RED DEER – Pushing dairy cows to produce more milk has been linked to fertility problems.
“If performance or fertility really have gotten worse since Grandpa’s time, to what extent can we blame it on higher production,” said Stephen LeBlanc of the Ontario Veterinary College at Guelph.
His large scale study of dairy statistics failed to show whether pregnancy rates in dairy cattle are declining, and he is now recommending more large scale trials.
Cows are producing more milk but calving records may be biased, he told the recent Western Dairy Seminar in Red Deer.
LeBlanc examined the records of 3,300 Canadian herds from Canwest DHI for 2005 and 2009, looking at rates of pregnancy, insemination and estimated conception.
Canwest DHI is a dairy management program that generates re-cords to improve productivity, milk quality and profitability at the farm level.
LeBlanc analyzed 100,000 cows for milk production, calving interval
to next pregnancy, cull and open rates.
The average cows produced 36 kilograms of milk per day, and LeBlanc found the higher producers were bred sooner. They also seemed to become pregnant sooner than the lower producing cows.
His results also suggested that high producing cows are not treated the same as lower producing cows.
He found high producing cows are bred more times and for longer spans of time than low producers. Low producing cows are given fewer chances before being culled. He defined the open rate as the time the cow calved until it became pregnant again.
“High producing cows on average have longer days open and more services,” he said.