The flow of nutrients from the abomasum in calves fed on heat-treated milks

Abstract

Three 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 diets: (1) fresh milk; (2) spray-dried low-heat whole milk powder (LS); (3) spray-dried high-heat whole milk powder (HS); (4) roller-dried whole milk powder (RD). 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. When calves were fed once daily on the severely heat-treated milks (HS and RD), a more rapid flow of nutrients from the abomasum occurred in the first 12 hr after feeding, and a lower flow between 12 and 24 hr after feeding, than when they were given fresh milk or the LS milk. In the first 6 hr after feeding calves on fresh milk or LS milk a greater proportion of the casein nitrogen tended to be hydrolysed in the abomasum than in those fed on the HS milk. Subsequently the situation was reversed. The hydrolysis of fats in the abomasum was greater when the calves were given the severely heat-treated milks (HS and RD) than when they were fed on the other milks. Many of the changes observed may be related to the density of the milk clot formed in the abomasum.