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A study of the protein requirements of the mature breeding ewe

Maintenance requirement of the non-pregnant ewe

Published online by Cambridge University Press:  09 March 2007

J. J. Robinson  and
T. J. Forbes
J. J. Robinson
Affiliation:
Agricultural Research Institute of Northern Ireland, Hillsborough and The Queen's University of Belfast
T. J. Forbes
Affiliation:
Agricultural Research Institute of Northern Ireland, Hillsborough and The Queen's University of Belfast
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Abstract

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1. An experiment was carried out to study more precisely by nitrogen balance techniques the intake of digestible crude protein required for maintenance in the mature non-pregnant ewe. 2. Four isocaloric diets supplying adequate energy, approximately 90 kcal/kg W0.73 metabolizable energy daily, and differing in crude protein content were each given to eight individually penned ewes. The diets provided 2.4, 4.9, 7.7 and 9.5 g digestible N per ewe per day. 3. The average weight of the ewes was 57.4 kg. They were rationed according to metabolic body-weight (W0.73) at a rate of approximately 800 g dry matter per 50 kg ewe per day for a 4-week period before N balance studies were carried out over an 8-day collection period. 4. The mean apparent digestibilities of dry matter were 67.3±0.8, 68.1±0.7, 70.9±1.0 and 68.8±0.8 respectively. The apparent digestibilities of N, increasing with increasing N intake, were 30.6±2.1, 46.3±2.1, 58.2±0.6 and 61.5±1.3 respectively. 5. The intake of apparently digested N required for maintenance was calculated in three ways, from the regressions of apparently digested N on N retention or on urinary N and from the underlying relationship between N retention and urinary N. The estimates so obtained were respectively 0.185±0.037, 0.148±0.020 and 0.150±0.020 g N per kg W0.78 per day, corresponding to 1.16, 0.93 and 0.94 g apparently digestible crude protein per kg W0.73 per day. 6. Metabolic faecal N, determined by the extrapolation method, was 0.629±0.047 g/100 g dry matter consumed. 7. The results are discussed in relation to practical feeding standards and other research findings.

Type
Research Article
Information
British Journal of Nutrition , Volume 20 , Issue 2 , May 1966 , pp. 263 - 272
Copyright
Copyright © The Nutrition Society 1966

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