Calving problems are costly in terms of £’s and welfare. Obvious associated costs include increased labour, veterinary bills, dead calves, and injured cows. However, the detrimental effects of dystocia (difficult calvings) on cow fertility, milk yields, growth rates and increased culling rates are often more significant. The single major cause of calving problems is a disproportion between the size of the calf at birth (birth weight) and the cow’s birth canal (pelvic area). Think cork and neck of the bottle!
Improving heifer calving ease
Selecting bulls
The risk of calving problems from oversized calves can be reduced by selecting bulls for calving ease, birth weight and gestational length using Estimated Breeding Values (EBVs).
Selecting heifers
Heifers should achieve pre-breeding target weights and conditions before service. Pelvic size can also affect calving difficulty due to restricted birth canal diameter. Whilst heifers of increased skeletal size tend to have larger pelvic openings, they also tend to have heavier calves at birth, hence selection for dam size, weight and age alone can be ineffective. External dimensions such as the width of hooks and length of rump are not necessarily good indicators of internal pelvic area or calving difficulty.
An additional tool for heifer selection: Measuring Pelvic Area
Internal pelvic measurement can therefore be a useful management tool to identify heifers with a higher potential for calving difficulty. It is a simple procedure carried out on heifers between 8-19 months.
The procedure is quick and easy providing a pelvic area measurement which, using reference charts, can determine the size of the calf the heifer should be able to safely deliver. An informed decision can then be made before the service period; whether to breed or cull heifers with abnormal pelvises. Selecting heifers each year based on the pelvic area will allow generational increases in calving ease. This examination also provides a good opportunity for your vet to check the reproductive tract for abnormalities (such as abnormal pelvic conformation, free-martinism and cystic ovaries) and also check infectious diseases affecting fertility are controlled (e.g. BVD, IBR, Neospora and Leptospirosis).
Bigger isn’t always better…
Heifers with large pelvic measurements do not necessarily calve more easily than average-sized heifers. However, heifers with abnormally small pelvises or abnormally shaped pelvises generally experience a higher-than-normal incidence of calving difficulty.
Whilst there is an associated cost with a quick vet visit to examine prospective heifers (usually charged on time) it is a better investment than a late-night calving with a dead calf! You can qualify for a free vet visit under the Animal Health & Welfare Pathway, which can be used for pelvic measurements. 
For further information on maximising your beef herd, please speak to your local NWF Sales Specialist or call 0800 756 2787.
Thank you to Janet Horsfield, Director and Farm Vet at Lanes Vets.
