SEASONAL-CHANGES IN INTAKE AND DIGESTION OF CHOPPED TIMOTHY HAY (PHLEUM-PRATENSE) BY 3 BREEDS OF SHEEP

The voluntary food intake (VFI) and apparent digestibility of chopped timothy hay by six Scottish Blackface (BF), Shetland (SH) and Dorset H orn (DH) non-breeding ewes were assessed in summer and winter. In two experiments VFI was higher in summer than in winter but did not differ between the breeds. In Expt 1, the seasonal difference in VFI was gre ater in BF and SH than in DH ewes and the apparent digestibility of dr y matter (DM), organic matter (OM) and total nitrogen was consistently higher in all three breeds in summer than in winter. The higher diges tibility of DM of the hay in summer than in winter was confirmed in Ex pt 2, in which the whole tract mean retention time (MRT) of the undige sted residues was measured using (103)ruthenium-phenanthroline as a ma rker. The MRT was lower in all three breeds in summer than in winter. In a third experiment, following at least 6 months ad libitum feeding on the hay, for all three breeds the contents of DM and liquid in the reticulorumen were smaller in summer, and the liquid fraction formed a greater proportion in summer than in winter. The results contrast wit h the expectation that intake and digestibility within a given forage type are negatively correlated. Although an increase in digestibility may facilitate a higher VFI in summer (BF and SH) it does not necessar ily do so (DH).