Effect on calf growth of accounting for early in vitro degradation kinetics when composing a calf starter ration

The degradation kinetics of five concentrates (steam dried sugar beet pulp; drum dried sugar beet pulp; toasted faba beans; untreated faba beans and soy bean hulls) were estimated using the in vitro gas production technique in two 48 hour fermentations. Two pairs of calf starter rations were formulated based on the in vitro degradation profiles of the individual concentrates. The rations were balanced using NorFor – the Nordic feed evaluation system- to provide a similar net energy (MJ/day), but with differing in vitro degradation kinetics during the first 16 hours of fermentation. Each pair consisted of rations made with ingredients that had an expected in-vitro “fast” degradation and an expected in-vitro “slow” degradation relative to each other during the first 16 hours of fermentation. The first pair (Fast_1 and Slow_1) consisted mainly of a single fast or slow in-vitro degraded ingredient, either steam dried sugar beet pulp (48.5%) or drum dried sugar beet pulp (49.5%), respectively. The second pair (Fast_2 and Slow_2) included a second expected fast or slow in-vitro degraded ingredient, in addition to the steam or drum dried sugar beet pulp. The extra “fast” ingredient was untreated faba beans (40%), while the second “slow” ingredient was toasted faba beans (38.5%). 
The calf starter rations were fed to a total of 154 calves on two different farms for 8 weeks. Each calf was weighed weekly. The mean total weight gain of each calf after trial was 68.6 kg and 68.5 for Fast_1 and Slow_1, respectively. For Fast_2 and Slow_2 the mean total weight gain was 64.9 kg and 63.8 kg, respectively. No significant differences were found in the calves’ weight gain or feed efficiency.