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By Brian Nelson, M.Sc. ,
Ruminant Nutritionist

Although we are off to a slow start for spring planting, summer is right around the corner and it’s time to start thinking about summer feeding programs.

The first thing to keep in mind is the seasonality of components. Dairy cows respond to increasing day length in the spring and summer and naturally reduce their daily fat and protein concentrations in milk. This is typically by 0.2 – 0.25%, and this is just a result of cow biology. Cows are already starting to shift towards this annual change, with the lowest components to be expected in July.

TMR Management
All rations balanced by the GVF Nutrition Direct Team will check all the boxes on paper… but a cow doesn’t always eat the ration as balanced. We need to take steps to reduce opportunities for sorting and encourage dry matter intake. It’s important to maintain enough effective fiber in the TMR, but too many long particles encourage sorting. We should be targeting 3-8% of particles on the top sieve of the Penn State Particle separator. We also need optimal moisture in the TMR (Target 45-50% DM) to encourage intakes and reduce the potential for sorting. Water should be added when needed. The basics like frequent feed pushups, and twice a day feeding also help encourage intakes and reduce sorting. Additionally, we should also be ensuring adequate space at the feed bunk, ideally 24” per cow.

Water Management
We need to remember that milk is 87% water and so water availability and quality is important! Trough space in the barn should allow for 4” per cow. If not, additional waterers should be considered. We should also consider water availability and flow rate. Most cows are going to drink after milking, consuming up to 60% of their daily water intake immediately after milking. Some farms would benefit from a water holding tank, when wells struggle to keep up during peak usage, or dry months.

I’ve never heard a dairy producer complain that they have too many fans. Regardless of the setup, we should be targeting a windspeed of 2.0 m/s, especially during periods of heat stress.

Forage Quality
We’ve done a good job of introducing highly digestibility grasses (rye, triticale, etc.) into our crop rotations. Summer is the time to feed them to capture the greatest value. Feeding forages with higher NDF digestibility (NDFd 30hr) and lower undigestible NDF (uNDF240hr) allows for higher forage rations to promote rumen health, without sacrificing intakes. We can always add additional fibre to a ration with chopped straw or hay, but we can’t make poor quality forages more digestible.

Starch Sources
High moisture corn and cobmeal are economical starch sources but can provide too much rapidly digestible starch in the summer once they have reached peak fermentation. Swapping out some fermented starch for dry corn, or soluble fibre sources (soy hulls, wheat shorts, beet pulp) can have a positive impact on summer fat test.

RUFAL Levels
Rumen health can be greatly impacted by levels of fat in the ration, particularly unsaturated fats. When there is too much unsaturated fat in the diet, ruminal biohydrogenation (process occurring in the rumen where bacteria converts unsaturated fatty acids to saturated fatty acids) is impaired, resulting in milk fat depression. In herds that are prone to milk fat depression, swapping out high RUFAL feeds like raw beans, roasted beans, corn distillers’ grains, bakery meal, etc. for lower RUFAL alternatives (canola meal, bypass soy, Nova meal) can remove the barrier to milk fat synthesis and produce a nice butterfat response in the bulk tank.

There are many options when it comes to ration additives for summer. The two essential additives are sodium bicarbonate and yeast. Sodium bicarbonate should be added to the summer ration at a rate of 150-200g per head per day. This helps to provide rumen buffering and will maintain sodium levels in the cow. Sodium bicarbonate and salt offered free choice at the bunk is also a good
visual indicator of potential stressors, or dietary changes experienced by the herd. Live yeasts or yeast fermentation products also have a role in improving rumen pH and improving fiber digestion and overall health. During periods of heat stress, it can be beneficial to feed a higher rate of yeast.

The next group of additives are more farm specific. Palm fat is the most common additive, but also the most costly ($0.40 – $0.60 / hd / day depending on feeding rate). Some additives that you may wish to consider are MHA, Natural Edge, Chromium, Kelp, and Agolin. These additives have various modes of action but generally result in either improved energy extraction from the diet, or increased butterfat synthesis. The cost of these additives ranges from about $0.07 – $0.20 / cow / day.

Summer Premix – DCAD
Milk cows respond to higher dietary cation-anion difference (DCAD) diets during periods of heat stress. Heat stressed cows lose potassium through sweat and milk production. Increasing total potassium in the ration has been shown to increase fat corrected milk. The EcoLac DC premix lineup has been designed to provide additional potassium during summer months. This change should be made in May, prior to any heat stress.

Don’t forget about the dry cows!
Late gestation dry cows are most susceptible to heat stress. The developing calf has large nutritional demands in the third trimester, and the close-up period is marked by a reduction in dry matter intake. Keeping dry cows cool, and an optimal ration in front of them will help keep the milk tank full, and vet bills down.

Take Home Message
Summer success requires a multi-disciplined approach. Focusing on factors that keep cows comfortable, while maximizing dry matter intake and also feeding optimal ingredients goes a long way towards keeping rumens healthy, and farmers happy. We encourage you to reach out to your GVF Dairy Specialist if you would like to review your strategy for managing heat stress on your operation this summer.

This article was written for the Summer 2024 Central & Atlantic Dairy Grist. To read the whole Dairy Grist, click the button below.