Causes and prevention of free-martinism in cattle
THIS week we are going to discuss the issue of an infertile cow or heifer in your herd.
This may appear to be a small issue but it is very important to a serious farmer because an infertile cow is a waste both in terms of time and resources. I know this for a fact after being duped into buying an infertile cow and seeing two years being wasted in waiting for it in vain to reproduce. While there are many causes of infertility in cattle, some of them being nutrition based while others are disease induced I would like to look at free-martinism.
A free-martin (inyumba) is an infertile female animal. Free-martinisim causes infertility in the female cattle born twin to a male. When a female twin shares the uterus with a male foetus they also share the placental membranes connecting the foetuses with the dam. In most cattle twins the blood vessels in the chorions become interconnected creating a shared circulation for both twins.
If both foetuses are the same sex this is of no significance but if they are different male hormones pass from the male twin to the female twin. The male hormones then masculinise the female twin and the result is a free-martin.
A joining of the placental membranes occurs at about the fortieth day of pregnancy, and thereafter the fluids of the two foetuses are mixed. This causes exchange of blood and antigens carrying characteristics that are unique to each female and male offspring.
Although the male twin in this case is only affected by reduced fertility, in over 90 percent of the cases, the female twin is completely infertile. Due to the transfer of hormones or a transfer of cells the heifer’s reproductive tract is severely underdeveloped and sometimes even contains some elements of a male reproductive tract.
A free-martin is genetically female but has many characteristics of a male. The ovaries of the free-martin do not develop correctly and they remain very small. Also the ovaries of a free-martin do not produce the hormones necessary to induce the behavioural signs of heat.
The external vulvar region can range from a very normal looking female to a female that appears to be male. Free-martinism cannot be prevented but it can be diagnosed in a number of ways ranging from simple examination of the placental membranes to chromosomal evaluation.
The cattleman can predict the reproductive value of this heifer calf at birth and save the feed and development costs if he is aware of the high probability of free-martinism. In some cases there are no symptoms of free-martinism because the male twin may have been aborted at an earlier stage of gestation.
Free-martins are, however, not very common as only about five percent twin births are recorded in a herd.
The male twin is largely unaffected by the fusion, although the size of the testicles may be slightly reduced. Testicle size is associated with fertility so there may be some reduction in bull fertility. A free martin is also usually in good body condition but not going on oestrus. This means as a farmer you should be sceptical of a person who sells you a good looking cow or fully matured heifer if its production records are not provided.
He could be disposing his free-martin to you. In case you already have an infertile animal in your herd, my advice is that just gather your relatives and give them a rare braai! Someone says no ways I will sell it and redeem some value from it but in my language they say “zanda ngomkhonto”.