The effect of age of pre-ruminant calves on digestibility of organic nutrients and nitrogen retention

Apparent digestibility of organic nutrients and nitrogen retention were stu died in 23 three-day balance periods with five male calves of Czech Red Pie d breed at the age of 9 to 91 days. Animals were fed on milk replacer ad se mi-libitum. The digestibility and nitrogen retention were determined using the chromic oxide indicator method. The average values of digestibility wer e as follows: crude protein (CP) 0.642 +/- 0.0162, crude fat(CF) 0.776 +/- 0.0104, nitrogen-free extract (NFE) 0.940 +/- 0.0027. Digestibility of nutr ients under study changed highly significantly (P < 0.01) with the age of c alves. The dependence of determined values on age was expressed by the 2nd degree parabola equations with the maximum values on Days 62, 67 and 74 for CF, NFE and CP, respectively. The most marked increase was observed in the first weeks of experiment. Percentage of nitrogen retention changed highly significantly (P < 0.01) with age and the dependences expressed by the con cave parabola equation achieved their maxima on Days 81 and 63 for nitrogen consumed and digested, respectively.