Don’t let sore feet trample reproduction
You can’t afford to ignore the impact of early-lactation lameness on reproduction.
By Kimberlee Schoonmaker
| Wednesday, November 13, 2002
Each case of lameness on a dairy results in an economic loss.
In fact, it has been estimated that each case of lameness trims roughly $300 from your bottom line — making it the third highest loss due to health problems on dairies.
Recent research shows lame cows produce less milk long before they start to limp. (Please see, “Don’t let lameness limp off with your profits” in the September issue of Dairy Herd Management.) And as lameness symptoms worsen, milk losses climb.
There is, however, another reason to head off lameness early.
A growing body of research suggests early-lactation lameness — lameness that begins during the first 30 days of lactation — hurts reproductive performance.
Here’s what some of the latest research has to say about the relationship between lameness and reproduction and why you need to pay closer attention to early-lactation cows with sore feet.
A time of great risk
At the time of calving, a cow undergoes a tremendous amount of stress.
Many factors — hormonal changes at calving, a ration change or a new environment, for example — trigger stress immediately at or shortly after calving. These factors put an early-lactation cow at risk of becoming lame — perhaps more so than at any other point during her lactation.
Recently, European researchers have suggested hormonal changes at calving might trigger lameness. Their theory suggests relaxin — a hormone that softens the birth canal for calving — also may cause tissues in the hoof to soften. This causes the pedal bone in the hoof to sink, resulting in damage to the sole. This, in turn, may initiate lameness around the time of calving.
Furthermore, cows are at a very high risk of developing foot warts — a major source of lameness — during the first month after calving. (Please see, “Lameness risk high during early lactation” on page 32.)
Certainly, the risk of cows falling lame early in lactation is reason enough to pay close attention to cows’ with sore feet at this time.
Prevalence underestimated
Although the risk of lameness is high shortly after calving, many producers still underestimate the level of lameness in their herds.
That was evident in a study involving 17 Minnesota and Wisconsin herds reported in the Jan. 1, 1993 Journal of the American Veterinary Medical Association. According to the study, the prevalence of clinical lameness scored by researchers — identified as a score of 2 or greater on a four-point scale — was 2.5 times higher than that estimated by herd managers. In fact, the herd managers estimated only 40 percent of the cows diagnosed with clinical lameness by the investigators to be lame.
The tendency for producers to underestimate lameness in their herds hasn’t improved much either. A study reported earlier this year at the 12th International Symposium on Lameness in Ruminants found 51 out of 53 British producers underestimated the level of lameness in their herds.
If the level of lameness in an entire herd is largely undetected, chances are you may not see the true prevalence in early-lactation cows either.
Reduced conception
Cows need to be in peak condition during early lactation in order to breed back in a timely manner. However, when cows suffer from lameness during the first 30 days of lactation, it takes them longer to become pregnant.
For example, research presented at the 12th International Symposium on Lameness in Ruminants shows lameness during early lactation reduced first-service conception rates.
The study took place on a 3,000-cow Florida dairy. Cows that were lame during the first 30 days of lactation experienced a first-service conception rate of 17.5 percent, compared to 42.6 percent for non-lame cows. (Please see the table, “Lameness reduces reproductive efficiency,” above.)
Another study, published in the May 15, 2001 Journal of the American Veterinary Medical Association, showed lame cows required more breedings per conception. In fact, lame cows required five services per conception, on average, compared to three for non-lame herdmates.
The study also showed the effect of lameness resulting from different types of foot lesions on days to conception. For example, lame cows with claw lesions required 40 more days to become pregnant than non-lame cows. And, lame cows with multiple lesions — such as foot warts and claw lesions — required an additional 70 days to conceive, compared to non-lame cows.
Increased risk of ovarian cysts
In addition to suffering reduced conception rates, lame cows also run a greater risk of developing cystic ovaries.
According to the study that took place on a 3,000-cow Florida dairy, cows that became lame during the first 30 days of lactation were 2.63 times more likely to develop ovarian cysts prior to first breeding than non-lame cows. (Please see the table, “Lameness reduces reproductive efficiency,” above.)
Although the study is the first of its kind to explore the association between lameness and ovarian cysts, it is of interest because ovarian cysts can lead to infertility in dairy cattle.
Economic consequences
Lameness in early lactation can be costly.
For example, the May 15, 2001 Journal of the American Veterinary Medical Association study cited previously shows lame cows needed five breedings, on average, before they conceived compared to three for non-lame herdmates. At a cost of $15 per straw, those two extra breedings cost you $30 per cow in semen cost alone. And that doesn’t include the cost of the inseminator’s time.
Lame cows that take longer to become pregnant experience more days open. In fact, the same study shows a lame cow requires 40 additional days to become pregnant. At a cost of roughly $2 for each extra day open, a lame cow that fails to breed back in a timely manner skims $80 off your bottom-line.
Culling due to lameness also has its consequences.
The study conducted on a 3,000-cow Florida dairy and reported at the 12th International Symposium on Lameness in Ruminants identified a 30.8 percent cull rate for lame cows, compared to 5.4 percent for non-lame cows. But what is perhaps most startling about these findings is that the lame cows left the herd before they came back into heat and were bred.
If first-calf heifers — a group of animals highly susceptible to lameness during early lactation — don’t get bred back, they don’t pay for themselves either. And, with milk prices and the cost of replacement heifers at opposite ends of the spectrum, you can’t afford to lose these animals during their first lactation.
Although it’s difficult to put a price on the cost of early-lactation lameness, a growing body of research indicates it limits your cows’ reproductive efficiency. Add to that the fact that it subtly chips away at your profits, and you have good reason to be concerned about lameness during early lactation.
