For the rumen to function properly, the rumen conditions must be optimal, with a pH greater than 6. Feed additives, such as live yeast, are frequently included in rations to help stabilise fluctuations in rumen pH. Particle size, along with other aspects of feed delivery and animal housing – such as ration mixing, feeding times and social interactions between animals – can impact feeding and rumination behaviour and rumen function. Poor fibre digestion due to rumen upset or an imbalanced ration can lead to reduced feed intake and increased amounts of undigested fibre in the faeces. If the cow eats less feed, and if that feed is less digestible, her ener- gy supply will decrease, subsequently affecting her ability to produce milk. Reduced milk fat and laminitis are two of the most common symptoms of impaired rumen function and can be linked to low rumen pH.


Nutritional applications The main driver of rumen function is the ration fed to the cow. Along with the forages, grain and protein sources in- cluded in the ration, other small inclusion ingredients can sig- nificantly impact rumen function. There is evidence that feed- ing live yeast can increase feed efficiency in lactating dairy cows, especially when cows are heat-stressed. These additives can generally improve digestive efficiency and nutrient utili- sation, resulting in more milk from the same feed quantity or, conversely, less feed needed to produce the same milk. Dietary inclusion of the live yeast Yea-Sacc (Alltech Inc.) can rapidly promote an anaerobic environment, helping desirable, fibre-digesting microbes to proliferate and effi-


ciently colonise feed particles, resulting in improved fibre digestion. Yea-Sacc also stimulates lactate-utilising bacteria, which helps to reduce the acid load in the rumen and avoid significant drops in rumen pH, creating an optimal rumen environment. Cellulolytic bacteria then thrive and generate more energy for the cow. This creates more efficient and com- plete digestion of the ration, particularly the fibre portion, leading to improved feed efficiency (Figure 1). Feed additives should be selected for their ability to meet the needs of a particular ration and for their return on invest- ment, usually in the form of improved milk production or reduced feed costs. Yea-Sacc is a proprietary strain of the live yeast Saccharomyces cerevisiae, with specific rumen activity, and its benefits are supported by more than 230 research studies globally. Current challenges are causing dairy producers to re-examine feed management strategies and find ways to save costs. To sustain profitable production, producers must focus on maximising feed efficiency and ensuring that rumen function is not compromised. The rumen is responsible for a large por- tion of the cow’s energy and protein supply, and good rumen function is critical to milk production and feed efficiency. Producers can minimise feed-related losses by using good quality forage, supporting rumen health and following a tailored ration formulation, thereby keeping their operations and their animals running more efficiently and resulting in potential cost savings.


References available on request. ▶ DAIRY GLOBAL | Volume 9, No. 2, 2022 27


Feed additives should be se- lected for their ability to meet the needs of a particular ration and for their return on investment.


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