Flones, D. A., PHrr-r-tp, L. E., Vnrna, D. M. aNo IvaN, M. 1986. The significance of silage protein degradation and plasma amino acid ratios in the control of food intake by lambs fed ensiled and fresh alfalfa. Can De la luzerne (30%o de matidre sdche) r6colt6e en brins de 0,6 cm de longueur et conserv6e fraiche (congel6e) ou ensil6e a servi i alimenter huit moutons pendant deux p6riodes de 27 jours. L'ensilage a eu pour effet de d6grader la lysine, la thr6onine, I'histidine, 1'arginine, le tryptophane et la tyrosine contenus dans I'herbage original. L'isoleucine, la leucine et la valine n'ont toutefois pas subi de d6g-radation au cours de l'ensilage. L'une des consdquences de ces changements a 6t6 que les rapports de la tyrosine aux gros acides amin6s neutres et ceux de

A study was conducted with six sheep equipped with rumen and duodenal re-entrant cannulae to investigate differences in duodenal amino acid supply with fresh and ensiled alfalfa. The experiment was conducted as a cross-over design with two 12-d periods consisting of an adaptation phase (5 d) followed by feces collection (5 d), and finally on day 12, 24 h continuous collection of duodenal digesta and sampling of rumen fluid. During the experiment the sheep were restricted on feed to 52 g DM d−1 kg−0.75. Analyses of the forages revealed extensive breakdown of threonine, lysine and other basic amino acids, and high degree of preservation of branched chain amino acids. Relative to the amount consumed, there was a net loss of amino acids at the duodenum with fresh alfalfa but a net gain with silage. The relationship between intake of individual essential amino acids and duodenal recovery was inconsistent. Duodenal recovery of total essential amino acids was 28% higher with fresh than with ensiled alfalfa, a difference which was most pronounced with threonine and lysine. Digestion of organic matter and fiber was unaffected (P > 0.05) by ensiling of alfalfa. Estimates of ruminal pH were higher (P < 0.05) for silage than fresh forage (6.9 vs. 6.7) but VFA concentrations were lower (P < 0.05) for silage (52.1 vs. 64.1 mmol L−1). Rumen ammonia levels were similar for the two forages. The deficit in duodenal supply of essential amino acids with silage is discussed in relation to the problem of silage intake in ruminants. Key words: Alfalfa silage, duodenal amino acids, sheep, rumen digestion

No abstract

As with forage diets in general, ensiled tropical residue feeds and temperate grass and legume herbage tend to have lower fibre digestibility, ruminal biomass production and feed bypass, resulting in limited protein nurition and intake in the animal. Various modified (recombinant and mutated) microbial inoculants might be used mainly to : (1) boost lactic acid production in temperate silage to stabilize against further clostridial protein breakdown during the ensiling process and effect silage fibre (lignin, cellulose, and hemicellulose) digestion to increase digestibility and (2) increase microbial digestion of fibre along with boosting microbial protein synthesis to increase microbial biomass production in the rumen.

The N retention data, Table 1, as reported by the same author in this mini-review from the original research paper reported in the Can. J. Ani. Sci. 66: 1029-1038 is erroneous and thus comparisons of N retention and intake with ensilage cannot be made based on the study.