Changes in nitrogen and nucleic acid contents of the liver and muscle of preruminant lambs given high and low protein diets

Abstract

Twenty-one crossbred lambs (aged 2-5 days) were allotted at random to three groups. A control group of six lambs was slaughtered immediately. Six lambs were given a low protein diet (diet A) and nine lambs a high protein diet (diet B). Subgroups of three lambs given diet A were slaughtered after 2 and 6 weeks on experiment; subgroups of three lambs given diet B were slaughtered after 2, 4, and 6 weeks. At slaughter the deoxyribonucleic acid (DNA), ribonucleic acid, and nitrogen (N) contents of the liver and vastus lateralis muscle were determined. It was possible, from a knowledge of the DNA phosphorus contents of these organs at different ages, to determine the relative increase or decrease in cell numbers per organ and in cell size. A comparison of (1) the comparative slaughter method and (2) the N/DNA phosphorus ratio method, for estimating the protein gain or loss from the liver and muscle, showed poor agreement between the two methods. The reason for the discrepancy was the change in the total DNA phosphorus content of the liver and muscle during growth.