Diet Adjustments

2UW-Extension and industry continue discussing how heat stress affects nutrition and what producers can do with the diet to help minimize production losses.


Randy Shaver, PhD, Dairy Nutrition Specialist, UW-Madison/UW-Extension

Matt Lippert, Wood County Agriculture Agent, UW-Extension

Liz Binversie, UW-Extension Brown County Agriculture Educator


Time: 8:42 minutes


Liz Binversie: Greetings. I’m Liz Binversie, Agriculture Educator for UW-Extension in Brown County, Wisconsin.  We talked last week about the high risk groups on the dairy farm that are especially impacted by heat stress. Today we will continue our conversation and talk about what we can do in the diet to help limit losses from heat stress. On the panel today is Randy Shaver, Dairy Nutrition Specialist and Professor for UW-Madison and UW-Extension; Matt Lippert, Agriculture Agent for UW-Extension in Wood County; and myself.

Now, there are various ways we can change the diet during the summer. Matt, what are some adjustments we can make in the diet to help reduce losses on the dairy farm caused by heat stress?

Matt Lippert: Well thank you Liz. In my experience, if you’ve got a very well balanced diet initially, that diet is going to serve you well even under heat stress. What we tend to see is if diets are pushing the edge of some parameter in the ration for whatever reason, we’ll see those problems manifest themselves more under heat stress. We also see sometimes that dry matter intakes will drop considerably and suddenly. For obvious reasons this will be of great concern to the management, the feeders, and sometimes we make quick adjustments that probably don’t fit in the realm of being consistent and well-balanced. I judge on the err of caution not to do too many things drastic. You are going to see dry matter intakes drop. I think we should avoid in any of these diets any extremes in starch or fiber or fat or protein. Moderation in heat stress situations is a very good thing. We know that in heat stress that cows behave differently. They’ll sort feed more. They’ll gather and they’ll crowd in areas and they’ll eat less frequently. Sometimes the diets that they eat will actually be in a larger individual meal size than normal. Even though their intakes are down, they may have a situation of some slug feeding going on. We’re also going to see if there’s any crowding in the groups that the effects of social hierarchy is going to manifest itself more under heat stress situations. Some cows are going to manage alright and some others are going to be more challenged. Another area that would be, is that sorting could be an issue. If the diet is delivered well initially but cows are showing up after the ration is sorted, they may not have the diet that we want. There’s some obvious things that I feel normally are in well-balanced rations anyhow but we want to make sure that we pay attention to adequate intakes of buffers, salt levels in the ration, potassium. We feed a lot of high concentrate, high corn silage, high by-product rations these days and it’s very typical that those diets could be low in potassium. I think if we go back in time, that usually was not a mineral that we were too concerned about in the diet, but certainly that’s one that could show up more so under heat stress. Certainly inclusion of things that are going to stabilize rumen environments such as yeast or some microbial products have a place in diets for heat stress situations. Personally, I like a moderate, not a high level, but some level of fat. It doesn’t generate heat. It’s energy dense. In the summer when cows are eating less and need more energy, we can’t go overboard with that because we want to keep a healthy and stable rumen. We should look at the type of fat but I think a little bit of that in the diet is going to be helpful under heat stress situations. Then I would say, use your best forages if at all possible. That’s going to help with intakes. We know that some lower digestibility forages actually generate more heat in the diet. If you can have something that’s very appealing to the animals, they’re going to eat. That will help you in a lot of ways. I know Randy is going to have a lot to add to that so Randy could you comment further?

Randy Shaver: Sure, Matt. You really covered things nicely. Just a few things that I would add: Nutrition is certainly part of the puzzle, but it’s really not the major factor. I would step back a little bit and just think about cow comfort, crowding issues, make sure cows are using the stalls, lying vs. standing, and then it’s ventilation and cooling. Those things are really what is most important. Then we move into some of the nutritional aspects. I would agree with Matt that really try to avoid the extremes, but much of what we do normally to feed cows really is very impactful during these periods of heat stress. Kind of key on the list, in terms of most important, would be water, salt, as was mentioned, and certainly the buffers, not just sodium bicarbonate but also potassium on these higher corn silage diets. Then really recognizing that under periods of heat stress, cows do not ruminate as much and they actually spend more time panting and trying to get rid of the heat. We need to be aware of that, but, as was mentioned, fiber and forage do need to be fermented in the cow’s rumen and do produce heat. Really key to this is making sure we’re minimizing sorting, trying to maybe feed more frequently so that we don’t have a lot of slug feeding, avoiding overcrowding so that we don’t have a lot of slug feeding, then making sure we have adequate particle length on our forage fiber so that we do get as much rumination as we can to maintain rumen pH and keep those cows healthy. I would agree wholeheartedly that some level of fat to provide energy in kind of a cool form. A high energy density and an energy source that does not create a heat of fermentation is very important. I would certainly look towards many of the key management components and some of the major nutritional factors when we try to do a better job of feeding cows that are exposed to heat and humidity during the summer.

Liz Binversie: Well thank you again to our wonderful panel today. If you have any questions or would like to reach any of our panelists, you can reach them by email. Tune in next time to learn how you can manage feed storage during this Wisconsin summer.