Agricultural Science 2020 Jamb Examination

Plant breeders focus on traits that improve crop performance and yield such as tolerance to adverse climatic conditions, resistance to pests, and uniformity in the time of maturity to ensure synchronised harvesting. Adaptation of pollination is not a breeding objective because pollination mechanisms are natural reproductive processes, and breeders are more concerned with ensuring controlled pollination rather than altering it for adaptation. Hence, while the other traits are intentional targets, adaptation of pollination is not considered a breeding aim.

In birds, food is temporarily stored in the crop, a thin-walled muscular pouch located near the throat. The crop softens and moistens food before passing it to the stomach for digestion. The gizzard is responsible for grinding food, the proventriculus is the glandular stomach where enzymatic digestion begins, and the duodenum is part of the small intestine where absorption occurs. Therefore, only the crop serves as the temporary storage site.

Ruminants such as cows, goats, and sheep chew the cud as part of their unique digestive process. Their stomach is divided into four compartments, and partially digested food is regurgitated, re-chewed, and swallowed again for complete digestion. Amphibians, aves (birds), and reptiles do not exhibit this behaviour. Chewing the cud is a defining characteristic of ruminants.

Spermatozoa are produced in the testicles, specifically within the seminiferous tubules where spermatogenesis takes place. The penis only serves as a copulatory organ, while the prostate gland and Cowper’s gland contribute secretions to semen that aid sperm motility and survival. The production of sperm, however, occurs solely in the testicles.

Signs of heat in farm animals include restlessness, loss of appetite, increased vocalisation, mounting behaviour, and in some cases, grunting. Udder enlargement is not associated with heat but rather with late pregnancy or the onset of lactation in preparation for feeding offspring. Therefore, it is not a sign of heat.

The act of giving birth in farm animals is called parturition. Brooding refers to a mother hen keeping her chicks warm, cloning is an artificial method of producing genetically identical organisms, and gestation is the period of pregnancy. Only parturition correctly refers to the act of birth.

Cross breeding refers to the mating of animals from two different breeds, such as a white Fulani bull and an N’dama cow. Inbreeding involves closely related animals of the same breed, line breeding is a mild form of inbreeding, and outbreeding usually means mating unrelated animals within the same breed. Therefore, the mating described here is cross breeding.

The colour of an egg yolk is primarily influenced by the type of feed given to the hen. Feeds rich in carotenoids such as maize, sorghum, or leafy greens produce deeper yellow or orange yolks. The age of the hen, type of housing, or colour of the cock has little or no direct effect on yolk colour. Therefore, feed type is the determining factor.

Sound piggery management involves practices such as disinfecting pens to reduce disease spread, regularly cleaning feeding and watering equipment, and isolating sick animals to prevent outbreaks. Vaccination is also essential but is not carried out weekly. It is done according to recommended schedules, often monthly or at specific intervals. Therefore, weekly vaccination is not a standard management practice.

Weaning is the process of withdrawing milk feeding from young animals and transitioning them to solid or alternative feed. This is important for their growth and independence. Culling refers to removing undesirable animals from a herd, breeding is mating for reproduction, and isolation is separating animals, usually for health reasons. Only weaning describes the feeding transition process.