Nutritive value of live and dead components of two bunchgrasses

On northern latitude winter rangelands, the effects of low forage nutritive value on animal performance are usually mitigated by supplementing livestock, although the amount of supplement is often not adjusted for available forage quantity and nutritive value. The objective of this study was to assess the potential of live (fall, spring) and dead component of two cool-sea-son bunchgrasses to meet nutritional requirements of cattle from fall through spring on a foothills range site in southwestern Montana. Several nutritive characteristics of live and dead components of bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) and Idaho fescue (Festuca idahoensis Elmer) were assessed during the winters of 1991–1992 and 1992–1993. In addition, rate and extent of dry matter disappearance, and extent of crude protein disappearance were determined in-situ using ruminally cannulated beef cows. Nutritive value of forage components of bluebunch wheatgrass and Idaho fescue were similar fall through spring. Fall growth was similar in CP and digestibility to April growth, and maintained these levels through winter. With normal forage intake rates on winter range, CP levels of standing dead material would not meet animal protein requirements fall through spring. When fall growth is not abundant, more protein supplement would be needed than when it is abundant. Matching animal requirements to forage availability and nutritive value, supplementing only when necessary and in appropriate amounts, could help reduce costs of winter feeding. Key words: Winter grazing, bluebunch wheatgrass, Idaho fescue, forage quality, cattle

Alfalfa plant death during the summer versus the winter in interior British Columbia

Single plants of 12 alfalfa (Mediccigo sativa L.) cultivars, chosen to represent a range of winter hardiness and resistance to verticillium wilt (Verticillium albo-atrum), were space planted to determine the time of plant death during the year. Plant mortality was assessed in spring and fall for three consecutive years. The relationship between plant survival during summer or winter and the cultivars’ resistance to verticillium wilt or fall growth was examined. During the first 2 yr of this field study, natural mortality during both summer and winter ranged from 1.0 to 2.1%. But by the third year an average of 9% of the plants died during the summer. Survival during the third summer was correlated (r = 0.76, P = 0.004) with the veritcillium wilt resistance measured using a greenhouse screening test, but was not correlated with fall growth of the cultivars. During the third winter, plant death for all cultivars averaged 67%. Survival of a cultivar during the winter was negatively correlated (r = −0.84, P = 0.001) with its fall growth, but not with its verticillium wilt resistance. These results indicate that programs to develop alfalfa cultivars with long-term persistence in the interior region of British Columbia should include both fall growth and verticillium wilt resistance in their selection criteria.Key words: Verticillium wilt, winter injury, fall dormancy, winter hardiness, stand persistence