Oat (Arena sativa L.) varieties differ in their susceptibility to Mn deficiency. A Mn-efficient plant utilizes a limited supply of Mn, whereas a Mn-inefficient plant, grown under identical conditions, develops Mn-deficiency symptoms. The objective of this study was to characterize these differences. Four Mn-inefficient oat varieties (‘Star,’ ‘Maelor,’ ‘Cayuse,’ and ‘Vicland’) and four Mn-efficient oat varieties (‘S171,’ ‘Avon,’ ‘Park,’ and ‘Golden Rain’) were grown in nutrient solution containing increasing amounts of Mn. All of the Mn-inefficient varieties except Star developed Mn-deficiency symptoms when grown at 0.005 mg/liter Mn. None of the Mn-efficient varieties developed the symptoms. Concentration of Ca was consistently greater in tops of the Mn-efficient than in those of Munificent oat varieties. Where the concentration of P was increased in the nutrient solution, Vicland contained more P and less Ca than Golden Rain. It is suggested that Ca may physically substitute for Mn at nonspedfic sites in the plant, thus making more Mn available for specific chemical reactions that require it.

Non-pregnant Cheviot ewes and Cheviot x Suffolk ewe lambs were used in a series of in vivo trials over a 2-year period. Silages fed included corn silages made from early (Seneca SX 155) and late (Seneca 285) maturing varieties, harvested at the early dough and early dent stages respectively. Digestibility by sheep was determined by total collection in all experiments. Chemical composition, dry matter (DM) solubility, as well as in vitro digestibility of cellulose, organic matter and DM of corn silage samples were determined. The relationships between voluntary silage consumption and its chemical composition as well as in vitro digestibility suggest that both DM and digestible energy (DE) intakes of corn silage were highly related to its lactic acid, pH, DM and crude protein contents in descending order of importance. Lactic acid and, subsequently, pH of the silage accounted for 66 % of the variation in DM intake. Chemical composition predicted corn silage DM intake to a slightly greater degree than in vitro methods. On the other hand, the silage components tested accounted for no more than 15 % of the variation in DE intake, but in vitro digestibility analyses accounted for 41 % of the variability. Nutrient composition could not reliably predict DE intake of corn silage. In vitro digestibility analyses suggested that either 12-hour in vitro cellulose digestibility, in vitro organic matter or DM solubility could predict corn silage DM and DE intakes.