10. Reproductive problems in farm animals
This session looks at the issues of reproductive problems in farm animals:
At the end of this session you will be able to:
- Explain the causes of infertility in farm animals
- Describe the term freemartin
- Explain the term dystocia, and the main causative factors
- Describe the nutritional disorders around reproduction
- Name the main inherited disorders associated with cattle and sheep.
Fertility and infertility in farm animals
Fertility is the ability of the male or female animal to reproduce.
The reproductive system of both is under the influence of range of gonadotrophins that act in sequence.
The dairy cow
Calving interval = an interval of 365 days between calvings is ideal in the dairy cow.
Components of a 365-day calving interval:
- elimination of uterine infection
- regular oestrus cycle
- heat detection
- fertilization
- implantation of embryo
- minimal embryonic deaths
- avoiding abortions
- production of a live calf
The main causes of low conception rates in dairy cows
The main causes of low conception rates:
- Poor embryo recognition
- Serving too soon after calving
- Poor heat detection
- Poor timing of Artificial Insemination
- Endometritis
- Fatty Liver
- Genital and other infections, e.g. Leptospirosis
- Stress
- Poor handling facilities
- AI operator technique
- Semen quality
- Nutrition
Main health reasons for poor fertility in the dairy cow
- Endometritis
- Fatty Liver
- Cystic ovaries
- Poor nutrition-low energy intake
- Lack of trace element or vitamin
Abortions caused by:
- Leptospirosis
- BVD
- Infectious Bovine Rhinotracheitis
- Neospora
- Salmonellosis
- Genital infections, e.g. Brucella abortus, Trichosomonas foetus and Campylobacter
Main reasons for poor fertility in the ewe and poor conception rates
- Low ovulation rates – linked to body condition score: too fat/thin
- Low conception rates – linked to body condition score: too fat/thin
- Reabsortion of the foetus at early stage – stress nutritional/actual
- Late foetal death
- Abortion
- Stillbirth
- Dystokia-difficult lambing
- Prolapses
- Poor mothering ability
Freemartin
Definition:
‘A hermaphrodite or imperfect sterile female calf which is the twin of a male calf whose hormones affected its development.’
The female and the male share the same blood supply in utero and as such the testosterone is dominant and affects the development of the female ovaries.
They can be absent or stunted.
Dystocia
Dystocia refers to abnormal or difficult birth.
Common causes:
- the cervix not completely dilated
- large calves/lambs compared to the mother
- mis-presentation at birth
Nutritional and Metabolic issues associated with reproduction
A metabolic disease or disorder is the name given to a group of illnesses in cattle and sheep that are caused by the imbalance of the inputs to the animal compared to the expected outputs.
It is the over-exertion of the normal metabolism.
Usually the imbalances occur at key times of pregnancy and lactation, where the food an animal gets is not enough to cover the demands on its body. This is why they are sometimes called production diseases.
Main Metabolic Disorders
Cattle
- Hypocalcaemia - Milk fever
- Hypomagnesemia-Staggers
- Rumen Acidosis
- Acetonemia
- Fatty Liver Syndrome
Sheep
- Hypocalcaemia - Milk Fever
- Hypomagnasemia - Staggers
- Rumen Acidosis
- Pregnancy Toxaemia -Twin Lamb Disease
National Animal Disease information service
This site will provide excellent notes and interactive quizzes on all health matters relating to farm animals.
https://www.nadis.org.uk/Inherited diseases in cattle and sheep
Genetic transfer with a defective gene must occur if the disorder is truly described as inherited. The parent may not have the condition but may be a carrier.
Examples:
- CVM in cattle
- Entropion
- Resistance to scrapie
- Overshot/undershot jaws in sheep
CVM: Complex Vertebral Malformation
CVM is a genetic disease, which results in abnormal calves. It is a recessive condition, which means that both dam and sire must be a carrier of the CVM gene if the calves are to be affected. This also means that even if both parents are affected, only ¼ of calves will be abnormal. So far the disease has been reported only in Holstein cattle.
NADIS
Entropion
Entropion (in-turned eyelid) is a common hereditary problem of many sheep breeds and their cross-bred offspring.
The genetic link is not fully understood, however some rams seem to be more at risk of passing the condition to their offspring.
Conclusion
At the end of this session you should now be able to:
- Explain the causes of infertility in farm animals.
- Describe the term freemartin.
- Explain the term dystocia, and the main causative factors.
- Describe the nutritional disorders around reproduction.
- Name the main inherited disorders associated with cattle and sheep.