Rural veterinary practice
Overlaying of piglets
Delivery of a goat
Foot and Mouth Disease
Bovine Virus Diarrhoea
Herd health management
24. Herd health management
For the sake of herd health management, I visited around twenty dairy farms every six weeks. All animals from old to young were inspected to gain an impression of their health and productivity or their growth respectively. The fertility of adults is of crucial importance for their milk production. A heifer only 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. Therefore, a 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. That's why fertility control makes up the greatest part of herd health management by the veterinary surgeon on a dairy farm.
When I arrive, after the morning milking, the cows are closely lined up along the feed railing for a health inspection. Holding the working list in his hands the farmer then walks on the feeding alley in front of the cows. I walk behind them, across the grids, wearing company overalls and boots. This gives me a good view of the stand of their rear legs, the udders, paunch volume and the manure, which gives an impression about the digestion of the food. But the management does not involve only inspection, there are things to do: a number of cows have been marked with a chalk because they require an examination.
1. gestation examination
By means of a rectal examination, meaning through the intestinal wall, the uterus must be explored by hand to check for the possible presence of a gestational sack. This is called ‘palpation’. To ensure a regular and high level production, a cow must calve every year, as you know. Or in technical terms: the calving interval must not be much longer than 365 days. A delay of some weeks to a month is warranted for cows with a high production rate. But they must be with young again about four month after calving to reach the expected production level in the next year. 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' after some time.
loose housing barn with one hundred cows
2. oestrous control
A second group of cows that require a rectal examination during the herd health management visit concerns the animals that failed to timely become oestrous after calving. Deviations in their uterus or ovaries must be detected in time. Because time is of the essence in the modern cattle-breeding industry. A cow must return to its normal sexual cycle two months after calving. However, highly productive cows in particular sometimes take many 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 that may remain inactive altogether, so that these animals do not become oestrous for a prolonged period. Another possibility is that a follicle (ovisac) does indeed develop, but this is not followed by an ovulation: the follicle becomes 'cystic' without the cow demonstrating that it is oestrous. 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. Managing a hundred highly productive cows involves examining a dozen or so cows for being not oestrous during the six-weekly visits to the farm.
3. working list
“A lot to do today?” The farmer looks up from his list. “Let’s see: I have thirty-two on my list.” I am wearing a long plastic glove on my right arm now. 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 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’ll 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. One of the top production cows has as yet failed to be in heat after calving. Her ovaries feel particularly small (inactive). Other animals that have not yet appeared to be oestrous, are found to have a large ovary containing a big follicle (cyst). Obviously that follicle didn't ovulate. I can feel a yellow body (corpus luteum) on the ovary of a few others: so these cows have actually been oestrous but that wasn't noticed. The uterus of one of the cows feels pregnant; but she calved only six weeks ago and is not yet inseminated. Whatever is in her uterus, it cannot be a calf. When 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.
a look in the vagina
From the car, I fetch syringes, needles and bottles with various hormones that I need for the treatments and I put everything in a plastic carrying bin. I also include a plastic coil (PRID). This time, the farmer joins me on the grids with the worklist in his hand. The highly productive cow with inactive ovaries gets the PRID (Progesterone-Releasing Intravaginal Device) implanted into its vagina. The device is impregnated with progesterone and it must stay in place for a week. The cow will become oestrous two days after its removal. Next, the animals that were not in heat because of a cyst in one of their ovaries that did not ovulate, get a hormone injection. That stimulates the pituitary gland (in the brains) to initiate the sexual cycle.
The cows carrying a yellow body in one of their ovaries are injected with a hormone called prostaglandine. A few days later they will come into heat. The same prostaglandine is injected in the cow with its womb full of muck; during the heat that is induced in that way the uterus will contract and clean itself.
Young cattle shed
The young cattle shed accommodates the calves and yearlings from three months to two years of age. They stand at both sides of a feeding alley, divided into groups of about the same age. Normally they walk there freely over the grids, but now their heads are fixed in the feed railing. They all look well and healthy. The main problem in cattle of this age is coughing. That’s why I vaccinate the calves against BRSV (Bovine Respiratory Syncytial Virus) and the yearlings against BVD (Bovine Viral Diarrhoea). The latter name does not suggest that a BVD-virus infection may induce airway and lung problems in young cattle. However, it really can do so because this virus paralyses the immune system of infected animals. (LRM Verberne. BVD-aanpak: vaccinatie en eradicatie. Tijdschr Diergeneeskd 2000; 125: 218-21).
But not all of the yearlings are vaccinated against BVD: only the animals that have not yet been inseminated (not pregnant) are vaccinated. Yearly testing of random samples of blood showed that the pregnant yearlings, the heifers and cows on this farm all had anti-bodies against the BVD-virus. Which is partly due to the vaccination programme that is followed in this respect. Because all pregnant animals are protected against BVD infections, no virus carriers can be born here anymore. And that is precisely the goal of the vaccination programme. So in the long run, this livestock will be free of BVD-virus by the systematic complementary vaccination of animals that are lacking those antibodies. In recent times, the national programme of the Animal Health Service to eradicate BVD from the Netherlands makes local initiatives to prevent BVD-problems in individual dairy farms little by little less urgent.
The new-born calves live together in one large open shed on a thick straw bed. A dispenser for the milk replacer with several teats is in the corner. The calves play around in the shed, their coats shining. Diarrhoea is the most frequent problem in such young animals. Therefore, dispensing the milk in small portions and careful hygiene are the most important preventive conditions. The calves aged one to two months old must have their horn buds burned away. To that end, they are sedated and locally anaesthetized. Next, the buds are removed using a round branding-iron. That prevents the growth of the horns. Thus it will be unnecessary to dehorn them at a later age.
Keeping proper records is an essential part of herd health management. While sitting in the kitchen I write my herd management report. 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. They are presented in the form of ‘index numbers’. Information technology has meanwhile been introduced on farms. Other things are discussed in the kitchen as well, like the necessity to invest even more in the milk quotum; and the newest government regulations regarding the storage of manure, which again require 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