Her soundness can impact her reproductive success. It's well-known that lame cattle can have reduced milk production and increased disease incidence, but the effects of lameness can also negatively affect fertility and reproduction.
Jeff DeFrain, PhD, Dipl. ACAN, Zinpro Performance Minerals, says the link between lameness and fertility is what he considers as a “hidden transaction” in the profitability equation. “Checks are either written or cashed when it comes to milk income, hoof trimming and culling,” he says. “However, the true cost of poor fertility, especially as it relates to lameness, becomes difficult to assess in most cases.”
The 2007 National Animal Health Monitoring System survey found that 16% of cows are culled for lameness, and lameness may increase the number of cows culled due to reproductive failure. Generally speaking, non-infectious claw lesions, such as sole ulcers or white line disease, tend to be more damaging to reproductive performance than would infectious claw disease, most notably digital dermatitis (hairy heel warts), DeFrain explains.
AGE AND LAMENESS
DeFrain says throughout the United States and abroad, Zinpro has conducted numerous herd lameness investigations using hoof-trimming records, and routinely observes an increase in infectious claw lesions in the first 60 days in milk. “Generally speaking, after 60 days in milk, the infectious claw lesions tend to trend downward and we begin to find more non-infectious lesions,” DeFrain says.
The increase in infectious claw disease in the first 60 days in milk coincides with the immunosuppression typically observed in transition cows. “Activation of the immune system to overcome these infectious challenges, both in the claw and the uterine environment, comes at a significant energetic cost,” DeFrain says.
It should be noted that optimal reproductive function is only possible after the energetic needs for maintenance (including immune function), growth and milk production have been met. “Therefore, herds which focus on minimizing lameness in early lactation tend to have greater reproductive performance,” DeFrain adds.
Similar modes of action will apply to both heifers and cows when it comes to the impact of lameness on reproductive performance. Research clearly shows older cows are at greater risk for lameness, especially the more complex, more painful, non-infectious claw lesions. “Therefore, by default, older cows will be at greater risk for compromised reproductive function compared to their younger herd mates,” DeFrain says. ”However, it should be noted that we have been finding greater levels of digital dermatitis in replacement heifers returning to the dairy.”
THE PHYSIOLOGICAL EFFECTS OF LAMENESS
Relative to their healthy, non-lame herd mates, research indicates that lame cows have decreased conception rates, more services per conception, increased presence of ovarian cysts and an overall decrease in pregnancy rate.
DeFrain says that research shows severely lame cows have lower maximum progesterone concentrations, which is responsible for maintenance of pregnancy, compared to non-lame cows. “Lameness is a chronic stressor. Once a stress is detected by the animal, chemical signals are sent to the brain in the form of pro-inflammatory mediators.”
The brain is constantly interpreting these signals and directing metabolic processes such as the release of reproductive hormones from the hypothalamic-pituitary-adrenal (HPA) axis. In essence, the animal goes into “conservation mode” and puts strict limits on nutrient use until the problem/stressor is eliminated. “Therefore, until the stressor is removed, levels of hormones such as progesterone will not return to normal,” DeFrain says. Because of this, poor reproductive performance should be expected if one chooses to inseminate lame cows.
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