Growth of Periruminant Holstein Bull Calves Fed a Fermentation Extract of Aspergillus oryzae
A fermentation extract of the fungus Aspergillus oryzae can be utilized as a direct fed microbial. The objective was to determine if dietary inclusion of an extract of A. oryzae would improve the growth of Holstein bull calves from birth thru 1wk post weaning; it was hypothesized that it would. Bull calves (n=52) were used in this experiment. Calves were randomly assigned to a slaughter age, 4 wk (n = 16) or 8 wk (n = 36) and treatment, control (CON; n = 27) or direct fed microbial (DFM; n = 25). Calves averaged 43.2 ± 1.0 kg BW and 2.8 ± 0.3 days of age at the beginning of the experiment. Calves were housed and fed individually; no bedding was used. Calves assigned to DFM were fed 2 g of DFM daily. Liquid DFM was delivered in milk replacer for the first 4 wk of the trial; solid DFM was top-dressed on texturized grain thereafter. Calves were fed non-medicated milk replacer twice daily (22.0% CP, 20.0% fat DM basis; 680 g/d) and were weaned upon consumption of 0.91 kg of grain (20% CP, 2.0% fat; medicated with decoquinate) for 3 consecutive days or on d 45 of the study, whichever came first. Calves had ad libitum access to grain and water throughout the trial. Feed intake was recorded daily. Body weight (BW) was recorded weekly. There was no effect of treatment on BW; 8 wk BW was 74.5 ± 1.9 kg for CON and 74.6 ± 1.9 kg for DFM. Total dry matter intake per calf did not differ: from 0 thru 4wk (19.48 ± 0.67 kg of DM), 5 thru 8wk (39.44 ± 2.05 kg of DM), or for the whole trial (58.70 ± 3.30 kg of DM). Lastly, the gain to feed ratio did not differ by treatment: from 0 thru 4wk (0.59 ± 0.05), 5 thru 8wk (0.53 ± 0.03), or for the whole trial (0.56 ± 0.04). Here, dietary inclusion (2g/d) of an extract of A. oryzae did not result in improved calf growth when supplemented animals were compared to cohorts not fed the direct fed microbial. It is possible that the dose used here was not high enough to elicit treatment effects. Given that effects have been noted in other species, a follow-up dose titration study with similar diets as used here seems warranted.
dairy calf, direct fed microbial, growth, nutrition