Relation between Age of Calf, Blood Glucose, Blood and Rumen Levels of Volatile Fatty Acids, and in Vitro Cellulose Digestion

Absorption of acetate-1-C14 from the reticulo-rumen of Calves 3 to 4 days old

“…The increasing capacity of calves reared on solid feeds to assimilate VFA (Sutton, McGilliard, and Jacobson 1963;McGilliard, Jacobson, and Sutton 1965) must therefore be attributed to the expansion of pre-existing mechanisms and not to the establishment of new ones. Physical factors that would contribute to this increase in passive transfer include: a rise in the VF A concentration and acidity of rumen contents (McCarthy and Kesler 1956;Conrad, Hibbs, and Frank 1958); an expansion in the relative capacity and surface area of the rumen (Brownlee 1956;Warner, Flatt, and Loosli 1956;Tamate, McGilliard, Jacobson, and Getty 1962); and an enhancement in the vascularisation of and blood flow through the rumen wall (Dobson, Brown, Dobson, and Phillipson 1956). …”

Effect of forage addition to the diet on rumen development in calves

“…In adult ruminants rates of glucose oxidation remain lower than what is observed at birth (6.11) (Baldwin and Jesse, 1992). This decline in glucose oxidation by rumen epithelial cells causes blood glucose levels to decline as the calf ages (McCarthy and Kesler, 1956;Young et al, 1970). However, insulin concentrations remain constant with age of the animal (Young et al, 1970).…”

“…Ruminai VFA concentrations, including butyrate, increase with consumption of solid feed McCarthy and Kesler, 1956;Godfrey, 1961b;Bomba and Zitnan, 1992;Zitnan et al, 1993;Lane et al, 2000). There is a rapid rise in ruminai VFA concentrations from 12.7 mmoles/1 at 1 week of age to 67.4 mmoles/1 at 5 weeks (Godfrey, 1961b).…”

“…This decline in glucose utilization along with a subsequent increase in concentrations of VFA is correlated with the development of the rumen and the consumption of solid feed. Measurement of ketones such as BHBA and acetoacetate reflect VFA utilization by the rumen epithelial cells (McCarthy et al, 1956). …”

Functional development of epithelial tissue of the reticulo-rumen in calves

“…Rumen VFA concentrations are very low at birth and change little on a diet of milk only (Conrad et al, 1954;Godfrey, 1961b;Wardrop and Coombe, 1961). When solid feed is included in the diet, the VFA level of the rumen contents increases to adult levels within 2 or 3 months (Conrad _et al, 1954;Godfrey, 1961b;McCarthy and Kesler, 1956;Wardrop and Coombe, 1961). An almost parallel rise in blood VFA concen trations on solid diets (Conrad et al, 1958a;McCarthy and Kesler, 1956;Held, 195-3) indicates that absorption takes place.…”