18 September 2006

3 minute read

If this basic requirement is compromised then efficiency and accuracy of heat detection will be low. On average, cows are in heat for approximately 7 to 8 hours. This is a narrow window of opportunity to detect healthy cows in heat and presents a real challenge to detect lame cows in heat.

What is the impact on reproductive performance? The following relationships are very important so I am repeating them again in this article. Results from a British study involving 770 cows with nearly 1500 lactations showed that lameness caused by lesions on the hoof was associated with a 7-day increase in days to first service and 11 more days open compared with herdmates without lameness.

These differences were greater for cows with sole lesions that developed between 36 and 70 days postpartum, the time when cows should first be detected in heat. For those cows, the interval to first service and days open increased 17 and 30 days, respectively. Data from a study in Florida involving 837 cows, 30% of which were diagnosed as lame most with claw lesions, showed that services per conception was significantly higher in lame cows than healthy (nonlame) cows. The median time to conception for lame cows with claw lesions was 140 days compared to 100 days for healthy cows.

New information recently published in the Journal of Dairy Science (December 2004) by a team of researchers at the University of Florida reported the results of a study, which examined the relationship between lameness and the onset of cycling during the first 60 days of lactation (Garbino et al. J. Dairy Science, 2004).

Using the new modified six-point locomotion scoring system; cows in a large commercial dairy were examined weekly during the first 35 days of lactation for diagnosis of lameness. Three of the six locomotion scores are described as follows: "0" normal - cow stands and walks with level-back posture and normal gait, score "4" lame - arched back posture is always evident and a gait is described as one deliberate step at a time. Cow favors one or more limbs.

Score "6" severely lame - cow demonstrates an inability or reluctance to bear weight on one or more limbs. In addition, blood samples were obtained to determine the concentrations of progesterone, which indicate the onset of the first estrous cycle. Cows classified as lame (score 4) were 3.5 times more likely to have delayed ovarian activity, compared to non-lame cows. Furthermore, it was determined that ketosis was a factor that delayed resumption of estrous cycles.

The researchers suggested that lameness and ketosis might interact to delay onset of estrous cycles. As shown in several other studies, lameness depresses dry matter intake causing negative energy balance and production of ketone bodies. If cows are in pain due to lameness they spend less time eating, ruminating and more time lying down. Consequently, dry matter intake will be reduced which may likely delay the onset of cycling during early lactation.

Lameness is a significant factor affecting reproductive performance by inhibiting estrous behavior as well as delaying ovarian activity. It is a complex problem. As stated in a previous article, dairy producers should develop the skill of scoring locomotion so cows can be evaluated for lameness on a routine basis and problems identified and treated early. Information about scoring locomotion can be found at http://www.availa4.com/locomotion/.

April 2005