Rural veterinary practice
Overlaying of piglets
Delivery of a goat
Foot and Mouth Disease
Bovine Virus Diarrhoea
22. Fertility control (herd health management)
A heifer starts to produce milk once she has calved. The daily production reaches its maximum approx. two months after calving and then gradually decreases to about half that amount after a year. The cow must calve every year to ensure a high milk production. And because the gestation period takes nine months, the cow must become with young again approx. three months after calving. The fertility is crucially important to the milk production.
Once every six weeks, the cows are lined up along the feed railing after the morning milking for a health inspection. Wearing overalls and boots, I walk across the grids behind the cows. This gives me a good view of the stand of their rear legs, the udders, paunch volume and the manure. But the inspection does not involve only having a look, there are things to do: a number of cows have been marked with a chalk because they require a gestation examination. By means of a rectal examination, meaning through the intestinal wall, the uterus must be explored by hand. This is called ‘palpation’. To ensure a regular and high level production, she must calve every year. Or in technical terms: the calving interval must not be much longer than 365 days. A delay of 15 to 30 days is warranted for cows with a very high production rate. A reliable gestation diagnosis can be obtained through a rectal examination starting from five to six weeks after the fertilisation. In a herd of one hundred dairy cows, the gestation examination involves an average of fifteen to twenty-five cows and heifers during the six-weekly visit to the farm, because there are also so-called ‘recurring patients’: animals that have been inseminated more than once and must be examined again. Not every insemination will immediately result in fertilisation. And there are also animals in which the young embryo dies for no apparent reason and therefore 'recur'.
loose housing barn with one hundred cows
A second group of cows that require a rectal examination during the herd health management visit concerns the animals that fail to timely become oestrous after calving. Time is of the essence in the modern cattle-breeding industry and a cow must return to its normal sexual cycle two months after calving. After all, she must be with young once again in three months or so. Because the milk production will reduce if the calving interval becomes too long. It is important to examine the uterus and ovaries of the animals that fail to become timely in heat to rule out deviations. Highly productive cows in particular sometimes take months to reach this state. They produce so much milk that their bodies burn more energy than they can consume through the feed. This lack of energy curbs the functioning of the ovaries. A possible consequence could be that the ovaries remain inactive altogether, so that these animals do not become oestrous for a prolonged period. Another possibility is that a follicle does indeed develop, but this is not followed by an ovulation: the follicle is ‘persistent’ without the cow demonstrating that it is oestrous. This is referred to as a ‘silent heat’. A third cause of a cow not becoming oestrus is the presence of pus in the uterus as a result of, for example, the afterbirth remaining behind after calving. I can imagine that the cow could experience this filling in her uterus as a ‘false pregnancy’. It is also possible that a cow was indeed in heat without the farmer being aware of this. In any event: the animals must become oestrous in time in order to have them become with young in time. The management of a hundred highly productive cows involves examining a dozen or so cows for being not oestrous during the six-weekly visits to the farm.
“A lot to do today?” The farmer looks up from his list. “Let’s see: I have thirty-two on my list.” The cows are standing close to one another with their heads in the feed railing. With the records in hand, the farmer walks along the feed alley in front of the cows; I am on the grids behind them. I am wearing a long plastic glove on my right arm. One of the cows has a stripe on its head: “This one should be with young”. I feel through the wall of the rectum to check the size of the uterus: “Yes, with young.” The same goes for the next twelve cows. But then I feel two curled uterine horns like thick fingers. “This one is not pregnant.” There is a ripe follicle on the ovary and so: “She will be in heat tomorrow.” “The shrew; well, I’ll see what I do about that.” She is a recurring patient that has already been inseminated three times, the last time being eight weeks ago. After three fruitless inseminations, a cow is generally milked for a couple of months and then replaced by a heifer. The farmer makes a note on his list and we continue. A number of animals that have not yet appeared to be oestrous have a persistent follicle. I feel a yellow body on the ovary in a few others: so these cows had been (inconspicuously) oestrous. Both of the ovaries in one of the top production cows are particularly small (inactive). One cow appears to be pregnant, but she calved only six weeks ago and is not yet inseminated. Whatever is in her uterus, it cannot be a calf. I look in her vagina using a tube and a small light. A string of white muck is protruding from the cervix.
After internally examining all thirty-two marked animals, I clean my boots at the entrance to the shed with a high-pressure water spray pistol. From the car, I fetch syringes, needles and bottles with various hormones that I need for the treatments and I put it in a plastic carrying bin. This time, the farmer joins me on the grids with the worklist in his hand. The animals mentioned on it, are treated now.
a look in the vagina
In order to keep track, it is essential to keep proper records. I write my report in the kitchen. It will also serve as a mnemonic for the next scheduled visit. The farmer will enter his notes in the farm computer later. Using a print-out from the computer, we discuss the operating results of the past six weeks. They are presented in the form of ‘index numbers’. For example, the fertility of the cows is indicated by the calving interval (in days) and the insemination number. That number indicates how often the cows needed to be inseminated, on average, before they became with young. The milk production is expressed as the Farm Standard Cow (Bedrijfs Standaard-Koe): that is the average daily production under standard-conditions. And so it requires some specialist knowledge to be able to evaluate the operating results; information technology and agricultural science have meanwhile been introduced on farms.
But we also discuss other things in the kitchen as well, for example the necessity to invest even more in the milk quotum; the newest government regulations regarding the storage of manure. Protection of the environment again requires major investments. A lot of time is ‘lost’ with all that talking. But I consider it an indispensable part of good herd management. And I think that the farmers felt the same.
© Leo Rogier Verberne