ARTICLE FEED & ADDITIVE MAGAZINE May 2025 59 The rumen is the most well discussed part of the dairy cows’ digestive tract; it is often called the engine of the cow. The rumen's anaerobic environment and a pH of between 5.8 - 6.8 favours the growth of microbes. These microbes digest or ferment feed within the rumen and make volatile fatty acids (VFAs) which are absorbed through the rumen wall where they can be used as a source of energy by the cow. The major nutrients required by rumen microbes are carbohydrate and protein in which there is a fine balance between the two to meet the microbial requirement. An imbalance can affect the microbial population and have a negative impact on nutrient digestibility, feed efficiency and the production of the dairy cow. Optimal rumen function is crucial for maximising microbial protein synthesis and the quality of the protein reaching the small intestine. The small intestine is not as widely discussed in dairy cows, however it has a role to play in the digestive process. The small intestine consists of three sections: The duodenum, jejunum and ileum. The small intestine completes most of the digestive process and absorbs many nutrients through villi (small finger-like projections). From the villi the nutrients enter into the blood and lymphatic systems. RUMEN NUTRITION Carbohydrates Carbohydrates are the primary source of energy in the dairy cows’ diets. The majority of carbohydrates are digested in the rumen through microbial fermentation where almost all the digestible carbohydrates are converted to VFA’s (acetic, propionic and butyric acid) and absorbed through the rumen wall as a source of energy. The ratio of acetate, butyrate, and propionate is determined by the source of carbohydrates and the rate of digestion. It is one of the major factors controlling the energy available for microbial growth and consequently the energy and protein available to the cow. Ruminal fermentation of carbohydrates affects productivity and is a critical consideration for diet formulation. Protein Protein is a key nutrient but in deficit (less RDP) or in excess (high RDP) it can have a negative effect on the cow. A lactating cow’s protein requirement is between 14% and 17%, depending on yield. Cows have a greater bypass protein (DUP) requirement as their yield increases.
RkJQdWJsaXNoZXIy MTUxNjkxNQ==