We are all well aware that sick cows are less likely to get in calf but what are the actual numbers like for lameness and can you do anything about how much a lame cows’ reproductive performance is affected. 
 
So why would a lame cow be less likely to get in calf early or at all? 
Like mastitis and other diseases, lameness causes inflammation and the inflammatory process can reduce conception rates by affecting the quality of the corpus luteum which is what sustains pregnancy in the first couple of weeks. However, lameness also has the potential of severely impacting energy intakes. Research shows that milk production and dry matter intakes often drop well before lame cows are detected as lame. Lame cows walk less, walk slower, graze less and sit more; all factors that lead to severe negative energy balance if not corrected. 
 
From my experience analysing herd reproductive records over many years and from the InCalf data, we know that there is a huge range in how much lameness impacts reproductive performance at both the cow and herd level. 
 
Australian InCalf research indicated the variation in impact on 6 week incalf rate with a lame cow to be between 2 and 17% reduction with a 3 to 12% increase in not in-calf rate. That is a variation of up to 8 times! New Zealand InCalf research puts the average impact at 6% reduction in 6 week incalf rate and 3% increase in not-in-calf rate. At the individual cow-level there is always an negative impact but at the herd-level of course the size of the impact depends on how many lame cows you have. 
 
Some factors that are likely affecting the size of the impact are at cow level are; when did she get lame (before or during mating), how early in her lameness was she was detected and treated, how successfully was the lame cow treated, how much BCS loss has she suffered as a consequence of her lameness i.e. how well has she been managed since she was first lame (own mob, adlib feed, OAD are all tools), are the lame cows able to show heat (are there sound cows in the lame mob that can mount them) and if they show heat are they mated i.e. are there bulls in the lame cow mob. 
 
So if you are getting a few lame cows coming into mating, firstly make sure you  record them, so you can review their performance at the end of the season, secondly make sure you  look after them  (draft and treat promptly, run in their own mob, reduce walking, increase access to feed, use tools such as cowslips/blocks and anti-inflammatories to speed up the recovery process). 

Anexa resources you might find helpful:

In One Ear & Out The Udder Podcast – How to manage sick and lame cows during mating