Ian stepped conference attendees through the role for feed additives in dairy rations, with a specific emphasis on those associated with management and control of rumen acidosis. Starting the presentation with an overview of ruminal acidosis, Ian stepped us through the definitions of clinical and sub-clinical acidosis and that acidosis is a continuum and is not defined by specific cut points, nor by rumen pH. Valerate for example is an excellent marker for rumen acidosis.
Substrates in the diet that drive ruminal pH are explained, with a specific discussion around the role for sugars vs. starches, “substrate matters”.
An excellent overview of where H+ “hides” in the rumen is provided, acknowledging that it’s not only about the well known H+ sinks such as methane, but also bacterial protein as a sink also.
Sampling methods for rumen pH monitoring (stomach tube, fistulates, rumenocentesis) is discussed and the variation of rumen pH throughout the day explained.
Assessing cattle for signs of ruminal acidosis is explained at a practical farm level, everything from culling history (carcase feedback) dietary investigation including physically affective NDF through to NFCs, secondary signs to note in cows including laminitic rings on the hooves is explained. A summary diagram of signs to look for on farm is including in Ian’s presentation.
Ruminations per day with cow wearables – Ian nominated 580-600 minutes per day, with attendees highlighting that that “typical” NZ values are more like 450 minutes per day – good discussion. “Physically effective NDF has not been adequately defined for NZ high quality pastures” says Ian – more work needs to be done.
A summary of key factors to optimise excellent rumen function is provided by Ian, including a range of sensible, practical strategies to implement on farm.
Rumen modifiers are reviewed and explained, with monensin impact on methane production discussed, as well as multiple other rumen-centric changes by monensin including reduced proteolysis and changes to growth rates of S. bovis and protozoa. Milk responses and animal health modifications by monesin are defined, illustrated by the use of metanalysis to incorporate multiple studies and tens of thousands of cows.
Not limiting discussions to dairy, Ian provided an overview of the effects on feed conversion efficiency, and coccidiosis control of monensin.
The role for Lasalocid is discussed, including changes to VFA and protein metabolism in the rumen, coccidiosis control in calves and changes to feed conversion efficiency in finishing cattle.
Yeasts “everybody has one, and wants to sell it to you” says Ian. In a single slide, Ian listed a number of products and defined what linkages each product has to yeasts yeast cell walls and/or e.g. saccharides. Products are “mixed” and are not a “clean” product Ian says. He challenges us to be data-driven, and ask for data to give us confidence to take a product to his farmers.
Modes of actions of yeasts are discussed and potential challenges or limitations of products are defined by Ian for products that are live, killed and/or cultured. A study that investigated the effect of hydrolysed yeast and probiosis on cryptosporidia (Lucey et al, 2021) is presented, demonstrating potentially reduced shedding of crypto, however as a physical binder this will only be the case when crypto load is moderate to low, if load is too high, crypto shedding is less likely to be effective.
Combinations of additives can be useful, for example a combination of monensin and yeast can be more effective in the management of rumen acidosis. Other combinations are discussed, however Ian concluded that combinations are really hard to study technically but also commercially when products are from different companies.
Enzymes as feed additives – Ian said we may not choose to use these, however provided an overview for us. Examples include xylanase and cellulase. Results of enzyme products included in feed on milk production were “heterogenous and variable” Ian concluded.
Oregano – an essential oil offers benefits potentially in the anti-bacterial space and/or a role as a probiotic – possibly doing positive things in the rumen. Meta-analysis on the role for oregano in dairy cow diets can’t yet be done due to the low numbers of studies. A meta-analysis on beef diet suggests some good liveweight gain benefits based on inclusion of oregano in diets.
Methane effects of essential oils – possibly due to killing some bacteria!
3-NOP vs methane production / yield and methane intensity, as was the role for seaweed extracts was discussed by Ian. There is a possibility that these extracts may reduce dry matter intake however. Monensin and methane as a dataset is highly heterogenous – suggesting methane is not suppressed for all types of diets.
Methane as influenced by nitrate, lipids, wheat, essential oils, probiotics, tannins and microalgae is summarized by Ian.
Final additives discussed by Ian were biotin, choline, mycotoxin binders, and probiotics, with a brief synopsis on where Ian felt these additives might or might not fit in cattle diets.
NZARN members a copy of the presentation is available below if you are logged in.
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