If farmers have a better understanding of the cow’s reproductive anatomy, then it becomes easier for them to understand the factors that come into play when it comes to getting her pregnant, according to UK veterinarian Roger Blowey.
“For example, at a very practical level, the tip of an insemination gun should always be placed at the entrance to the cervix during the AI process. If it is pushed up beyond this point, damage to the uterus can result, which will diminish the cow’s chance of becoming pregnant.”
Blowey confirmed that 90% of eggs will be fertilised if the cow is inseminated at the right time.
“But problems can follow, when it comes to the new embryo implanting itself onto the wall of the uterus,” he said.
“This is because the cow does not pick up the signals coming from the fertilised egg and, as a result, does not respond in the ways required to allow implantation.”
Blowey said that both external and internal factors can come into play, when determining whether or not implantation can take place.
“Extraneous stimuli include lameness, mastitis, over-crowding, poor handling and other management related issues,” he added.
Internal factors include endometritis and the physical condition of the uterus. For example, if full involution has not taken place, then the cow will not become pregnant.
“This issue raises its head if a cow is inseminated too soon after having her previous calf.”
Blowey also highlighted the implications of twin calves – a heifer and a bull – being born while attached to the same placenta during pregnancy.
“Invariably the heifer will be a freemartin. This is because male hormones from the growing bull will be circulating prior to the heifer producing her own compliment of female hormones. As a consequence, the heifer will be born with both male and female sex organs.
“Sometimes, the bull calf will be re-absorbed by the mother. However, the resulting single heifer calf will still be a freemartin.”
