Choosing the right bull is key to improving a beef herd. If you buy a registered bull from a reputable breeder, you can be assured that it has been selected on performance, including the genetic ability to efficiently convert feed to beef. However, its performance will also depend on other factors, including the farming system and environment. Each bull has its own genetic characteristics – or traits – to consider.
The bull must be adapted to its environment and production system. For example, in an area with a tick problem, a bull with a thicker skin and tick tolerance will perform better.
This is a highly heritable trait that reacts quickly to selective breeding. In technical terms, it is up to 55% heritable. Heritability is the measurement of how easily and quickly a trait is passed from parent to offspring.
The feed conversion ratio (FCR) trait is passed on more slowly – its heritability is 30% – but it is economically more important than the growth potential. FCR is the ratio between the amount (in kilograms) of food eaten to the amount (also in kilograms) of beef produced. The lower the FCR, the greater the feed conversion efficiency.
The bull genetically influences the calving ease of his daughters. Their potential calving ease is reflected in the birth weight and calving ease records of his female ancestors. Ask the bull breeder you’re buying from how to use these ‘breeding values’ to select a good bull.
The frame shape and size is highly heritable, and leanness traits will vary from breed to breed. Match the bull’s frame size to that of the cow herd to produce offspring that will suit the market needs. A larger frame type generally matures more slowly and needs more food. Be aware, too, of the quality of the carcass and its cutability – the percentage and proportions of boneless, trimmed, saleable cuts of beef it provides. If there is too much fat and it is poorly distributed in the carcass, this will affect the cutability.
A bull’s scrotum size and shape reflects its fertility and reproduction potential. There are four basic shapes. The bottle-neck shaped scrotum is ‘normal’. Bulls with long and flat-sided testes sire less fertile daughters, while wedge-shaped testes – smaller and less mobile than average – mean impaired semen quality. Hydroplastic testes are underdeveloped – one or both testes may be affected – and should also be avoided.
The quality and quantity of semen improve if the circumference of the scrotum is 38cm or more. In tests, only 13% of bulls with a scrotal circumference below 32cm had good quality semen, while 88% of bulls with a scrotal circumference above 38cm had good quality semen. Scrotal circumference is highly heritable, so a bull with a good scrotal circumference will produce fertile sons and daughters. The ideal scrotum size may vary between breeds. For example, in bulls with strong Brahman influence, the minimum circumference may be 28cm.
A bull carrying a lot of fat should be avoided, as it lacks the stamina of a veld-reared bull and fat deposits may reduce its fertility. When selecting, study the overall appearance of the bull, starting at the ground and moving upwards. Inspect the bull’s feet, toes, heels, pasterns, knees, hocks, sheath, and scrotum. Study his movement carefully; he must move freely and strike the ground evenly with each hoof. This exercise will also give you an opportunity to evaluate the bull’s disposition and see if he’s easy to work with.
Selecting a good bull becomes easier with experience. You will learn more quickly with a mentor or a breeder who is willing to spend time with you. Remember, though, that a bull’s potential genetic contribution in a herd is meaningless if he is not structurally sound and physically fit to seek out cows on heat and service them.
Sources: Beef Cattle Management, ARC Animal Production Institute, Irene; the SA Stud Book and Livestock Improvement Association; Embryoplus.com; Modern Commercial Beef Sire Selection, by John Massey of the University of Missouri’s Department of Animal Science.