Effect of the type of concentrate, cereals vs. sugar beet pulp, on rumen fermentation, plasma concentration of methylmalonate and quality of subcutaneous adipose tissue of intensively reared lambs

The aim of this study was to investigate the effect of substituting wheat a nd barley by sugar beet pulp on the quality of subcutaneous adipose tissue of intensively reared lambs. Rumen fermentation and methylmalonate plasma c oncentration, both considered as indicators of lamb metabolism, were also s tudied. Forty-nine male lambs of the Lacaune dairy breed were fed from 23.6 (+/-4.1) kg to 41.0 (+/-1.9) kg live weight with hay and a pelleted concen trate containing either wheat and barley (80%, group C) or sugar beet pulp (70%, group P). Rumen fluid samples were collected at 0, 1, 2, 4 or 6 hours after the last meal before slaughter from 5 lambs per diet at each time. T he plasma concentration of methylmalonate was measured in two samples per l amb collected 12 and 36 d before slaughter. The calculated metabolisable en ergy intake and average daily gain were not significantly different between group C and P (3.27 Mcal.d(-1) and 309 g.d(-1)). Six hours after the last meal, the rumen concentration of total volatile fatty acids was higher in g roup C than in group P (186 vs. 137 mmol.L-1, P<0.01) and the acetate/propi onate ratio was lower (0.91 vs. 2.07, P<0.01). The average concentration of methylmalonate in plasma was higher in group C than in group P (2.76 vs. 1 .92 mmol.L-1, P=0.09). However, the diet had no significant effects on the firmness and colour of subcutaneous adipose tissue; globally, the quality w as poor. No relationship between plasma concentration of methylmalonate and fat firmness scores was observed.