Dietary effects on the flow of nutrients from the abomasum of the preruminant calf

Abstract

Six Friesian bull calves were fitted with re-entrant duodenal cannulae within the first week of life. Within 2 days of surgery the calves were allotted to one of four experimental treatments which were either whole milk or a commercial milk substitute offered once or twice daily. At weekly intervals the calves were reallotted to another diet at random, so that each calf was fed for 1 week on each diet.

The flow of digesta from the abomasum decreased as the time after feeding increased. It was about 1l in the first hour after feeding and decreased to 100–200 ml per hour by 10 hr after feeding. The flow of digesta was greater and more uniform in calves fed twice daily than in those fed once daily.

The pH of the digesta increased to about 6 immediately after feeding, and then decreased to the pre-feeding levels of about 2 within 8 or 13 hr in calves fed twice and once daily respectively. The pH of the digesta of the calves given milk substitute was initially higher and subsequently lower than that of the calves given whole milk.

The flow of lactose to the duodenum was high immediately after feeding, and only about 3% of the ingested lactose entered the duodenum over the last half of the collection periods.

The flow of lipid and of nitrogen was high immediately after feeding and decreased gradually over the collection period. Of the daily intake of lipid, 10% reached the duodenum between 18 and 24 hr after feeding once daily. Initial flow of lipid and of nitrogen, expressed as a percentage of intake, was greater in calves given the milk substitute than in those given whole milk, but smaller over the latter part of the collection periods.

The concentration of free fatty acids in the digesta increased with time after feeding, and was greater for the calves fed once daily than for those fed twice daily. A greater percentage of the lipid (tallow) in the milk substitute was hydrolysed than of the lipid of whole milk. Proteolysis of casein proteins was greater for calves given whole milk than for those given the milk substitute.