My favorite task as a herd health veterinarian is making herd consultation visits with my students. We look at the entire beef operation, and our goal is to find areas of the business to improve.
Recently, we visited a herd that is solving many of its business deficiencies.
“You found the weak links in the chain,” this operator told us, “but we're still having trouble with baby calf sickness and keeping heifers and young cows in the herd. And, I was really disappointed with the last set of bred heifers we purchased.”
While baby calf sickness is not a major problem on many farms, problems with heifers are almost universal. The two most frequent problems are dystocia in 2-year-old heifers and infertility in nursing 2-year-old heifers.
This particular herd had few problems with dystocia because purchased heifers were bred artificially to a calving-ease bull. Yet, 27% of the nursing 2-year-olds were open after the ideal 65-day breeding season. The owner asked our students why he was having such a tough time getting his heifers bred back.
After analyzing records, we concluded:
His heifers were calving in an average body condition score (BCS) of 5 (on a 9-point scale), while a BCS of 6.5 was desired (adult cows should calve at BCS 5-5.5).
The heifers open at pregnancy check tended to calve later in his 65-day calving season than heifers that were bred. Thus, these heifers had less time to return to heat and conceive.
The open heifers tended to be 75% or greater of a single breed, so hybrid vigor was sub-optimal.
Based on this, we advised him to:
Calve his heifers in BCS 6.5. Generally, a whole BCS is equal to 75 lbs. of body weight. If heifers need to gain 1.5 BCS, his heifers need to weigh 112 lbs. more at calving than they did in 2001.
Purchase bred heifers that will calve two to four weeks before his cowherd and calve over a period of 30-42 days.
Purchase crossbred heifers. For this particular herd, we suggested heifers of 50-75% British and 25-50% Continental genetics. The highest priority was to add genetics that would fit his environment and excel in fertility.
The owner was eager to implement our recommendations but asked:
“Wouldn't heifers in BCS 6.5 have increased calving difficulty compared to heifers in BCS 5?” Also, “What about the baby calf sickness the previous year?”
Our students found that when heifers calved in BCS 6.5 versus 5.0, the calves weigh about 4 lbs. more at birth. Research proves this small increase in birth weight should not increase dystocia.
Meanwhile, the benefits of heifers calving in an ideal BCS are:
Calf vigor improves.
Colostrum quality and quantity improves.
Calf survivability improves.
Days to first heat decline.
Conception rate increases.
Weaning weight increases.
As far as improving calf health, the owner was already doing many things well. He followed a timely herd vaccination schedule, bought his bred heifers from a “high-health” status herd many months before calving and calved in the driest areas of his farm.
Our investigation did turn up one potential problem: wintering and calving heifers and cows together.
Research in Canada shows calf morbidity increases threefold when heifers and cows winter and calve on the same ground. Separating the heifers for at least 50 days precalving should greatly reduce this and help get heifers in better flesh at calving.
A ration was formulated to get the current bred heifers in BCS 6.5 at least 50-60 days precalving because of the efficiency of adding this gain in milder weather. The heifers in this herd started on the new ration of 6 lbs. mixed hay, 16 lbs. dry corn gluten and 0.1 lbs. limestone/head/day 110 days precalving.
If the owner waited until 70 days precalving to increase their BCS 1.5 points, the ration would have to be 6 lbs. mixed hay, 20 lbs. dry corn gluten, and 0.1 lbs. limestone/head/day.
W. Mark Hilton, DVM, a clinical instructor of beef production medicine at Purdue University in West Lafayette, IN, wrote this article. Mike Apley, DVM, PhD, is an assistant professor of beef production medicine at Iowa State University in Ames, and also contributed.