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Two feeding trials were simultaneously conducted using ,.* and +,* broiler chicks (Hubbard) for evaluating the mineral retention by tissues and immune competence, respectively as influenced by manganese (Mn) levels in feed. Mn was added at *, +**, .**, 2**, +0** or-,** ppm levels to a corn-soya basal diet, using sulphate salt. In both trials, chicks were uniformly distributed into 0 experimental groups and housed in stainless steel battery brooders. From 2ῌ,2 days of age, each experimental diet was fed ad libitum to one test group. Results indicated that Mn supplementation from *ῌ2** ppm did not influence body weight gain or feed consumption, but a significant depression in both parameters was noticed at +0** and-,** ppm levels. The feed conversion e$ciency was however, not a#ected by dietary Mn levels. Excess (+0** ppm and above) or nonsupplementation of Mn increased leg abnormality scores. Mn levels above .** ppm significantly decreased Ca, P and Zn retention in tibia, which was related to higher leg scores. A linear increase of Mn content in bone, kidney, liver and pancreas was noticed with the increase of Mn in feed. The antibody titers against inoculation of sheep red blood cells or cutaneous basophil hypersensitivity to phytohaemagglutinin-P were not influenced by the dietary increases of Mn up to 2** or +0** ppm levels, respectively. Both responses were negatively a#ected by increased Mn levels in feed. Heterophil to lymphocyte ratios, the indicators of stress were not altered by Mn supplementation up to 2** ppm, but higher levels produced wider ratios. In conclusion, supplementation of Mn at +** ppm level was essential for leg health, better retention of Ca, P and Zn in bone besides optimum immune response. Mn supplementation at +** ppm level was as e$cient as higher levels (upto 2** ppm). Higher levels of Mn (+0** ppm and above) had negative e#ect on all parameters studied in broilers up to ,2 days of age.

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This study aimed at targeting fixed increases in body weight (100 g/wk) by quantitatively regulating energy allowances (ME) in broiler breeders from 5 to 20 wks of age. Four energy regimes were tested: 1. The energy required for maintenance, activity and growth was calculated for 100 g increases in body weight/wk and a measured quantity of grower diet (160 g protein and 2,600 kcal ME/kg) was offered to the control group (ME-100) to achieve the anticipated weight gain. The energy allowances increased with age from 132 to 294 kcal/d. 2. Additionally, three energy regimes were considered, quantitatively reducing ME by 10% (ME-90) or 20% (ME-80) and increasing by10% (ME-110) over the control group. Each test group had 23 replicates×5 female chicks housed in cages. The influence of energy regimes and age on growth, nutrient digestibility, carcass attributes, bone parameters and stress was evaluated at 4 wk intervals. Quantitative ME restriction by 10% (119-265 kcal/d) produced an average weight gain of 98.1 g/wk, which was closer to the targeted increase of 100 g/wk, whereas the control group attained it nine days earlier. Restriction of energy by 10 or 20% produced better conversion efficiency of feed, energy and protein and apparent digestibility of protein, Ca and P than 10% excess ME. Energy regimes did not influence eviscerated meat yield, but higher energy allowances (ME-110) significantly increased abdominal fat pad and liver weights and decreased giblet weight, percent muscle protein and tibia ash. Relatively higher stress was recorded in ME-restricted groups, as reflected by wider heterophil and lymphocyte ratios and increased bursa weight. Early age (5-12 wk) significantly influenced bone mineralization, conversion efficiency of feed, energy and protein and apparent digestibility of protein, Ca and P, while later ages (13-20 wk) increased eviscerated meat yield, abdominal fat, tibia weight and muscle protein and reduced stress. Energy regime x age interactions were significant and are discussed. In conclusion, the synthetic broiler line used in our study responded positively to controlled energy feeding during the rearing period. Breeders offered 119-265 kcal/d, a reduction of 10% energy over the control group, were more effective in regulating grower performance than the latter. In addition to energy regimes, age intervals also exhibited significant influence on specific parameters during the grower phase.

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