As we bed down for Autumn, cows will increasingly be turning to winter rations, and where used, maize silage will be well integrated into the diet. Managing this transition is key to a successful winter feeding program, but we must be prepared to react quickly to ensure our herd’s performance is maximising the milk contract requirements.
In August 2017 the average milk price for Great Britain stood at 6.5% higher than July and 36% higher than the same time last year, but some milk contracts have a large variation depending on milk constituents. Whilst the last 2 years low milk price means farmers should still be keeping costs down, there is an opportunity to increase milk price by feeding for milk solids which could impact farm profitability.
NWF Agriculture Head of Technical, Adam Clay says; “Whilst we should always look at our own situation, typically 2017 1st cut and 2nd cut grass silage averages have been better quality than 2016 (11ME Vs 10.7ME and 14.9% Vs 14% crude protein respectively for 1st cuts, source Trouw Nutrition). Similarly, July and August milk production has increased on last year by 1.2% and 1.8% respectively. Comparing this trend to milk constituents, both milk fats and proteins have slightly increased through the same period, indicating improved energy and fibre digestibility. With some milk contracts, a 0.1% rise in protein and fat percentage can increase milk price by 0.45ppl and 0.32ppl respectively, that’s £7,700 extra income per 1 million litres sold.”
Managing Milk Constituents
There are many factors involved including breed and selection, but diet and balance play a critical role in manipulating milk constituents and can be effectively used to drive certain nutritional traits. The split can be broadly made in two parts; milk proteins can be influenced by energy, and more specifically fermentable carbohydrates, whilst milk fats can be influenced by fibre and rumen health.
Energy status and milk proteins go hand in hand, milk protein percentage is a key indicator for early negative energy balance and therefore fertility, feeding highly digestible feeds and forages will have a positive impact on milk proteins. More specifically feeding starch and sugars will drive a propionate response from the rumen, this impacts on amino acid synthesis and therefore milk protein. This is why we can see a positive response to both milk yield and milk proteins when maize and cereal silage is included in the diet.
Driving starch and sugar levels in the diet can offer continual improvement until the balance is tipped too far. Starch and sugars drive a bacteria in the rumen that thrive at lower pH levels, whilst this is beneficial if this drops too low fibre digesting bacteria die off which will reduce milk fats.
Milk fat percentage is largely driven by an acetic acid response from the rumen bacteria that are responsible for breaking down fibre. These bacteria thrive at a higher rumen pH and therefore like a stable and buffered rumen environment with lower and slower levels of fermentation. Of course, because fibre is a key element to milk fats, the digestibility of that fibre also plays a crucial role.
What should we do on farm to drive milk constituents?
Firstly, identify what are your limiting factors, and therefore what element is going to provide the greatest return. For example – if milk proteins are low and forage quality is below average and mature, drive glucogenic energy through increasing fermentable carbohydrates such as maize, cereals and/or molasses products. If milk fats are limiting and forages are high quality with limited structure, add digestible fibre such as sugar beet, pulp or soya hulls and possibly structural fibre to slow down the rumen throughput and allow the rumen microbes more time on attachment to the feed to break it down. Buffers and probiotics may also be required to raise rumen pH to the optimum of 6.2pH, creating a more favourable environment for fibre digesting bacteria.
Adam Clay concludes; “As is always the case, the most efficient diet will be the one that finds the optimum balance for milk proteins and milk fats. It is important to work closely with your feed nutritionist, to utilise accurate forage analysis and ration formulation systems to offer the best prediction of performance and response.”
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