Why Supplement the Cows by Mike Mehren Ph.D.

A client hit me with a great question the other day. We were discussing a supplement to go with his grass hay. We tested the hay, and I said that it was low in protein and the cows would benefit from a protein supplement. His response: ‘Prove it’. This question lead us into a great discussion about his herd. What records could we use to determine whether a supplement could be a benefit? Some of the records that I think are necessary follow:

1. Percent live calf crop relative to cows bred

2. Percent of weaned calves related to the cows that were bred

3. Weight of calves at weaning

4. Cow body condition at calving

5. What are cows fed before & after calving

6. How much is fed to cows before and
after calving

I chose to use a very recent publication from Oregon State University in my attempt to prove the value of supplementing the cows.

Some of you may have missed an excellent study on the effects of supplementing cows during late pregnancy. This work was reported Dr. Dave Bohnert of the E O Ag Res Center in Burns, Randy Mills, of OSU Extn Svc in Umatilla and Union Co. and their co-workers. This study showed the consequences of NOT keeping cows in moderate flesh as calving season approaches. Although this research was conducted on range that is typical for much of Eastern Oregon, Eastern Washington, and Southern Idaho, the principle of feeding for cow body condition applies anywhere.

Cows should be separated into groups depending on their condition. You may group heifers and second calf heifers and put them with thin cows. It is really important, no matter how you do it, to recognize that a thin cow needs a ration that is different
from a cow in moderate flesh. The thin cow needs to gain enough weight to be in moderate flesh at calving. Heifers also need extra nutrition so that they can gain weight before calving.

Our version of the BCS can actually determine a winner! Body Condition Scoring will definitely determine which cows can remain productive and which cows need extra nutrients or they may have to go down the road. The ranking goes from 1 (extremely thin) to 9(extremely fat). We want the heifers to be in condition 6 –slightly fleshy, and the cows to be in condition 5 –moderate flesh.

Here are some of the keys for scoring (Adapted from the Cow Calf Management Guide. If you don’t happen to have this excellent handbook, you can purchase one from
Jerry Adams U of I Ag Communications, phone 208-885-7235.

	very thin	slightly thin	moderate	slightly fleshy
Keys to scoring cows	3	4	5	6
	body condition score
Muscle Loss	slight*	no	no	no
Outside of spine visible	yes	slight	no	no
Ribs visible	all	3-5	1-2	no
Hip and Pin Bones visible	yes	yes	yes	yes
	(muscles of loin, rump sunken)*

There are pictures to help you identify these conditions in this publication. Oklahoma State Univ also has a publication entitled Body Condition Scoring of Beef Cows written by Dr. Selk. The publication number is ANSI 3283. It also has pictures. If you’re handy with a computer you can read and print that out. It is located on their website.

One point that came through clearly in the Or State study was the effect that doing a good job feeding the cowherd on their calves. Feeding the cow to achieve moderate flesh by the time she calves increases her chance of her having plenty of energy to calve and breed back early during the breeding season. Thin cows may have difficulty during calving. Research from many different Universities has shown that thin cows are more likely to have calving problems (dystocia), the number of weak calves is increased, and quality of their colostrum is inferior to that from a cow in moderate flesh. Calves from thin cows will have a higher incidence of health problems, and will be lighter at weaning.

It is important to understand that there may be a good reason for cows to be thin in the fall. The cow may have weaned a great big calf despite having to draw from her own body condition to do so. Conversely a beautiful fat, slick, cow may not have weaned a calf and was able to put all her feed into her well-being. Some ranchers give that beautiful open cow a chance if there are special circumstances that affected the calf. The calf may have gotten injured, become sick, or attacked by predators. These situations had nothing to do with her performance.

Now back to the OSU research. What effect did supplement have on the cows?

1. The supplemented cows had a higher BCS than unsupplemented cows.

2. Number of live calves born was not different due to supplement.

3. However, the number of live calves for BCS 6 cows was 100%, while the number of live calves for the BCS 4 cows was 90%.

4. The number of live calves at weaning was 99% for BCS 6 cows and number of live calves at weaning for BCS 4 cows was 88%

5. Number of cows pregnant was not different due to supplement, however BCS 6 cows was 91% while BCS 4 cows was 79% during a 60 day breeding season.

What effect did supplementing have on the calves?

1. Calf birth weights went from 85 lb average to 91 lb. No, repeat No calving difficulty was seen due to increased weight.

2. Calf weaning weights were greater for BCS 6 and supplemented cows than for . for BCS 4 and non-supplemented cows.

3. There was no difference in performance for steers in backgrounding or finishing feedlot. However the calves from the BCS 4 cows never caught up to the BCS 6 calves while in the feedlot.

4. There were no differences in carcass measurements.

So does this prove that supplement the cows during the fall and winter? I think it does. There was 11% more calves at weaning for the BCS 6 cows. If the supplement cost was $.25/cow/day for 100 days that equaled $25.00/cow. Adding 11 more calves for 100 cows increases the value of the cowherds production for the year substantially above the cost of the supplement. It should be noted that good old alfalfa hay was used as the source of protein supplement in this experiment. All groups of cows were fed a free choice vitamin-mineral supplement during the study.

Michael J. Mehren Ph.D. is a livestock nutritionist living in Hermiston Oregon who is mighty cold despite Global Warming. He may be contacted by Email at mehrens@eotnet.net.