged from 43.77-47.50 g. Brooding pens were installed with 100 watts of infrared fluorescent brooding bulbs to provide heat. Bedding materials, consisting of wood shavings, were spread to about 2 mm in thickness. Drinkers and feeders were also provided in the pens for the chicks according to recommended spacing and water was provided ad libitum. Birds were vaccinated against Newcastle disease virus and Gumboro and medicated according to a recommended schedule approved by the Veterinary Service Directorate of Ghana’s Ministry of Food and Agriculture.
Experimental design: A total of 240 day-old Cobb 500 broiler chicks were randomly distributed in completely randomized design in a 3×2 factorial arrangement with 3 levels of feeding strategies and 2 levels of water treatments and 2 replications with 20 birds in each replicate. The treatments were: T1 (control-ad libitum feeding), T2 (feed withdrawn between 11 am to 4 pm and T3 (ad libitum feed +1% palm oil). Two levels of water treatment were: Plain water (P1) and Aidan Fruit (prekese) water (P2) as anti-stress, water was given unrestricted. On the second day, experimental feed and water were administered. From the first week, leftovers were weighed and recorded. Weekly body weight and body weight gain (BWG) were recorded and calculated by deducting the initial body weight of the previous week from the final body weight of the current week. The birds were transferred from the brooder pens to the grower pens after three weeks of brooding while maintaining their respective treatment groups.
Experimental diets: Standard broiler starter feed (Galdus pre-starter mash) with crude protein of 22.00% and metabolizable energy of 3150 kcal kg1) was purchased to feed birds for the first three weeks13. Palm oil (1%) was added to the feed to constitute treatment 3 (T3) to feed the birds from week four to week seven. Locally available feed ingredients were compounded to formulate the broiler finisher feed that meets the broiler requirements according to NRC14 (Table 1). Nutrient compositions of both starter and finisher diets were calculated and proximate analysis of the diets was performed according to the AOAC15 (Table 2 and 3), respectively.
Growth performance: The following parameters were measured on weekly basis: Body weight, body weight gain, feed intake and water intake. Mortality was recorded daily and the feed conversion ratio was calculated as the feed intake divided by the body weight gain. At 7 weeks of age, two birds from each replicate were selected and euthanized by cervical dislocation and scalded in boiling water for carcass analysis.
Slaughtering of birds and carcass analysis: Two birds from each replicate were selected and their live weights were recorded and then slaughtered. The bled weight of the birds was also recorded after bleeding for about 5-10 min after slaughtering. They were then wet-plucked and eviscerated. Internal organs (liver, heart, intestine and gizzard) were excised and separately weighed to determine the dressing weight and the dressing percentage. The weights of the shank, head and neck were also recorded. Pelvic and abdominal cavity fats and those around the gizzard were removed and weighed. The breast muscles were split into minor and major breast muscles and weighed separately and then put together and weighed.
Hematological analysis and biochemistry: Blood samples were collected from the neck region of 2 birds into separate labeled centrifuge tubes containing an anticoagulant (EDTA). The blood samples were analyzed for total platelets, hemoglobin (Hb), red blood cells (RBC), white blood cells (WBC), mean corpuscular volume (MCV) hematocrit (HCT) and mean corpuscular hemoglobin concentration (MCHC) using a Hematological Auto Analyser (Cell-DYN 1800). Total cholesterol (TCHOL), Triglycerides (TG), high-density lipoprotein (HDL), Low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) in blood were analyzed according to the procedure of chemistry using an analyzing kit which was supplied by med source Ozone Biomedicals Pvt Ltd, using enzymatic (cholesterol Esterase, cholesterol Oxidase and Peroxidase) method at the CAN LAB, KNUST. A 1000 and 10 μL of cholesterol reagent and serum were pipetted into a test tube and labeled as Total cholesterol (Tc) respectively. Another 1000 μL of cholesterol reagent was again pipetted into a test tube and labeled as Blank (B). Samples were then mixed thoroughly and incubated for 5 min at 37°C. The absorbance of total cholesterol was read against the Blank using a calorimeter. Results were expressed as mg dL1. Triglycerides in blood were also analyzed by using the enzymatic (lipoprotein lipase, Glycerol kinase, Glycerol-3-Phosphate oxidase, Peroxidase, 4-Aminoantipyrine and ATP) colorimetric method. 1000ul and 10ul of Triglycerides reagent and serum were pipetted into a test tube respectively and labeled as (T). Another Triglycerides reagent was pipetted and labeled as Blank (B). Samples were mixed thoroughly and incubated for 10 min at 37°C. The absorbance of test (T) was then read against the Blank with a calorimeter. HDL (high-density lipoprotein)-cholesterol was estimated using 300 and 200 μL of precipitating reagent and serum respectively and was also pipetted into a centrifuge tube and mixed well. It was then centrifuged to stand at 25°C for 5 min and centrifuged again at 300 rpm for 10 min to obtain a clear supernatant. A 1000 and 100 μL of cholesterol reagent and the supernatant obtained respectively were mixed in a test tube and labeled as Test (T), another 1000ul and 100ul of cholesterol reagent and distilled water were mixed in a test tube labeled as Blank (B). Both test tubes were incubated at 37°C for 5 min. The absorbance of the test (T) was read against the Blank with a calorimeter. LDL (Low-density lipoprotein) in blood was determined using the following equation:
LDL (Low-density lipoprotein) = Total cholesterol-HDL (High-density lipoprotein)-Triglycerides
Statistical analysis: Data were analyzed using two-way ANOVA with the help of Generalized Linear Model procedure of SAS16. Where a significant treatment effects were exists, differences between treatment means were compared by Duncan Multiple Range Test. Differences of p<0.05 were considered statistically significant. The statistical model included the fixed effect of 3 feed treatments, the fixed effect of 2 water treatments and the interaction of feed and water treatments as shown in equation 1:
Yijk = μ+αi+βj+αβij+εijk (1)
where, Yijk is the response to treatment, μ is the overall mean from the treatment, αi is the fixed effect due to feeding treatment, βj is the fixed effect due to water treatment, αβij is the interaction between the two treatments and εijk is the residual error terms.
RESULTS AND DISCUSSION
Nutrient composition of Tetrapleura tetraptera (fruits): The phytochemical composition of the different parts of the Tetrapleura tetraptera was reported by Akin-Idowu et al.17 and is presented in Table 4. The composition shows different antinutritive and nutritive characteristics of the plant. These phytochemical characteristics identified in the above plant are known to have biological and beneficial effects including growth promotion, increased carcass characteristics and meat quality of animals through the enhancement of physiological, digestion and nutrient absorption capacities18. Additionally, the proximate analysis (Table 5) showed that crude fiber (CF), ash and ether extract (EE) values were higher than the range of 17-20.24% CF, 9% ash and 4.98-20.36% EE as reported by Okwu19. The CP value was lower but within the range (7.44-17.56%) as reported by Okwu19. The NFE value obtained (74.24%) was high. The variation in the nutrient composition could be attributed to the different geographical conditions, edaphic factors and processing methods used. However, the quantitative and qualitative composition of the phytochemicals found in the fruit was not determined in this study.
Growth performance of broilers
Feed treatment: The initial chick weights were not different between the feeding treatments (Table 6). Among feeding treatments, there was a significant difference in total feed intake (p = 0.0374), final body weight (p = 0.0365) and average weight gain (p = 0.0378) of the birds during the 7 week period. Birds in T2 and T1 had the same final body weight and the same was true for birds in T2 and T3. The significantly higher growth performance of birds in T3 group confirm the results of a study conducted by Hake et al.20 who found that palm oil has a positive effect on the live weight of broilers. Also, the palm oil was reported to improve the growth performance of birds by increasing feed intake and absorption and decreasing heat increment of the supplemented diet, resulting in an enhanced utilization of the metabolizable energy21.
In addition, Das et al.22 reported that the inclusion of palm oil in the diet of broilers improved its palatability and reduced its dustiness thereby increased the feed intake. According to Das et al.23, up to a 4% inclusion level of palm oil in broiler diets improved the weight gain as well as feed conversion ratio. The present findings are comparable to a previous study conducted by Zhang et al.9 who observed that average daily feed intake, final body weight and average daily body weight gain of feed restricted birds at 63-day of age remained the same as the ad libitum fed birds. In a related study, however, Mahmood et al.24 reported that birds kept off feed for 10 hrs gained significantly more weight and utilized their feed more efficiently than those of ad libitum fed birds. The water intake, FCR and mortality were not different between the feeding treatments. Birds in T3 had higher water intake and a better FCR.
Water treatment: Water treatment had no significant effect (p<0.05) on the growth performance of the birds. However, 'prekese' water improved the total feed intake, final body weight and the average body weight gain of broiler chickens in this study. This result showed that 'prekese' water increased the total feed intake of the birds and this showed the ability of T. tetraptera to stimulate appetite as well as improve feed intake. Similar results were reported by Essien25 who showed that feed intake did not differ significantly between diets with different levels of T. tetraptera but increased as the level of T. tetraptera increased.
Interaction of feed and water treatments: Interaction of feed and water treatments had no significant effect on the overall growth performance of the birds. However, numerically total feed intake of birds in the T3*P2 interaction treatment group was higher (4869.72 g) than those of the other interaction groups. In agreement with the current results Das et al. 22 and Essien25 noted that, the inclusion of palm oil in the diet of broilers improved its palatability and reduced its dustiness thereby increased the feed intake and also the feed intake did not differ significantly between diets with different levels of T. tetraptera but increased as the level of T. tetraptera increased. Also, T3*P2 had a better FCR Value (1.80) compared to the other treatments.
Feed treatment: Table 7 shows the weight differentials of the various carcass components measured at the end of the study period. No significant differences (p>0.05) were recorded in the live weight, bled weight, dressed weight, shank weight, neck weight, liver weight, heart weight, full and empty gizzard weight, full intestine, breast minor weight and abdominal fat weight of the birds in all the feeding treatments. With regards to the breast major weight (p = 0.0050) and full breast weight (p = 0.0222), significant differences were recorded among the feeding treatments. The breast major weight and full breast weight of birds in T3 were significantly higher (0.5125 and 0.6375 g), respectively than those in T1 and T2 treatments, whereas the weight of the breast major and full breast of T1 and T2 were not statistically different. This result concurs with a study conducted by Zhang et al.26, when birds fed a diet containing oils had significantly heavier breast muscle than those of the control. Das et al.23 reported that meat yield characteristics of broilers taking different palm oil levels in diets were not significantly different except for wing meat, gizzard and dark meat. Meanwhile, the inclusion of 4% canola oil and tallow mixture resulted in a significant increase in breast muscle and drumstick production.