The aim of this research was to compare energy values, nitrogen metabolism and diet digestibility of four barley (Hordeum vulgare L.) cultivars grown in two different years, to identify the most important factors affecting variation. Six wether lambs (39.4 ± 1.6 kg) were assigned within period in a randomized complete block design to barley cultivar (1990 Camelot, 1990 Cougbar, 1990 Steptoe, 1991 Boyer, 1991 Camelot and 1991 Steptoe) and consumed a diet of 83% barley, 10% alfalfa pellets and 7% supplement on a DM basis. During each 14-d period, feed, orts, fecal and urine samples were collected during the last 7 d and methane emissions were quantified. Digestibility of NDF polymeric monosaccharides was lower (P < 0.10) for weathers fed 1990 Steptoe than all cultivars other than 1991 Boyer and was positively correlated to methane production (r = 0.52). Barley DE was not different among cultivars but, because methane production was greater (P < 0.10) for lambs fed 1991 Boyer (38 L d−1) than for those fed 1990 Steptoe (21 L d−1) and 1990 Camelot (26 L d−1), barley ME content of 1991 Boyer (12.3 MJ kg−1 OM) was lower (P < 0.10) than for 1990 Steptoe (13.4 MJ kg−1 OM). Nitrogen digestibility in lambs fed Camelot grown both years was greater (P < 0.05) than for most cultivars. Absorbed nitrogen was greatest (P < 0.10) in lambs fed 1991 Camelot and nitrogen retention (g d−1) tended to be greater than 1990 Cougbar (P = 0.14) and 1990 Camelot (P = 0.16) fed lambs. Cougbar, Boyer and 1991 Steptoe had lower feeding quality for ruminants because of lower energy and/or nitrogen metabolism, while both years of Camelot and 1990 Steptoe had greater ME values. Methane production, digestibility of NDF polymeric monosaccharides and nitrogen metabolism were major factors contributing to variability among barley cultivars within and between years. Key words: Barley, lambs, methane, metabolizable energy
Factors Affecting the Metabolizable Energy Values of Four Different Poultry Feedstuffs