Development of a functional rumen in the pre-weaned calf is critical for the transition from a milk-based diet to a forage and solids-based diet at weaning. Feeding highly fermentable carbohydrates in the form of starch and fiber in starter grains produces the volatile fatty acids (VFA) that stimulate rumen papillae development. This raises the question of whether enhancing VFA level in the developing rumen can increase rumen development to either increase growth of the milk fed calf or decrease age of weaning. Research published in the Canadian Journal of Animal Science asks the question of whether feeding extra ketogenic (sugar) or glucogenic (propionate) substrate with the starter grain enhances pre-weaned calf growth.
Starter grain ingredients, CP and NFC levels as % of DM.
The VFA (acetate, propionate and butyrate) from rumen fermentation stimulate the development of rumen papillae. Butyrate results from the fermentation of sugars and is a ketogenic energy source which raises blood levels of beta-hydroxy butyrate (BHBA). Propionate is a glucogenic VFA used by the liver to generate blood sugar. Propionate results from fermentation of starch in the rumen.
The study involved milk fed bull calves fed either a control starter grain, starter with sugar or starter with propionate as shown in the table above. Calves were on study from birth until weaning, when they consumed 1 kg of starter grain for 3 consecutive days, which was about day 70 of life. Calf growth measurements were conducted weekly and included body length, hip height, hip width, heart girth, and body weight. DMI, ADG and FE (Feed Efficiency) were computed weekly. Rumen fluid was obtained orally and analyzed for VFA. Blood samples were analyzed for BHBA. Calves initially received colostrum at 10% of BW for the first 3 days, and then pasteurized waste milk at 10% of birth weight or about 4 kg/day for the duration of the study. This was to enhance intake of the test starter feeds.
Overall there were no differences in growth parameters, ADG or feed efficiency due to dietary treatment. Blood BHBA was higher for the sugar supplemented calves. The authors concluded that neither supplemental sugar (ketogenic substrate) nor propionate (glucogenic substrate) improved calf growth or decreased age of weaning. However, this data does not indicate whether transition from a milk-based diet to a totally forage and grain-based diet differed by treatment. This study does not indicate whether rumen development was enhanced by diet or not, only that pre-weaned calf growth was not. It would be interesting to see if post weaning transition onto full ruminant diet was improved by supplementation of either sugar or propionate.