Energy and protein nutrition of early-weaned XXXX . 2. Effect of energy intake and energy: protein on energy utilisation and body composition of @entity1707 slaughtered at 32 d.

@entity1707 @entity1568 @entity1132 @entity1017 @entity3147 @entity62
1. The effect of energy and protein intake on the @entity1568 and energy utilization and carcass composition of artificially-reared @entity1707 was studied between 8 and 32 d of age in an experiment employing a 5 x 3 x 2 factorial design. The factors were initially energy:N value (1) (250, 355, 460, 565 or 670 kJ/g N), rate of increase of I (R) at 8 d intervals (0, 12.5 or 25%) and @entity3147 (three times daily to appetite or 75% of this intake). 2. The range of energy:N values was obtained by formulating five diets based on dried skim milk, @entity1132 and casein and feeding appropriate combinations of two diets. 3. The metabolizable energy (ME) intake, carcass @entity62 ( @entity62 ) content, carcass @entity1017 and carcass fat gain exhibited significant (P less than 0.001) quadratic responses to I. 4. The carcass fat content in the @entity62 increased from 200 to 342 g/kg ( less than 0.001) and the carcass crude protein (N x 6.25) content decreased from 657 to 519 g/kg with increasing level of I (P less than 0.001). The fat and protein contents were 309 and 556 g/kg and 242 and 610 g/kg respectively on the high and low @entity3147 ( @entity3147 ) and were significantly different (P less than 0.001). 5. There was a significant I x R interaction in relation to carcass @entity1017 with the maximum gain occurring at 460 kJ/g N when I was constant and at 355 kJ/g N when R was 25% per 8 d. 6. The proportion of apparent digested N intake retained (N retention (NR):apparent digested N (ADN)) was significantly (P less than 0.001) affected by all three factors and there were significant I x R (P less than 0.001), I x @entity3147 (P less than 0.01) and R x R x @entity3147 (P less than 0.01) interactions. The maximum value of NR:ADN was 0.80. 7. Carcass fat gain and carcass energy gain exhibited quadratic responses to I reaching maximum values at 460 kJ/g N. The energy content of the live-weight gain increased linearly (P less than 0.001) from 5.79 to 7.90 MJ/kg with increasing level of I. @entity3147 and R also produced significant (P less than 0.001) responses the means being respectively 7.52 and 6.39 MJ/kg on the high and low @entity3147 and 6.55, 6.94 and 7.38 kJ/kg with increasing value of R. 8. Multiple regression analysis of ME intake on live-weight (W), @entity1017 (FG) yielded the equation: ME (MJ) = 0.644 W0.75 + 32.6 @entity1017 " 48.2 FG. This result is discussed in relation to published values for the energy requirements of the young @entity1707 .
