Effect of starch level and roughage intake on animal perfomance, rumen wall characteristics and liver abscesses in intensively fed Frisian bulls

Summary

Organic dairy cows in Denmark has a higher frequency of liver abscesses, which is probably due to higher starch levels in the feed rations to high yielding cows compaired to conventional cows. Following abstract is based on experiments on young bulls and demonstrates whether replacing high-starch feeds with low-starch feed, such as dried grass pellets and sugar beet pulp, can reduce the problems with liver abscessation without reducing the performance level. The low-starch feed would be relevant to organic dairy production.
In total, 41 Danish Friesian bulls (154±20 kg LW) were allocated into four treatment groups in a 2x2 factorial design fed either a high starch (N) or a high fibrous concentrate (F) and either chopped barley straw (S) or a mixture of 75% chopped barley straw and 25% sugar beet molasses (Sm). In the F ration, 25% of the wheat from N was replaced by dried sugar beet pulp and grass pellets giving a starch level of 24.3% and 39.1% (wt) and an energy content of 0.99 and 1.04 Scandinavian Feed Units/kg feed, respectively. The ad libitum fed bulls were slaughtered at 11.5±0.2 mo. weighing 429±41 kg LW on average. Feed intake was higher for F than N (p=0.005) (7.1 vs. 6.4 kg/d), whereas the addition of molasses increased straw intake from 0.5 to 0.9 kg/d (p<0.001). The higher intake of Sm compared with S reduced concentrate intake (p<0.05), but did not affect total net energy intake. The average daily gain (1370 g/d) did not differ between groups. The rumen wall was more severely damaged with N compared with F (p<0.05) and with S compared with Sm (p<0.003). The higher straw intake prevented rumen wall damage, but did not reduce the number of animals with liver abscesses, like the lower starch level did (1 vs. 9 animals, p<0.005).