top of page
DSC_0039.JPG

The effect of supplementing Aspergillus oryzae fermentation product on milk production, rumen environment, and fibre degradability in Jersey cows grazing ryegrass pasture

The input costs of pasture-based dairy systems continue to rise, exerting pressure on profitability, and creating a need to find methods to increase milk production per cow or per hectare. Pasture availability throughout the year is often limited, thus, increasing cow numbers on farms is not always possible. Feed cost comprises 50-70% of the total input costs of dairy farms, therefore optimizing the efficiency with which feed is utilized, can play an integral role in improving the system's profitability. Feed efficiency in pasture-based dairy systems depends on the quality of the forage fed and the degradability thereof, which in turn relies on the rumen environment of the cow. Maintaining an optimal rumen pH is critical for microbial function within the rumen. Ruminal microbes such as bacteria, protozoa and fungi play a critical role in fibre degradability and fermentation. If rumen function is impaired, feed digestion and nutrient uptake will decline, consequently, less nutrients will be available to the cow for production.


Aspergillus oryzae fermentation product (AOFP; Amaferm - BioZyme Inc., St. Joseph, MO, USA) is a feed additive produced from a dried fermentation extract of the fungi Aspergillus oryzae. Previous research reported that AOFP supplementation to cows, stabilizes rumen pH and enhances rumen microbial activity, increasing fibre degradability, increasing dry matter intake, and consequently increasing the energy available for milk and milk fat synthesis in the cow. Most of the research on the effect of AOFP supplementation has been completed on total mixed ration (TMR) systems and research in pasture-based systems is lacking. Therefore, the aim of this study was to determine the impact of supplementing AOFP on milk composition, milk production, rumen environment and fibre degradability in Jersey cows grazing perennial ryegrass (Lolium perenne) pasture. Our hypothesis is that the supplementation of AOFP will increase milk production, milk fat content, and fibre degradability.


The study was conducted at Outeniqua Research farm in George, South Africa. The study comprised of a production study and a rumen study. The cows used in the study, were selected from a group of 54 lactating cows, based on various parameters including milk production, milk composition (milk fat, protein, lactose, and SCC), lactation number, and days in milk. Data on these parameters were collected during a 2-week pre-study period. Using this data and the data on previous lactations, thirty-four early-to-mid-lactation cows were selected (17 cows per treatment), blocked according to milk production, days in milk (DIM), and lactation number, and randomly allocated to one of two treatments for the production study. Treatments were as follows: Control – cows received 6 kg per cow per day (as fed) of a pelleted dairy concentrate (159.6 g/kg DM CP and 12.3 MJ ME/kg DM), and AOFP treatment – cows received 6 kg per cow per day (as fed) of the same dairy concentrate with AOFP mixed in at 5 g/kg (3 g/cow/day; as fed). Cows underwent a 3-week adaptation period (Spring, 4-25 September 2023) followed by a 6-week measuring period. Cows grazed ryegrass pasture and were milked twice a day. The respective dairy concentrates were fed in the milking parlour during milking (3 kg twice a day). Daily milk production was recorded using an Afimilk system, and milk samples were collected weekly to determine the milk fat, protein, and lactose content of the milk. Dry matter intake (DMI) was determined with the TiO2-method, where TiO2 was used as an external marker and indigestible neutral detergent fibre (iNDF) was used as an internal marker. For the rumen study, six rumen fistulated cows were used in a cross-over design with two treatments and two periods during spring, (September and October) 2023. A 21-day adaptation period separated each 7-day measuring period. The rumen study involved diurnal pH measurement (using a TruTrack pH data logger), an in sacco dacron bag study, and collection of rumen fluid for analysis of volatile fatty acids and rumen ammonia nitrogen.


The average daily milk yield did not differ (P=0.41) between treatments and was 20.9 and 20.4 kg/cow/day for the control and AOFP treatment, respectively. Milk fat content tended (P=0.10) to be higher at 52.9 g/kg for cows fed the AOFP treatment compared to 50.6 g/kg for cows fed the control treatment. Milk protein and milk lactose content did not differ between treatments at 40.3 and 40.4 g protein/kg milk and 47.8 and 48.0 g lactose/kg milk for control and AOFP treatment, respectively. The treatments did not affect weight gain (P>0.05), and cows fed control gained 36.2 kg while cows fed AOFP treatment gained 28.1 kg over the study period, indicating that cows on both treatments were in a positive energy balance. Supplementation of AOFP did not affect (P=0.17) the DMI of cows and were 12.9 kg/cow/day for cows fed the control and 14.2 kg/cow/day for cows fed the AOFP treatment. The average rumen pH over 24h was lower (P<0.05) for cows fed the AOFP treatment at pH 6.10 compared to pH 6.18 for cows fed the control treatment. The rumen pH remained within the optimal range for rumen function and did not have a biological impact on the rumen environment. The average rumen volatile fatty acid, acetic acid, propionic acid, and butyric acid concentrations of cows did not differ (P>0.50) and were 111.2 and 111.3 mmol/L; 81.0 and 80.3 mmol/L; 18.3 and 19.1 mmol/L; 9.07 and 8.94 mmol/L for the control and AOFP treatment respectively. The average rumen ammonia nitrogen content did not differ between treatments (P=0.18) at 11.4mg/dL for the control and 9.94 mg/dL for the AOFP treatment This indicates that the protein nutrition of the cows was sufficient. The in sacco dry matter (P=0.85) and NDF disappearance (P=0.82) of ryegrass after 30h rumen incubation did not differ between treatments and was 814 and 815 g/kg and 708 and 705 g/kg respectively for cows fed the control and AOFP treatments.


In conclusion, supplementation of AOFP at 3 g/cow/day to cows grazing grass did not affect milk production but tended to increase milk fat content. Dry matter intake of cows and the degradability of ryegrass were not affected by AOFP supplementation. Rumen pH was lower in cows receiving the AOFP treatment but remained in an acceptable range for proper rumen function. Supplementation of cows with AOFP did not affect rumen VFA and rumen NH3-N concentrations. Based on previous studies, AOFP may have a more pronounced impact on production and rumen parameters when the rumen environment is under significant stress, such as when the diet includes high levels of fermentable carbohydrates. In this study, the rumen environment was not under stress. Future research is warranted to explore the effects of AOFP in pasture-based dairy systems, focusing on different pasture types and qualities, as well as varying levels of concentrate supplementation.

Logo

Office

1067 Mike de Vries Building

Department of Animal Sciences

Stellenbosch University

bottom of page