This Research Paper addresses the hypothesis that the dietary inclusion of an Aspergillus niger fermentation product will alter the degradation kinetics and rumen fermentation patterns of feeds in dairy cattle. Fungal fermentation products often contain a suite of bioactive compounds and secondary metabolites, which can influence the microbial environment in the rumen and act as digestibility enhancers. As the cattle sector is under increasing pressure to enhance its sustainability, the investigation of dietary interventions that could improve the efficiency of production is warranted. In a previous experiment, Synergen®, a product of the solid-state fermentation of Aspergillus niger (ANP) containing residual enzyme activities, significantly increased the in vitro digestibility of a grass silage-based dairy total mixed ration (TMR), suggesting that in vivo studies would be valuable. Hence the present study aimed to quantify the effects of this ANP on rumen fermentation measures in cattle. Using a 4 × 4 Latin square design, the effect of four doses of ANP (0, 5, 10, 15 g/day) in four cannulated Jersey heifers was measured on the in sacco degradation of dry matter (DM), organic matter, crude protein and neutral detergent fibre in steam-flaked barley, grass silage and a grass silage-based TMR formulated for dairy cattle. Treatments had no significant effect on the rate, or extent, of degradation of any component in any feed investigated. Rumen volatile fatty acid concentrations and proportions, and rumen pH, were quantified at seven timepoints during each 48-h sampling period and were unaffected by treatment, as was the apparent total tract digestibility of DM. Under the conditions of this trial, ANP did not influence rumen fermentation kinetics; indicating that supplementing mature, non-lactating Jersey cattle with this fungal fermentation product is not an advantageous strategy to enhance feed digestibility.

The need to complement in vitro gas production measurements with residue determination is demonstrated by the recalculation and reassessment of published data on in vitro gas production, in sacco degradabilities and voluntary dry matter intake (DMI). The in sacco degradability — gas volume ratio was determined at 24 and 48 h of incubation, termed partitioning factor (PF) and combined with rate and extent parameters of in sacco degradability and in vitro gas production to predict DMI. In vitro gas production and in sacco degradability characteristics (a + b) and c as described by the equation y = a + b(1−ect) explained 0·373 and 0·668 respectively of the variation in DMI of 19 legume and grass hays. The complementation of gas production parameters by the PF24 increased the R2 value to 0·744 with PF24 accounting for 0·407 of the variation in DMI, the rate of gas production (c) for 0·218 and the extent of gas production (a + b) for 0·119 of the variation in DMI. As a single parameter, PF48 showed the highest correlation (R2 = 0·597) with DMI but the combination of PF4S with rate and extent of in sacco or in vitro gas production measurements did not improve the correlation further, probably due to an intercorrelation between rates of fermentation and PF4S. Hays which were degraded at faster rates had higher PF values indicating proportionally higher microbial yield and lower short-chain fatty acid production per unit substrate degraded. Generally, hays with high in sacco degradabilities but proportionally low gas production i.e. hays with high PF values showed higher DMI.