A variety of hormones are used within the dairy industry to treat reproductive disorders and to regulate the oestrous cycle for timed breeding. These hormones act directly on either the reproductive organs or on the pituitary gland itself to stimulate the release of naturally occurring hormones. These hormones then stimulate the reproductive organs. Prostaglandin, oestrogen and oxytocin act directly on the reproductive organs whereas gonadotrophic releasing hormone (GnRH) acts at the level of the pituitary gland.
GnRH causes the pituitary gland to secrete both LH and FSH. These two naturally occurring hormones (accompanied with other hormone levels) causes the ovulation of the dominate follicle present on the ovary. GnRH can be used to treat cows with cystic ovarian disease or cystic ovaries and may also be used in some oestrous synchronization programs. Injections of GnRH help to synchronize the follicular waves, resulting in better control over the timing of ovulation and consequently allows for more accurately timed breedings.
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Endometritis can be defined as the presence of a vaginal discharge containing pus, usually presented 21 days or more after calving. Infection will result in a slower rate of recovery of the uterus post calving and a delay in the start of ovarian activity. This will lead to an increase in the time to first service of around 30 days even when the cow is treated. Conditions which increase the likelihood of female cattle developing endometritis include:
- Retained membranes
- Calving difficulties
- Giving birth to dead calves and twins
- Being too fit at calving
- Developing milk fever
- Vitamin E/selenium deficiencies in the diet
Endometritis will reduce the chance of successful insemination and increases the risk of infertility culling; it is therefore an important cause of reduced fertility in dairy herds. According to ‘XL Veterinary’ typically 15% of cows may be affected.
On the farm at the clinical level, the vet will flush out the uterus with ‘Metricure’. This is an injector for intra-uterine use in cattle. The injector contains cephapirin, an antibiotic belonging to the group of cephalosporins. Cephapirin is active against a wide range of gram +ve and –ve bacteria involved in endometritis, such as Actinomyces pyogenes, Fusobacterium necrophorum, anaerobe Bacteroides spp. and Escherichia coli. After intra-uterine application of Metricure, high levels of cephapirin are obtained in the uterus lumen as well as in the uterus wall.
Metricure is for both the treatment and prevention of subacute or chronic endometritis in cows of more than 14 days post-partum, but it may also be used for repeat breeders (those with 3 or more unsuccessful inseminations to remove any infection present in the uterus).
Studies have shown that the reproductive tracts of over 80% of cows are contaminated after calving but that the processes that clear this infection such as uterine contraction and the cow’s immune system are very efficient at removing it if the cow is well looked after and not stressed unduly. So, attention to detail is the key!
More info at The Cattle Site.
‘Estrumate’ is a synthetic prostaglandin for controlled breeding in cattle and horses. As a potent luteolytic agent it causes functional and morphological regression of the corpus luteum (luteolysis) in cattle and horses followed by return to oestrus and normal ovulation. It is highly effective in treatment of clinical conditions of cattle such as; suboestrus, late term induction of parturition, termination of normal and abnormal pregnancy, chronic endometritis and ovarian luteal cysts. A typical does consists of 2ml of Estrumate. Estrumate contains the active ingredient Cloprostenol.
For suboestrus; This condition occurs in heavy yielding cows, usually at peak lactation, which have normal ovarian cyclicity but behavioural manifestation of oestrus is either very mild or absent. Such animals can be treated following diagnosis of a corpus luteum by rectal palpation and then closely observed for oestrus. Those showing heat should be inseminated. Animals not seen in heat should be re-examined 11 days later and may receive a further single injection and be bred at oestrus or at fixed times. Where re-examination is carried out 14 days later to fit in with routine fertility visits, animals should be bred on detection of oestrus rather than at fixed times.
Estrumate also induces parturition in the period around normal term. Induction should take place as close to the predicted calving date as possible and not more than 10 days before. Administration should not be attempted before day 270 of gestation measured from the confirmed day of conception except in pathological conditions (terminations of abnormal pregnancies such as a mummified foetus or hydrops of the foetal membrane).
Where cystic ovaries associated with persistent luteal tissue and absence of oestrus is diagnosed, Estrumate has also proved effective in correcting the condition and bringing about a return to cyclicity.
With regards to controlled breeding in cattle, control of the oestrous cycle is of value in the:
- Controlling oestrus in the individual animal giving better control of the individual calving index and reducing the number of cows culled as barren.
- To control oestrus in groups of cows; to promote management of the herd in groups of suitable size and facilitate the maintenance of a seasonal calving pattern.
- To permit the use of AI in dairy heifers; allowing the speeding up of the breeding programme.
- To facilitate the use of AI.
- To enable most efficient use of available bulls: where natural service is preferred.
- To permit better herd management at conception and calving: The shape of the calving pattern is improved, resulting in greater average age and weight of calves at weaning. Feeding and other programmes can be scheduled more easily.
More info at Partners in Reproduction
Jess Wray is currently a '2 in 1' Veterinary student at the University of Liverpool. Her qualifications include a BSc (hons) in Bioveterinary science and she also has vast 'hands on' experience working with both small and large animals.
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