Wagyu nutrition
Origins of the Wagyu breed
The Wagyu breeds have unique qualities that are attributed to origins from the Fourth Eurochs and they were isolated for almost the first two thousand years after arriving in Japan. This has enabled Wagyu to have retained key differences from other breeds while they are classified to be on the extreme within the Bos taurus pool.
Most Wagyu producers that introduced Wagyu cattle onto their cattle properties around the world had prior experience with other beef breeds or in milk production. Outside Japan, nutrition recommendations for Wagyu generally follow common practices that are applied within each country and there is a strong bias towards the principles that have evolved for the dairy industry. Most of the advances that have been made with genetics in Japan - such as the single step genomic predicted breeding values - have been adopted by progressive bodies outside Japan (such as Australian Breedplan). However, the philosophy that applies to fattening Wagyu in Japan has been more elusive.
Establishment of Wagyu International principles for Wagyu nutrition
Initially research data over 20 years from Japan was analysed and some preliminary principles were adopted by Wagyu International. Subsequently the translation of the Japanese Beef Feed Standard 2008 provided additional information.
The Japanese cattle industry requires a large component of feed that is imported and ongoing increases in production costs for beef have increased subsidies by prefecture for fattening (牛マルキン). In March 2015 the policy of Modernizing Dairy and Beef Cattle Production was announced by the Ministry of Agriculture, Forestry and Fisheries. Changes are necessary to strengthen competitiveness of beef cattle production by shortening the fattening period. LIAJ estimated that shortening the fattening period by each 1 month will reduce expenses by about 5%. However, it has been acknowledged that shortening the fattening period will have an impact on carcass weight and meat quality.
Calves in Japan are typically sold to the fattening industry between 8 and 10 months of age depending on strain/prefecture. Although there are differences of sex and strain of Black Wagyu, the weight for age at the calf markets is a useful indication of finishing potential. The traits related to yield tend to increase when there is a higher weight for age. The average is 1.0 kg per day of age from Hokkaido (Osawa et al. 2008). Individuals who exceeded this had invariably been overfed and meat quality was disadvantaged.
In order to minimise the impact on quality by the mandate to reduce age as implemented in 2015, research on feeding has taken on a different perspective. The numerous results have been reviewed by Wagyu International and any findings that have implications for either pasture or grain finishing of Wagyu in the global arena are applied. The effect of ADG and the time to reach the same end-point on marbling (IMF%) is illustrated below:
An increase in growth rate towards the left of the chart allows slaughter weight to be achieved at a younger age but this reduces IMF% in the lines that are darker in colour. The lighter coloured lines have higher marbling from lower growth rates.
The white line shows the conventional 2008 feed standard applied to Australian conditions. Of course, marbling to this extent is not rewarded by the prevailing price grid outside Japan except for isolated niche markets. Shifting to the left reduces cost but the economics in every enterprise will dictate which coloured line will bring in the highest return.
Fundamental principles of Wagyu International's "pre-2015 Japanese feeding model"
The primary energy sources for beef cattle are starch and cellulose. They are fermented by microorganisms in 
the rumen to produce volatile fatty acids and gases. The major VFAs produced are acetate, propionate, and butyrate and the type of diet, microbial species present in the rumen, and ruminal pH are the major factors that influence the percentage of each VFA produced.
The loss of energy in heat and methane during the conversion of starch and cellulose to VFA makes the process of fermentation inefficient. When acetate is produced in the rumen there is a loss of one carbon as CO2 which can be used to form methane. Butyrate is produced when two acetate molecules are combined so even though butyrate does not produce CO2 which can be converted into methane directly, the CO2 is produced when the acetate molecules were formed. Propionate is the only VFA that does not release an extra carbon that can be used for generation of methane. Because of these differences in carbon, the energy values for the VFA are highest for propionate, intermediate for butyrate, and lowest for acetate. Therefore, increasing propionate within the rumen will decrease methane production and increase animal performance for beef production.
The Wagyu breed thrives on roughage and Japan was traditionally supplied at an age that exceeded 30 months. The balance of forages and grain that provided optimum performance and beef quality culminated in propionic acid fermentation during finishing. On the other hand, the dairy industry relies on butterfat production and this is favoured by acetic acid fermentation.
The acetate:propionate ratio is important but there is a negative trend between NDF and IMF%. Research data from fattening trials in Japan have been reviewed by Wagyu International is continually monitoring progress in Japan and applying it through collaborations with producers in the northern and southern hemispheres. As always, the economics and end-points are different in every enterprise. Determination of the desired eating quality and carcass size will enable Wagyu International to recommend the growth profile and feeding program that will be based on local resources and feed components.
Many producers are content to follow their neighbours. Those that want excellence contact Wagyu International.
References
Luebbe 2014. Methane's Impact on Animal Performance - VFAs. University of Nebraska - Lincoln. March 2014.
Ogata et al., 2019. Effects of an increased concentrate diet on rumen pH and the bacterial community in Japanese Black beef cattle at different fattening stages. J. Vet. Med. Sci. 81(7): 968–974
Ogata et al., 2019. Long-term high-grain diet altered the ruminal pH, fermentation, and composition and functions of the rumen bacterial community, leading to enhanced lactic acid production in Japanese Black beef cattle during fattening. PLoS ONE 14(11): e0225448
Osawa et al., 2008. Image analysis of carcass cross-section in Japanese Black Genetic analysis of traits and meat-producing ability traits. Report posted in Japanese by Department of Bioproduction Science, Graduate School of Agricultural Sciences, Iwate University.
