Managing cows in drought conditions

Note: This is Part 2 of a 2-part Beef Cattle Mythbuster series.

Now back to the discussion of nutrients. Those of you that have heard me give presentations on forage quality and nutrition will probably remember that I emphasize protein being the “first limiting nutrient” when dealing with low quality forages. That means until the deficiency of protein is corrected, performance (keeping up body condition and milk production) will not be very good in those cows. During drought our forages have reached vegetative maturity, dried out, and can be very low in protein—just like winter forages. A cow on good quality forage might be expected to eat 2.0 to 2.5% of her body weight in DM per day, with low-quality forages that could drop to 1.0 to 1.5%. The lack of protein inhibits the rumen microbes from doing their digestive work, and the increase in antiquality components such as lignin in the forages act as a physical and chemical barrier to the rumen microbes. In all, both intake and digestion of forages goes down and therefore less energy is delivered to the cow. Remember, if you want to supply protein only, you must have adequate grass to unlock the potential energy from the forage. If grass is limited, then protein and energy supplementation may be in order.

Let’s look at a simple example of protein supplementation for a grass with low (4.5%) crude protein:

A 1,300 lb beef cow (ave. milk; 10 lbs/day) in the first 3 to 4 months after calving requires at least 2.2 lbs of crude protein (CP).

If the cow is only eating 1.5% of BW in dry matter (DM).

Then: 1,300 lbs x 1.5% (DM basis) = 19.5 lbs of grass daily (DM basis; IF grass is available). 19.5 lbs x 4.5% (CP in grass) = 0.88 lbs of CP from grass.

2.2 lbs CP needed – 0.88 lbs CP from the grass = 1.32 lbs of CP that needs to be supplemented.

Let’s try alfalfa hay (could use canola meal, dried distiller’s grains, soybean meal, lick tanks, etc.):

Need to supply 1.32 lbs of CP daily from alfalfa hay and let’s say we have alfalfa hay with a CP content of 18.5% on a DM basis.

Then:1.32 lbs of CP/.185 (protein content of the alfalfa hay) = 7.14 lbs of alfalfa hay DM to satisfy the protein requirement. On an as-fed basis if the hay was 90% DM: 7.14/0.90 = 7.9 lbs of alfalfa hay.

After balancing for protein, you can do the same thing for energy. If energy is lacking, you can add grain to the diet.

There are several considerations that should be followed when supplementing energy (usually accomplished with grain because of its high energy density). Generally, forage intake and digestibility will decrease with energy (grain) supplementation. This can be advantageous in making forage supply last longer or extending the grazing season. If forage quantity is limited energy can be supplemented (cattle can’t get the full benefit out of high protein supplements when the base forage is limited). Here’s a rule of thumb: If forage at present is less than 50% used up by the cattle, use a high protein supplement. If the forage at present is already greater than 50% used up by the cattle, then use a mix of protein and energy (canola meal, alfalfa hay, etc. for the protein, and alfalfa hay, canola meal, etc. for the protein). I can help you get it in the right proportions based on the nutrient requirements.

Cautions: Generally, a diet should have no more than 1/3 of the CP coming from urea. Don’t use urea if forage is limited. Another caution is that I generally recommend no more than 10% of the total grain to be wheat. This is because wheat is the fastest ruminally fermented grain which could cause cattle into the metabolic disorder called acidosis where the pH in the rumen falls precipitously (more acidic) and can make the animals fail to perform and at worst cause death. Grains such as corn, barley, oats, etc. are generally more forgiving if they eat a bit too much.

You can use grain in place of forage to increase body condition of cows, increase carrying capacity of pastures, or to extend grazing season. If you do, remember that in order for the cows’ rumen to stay healthy and function at full capacity, cows need roughage in the diet (1% of body weight in dry matter is a good minimum). Grains, while energy dense, are relatively low in protein. Based on Total Digestible Nutrients (TDN), producers can compare grains and forages for the suitability of substitution. For example, let’s compare barley and common mixed hay (50% grass and 50% alfalfa), tabular values of TDN for the mixed hay is 53% and the TDN of barley grain is 83%. 83%/53% = a factor of 1.6. This can be read as 1 lb of barley grain can substitute for 1.6 lbs of mixed hay. You can make the same calculation for a variety of grains, hays, and forages.

Everybody’s operation will have unique circumstances when dealing with drought. The best advice I can give is to assess your pasture conditions, get a forage quality test on all of the available feeds, and then figure out the best way to address the nutritional deficiencies. I’m here to help get those cows through tough times.

Stay safe and have some fun! Please let me know if I can assist you with your cattle, forages, and feed.

— Don Llewellyn is the WSU Lincoln County Extension Director in Davenport. He can be emailed at don.llewellyn@wsu.edu