Cow ID Date of last calving Date of AI service Pregnancy confirmed F12 15 Jan 2024 20 Apr 2024 Yes F18 03 Feb 2024 25 Mar 2024 No F23 10 Mar 2024 15 Jun 202...

(a) Oestrus (also called "heat") is the period in the reproductive cycle of a female mammal when she is sexually receptive [1] and willing to accept the male for mating. [1] In cattle, oestrus typically lasts 12-18 hours and occurs roughly every 21 days as part of the oestrous cycle. It is triggered by a surge of the hormone oestrogen from the mature follicle in the ovary, and ovulation occurs near the end of oestrus.

(b) Three signs a farmer would observe when a cow is in oestrus:

1. Standing heat: The cow stands still when mounted by other cows. [1] This is the most reliable sign and indicates she is at peak receptivity.
2. Swollen and reddened vulva with a clear mucus discharge. [1] The mucus is produced by the cervix under the influence of oestrogen and helps facilitate sperm transport.
3. Restlessness and increased vocalisation (bellowing). [1] The cow may pace, appear agitated, show reduced appetite, and attempt to mount other cows.

(c) Cow F18 was serviced on 25 March 2024, only about 50 days after calving (3 February 2024). This is likely too soon, because the uterus had not yet fully recovered (involuted) from the previous pregnancy. [1] The standard recommendation is to wait at least 60 days after calving before breeding, to allow the reproductive tract to heal and normal oestrous cycling to resume. Alternatively, the timing of insemination may not have coincided precisely with ovulation, or there may have been a reproductive infection or poor semen handling.

(d) The farmer waited approximately 60-90 days after calving before breeding cow F12 (calved 15 January, served 20 April = approximately 95 days) because:

1. The uterus needs time to return to its normal size and condition (a process called involution) after the physical demands of pregnancy and birth. [1]
2. Waiting this period allows the cow to resume normal oestrous cycles and significantly increases the chance of a successful pregnancy. [1] Cows bred too early have lower conception rates because the uterine environment is not yet optimal for embryo implantation.

(e) The role of the placenta during pregnancy in cattle:

1. The placenta attaches the developing foetus to the wall of the uterus, anchoring it securely throughout gestation. [1]
2. It allows the exchange of nutrients and oxygen from the mother's blood to the foetal blood across the placental membrane. [1] The foetus cannot feed or breathe independently, so the placenta acts as its supply line.
3. It removes waste products such as carbon dioxide and urea from the foetal blood, transferring them into the mother's circulation for excretion. [1]
4. The placenta produces hormones such as progesterone that maintain the pregnancy by preventing further oestrous cycles and keeping the uterine lining intact. [1]

(f) Three reasons the farmer chose artificial insemination rather than keeping a bull:

1. Cost savings: AI eliminates the expense of purchasing, feeding, and housing a bull year-round. [1]
2. Safety: Bulls, especially dairy breeds like Friesians, can be aggressive and dangerous to handle. Removing the bull from the farm reduces the risk of injury to farm workers. [1]
3. Access to superior genetics: The farmer can select semen from proven, genetically superior bulls located anywhere in the country or abroad, which would be impossible if limited to keeping a single bull on the farm. [1]