Dairy farmers who think they are saving money by dividing the bull semen straws they use to inseminate their cows are fooling themselves and contributing to infertility in their herds, a dairy expert has said.
Dr Tom Kelly, of the Teagasc research centre in Kildalton, Co Kilkenny, said the practice of breaking the tubes in which the semen is contained to service twice the number of cows was counter-productive.
"It could not be recommended especially if the source of the semen was not known and there was a distinct possibility that the semen has already been diluted before reaching the farm," he said.
The practice of breaking the semen straws, designed to be used for one service, is fairly widespread on Irish dairy farms because semen from quality bulls can cost as much as £80 per straw.
Dr Kelly was speaking at a seminar in Kildalton at which farmers were told that with rising milk yields, the average calving rate to the first service of a cow had fallen from 70 per cent in the late 1970s to less than 50 per cent.
The calving rate in pure Holstein dairy cows, the highest milk-producing animals in the national herd, has fallen below 40 per cent.
He said that research by Teagasc, the agriculture and food development authority, on 7,000 cows at 73 farms, was showing a clear linkage between high milk yields and low fertility.
Initial results from the study showed an average calving rate to first service of 48 per cent on the 73 farms, where there was a variation of between 26 per cent and 73 per cent.
The study also found that the average infertility rate was also very high and stood at 14 per cent, compared to a Teagasc target of less than 10 per cent. Infertility ranged from zero to 34 per cent across the 73 farms.