Response of the Gravid Gilt to Levels of Protein as Determined by Nitrogen Balance

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Abstract
A total of 73 nitrogen balance observations were made in five experiments utilizing 42 crossbred gilts. Diets composed of a mixture of corn and soybean meal (weight ratio of 4.4:1, respectively) and corn starch were formulated to contain from 0 to 15% protein. Total daily diet intake was 1.82 kg. Nitrogen retention plateaued at approximately 12.5% protein on the 85th and 105th days postcoitum. Gilts fed the 9, 12 and 15% protein diets showed superior ability to retain nitrogen at the latter time, i.e., an increased daily retention compared with the initial period of 1.8, 3.1 and 3.6 gm., respectively. Gilts fed the nitrogen-free diet had a mean negative nitrogen balance of about 6.5 gm. per day. Mean daily metabolic fecal nitrogen and endogenous urinary nitrogen excretions were, respectively, 1.37 and 6.5 gm. A nitrogen intake equivalent to 3% protein appeared to be slightly in excess of the maintenance need. Since the gravid gilt appears to satisfy her intrauterine amino acid and amino nitrogen needs prior to meeting her extrauterine needs, fetal weight has little or no influence on the efficiency of nitrogen utilization unless the intake is sufficient to meet the extrauterine requirement. Total serum protein concentration was lower at the completion of the experiments than initially, with the degree of reduction being closely related to the level of dietary protein. Of the individual serum components, albumin concentration closely resembled the changes in total protein. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science