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Plant sciences, sustainable farming systems and food quality
RESEARCH ARTICLE

Rumen characteristics, methane emissions, and digestion in weaned lambs reared in isolation

G. J. Faichney, N. M. Graham and D. M. Walker

Australian Journal of Agricultural Research 50(6) 1083 - 1090
Published: 1999

Abstract

Twelve Merino lambs were separated from their dams at 2 days of age. Six were reared in isolation and 6 were inoculated with rumen fluid when 4 weeks old. Apelleted, mixed diet was available from 10 days of age; milk feeding was restricted to maintenance from 2 weeks and discontinued when liveweight reached 9 kg. Three lambs from each group were given a medium intake and 3 a high intake of the diet.

The isolated lambs had virtually no rumen protozoa; rumen ammonia and volatile fatty acid concentrations were lower in these lambs but acetate:propionate ratios were higher. The rumen mean retention time (MRT) of a solute marker was longer but the microbial turnover time (TT) was shorter in the isolated lambs; both MRT and microbial TT were shorter on the high intake. Total microbial synthesis did not differ between groups. The digestibilities of energy, organic matter, non-structural carbohydrate, and crude protein were lower in the isolated lambs but those of cell wall constituents were not affected significantly; digestibilities were lower on the high intake. The isolated lambs emitted much less methane than the inoculated lambs; consequently, available energy (i.e. digestible less methane energy), was similar for the 2 groups. Recovery of reducing equivalents in the rumen fermentation was incomplete in the isolated lambs but could be accounted for if reductive acetogenesis provided 13% (medium intake) or 16% (high intake) of the acetate and butyrate formed.

Keywords: reducing equivalents, reductive acetogenesis, rumen ammonia, volatile fatty acids, acetate:propionate ratio, protozoa, microbial protein synthesis, microbial turnover time, mean retention time.

https://doi.org/10.1071/AR98195

© CSIRO 1999

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