5 A livestock farmer keeps a herd of beef cattle. The farmer wants to improve the quality of calves born on the farm. (a) State what is meant by the term oe...

(a) Oestrus is the period in the reproductive cycle when the female animal is sexually receptive and ready to accept the male for mating [1]. It is commonly referred to as being "in heat." During oestrus, a mature egg (ovum) is released from the ovary, making this the only time when mating can result in fertilisation.

(b) Two hormones involved in controlling the oestrus cycle in cattle (any two):

1. Oestrogen [1] - produced by the developing follicle on the ovary; triggers the behavioural signs of oestrus and prepares the reproductive tract for mating.
2. Progesterone [1] - produced by the corpus luteum after ovulation; maintains pregnancy if fertilisation occurs, and suppresses further oestrus cycles.

Other acceptable answers include follicle-stimulating hormone (FSH), which stimulates follicle development, and luteinising hormone (LH), which triggers ovulation.

(c) It is important for a farmer to detect when a cow is in oestrus so that the cow can be mated or inseminated at the correct time [1]. If mating or insemination is carried out at the wrong time in the cycle, the egg will not be present in the oviduct and fertilisation will not occur, wasting time, semen, and money [1].

(d) Three behavioural signs a cow shows when in oestrus:

1. The cow stands still when mounted by other animals, known as "standing heat" [1].
2. The cow shows restlessness, increased activity, or bellowing more than usual [1].
3. Swelling and reddening of the vulva, often accompanied by a clear mucus discharge [1].

Other acceptable signs include reduced appetite or milk yield, and attempting to mount other cattle.

(e) The farmer could use artificial insemination (AI) with semen from a bull that has proven superior meat traits, such as high daily weight gain or good carcass conformation [1]. This allows the farmer to introduce elite genetics into the herd to improve meat quality in the calves, without needing to purchase an expensive high-quality bull [1]. Embryo transfer from a genetically superior cow is also an acceptable approach.

(f) One disadvantage of relying on natural mating with a single bull: limited genetic variation in the offspring [1]. Over several generations, all calves carry genes from the same sire, which increases the risk of inbreeding depression (reduced fertility, lower productivity, and greater susceptibility to disease).