Animal Reproduction – Agricultural Sciences Grade 12 Questions and Answers

Animal Reproduction – Agricultural Sciences Grade 12 Questions and Answers

QUESTIONS

• Answer the questions below. Check your answers afterwards and do corrections.
• Give yourself one hour.
• Marks: 100

1. Name the reproductive organ in which the following processes take place:
   1.1 ovulation
   1.2 fertilisation
   1.3 spermatogenesis
   1.4 implantation
   1.5 lactation
   1.6 parturition. (6)
2. Hormones are release during the oestrus cycle. Name a function of the following hormones in the oestrus cycle:
   2.1 Progesterone
   2.2 Oestrogen (2)
3. Outline the main difference between infertility and sterility. (2)
4. List FIVE important factors to consider in the collection, examination and storage of semen to ensure that the product is of good quality. (5)
5. It is important for a farmer to be able to detect oestrus in a cow.
   5.1 Explain why it is important. (1)
   5.2 Describe TWO signs of oestrus/heat in a cow. (4)
   5.3 What is standing heat? (2)
   5.4 When is the best time to mate/inseminate a cow? Distinguish between beef cattle and dairy cows. (2)
   5.5 Is the oestrus cycle in cows seasonal? (1)
6. Describe the process of fertilisation. Explain where and how it takes place. (5)
7. Can a monozygotic twin be a freemartin? Explain your answer. (3)
8. Describe the difference between resorption and abortion. (5)
9. Outline the sequence of events when a cow gives birth. List and briefly describe all of the important processes. (10)
10. Incorrect foetal presentation is one of the main causes of dystocia in cows because it prevents the calf from moving through the birth canal.
    10.1 What are the main incorrect foetal positions that cause problems? (3)
    10.2 How are the positions referred to in (10.1) usually corrected? (1)
11. Milk production is under hormonal control.
    11.1 Which hormone is involved in the control of lactation? (1)
    11.2 Name FOUR common causes of a drop in milk production. (5)
    11.3 What normal physiological process can cause a drop in milk production three months after calving? (1)
12. Name the main categories of causes for a lack of libido in bulls.
    12.1 List four and provide a brief description of each one. (8)
13. Discuss the role of disease in the reproductive failure of cows. (6)
14. Cloning is the process of producing an exact replica of an animal.
    14.1 Would you use this technique as a replacement for natural mating? (2)
    14.2 Give reasons for your answer. (3)
15. Discuss the importance of correct feeding during the reproductive process. Provide and elaborate on at least two factors. (6)
16. Which THREE of these foetal presentations can cause dystocia?
    16.1 Anterior presentation
    16.2 Posterior presentation
    16.3 Breech presentation
    16.4 Anterior presentation with head retained
    16.5 Posterior presentation with limb retained (3)
17. Name THREE conditions of the calf that can cause dystocia. (3)
18. Name FOUR signs that indicate that a cow is about to calve. (4)
19. Define milk let down. (1)
20. Use the information below to draw a lactation curve. (5)

ANSWERS

1. Name the reproductive organ in which the following processes take place:
   1.1 ovary
   1.2 fallopian tubes
   1.3 testes
   1.4 uterus
   1.5 mammary gland
   1.6 uterus/vagina. (6)
2. Hormone functions:
   2.1 Prepare the uterus for the reception of the fertilised ovum; Supporting the attachment of the embryo; Maintain pregnancy (any one)
   2.2 Characteristics of oestrus; Increased blood supply to uterus to prepare it for the reception of the fertilised ovum (any one) (2)
3. Sterility is permanent infertility ; infertility is a temporary inability to reproduce which can be reversed. (2)
4. Prevent chilling during collection and handling, keep the sample as clean as possible, ensure the specimen is of good quality, use a suitable diluent which will protect the spermatozoa during storage, store at the correct temperature. (5)
5. Oestrus detection in a cow.
   5.1 To enable cow to be mated as close to ovulation as possible. (1)
   5.2 Cow off her food, shows as “bullstring” from vagina, mounts or is mounted by other cows, head butting, shows interest in bull (any two) (4)
   5.3 When cow stands to be mated by bull (2)
   5.4 Beef cattle as soon as heat is detected; dairy cattle 12 hours after heat detection (2)
   5.5 No, it is a 21 day cycle. (1)
6. Takes place in the cows fallopian tube. If the cow has been mated or inseminated at the correct time the sperm cells will be waiting in the FT s for the release of the ovum from the ovary. The cilia or hairs of the fallopian tubes help the ovum down the tubules where the sperm are then able to attach to the egg. One sperm cell finally penetrates the ovum after other sperm have achieved the process of capacitation. (5)
7. No, monozygous twins arise from division of the same fertilised egg and are therefore same sex. A freemartin is the result of twins being different sexes. (3)
8. Resoprtion occurs early in pregnancy before the foetus develops the skeleton so the tissues are reabsorbed. If the foetus dies off once the skeleton has developed it has to be aborted out through the vagina. (5)
9. Involuntary contraction of the uterus which pushes the foetus against the opening cervix, rupturing allantois and releases allantoic fluid ; cow now strains with abdominal muscles pushing foetus into vagina, rupturing amnion. Cow pushes until calf is expelled ; umbilicus detaches and afterbirth is expelled a few hours later. (10)
10. Dystocia in cows:
    10.1 Retained head or limbs. (3)
    10.2 Head or limb must be straightened out by vet/farmer. (1)
11. Milk production is under hormonal control.
    11.1 Somatotrophin (1)
    11.2 Infections (mastitis), fever, poor nutrition, and heat stress. (5)
    11.3 Oestrus (1)
12. Lack of libido in bulls:
    12.1 Immaturity, inexperience, nutrition, old age, disease/pain, overwork, breed, temperament/stress. (8)
13. Infections such as venereal diseases can prevent fertilisation, implantation or may cause resorption or abortion of the developing foetus. Infection of the genital tract will prevent successful conception. (6)
14. Cloning:
    14.1 No. (1)
    14.2 cloning of animals is at present not very successful, so using it to improve a herd or increase the number of animals with a desired characteristic such as disease resistance, is not practical. AI or ET are at present more effective means of herd improvemenr. (4)
15. Optimum nutrition is essential for fertility of the both the cow and bull, is essential for sustaining a successful pregnancy and for good milk production and return to oestrus after calving. (6)
16. Foetal presentations can cause dystocia:
    16.1 Breech presentation
    16.2 Anterior presentation with head retained
    16.3 Posterior presentation with limb retained (3)
17. Twins, extra limbs, hydrocephalus (swollen head). (3)
18. Enlarged abdomen, lactation, vaginal discharge, relaxation of pelvic ligaments, behavioural changes. (4)
19. The release of milk from the udder which allows the calf to drink or the cow to be milked. (1)
20. Lactation curve (give one mark for each of: X-axis; Y-axis; increments on each axis; graph line; indication of peak yield).