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.

Oitenta leitoas (24,2±1,52kg) com alto potencial genético para deposição de carne na carcaça foram distribuídas em experimento de blocos ao acaso para avaliar cinco níveis de lisina digestível (Ld) (9, 10, 11, 12 e 13g kg-1) durante a fase de crescimento (63 a 103 dias de idade). Os animais foram alojados em pares e alimentados à vontade. No início e ao final do período experimental, as leitoas foram pesadas e submetidas à análise de ultrassom para avaliação da área de olho de lombo (AOL) e espessura de toucinho (ET). Os níveis de Ld proporcionaram aumento linear (P<0,05) do ganho de peso diário (GPD) e, apesar dessa variação, não houve aumento no valor absoluto do GPD a partir do nível de 12g kg-1 de Ld. A conversão alimentar (CA) reduziu (P<0,01) de forma quadrática até o nível estimado de 11,9g kg-1 de Ld. A AOL das leitoas aumentou (P<0,05) de forma linear. No entanto, o modelo "Linear Response Plateau" foi o que melhor se ajustou aos dados, estimando em 12,5g kg-1 o nível a partir do qual ocorreu platô. Não foi verificada influência (P>0,05) dos níveis de Ld sobre o consumo de ração diário (CRD) e ET. Os níveis de 12,0 e 12,5g kg-1 de Ld na dieta, correspondentes, respectivamente, ao consumo de lisina digestível diário (CLdD), de 23,6 e 24,6g, proporcionam os melhores resultados de desempenho e área de olho de lombo de leitoas em fase de crescimento (63 aos 103 dias de idade).

Eighty gilts (24.2±1.52kg) with high genetic potential for lean gain were used in a randomized complete block design to evaluate five digestible lysine levels (9, 10, 11, 12 and 13g kg-1) during the growing phase (63 to 103 days of age). Gilts were housed in pair and fed their respective diets ad libitum. At the begging and the ending of the experimental period, gilts were weighed and scanned by ultrasound to measure loin area, as well as fat depth. The digestible lysine levels linearly increase (P<0.05) average daily gain and loin area of gilts in growing phase. However, there was no difference for average daily gain at levels above 12g kg-1 while the "Linear Response Plateau" model was that better fitted to the loin area data that stabilized in a plateau starting from the level of 12.5g kg-1. The feed:gain ratio was improved (P<0.01) quadratically until the estimated level of 11.9g kg-1 of digestible lysine. There was no effects (P>0.05) of the treatments on the fat depth and feed intake. The digestible lysine levels of 12 and 12.5g kg-1, corresponding to the intake of 23.6 e 24.6g dia-1, provide the best results of performance and loin area of growing gilts (63 to 103 days old).