high-grain diet fed production rate propionic acid production feed intake specific activity single dose glu much direct proportion lacta receivedfor publicationmarch14 pro pionate pool size considerable variability propionate pool size glucose synthesis 1-14c propionate glucogenic amino nants natural log major need significant quanti ruminant gluconeogenesis propionate production rate dairy steer propionate production abstract effect linear regression equation large continuous demand various author rumen fistula vivo rumen propio-nate production glucose turnover rumen propionate pool size propionate pro duction
Dietary cobalt and subsequent ruminal synthesis of vitamin B12 normally meet the requirement for vitamin B12 in ruminants. Under typical conditions, rumen synthesis of vitamin B12 would be functional by six to eight weeks of age, depending on intake of dry feed. Pre-ruminant calves, lambs and kids require supplemental vitamin B12. Vitamin B12requirements of the dairy calf are estimated between and µg per kg ( to µg per lb) body weight (NRC, 1989). On a dietary basis, the requirement of young dairy calves ranges from 20 to 40 µg per kg ( to µg per lb) of dry matter (Radostits and Bell, 1970).