Rumen fermentation and histology in light lambs as affected by forage supply and lactation length.

This study determined whether the rumen fermentation and histology traits may reflect the feeding strategy in light lambs (22-24 kg). Thirty-two single Rasa Aragonesa lambs were assigned to one of four treatments in a 2×2 factorial design. The factors were the inclusion of forage in the diet (alfalfa grazing vs. concentrate-fed indoors) and lactation length (weaning at 13 kg vs. suckling until slaughter). A multivariate canonical analysis discriminated individuals among feeding strategies. The main function differentiated weaned concentrate-fed lambs from the rest according to dorsal sac papillae height, ventral sac muscular layer thickness and the proportion of rumen valerate. The second function differentiated suckling concentrate-fed lambs from the rest according to plasma urea levels. Lactation length played an important role on rumen histology and protein utilization, especially in concentrate-fed lambs. Alfalfa grazing light lambs had similar rumen morphometric measures and fermentation characteristics, regardless of milk access.