NUTRITION ▶▶▶


Strategies to reduce nitrogen for more efficient ruminants


Reducing the amount of nitrogen that ruminants excrete is not only better for the environment but is also an opportunity for ruminants to produce more efficiently. Thus, balancing diets for amino acids can maximise dairy herd profitability and improve nitrogen efficiency.


BY DIEGO MARTINEZ DEL OLMO, PRODUCT MANAGER KEMIN R


uminant production systems convert vegetable pro- tein into animal protein, contributing substantially to human nutrition through the production of milk and meat. Rumen micro-organisms process ligno-


cellulose from low quality roughage into volatile fatty acids and energy, to transfer non-protein nitrogen into microbial protein. This is how ruminants can produce food of animal or- igin without competition for feed with non-ruminants and humans. Feed-efficient ruminant production is a complex system starting in many situations with better nitrogen (N) efficiency (Flachowsky et al., 2013).


Depending on the animal species, ration and management, between 5% and 45% of the N in vegetable protein is con- verted and deposited in the meat or milk. The other 55–95% is excreted (urine or manure) and can be used as a source of nutrients for plant production (Oenema and Tamminga, 2005). However, the efficiency of reconversion of the N into plant protein is limited: only a maximum of 60% of the N ap- plied to the soil can be converted to vegetable protein. The rest is lost, contributing to the environmental problem. This is especially important when we consider that the estimated


overall amount of N excreted by animals is comparable with the annual consumption of N fertilisers, if not higher.


Strategies to improve efficiency Strategies to reduce losses and improve efficiency of rumi- nant production systems rely on an optimal supply of ru- men-degradable N and an optimal efficiency of utilisation of absorbed amino acids (AAs) (Dijkstra et al., 2013). Generally, in ruminants the observed efficiency of conversion between N consumed and N deposited into protein varies between 20% and 32%, but the maximum theoretical efficiency should be between 40% and 45% (Van Vuuren and Meijs, 1987; Hvelplund and Madsen, 1995; Dijkstra, 2013). A practical ob- jective would be to achieve around 40% conversion; this goal can be reached by formulating for low crude protein (CP) and balancing for AAs, as described in this article. Ruminant protein nutrition has three big challenges. Firstly, the rumen contains a high number of microorganisms which makes balancing the protein profile difficult, and typically this leads to a very low feed and N efficiency. Secondly, it is not al- ways easy to obtain high fodder quality (that provides energy) in enough quantity (minimum 40% of the total dry matter in- take to avoid health problems and an even lower efficiency). Fi- nally, it is crucial to ensure a good mixing process in feed pro- duction to avoid the cow sorting the feed by preference and consequently running the risk of acidosis and low N efficiency. On the other hand, formulation is usually based on designing the lowest cost ration that provides the minimum level of re- quired nutrients for a level of milk production, but the feed cost is up to 70% of the total production cost. Improving effi- ciency of N conversion has one of the highest impacts on farm profitability (Bach, 2012; Tozer, 2012; McGrath et al., 2018).


Table 1 – Milk components and productivity expressed as percentage of increase after amino acid implementation related the non-amino acid use. TPAS-19-1075. (*) Return on investment.


Kemin Amino Acid Program References are available upon request. 48 ▶DAIRY GLOBAL | Volume 7, No. 3, 2020


Milk Production +7.5 %


Milk Fat +8.6 %


Milk Protein +5.6 %


Milk Casein +5.2 %


Plasma Urea -26.7 %


N efficiency +5.8 %


ROI (*) 4.9


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