Summer milk quality drop-off a threat to income over feed costs

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Milk pouring image

According to KW nutritionist Charlotte Ward, the average drop in milk quality through spring and summer can cut milk price by up to 3.2ppl depending on milk supply contract details. And although some drop-off in milk fat and protein levels appears inevitable even in housed herds, it can be significantly reduced through improved management and feeding, she claims.

“Lower butterfats and milk proteins during spring and summer might seem like a problem that’s a long way off, but plans need to be put in place now if the worst losses are to be avoided.

“The financial impact varies enormously depending on contract details, but the important thing to realise is that it’s not just grazing cows that are affected,” she adds.

Some contracts will allow producers to push for yield as long as minimum milk quality thresholds are still met, yet many herds face the prospect of a significant cut in milk price. And as Ms Ward points out, although this may be as little as 0.4ppl in some cases, for others the potential reduction in milk income – and income over feed costs (IOFC) – can be as high as 3.2ppl.

Seasonal quality trends

Data collated by DEFRA (figures 1 & 2)​ give an overview of what can be expected, with average milk proteins across the UK herd typically dropping by around 0.2% from their winter peak through the spring and summer. Butterfats can fall by up to 0.3%, and the effect is far more dramatic.

Figure 1 – Monthly variation in average UK milk composition for milk protein (Source: DEFRA)
Figure 2 – Monthly variation in average UK milk composition for milk butterfat (Source: DEFRA)

















“Low fibre levels in spring grass, unbalanced energy supply and low buffer feed intakes are all factors that commonly affect grazing herds following turnout,” Ms Ward states. “However, a similar effect is seen in fully-housed cows, with data from the US clearly showing the same milk quality depression during spring and summer (figure 2).”

Milk quality variation graph
Figure 2 – Milk composition for 206 US Holstein herds averaging 2,500 cows (Source: Total Dairy). Click to enlarge

The main cause is increasing daylight hours, and regardless of whether cows are housed or not, it appears that the greater daylength stimulates the hormones responsible for milk production, resulting in a seasonal rise in milk yield.

“The challenge is that unless action is taken to also boost milk solids production, this extra yield dilutes milk protein and butterfat percentages,” she continues. “Actual kg of milk fat and protein may remain the same or even be higher, but if a milk contract’s payment structure is focussed heavily on milk quality, milk price can be seriously undermined.”

The first step is therefore to recheck milk supply contracts carefully to confirm milk fat and protein payments, along with the penalties for failing to achieve minimum threshold levels. Using past milk quality figures from March through to September, combined with current yield projections, it should then be possible to estimate the overall likely impact on milk income.

Maintaining milk quality

“Any factor that alters feeding patterns and intakes can influence milk quality,” Ms Ward highlights. “So when developing a plan to counter milk quality depression through the spring and summer make sure you begin with a thorough review of overall feed and herd management.

“There’s…more to raising milk fat and protein levels than simply changing the…diet.”

“There’s much more to raising milk fat and protein levels than simply changing the nutrient profile of the diet. Maintaining the quality, consistency and intakes of any buffer feeds or total mixed rations (TMR), for example, is absolutely critical.”

Ms Ward recommends using only the highest quality forage available as the base for any ration, aiming for a ration dry matter (DM) of around 45% to minimise sorting and encourage intakes. Formulate ration energy supply carefully to reduce the risk of sub-acute ruminal acidosis (SARA), particularly in grazing herds, and pay particular attention to feeding accuracy.

“Avoid feeds and forage that are obviously spoiled, and clear away refusals daily to prevent fresh feed being contaminated with old. If possible, feed twice daily to reduce heating in the trough, or feed in the evening when lower temperatures​ will encourage consumption and reduce spoilage.”

Ensuring there’s adequate trough space and that feed is regularly pushed up will help reduce ‘slug-feeding’ and improve rumen efficiency, as will lowering cow stress levels. Stocking density, cow comfort, group management, ventilation and access to shade all need to be considered.

Targeting milk proteins

To specifically target milk proteins, the key is to recognise the​ close link between energy supply and subsequent microbial protein output from the rumen. Ensuring the right balance of energy feeds is therefore crucial, and although a good supply of rapidly available starch and sugars is required to drive microbial growth, care is needed if SARA is to be avoided.

“For grazing herds already getting plenty of sugars from grass, switching to slower fermenting starch feeds such as sodawheat or cereal silages will help support milk proteins through improved rumen function and a reduced incidence of SARA,” states Ms Ward. “

“For fully housed cows, replacing starch with sugars from molasses-based liquid feeds like Molale will have a similar effect. The sugars will also stimulate fibre digestion, which is good for milk fat production.

Molale liquid feed image
Molale offers energy, palatability, reduced sorting and a good supply of sugars.

“Alternatively, consider using energy feeds that already supply a balance of starch, sugars and oil. Good examples include the various confectionery and breakfast cereal blends such as SugaRich Dairy, which will not only help improve energy release in the rumen but also increase overall ration energy density.”

At higher yield levels (M+35 litres/cow/day), microbial protein supply from the rumen may need additional supplementation to fully support both milk yield and higher milk protein production. Including a high quality bypass protein such as rumen-protected soyabean meal (Soypass) will ensure sufficient metabolisable protein is available to the cow.

Focus on butterfats

The key to maintaining butterfat production is to boost the fermentation of fibre in the rumen, and subsequently increase the supply milk fat precursors. As a result, it’s important to make sure that rations for both grazing and housed cows contain sufficient digestible fibre, using sugar beet feed, soya hulls or the wheat-gluten moist feed Traffordgold to achieve a minimum NDF content of 35%.

“For this to be effective, the rumen environment also needs to be optimised for fibre digestion,” Ms Ward continues. “As for milk proteins, avoid supplying too much rapidly available starch, which can trigger SARA, and limit In-parlour feeding to 6kg/cow/day for the same reason.

“Adding sugars to housed cow rations will give fibre digesting microbes a boost, whilst the inclusion of at least 0.5kg/cow/day of chopped straw will help promote rumination and good rumen function.”

High levels of unprotected unsaturated fat should also be avoided. If too much is available in the rumen, it can result in the production of a specific fatty acid that effectively ‘switches off’ milk fat synthesis in the udder, as well as coating fibre in the rumen and restricting digestion.

“Many herds will see a response from the use of live yeasts and rumen conditioners (Vistacell, Optipartum-C, Acid Buf) during this time to further improve rumen function,” Ms Ward adds. “The same is true for high-C16 rumen-protected fats (Butterfat Extra), which act to directly increase the supply of milk fat precursors.

“Finally, remember that the rumen is a liquid fermentation chamber, so easy access to clean water is essential, particularly as the weather heats up. If you think current trough size or number may be a limitation, now’s the time to work out a plan to upgrade so that everything’s in place ready for when spring arrives.”

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