Study of the between-goat variation in feed efficiency with a high-concentrate diet

Feed efficiency in ruminants is largely linked to rumen digestive efficiency. Moreover, some recent research pointed out that feeding behaviour influences rumen pH. This work showed that twelve dairy goats (six Alpine and six Saanen) characterized by very different intake rates with a standard diet increased their intake rate when the diet was changed to a high concentrate one. The between-goat ranking for intake rates was not modified (P = 0.70) by the shift in diet composition. Organic matter digestibility of the high concen- trate diet decreased as level of intake increased, with a 2.2 points difference between the Alpine and Saanen breeds. This difference is mainly due to a difference in cell wall digestibility and can be explained neither by the rate of intake, nor by the sorting behaviour or by the fat corrected milk yield. Feed efficiency was, in this trial, linked to metabolic efficiency. Both items were explained by the fat-corrected milk yield. Feed efficiency was not correlated with digestibility and there was no difference (P = 0.72) between breeds. Differences between animals in feed efficiency were explained by differences in metabolic efficiency.