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Rumen Measurements in Periruminant Holstein Bull Calves Fed a Fermentation Extract of Aspergillus oryzae
Age and diet can affect morphological development of the rumen, which mainly refers to organ size and papillae characteristics. A fermentation extract of Aspergillus oryzae can be utilized as a direct fed microbial to alter ruminal VFA concentrations in mature ruminants. Dietary inclusion of a fermentation extract of A. oryzae on growing calves is not well studied. The objective was to determine effects of age and dietary inclusion of an extract of A. oryzae on morphological development of the rumen. Individual calves (n=52) 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 were housed and fed individually; no bedding was used. Liquid DFM was delivered in milk replacer (2 g per day) for the first 4 wk of the trial; solid DFM (2 g per day) was top-dressed on 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 texturized grain (20% CP, 2.0% fat) 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. Treatment and the interaction of treatment and age did not affect full or empty rumen weights. However, full and empty rumen weights at 8wk (5.29±0.21and 1.31±0.04 kg, respectively) were greater than 4wk (1.81±0.30 and 0.52±0.06 kg, respectively). At each slaughter point, punch biopsies (2.54 cm internal diameter) were obtained from 4 regions within each rumen (cranial dorsal, cranial ventral, caudal dorsal and caudal ventral). Biopsy samples were weighed and separated into 2 fractions; epithelium and rumen wall. Biopsy results were similar to full and empty rumen weight results, as expected. An age by region effect was noted for both epithelium and rumen wall. Lastly, within the cranial ventral region of the rumen of 8wk old calves (4wk samples not measureable), treatment had no effect on papillae area (6.52±0.39 mm2, CON; 6.65±0.41 mm2DFM). Results here are perhaps not surprising given that no differences in final BW, DM intake, or gain to feed ratio were observed for these same calves (data in companion abstract). Study of VFA and microbial profiles in these calves may add further information on the use of this DFM in periruminant calf diets.
Keywords:
dairy calf, direct fed microbial, rumen development