Bull Number of calves Average daily weight gain / kg A 10 0.95 B 10 1.10 C 10 1.35 D 10 1.05 (a) The table shows the average daily weight gain of calves sir...

(a)(i) Bull C should be selected for future breeding because its calves achieved the highest average daily weight gain of 1.35 kg. [1] This demonstrates that Bull C transmits genes for superior growth rate to its offspring, which will translate into heavier animals at market age, higher carcass weights, and greater profitability. [1]

(a)(ii) The type of test being carried out is a progeny test. [1] It evaluates the breeding value of each bull based on the measured performance of its offspring rather than the bull's own characteristics.

(a)(iii) Each bull was mated with a similar but separate group of cows rather than the same cows to ensure the comparison is fair. [1] If all bulls mated the same cows sequentially, differences in the cows' age, condition, or milk production between matings could confound the results. Using similar groups ensures that any differences in calf performance are attributable to the bull's genetics, not the dam's.

(b) Two advantages of using AI instead of keeping the bull on the farm:

1. Semen from a genetically superior bull can be used even if the bull is far away or no longer alive, because frozen semen stored in liquid nitrogen remains viable indefinitely. This gives access to the best genetics regardless of geography. [1]
2. One semen collection can inseminate many cows, spreading the genetic improvement from Bull C across the entire herd much faster than natural mating would allow. It also eliminates the cost of feeding, housing, and managing a live bull on the property. [1]

(c) After several generations of selecting from the same genetic line, the farmer should introduce unrelated genetics because:

1. Continued selection within a closed population causes the animals to become increasingly related (inbred). The effective population size shrinks and homozygosity rises with each generation. [1]
2. Inbreeding can lead to inbreeding depression, manifesting as reduced fertility, weakened immune function, slower growth rates, and higher calf mortality. Hidden deleterious recessive alleles become expressed when both parents carry copies. [1]
3. Introducing an unrelated bull or semen from a different bloodline restores heterozygosity, brings in new alleles, and can reverse the negative effects of inbreeding while maintaining the accumulated genetic gain for growth rate. [1]