Effect of dietary calcium and phosphorus levels on growth, carcass characteristics and liver and kidney functions of growing Egyptian geese

The present study investigated the effect of different dietary levels of calcium (Ca) and non-phytate phosphorus (P) on the growth performance, carcass characteristics, and blood components of growing geese. A total of 120, 4-wk-old Egyptian goslings with similar body weights were randomly distributed to four groups in a 2 × 2 factorial arrangement, which included 2 levels of Ca (0.85% and 0.70%) and 2 levels of non-phytate P (0.45% and 0.35%). Each group was subdivided into 6 replicates of five birds. The experiment lasted 8 wk, from 4 to 12 wk of age. Results show that dietary Ca level had no significant effect on any of the studied growth performance traits over the full experimental period. Dietary P level also had no significant impact on these traits, with the exception of daily body weight gain and feed conversion ratio at 8 to 12 wk of age; these improved significantly with the low P diet. Geese received a diet containing 0.70% Ca + 0.45% P had the lowest body weight values at 12 wk of age and the lowest daily body weight gain, and feed intake at 8 to 12 weeks of age. While, the lowest value of feed conversion ratio was recorded in geese fed low level of Ca with low level of P (0.70% Ca + 0.35% P). There were no significant effects of the different dietary levels of Ca, P, or their interaction on all studied carcass parameters. Low dietary Ca level significantly increased the plasma levels of total protein, albumin, alanine transaminase (ALT), aspartate transaminase (AST), and creatinine and significantly decreased the plasma levels of Ca and P. Different dietary P levels had no significant effect on plasma levels of albumin, AST, ALT, ALP, and urea, whereas the 0.35% P-based diet significantly decreased the plasma contents of total protein, creatinine, Ca, and P. Plasma levels of albumin, creatinine, urea, Ca, and P were not affected by an interaction between Ca and P. Diets containing 0.70% Ca and 0.45% P lead to the highest plasma values for total protein, ALT, AST, and ALP compared with the other dietary Ca and P combinations. In conclusion, dietary Ca and P levels can be simultaneously reduced without negative impacts on growth performance, carcass characteristics, or blood biochemical components. We advise to avoid increasing the dietary Ca: P ratio, as it leads to negative effects on growth performance and blood biochemistry in growing geese. So, the findings of the current study recommended the low levels of Ca (0.70%) and non-phytate P (0.35%) for the performance of Egyptian geese during the fattening period.