One thousand male Hubbard chicks were used in a 21-d study (10 birds per battery cage) to determine relative biological availability of phosphorus in seven samples of commercial dicalcium phosphate, expected to contain variable amounts of monocalcium phosphate. Five samples were from established producers in Brazil and two from the U.S. Pure calcium phosphate dibasic dihydrate was used as the reference standard. Phosphates were added to the corn-soybean basal diet (22.5% CP; 0.4% total phosphorus) to provide 0.1, 0.2, and 0.3% supplemental phosphorus. The calcium level was 1.0% for all diets. Left tibias were removed for bone ash (BA) and bone strength (BS) determination. Body weight, feed intake (FI), BA, BS, and plasma phosphorus increased (P < 0.01) and plasma calcium and alkaline phosphatase decreased (P < 0.01) with increasing dietary phosphorus regardless of source. The availability of phosphorus for each test phosphate was determined by slope ratio, with BW, BA, and BS regressed on phosphorus added within each phosphorus source. A relative biological value (RBV) was calculated based on BW, BA, and gain:feed ratio. Availability based on BW ranged from 97.07 to 110.41%. When BA was the criterion, values were 80.32 to 107.84% and for BS were 79.34 to 110.52%. The RBV ranged from 97.55 to 100.60%. Phosphate sources did not vary greatly in phosphorus availability. Overall phosphorus availability averages were higher for BW (103%) and RBV (99%) and lowest for BA (96%) and BS (94%).

Os pesos individuais semanais da desmama ao abate de 2.882 coelhos, sendo 1.512 da raça Califórnia e 1.370 da raça Nova Zelândia Branca foram analisados pelo método dos quadrados mínimos para verificação dos efeitos da endogamia, uma covariável no modelo matemático, no desempenho desses animais. Tanto os efeitos lineares quanto quadráticos da endogamia dos coelhos foram importantes para pesos individuais a diversas idades. A endogamia dos coelhos não afetou seu desempenho à desmama (realizada em média aos 28 dias) e nem às cinco semanas de idade, mas afetou significativamente os pesos corporais de 6 a 11 semanas, com aumentos de pesos para endogamia variando de 0 a 10% e diminuições do desempenho após este nível. Nas características de carcaça e abate, o efeito foi pequeno, com uma tendência geral de decréscimo com o aumento do coeficiente de endogamia, o mesmo sendo verificado com o rendimento de carcaça. Estes resultados demonstram a importância do controle dos níveis de endogamia em coelhos, pois, mesmo quando mantidos abaixo dos 10%, podem afetar significativamente o desempenho produtivo.

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