(a) State what is meant by the term progeny testing. [2] (b) A beef farmer wants to select a bull for breeding. Explain why progeny testing is more reliable...

(a) Progeny testing is the practice of judging the breeding value of an animal [1] by examining the quality and performance of its offspring (progeny). [1] Rather than assessing the animal itself, the breeder measures traits in the next generation to determine what genes the parent actually transmits.

(b) Progeny testing is more reliable than judging the bull by its own appearance because:

1. A bull's external conformation does not reliably predict the quality of calves it will produce. A bull may look impressive but carry hidden recessive alleles that only manifest in offspring. [1]
2. Some economically important traits, such as milk yield and maternal ability, can only be measured in female offspring. A bull cannot express milk production itself, so its genetic potential for dairy traits can only be assessed through daughters. [1]
3. Progeny testing reveals whether the bull actually passes on desirable genes rather than merely possessing them. A heterozygous bull may not transmit a trait consistently, and only offspring data reveals this. [1]

(c) Procedure for a progeny test comparing Bull A and Bull B:

1. Mate Bull A with one group of cows and Bull B with a separate, similar group of cows. The cow groups should be of the same breed, similar age, and similar body condition to eliminate maternal effects as a confounding variable. [1]
2. Rear all offspring under the same conditions of feeding, housing, and management, so that any differences in performance are attributable to the sire's genetics rather than environmental factors. [1]
3. Record the performance of each group of offspring over a defined period, measuring traits such as daily weight gain, feed conversion efficiency, carcass quality at slaughter, and disease resistance. [1]
4. Compare the average performance of Bull A's offspring with Bull B's offspring. The bull whose progeny have the superior average for the target traits (e.g. higher growth rate, better carcass grade) is selected for future breeding use. [1]