The current study investigated the effects of sex and stocking density and their interaction on growth performance and carcass characteristics of broiler chickens in a semi-arid subtropical environment. A total of 1008 day-old Cobb Avian48 chicks, namely 462 males and 546 females, were reared at final stocking densities of 30, 35, and 40 kg bodyweight per square metre (BW/m 2) corresponding to 44, 51 and 59, and 52, 61 and 69 chicks per pen for males and females, respectively, during a 42-day production period. The experiment was a 2 × 3 factorial completely randomized design, with each sex-stocking density combination being replicated three times. After the initial weighing, the birds were weighed individually [grams (g)] each week until the 42 nd day. At day 42, four birds from each pen were randomly sampled and slaughtered, and carcass characteristics were measured after 48 hours, and expressed as percentages of bodyweight. Growth performance and carcass characteristic parameters were subjected to analysis of variance using the general linear model procedures of Minitab statistical software version 17. Treatment means were compared using Tukey's test (at α = 0.05). Males gained more weight and were significantly heavier at slaughter age (2649 ± 43.1 g) than females (2270 ± 43.1 g). There was a progressive reduction in feed intake with increasing stocking density, but neither sex nor stocking density influenced feed conversion ratio and mortality rate. Sex significantly affected dressing percentage and carcass parts percentages, namely breast, neck, shank, heart and abdominal fat and thigh, liver and gizzard. On the other hand, stocking density significantly influenced dressing percentage and carcass parts percentages such as breast, thigh, drumstick, neck, shank, liver and gizzard. There was a significant sex x stocking density interaction effect on percentages of thigh and liver. It is therefore suggested that for efficient 42-day production cycles of broilers in the subtropics, Cobb Avian48 males reared at the stocking density of 40 kg BW/m 2 could be considered the best option.
The effect of the stage of maturity on the productivity, chemical composition, and ruminal degradability of Napier grass (Pennisetum purpureum) leaves under irrigation was studied. Samples were collected at three stages of maturity, at intervals of four weeks starting from the fourth week until the twelfth week (AprilJuly) after sprouting and then harvested to determine biomass. The stages of maturity had significant effects on longest leaf length per plant and plant height, but had no effect on number of leaves per plant and number of tillers. Dry matter (DM) increased significantly with maturity, while crude protein (CP) and fat content decreased significantly, with no significant effect on acid detergent lignin (ADL), ash, acid detergent fibre (ADF) and neutral detergent fibre (NDF). Maturity significantly decreased potassium, copper and sodium, while calcium and zinc increased significantly up to the intermediate stage, then declined toward the late stage of maturity. Maturity did not affect the magnesium, phosphorus, manganese and iron contents of the forage. Ruminal degradability of CP at 48, 72, 96 and 120 incubation hour decreased significantly with maturity, with no effect on all other incubation times for DM and CP. Maturity significantly decreased the soluble fraction (a) of DM, with no significant effect on other fractions of DM and CP. Effective degradability (%) of DM and CP decreased with maturity when the rate of passage increased from 2% to 8%. Napier forage should be harvested before maturity to retain its high nutrient content, and the degradability of DM and CP. ______________________________________________________________________________________
Unsexed Ross 308 broilers were raised under three stocking densities (30, 35, and 40 kg BW/m) and three daily feed withdrawal periods (0, 8, and 12 h daily) during a 42-day production period. The effects of stocking density and feed withdrawal on growth performance and carcass characteristics were investigated. The feed intake of broilers raised at the stocking density of 30 kg BW/m was higher than those of broilers reared at 35 and 40 kg BW/m, but broilers raised under the different stocking densities did not differ significantly in 42-day body weight, body weight gain, feed conversion ratio, and mortality rate. Forty-two-day body weight, body weight gain, and feed intake were reduced as the duration of feed withdrawal increased, but feeding program affected neither feed conversion ratio nor mortality rate. There was a stocking density effect on thigh percentage while feeding program influenced breast, back, wing, neck, liver, gizzard, and heart percentages. There were stocking density × feed withdrawal interaction effects on feed intake during the starter and grower periods. It is suggested that for profitable broiler production in the tropics stocking density of 40 kg BW/m and daily feed withdrawal for 8 h from 7 to 35 days of age be considered.
Dry seasons pose a major nutritional constraint on ruminant livestock production in tropical regions, which justifies forage conservation to meet the dry season feed requirement. Napier grass is a tropical forage that is used for silage in South Africa. The present objective was to determine the effects of Napier grass fertilization with bio-digester slurry (BDS) and the inclusion of fermentable carbohydrate additives at ensiling on the chemical composition and ruminal degradability of Napier grass silage. Napier grass was established in 5 x 4 metre plots, replicated three times in a completely randomized design, and irrigated weekly with either BDS or water. After 12 weeks, the Napier was cut and ensiled for 90 days in 1 liter glass jars in a 2 (BDS, Water) x 4 (no-additive, molasses, brown sugar, and maize meal) factorial arrangement replicated three times. The nutrient composition was determined using standard protocols. The ruminal degradability of dry matter (DM) and crude protein (CP) were determined using the nylon bag technique. Fertilization with BDS increased (p < 0.05) pH and CP and reduced (p < 0.05) fat content of fresh cut Napier. Additives increased (p < 0.01) silage DM content and reduced (p < 0.01) ADF, NDF content. The BDS fertilization with molasses inclusion increased (p < 0.05) silage DM relative to the no-additive and maize meal inclusion, and decreased (p < 0.05) fat content compared to the no-fertilizer, added maize meal silage.. Molasses increased silage WSC and decreased the NH3-N content (p < 0.05) compared to the no-additive and maize meal treatments. For DM, the BDS fertilized, no additive silage had the least “a” fraction (p<0.01), while the no BDS, no- additive silage had the least “b” fraction (p<0.01), with least (p<0.01) potential degradability observed for the no BDS, no-additive treatment. Fertilization increased (p<0.01) effective degradability of DM at outflow rates k = 0.02, 0.05, 0.08, with same effect for molasses and maize meal inclusion. Relative to the control, molasses inclusion increased (p<0.01) potential degradability of silage CP. In conclusion, our results suggested BDS fertilization of Napier grass ensiling with added readily fermentable carbohydrate substrate, particularly from molasses, induced changes in silage chemical and fermentation characteristics likely to promote better forage preservation and ruminal microbial function.
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