Fertility problems in maiden beef heifers could be due to an increase in the age at which they have reached sexual maturity.
According to Colin Penny of Edinburgh’s Royal Dick vet school, a group of maiden heifers run with a bull for six or seven weeks should achieve 90% pregnancy.
“But at SAC’s beef unit we have been struggling to achieve AI pregnancy rates in heifers of more than 60%.”
These heifers should reach puberty at 12 months to conceive at 15-16 months.
However, he believes the farm’s decision to breed for extreme beef for the past seven years, diluting dairy genetics, means sexual maturity is getting later.
“Our heifers are free of bovine viral diarrhoea, vaccinated against leptospirosis and we have no evidence of infectious bovine rhinotracheitis.
Plus, there is no evidence of copper or selenium deficiency and AI is carried out by the same technicians who achieve excellent results in cows.
“From doing blood progesterone tests in heifers prior to synchronisation before AI, we have found 10-20% of animals are non-cyclic in some years.
We believe these may not have reached puberty in time , despite being in good body condition and being 12-14 months old,” he said.