Final answer:
To calculate nitrogen intake, use the Biological Value formula and for protein catabolic rate, use the Protein Efficiency Ratio formula.
Step-by-step explanation:
Nitrogen intake can be calculated using the formula for Biological Value (BV), which is (grams of nitrogen retained / grams of nitrogen absorbed) x 100.
This calculation provides a measure of the efficiency of protein absorption and retention.
Protein catabolic rate can be calculated using the Protein Efficiency Ratio (PER) formula, which is (grams of weight gained / grams of protein consumed).
This calculation provides a measure of the efficiency of protein utilization for weight gain.