Heifer Development

If you have open heifers to breed that will calve at 22-24 months of age, there are things to do now to set them up for success. The old recommendation was to breed heifers at 65% of their mature body weight. For a 1450# cow – yes, that is likely the average for the Midwest (and too big in my opinion, but that is another article)– 65% of mature weight is 943#. Due to some excellent research out of Nebraska the target has been reduced to 58-60% of mature weight or 841-870#.

If you own a scale, now would be a great time to weigh your heifers. If they weigh 600# on January 1 and you will breed them on June 15, they need to gain 250# or about 1.5#/day. That should be quite easy with a ration of good quality hay, DDGS, and a salt-vitamin-mineral mix with Rumensin. It is vitally important to have them gaining weight the month before breeding and continue gaining after breeding.

What we do not want is for the heifers on 1/1/26 to weigh below 500# or over 700#. The lightweight heifers will need a much higher energy ration to make it to the target, but the heavy heifers also present a problem.

Research at Purdue University and the University of Wyoming looked at heifers that were developed on a higher plane of nutrition during the winter and then had reduced energy intake closer to breeding. The results showed a significantly reduced conception rate compared to heifers that were grown more slowly and gaining near breeding.

If these over-conditioned heifers are turned out to grass a month or so before breeding and get no supplemental feed, they can actually lose weight due to the extremely high moisture content in spring grass.

I had a herd a few years ago that had an extremely poor first service artificial insemination (the original AI) conception rate. After gathering the history, I strongly suspected over-conditioned heifers that were losing weight due to being turned out to “washy” spring grass a few weeks before AI. As the owner gave me more history, a few comments made me think there might be something else going on, so I called a DVM friend who is a reproductive specialist.

After our discussion, we were convinced that over-conditioned heifers were the culprit. The following year, 30 days after weaning, replacement females were turned out to corn crop residue with no supplemental feed, only a salt-vitamin-mineral mix free choice for 60 days. The heifers were weighed before going to stalks and again when they returned. The average gain was 14#/heifer, which was fine with us. Interestingly, a few of the heifers lost over 75#. The owner thought these heifers were telling her that they were going to be harder keeping females, so they received a growth implant and went to their feedlot.

If your heifers are too heavy right now and you are not breeding until spring, kick them out on an ungrazed, harvested cornfield and let them ‘survive’ for a month or so. Weigh them before and after they come off of the crop residue grazing. Now, figure a target gain to get them to 58-60% of their mature body weight at breeding. Your nutritionist, extension educator, or herd health veterinarian should be able to help you formulate a balanced ration to help you hit your target for weight at breeding.

Speaking of targets, research done in Texas showed that a heifer that conceived in the first 21 days of the breeding season had an ROI of 10.7% over her lifetime. How many of you would invest your money at a guaranteed 10.7%? I am guessing nearly everyone. Those that conceived in the second and third 21-day periods had an ROI of -0.4 and -2.8% respectively.

This and many other studies suggest that we should breed heifers for only 30-42 days. A late calving heifer becomes a late calving cow or an open cow, and neither is good for your business. There is no reason to start with a heifer that will likely never add to your beef business. In every herd I have consulted with that has had poor reproduction, we keep more heifers than typical and breed for only 30-42 days. It is amazing after a few years. The owner has selected for inherent fertility, and they no longer have a fertility issue.

A newer technology in heifer selection is the use of DNA or genomic testing of the heifers. With a 500# weaned heifer worth $2000, it seems prudent to spend $30 (1.5% of the total value of the heifer) to learn if her DNA says she is a keeper. Both Neogen and Zoetis offer this service. After testing, you will receive information on about 20 different traits. For replacement females, traits like stayability (will the heifer most likely be in the herd at age 6 after having 5 calves), cow fertility, calving ease, weaning weight, carcass traits, etc. The information can be a bit overwhelming, and the sales representatives from either company can walk you through the data.

It is never a good time to keep a heifer as a replacement that does not have the genetics to be a profitable cow, but with prices at record highs, it is imperative that heifers that are selected as replacements fully deserve to be in the replacement pen.

I spoke with a beef producer who has been DNA testing his heifers for 5 years now, and he said, “There is no way I would ever keep a heifer again without DNA testing. I am surprised by a few of the results every time. There are heifers I thought would make outstanding cows, and they have serious flaws, and there are others that look very average that end up at the top of my list.”

In a typical herd, the nursing 2-year-olds have the highest percent open females. The top two reasons are (1) heifers calving late in their first year, which we discussed above, and (2) heifers calving too thin. Bred heifers are still growing and need more energy and protein than mature cows. Having them a bit ‘fleshy’ (target is Body Condition Score 6.5-7.0 out of 9 at calving) gives them a bit of reserve so they don’t have to gain as many pounds post-calving. I always encourage producers to ‘find a friend’ to BCS their cows. The owner sees their own cows too often and may not see them as too thin or too fat.

Bred heifers should not be fed with mature cows for three reasons. First, they have increased nutrient needs because they are still growing. Second, mature cows will dominate the heifers and cause the heifers to eat less than they need (when they actually need more than the mature cows), and lastly, if heifers and cows are wintered together, neonatal calf disease increases by 3 times.

A goal of 95% pregnant females in 65 days, with 65% of calves born by day 21, is an achievable goal. Having heifers that are selected properly and developed optimally that remain in your herd for 10, 12 or even 15 years should be every producer’s goal.