Bull buying checklist
Your breeding objective
Before selecting a bull it is important that you have clear breeding objectives set for your herd. The following points should be used as a guide to determining your breeding objectives.
- Traits of economic importance
- Customer/market requirements
- Herd production targets
- Current herd performance
- Breeding goals and selection criteria
EBVs can be combined into a $Index EBV which effectively ranks available animals with all traits weighted according to their effect on the profit drivers for the herd.
Make sure you keep your selection criteria in mind when selecting a bull. It is important that you rank your selection criteria in priority order. This will help you make a choice between bulls that generally meet your selection criteria. For more information see Breeding objectives.
Select genetically docile bulls to increase the probability that progeny will be quieter, have higher growth rate and transport better.
Temperament can be measured using ‘flight time’ or scored using a crush or yard test. The flight speed measure provides a more accurate and heritable measure of the trait to modify herd performance. For more information see Improving temperament and flight time.
Bull Breeding Soundness Evaluation
The Bull Breeding Soundness Evaluation (BBSE) was developed by the Australian Association of Cattle Veterinarians to standardise bull fertility testing and to provide a consistent descriptor of bull fertility.
The report indicates whether a bull has met a set of standards for five bull fertility components. The components of fertility assessed are those that indicate whether a bull has a high probability, but not a guarantee, of being fertile.
The two components of the BBSE are:
a) A summary of the five indicative components of bull fertility (see example below)
|AACV Top of the Rack||2.02||
b) A full report that identifies the bull, date of testing and by whom, where and comments associated with each test. A summary of the five components of bull fertility in the BBSE follows:
Scrotum – Scrotal circumference/size (SS) in centimetres (cm) where testes shape is within normal range. The current recommendations for tropically adapted bulls are a minimum scrotal size of 32cm (and average is 34–36cm) for a two-year-old bull.
Physical – Within the constraints of a standard examination, there is no evidence of any general physical/structural condition or of a physical condition of the reproductive tract indicating sub-fertility or infertility. This evaluation will identify structurally unsound bulls in legs, feet, sheath and general structure.
Semen – Crush-side assessment indicates that the semen is within normal range for motility, colour and per cent progressively motile and is suitable for laboratory evaluation.
Morphology – Semen examination of per cent normal sperm using high power magnification to ensure minimum standards for normal function are achieved.
Serving – The bull is able to serve normally as demonstrated in a standard test and shows no evidence of fertility limiting defects.
For more information see Bull breeding soundness examination (BBSE).
Serving capacity testing
Serving capacity testing provides:
- an indication of a bulls ability to mount and serve a cow/heifer and includes both reproductive and structural soundness (legs, feet, sheath, penis and overall anatomy)
- a measure of the sex drive (libido) or eagerness of a male to seek out a female on heat
- an indication of the subsequent pregnancy rates achieved following a restricted mating period (more particularly in Bos taurus breeds).
The summary table (like the example) will indicate:
|√||For this component, the bull met the fertility standards as published by the Australian Association of Cattle Veterinarians||x||The bull did not meet the standards for this fertility component|
|Na||Not Applicable e.g. certificate not required to indicate status for this fertility component||Nt||This fertility component was not fully tested/evaluated|
|P||(For Morphology only). The samples taken do not meet the full standards but indicate that the bull is very likely to be fertile under natural mating P=>50% and <70% N. Seek advice from your cattle vet. A ü = >70% Normal|
Estimated Breeding Values
Estimated Breeding Values (EBVs) are predictions of an animal’s genetic merit, based on available performance data on the individual and its relatives.
BREEDPLAN EBVs are expressed in the units of measurement for each particular trait. They are shown as positive or negative differences from the breed base (or breed average). EBVs provide the best basis for the comparison of the genetic merit of animals reared in different environments and management conditions. EBVs can only be used to compare animals within the same breed.
The differences in EBVs between animals are more important than the absolute value of the EBV. Particular animals should be viewed as being ‘above breed average’ for a particular trait only if their EBVs are better than the average EBVs of all animals born in their year drop.
EBVs are published for a range of traits including fertility, growth and carcase merit. When using EBVs to assist in selection decisions it is important to achieve a balance between the different traits and to place emphasis on those traits that are important to your herd, your markets, and your environment.
Calving Ease Traits
Calving ease is an important economic trait because of its impact on calf and heifer mortality, labour and veterinary expenses at calving time, and subsequent re-breeding performance of female cattle.
Calving Ease (DIRECT) EBVs
Calving Ease (DIR) EBVs are estimates of genetic differences among animals in their ability as a direct effect of the sire. The EBVs are reported as differences in the percentage unassisted calvings. Higher, more positive, Calving Ease (DIR) EBVs are more favourable.
Calving Ease (DTRS (daughters)) EBVs
Calving Ease (DTRS) EBVs indicates the genetic differences for calving ease of an animals daughters. The EBVs are reported as differences in the percentage unassisted calvings. Higher, more positive, Calving Ease (DTRS) EBVs are more favourable.
Gestation Length EBVs
Gestation Length EBVs are estimates of genetic differences among animals in the number of days from the date of conception until the calf birth date. Lower, or more negative, Gestation Length EBVs are generally more favourable. This EBV is only available where the mating and calving dates are known.
Birth Wt EBVs
Birth Wt EBVs are estimates of genetic differences between animals in kg of calf birth weight. Small, or moderate, Birth Wt EBVs are more favourable.
Fertility is a critical component influencing the profitability of a breeding herd. EBVs are provided for two fertility traits – Days to Calving and Scrotal Size. These traits contribute important information to assist in making breeding decisions to maintain herd fertility.
Days to Calving EBVs
Days to Calving (DC) EBVs are estimates of genetic differences in fertility, expressed as the number of days from the start of the joining period until subsequent calving. Lower, or more negative for Days to Calving EBVs are more favourable.
Scrotal Size EBVs
Scrotal Size EBVs are estimates of the genetic differences among animals in scrotal circumference at 400 days of age. Larger, or more positive, Scrotal Size EBVs are more favourable.
EBVs are provided for three growth traits: 200-Day Wt, 400-Day Wt and 600-Day Wt. Selection for growth traits should be relative to the target market weights.
200-Day Wt EBVs
200-Day Wt EBVs are estimates of the genetic differences among animals in weight at 200 days of age. Larger, more positive, 200-Day Wt EBVs are generally more favourable.
400-Day Wt EBVs
400-Day Wt EBVs are estimates of the genetic differences among animals in weight at 400 days of age. Larger, more positive, 400-Day Wt EBVs are generally more favourable.
600-Day Wt EBVs
600-Day Wt EBVs are estimates of the genetic differences among animals in liveweight at 600 days of age. Larger, more positive, 600-Day Wt EBVs are generally more favourable.
Mature Cow Wt EBVs
Mature cow weight is recorded at the time the calf is weaned and taken over up to five calvings. It is an indication of the mature weight of the breeders and should be related to the nutrition available on the property.
Carcase Weight EBVs
Carcase weight EBVs are estimates of the genetic differences among animals in hot standard carcase weight at 650 days of age. Larger, more positive, Carcase Weight EBVs are more favorable.
Eye Muscle Area (EMA) EBVs
EMA EBVs are estimates of the genetic differences among animals in eye muscle area (cm2) at the 12/13th rib site on a 300kg carcase. Larger, more positive, EMA EBVs are generally more favourable.
Rib Fat EBVs
Rib Fat EBVs are estimates of the genetic differences among animals in fat depth (mm) at the 12/13th rib site, on a 300kg carcase. Rib Fat EBVs are used to change the progeny fat levels relative to the market specifications.
Rump Fat EBVs
Rump Fat EBVs are estimates of genetic differences among animals in fat depth at the P8 rump site on a standard 300kg carcase. Rump Fat EBVs are used to change the progeny fat levels relative to the market specifications.
Retail Beef Yield % (RBY%) EBVs
RBY% EBVs are estimates of genetic differences among animals in percentage retail beef yield in a 300kg carcase, with 2–3mm fat trim, adjusted to 85% chemical lean. Larger, more positive, RBY % values are more favourable.
Intra-Muscular Fat % (IMF%) EBVs
IMF% EBVs are estimates of genetic differences among animals in percentage intra-muscular fat (marbling) in a 300kg carcase. Depending on the market targets, positive IMF% EBVs may be more favourable.
Other issues to consider
This is a developing science and provides a key for the future. Markers are now available for Marbling and Tenderness traits. This technology has potential to identify animals carrying the desired markers, but may not provide its fullest benefit until further markers are identified for many traits.
Net Feed Efficiency (NFI)
Net Feed Efficiency identifies animals that are more efficient converters of available feed to kg of liveweight gain. A negative EBV for NFI will provide the opportunity for producers to select more efficient animals.
- Set your ‘breeding objectives’
- Select only genetically docile bulls (flight time test preferable)
- Ask for a Bull Breeding Soundness Evaluation (BBSE) before sale
- Research BREEDPLAN EBVs (available on line before sale).
John Bertram, formerly Queensland Government.