Reduction of calcium levels in rations supplemented with vitamin D3 or 25-OH-D3 for broilers

ABSTRACT An experiment was carried out to verify the response to the Ca reduction levels of diets with different vitamin D sources on performance, bone mineral deposition, serum concentrations, digestibility, carcass characteristics, and meat quality of broiler chickens in the period from 1 to 42 days reared in thermoneutral environment. A total of 504 male broilers with one day of age and average weight of 43.27±1.08 g were housed in climatic chambers and distributed in a completely randomized design. The study consisted of a 4 × 2 factorial, with four Ca reduction levels (0, 10, 20, and 30%) and two vitamin D sources (2760 IU of D3 or 25-OH-D3). The performance of animals at 21 and 42 days of age was not affected by Ca reduction by up to 30%, regardless of the vitamin source used. Dietary reduction from 10% decreased serum Ca concentrations. The use of vitamin D3 provided a serum P level greater than the 25-OH-D3. Calcium reduction decreased serum 25-OH-D3 levels. No effect of vitamin source or Ca levels on broiler carcass characteristics was observed at 42 days. The vitamin source did not influence meat quality, while Ca reduction of the diet provided lower losses by thawing and cooking and higher initial pH values. The b* color was reduced in diets with lower Ca levels of the diet. Reducing Ca up to 30% does not affect the performance and carcass characteristics, regardless of the vitamin D source used. The quality of broiler meat is improved with the Ca reduction in the diet, but the vitamin used has no effect on such characteristics. We can conclude, based on the results of performance, blood, and bone, that the performance variables are not adequate to determine the actual requirement of Ca, since as it is a priority to maintain performance, bone mineral mobilization occurs, which may compromise the carcass quality of the birds.

摘要 本试验旨在探究热中性环境下1~42日龄肉鸡的生产性能、骨矿沉积、血清指标浓度、养分消化率、屠宰性能及肉品质对不同维生素D来源日粮钙（Calcium, Ca）降低水平的响应。试验共选取504只1日龄雄性肉鸡，初始平均体重为43.27±1.08 g，将其饲养于人工气候箱中，采用完全随机试验设计。本试验采用4×2因子设计，设置4个钙降低水平（0、10%、20%、30%）与2种维生素D来源（2760 IU维生素D3（Vitamin D3）或25-羟维生素D3 (25-OH-D3)）。结果显示，无论使用何种维生素D来源，日粮钙降低幅度不超过30%时，21日龄与42日龄肉鸡的生产性能均未受显著影响。当日粮钙降低10%时，肉鸡血清钙浓度会出现下降。使用维生素D3组的血清磷（Phosphorus, P）水平显著高于25-羟维生素D3组。日粮钙降低会使血清25-羟维生素D3水平下降。42日龄肉鸡的屠宰性能未受维生素D来源或日粮钙水平的影响。维生素D来源对肉品质无显著影响，而日粮钙降低可降低解冻损失与烹饪损失，并提升初始pH值。低钙日粮组的b*色分值显著降低。将日粮钙降低幅度最高至30%时，无论使用何种维生素D来源，均不会影响肉鸡的生产性能与屠宰性能。日粮钙降低可改善肉鸡肉品质，但所用维生素D来源对该类指标无显著影响。综合生产性能、血液及骨骼相关试验结果可知，仅通过生产性能指标无法准确判定肉鸡的实际钙需求量：由于机体优先维持生产性能，会发生骨矿动员，这可能损害肉鸡的屠宰品质。