Cows Need a Sound Foundation To Exhibit Heat

Identifying the causes of poor reproductive performance can be frustrating. Generally the first area we assess is the heat detection program and then drill down to determine which management, cow or environmental factor is limiting the heat detection rate. In most cases, several factors are involved. Sometimes the obvious is overlooked. Consider what is needed for a cow to exhibit estrus. First, she has to cycling, which is affected by several factors. There has to be a surface that provides adequate support for herdmates to mount or for the estral cow to stand to be mounted. Finally, cows need sound feet and legs to seek out cows in heat, mount them or be mounted if they are in heat themselves. If these basic requirements are compromised then efficiency and accuracy of heat detection will be low. If lame cows are cycling they will be less likely to engage in estrous behavior. 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. If cows are in pain due to lameness they spend less time eating, ruminating and interacting with herdmates and more time lying down. Consequently, dry matter intake will be reduced and weight loss is noticeable which delays onset of cycling during early lactation.

What is the impact on reproductive performance? 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. More recently, results 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.

Confounding the problem is the fact that field studies have documented that herd managers underestimate the incidence of lameness in their herds. In one study, herd managers identified only 40% of the cows that were actually lame as determined by professionals. Lameness is a significant factor affecting reproductive performance and herd profitability. It is a complex problem. Herd managers should work with their nutritionist and veterinarian to develop a plan to minimize the incidence of lameness. For information on prevention and control of foot problems check the following website: http://www.das.psu.edu/dcn/catnut/PDF/Foot.PDF. Dairy producers should develop the skill of scoring locomotion so cows can be evaluated for lameness on a routine basis and problems identified early. Information about scoring locomotion can be found at
http://www.availa4.com/locomotion/

Michael O’Connor, Dairy and Animal Science Extension