Hartebeestloop

Pelvic Measurement

At Hartebeestloop we have been selecting for pelvic area since 2002. Our heifers are presented for final selection by the senior inspector of the Bonsmara Cattle Breeders Society when they are 24 months (2 years) old. We do a number of own selection procedures on the farm before the heifer is 24 months old.

We do the following initial selection procedures (please refer to the 2 articles selection procedures with our 14 month old heifers before we put them to the bull:

  1. Adaptability and functional efficiency are first priorities
  2. Selection for frame size that best meets our environment
  3. Pelvic measurements which were done at 12 months are taken into account and we do the following :
    • Group 1: All animals with anatomical defects of the pelvic bones are culled.
    • Group 2: Animals in the lowest 20% of pelvic index scores are not mated at 14 months but only at 24 months. These animals are sold off and we do not use them in the Hartebeestloop stud.
    • Animals that are in the lowest 20% and where there is a history of difficult calving in the mother line are moved to Group 1 and culled.
    • Group 3: These are the heifers that are just above the lowest 20% pelvic index group They present with pelvic index scores that are 95 and lower. Traditionally we have mated these heifers with specialist calving ease bulls. Our selection criteria are much stricter now (from the lowest 15% in the past to the current lowest 20% that are not mated at 14 months) and the management of this group is also better than in the past. We would still use calving ease bulls for this group but have moved away from the specialist calving ease bulls as identified in the past to open young heifers.
    • Group 4: These heifers present with pelvic index scores between 95 and 105. We mate them very successfully over a number of years now with all rounder bulls with moderate growth rate BLUP values.
    • Group 5: They are the top group and presents with pelvic index scores of 105 and more. We have tried our luck using bulls that should be used on cows only – broader framed bulls with high growth rates and well defined muscling. The idea was that the heifer’s pelvic index scores are so high that they would calve without problems from these bulls. It was a bad idea and an even worse plan! This group should be managed no different from Group 4 and all rounder bulls with moderate growth rates should be used.

We had tremendous success in reducing calving difficulty (distokia) and heifer casualties since pelvic measurements were introduced.
It is important to note that we only select for pelvic area once the selection for medium-framed animals are done.

Heifers ready for pelvic measurements to be done, note the frame size
Heifers ready for pelvic measurements to be done, note the frame size
The table underneath shows our progress in actual pelvic measurements from 2008 to 2010. The pelvic area measurement in square centimeters is the average pelvic size of the bulls and heifers that we select to continue with in the Hartebeestloop stud.

It was noted over the years that a heifer must have normally structured and anatomically sound pelvic bones with a pelvic area of about 16 square centimeters at 12 months of age to deliver a calf of 36 kg at 26 months without any calving difficulty. This is only an observation in our herd - provided that we use bulls from proven calving ease genetic lines. These are not necessarily specialist calving ease bulls but rather all rounder bulls that can be used on heifers but also have sufficient growth rates to be used on cows as well.


PELVIC MEASUREMENTS
Year of Birth
Average Pelvis Area (sq cm²)
2008 (male and female)
18.7
2009 (male and female)
21.1
2010 (male and female)
21.3


We believe that heifers should produce 36 kg (birth weight) calves without any calving difficulty at age 26 months. At Hartebeestloop we tend to move away from specialist calving ease bulls for heifers to a bit more robust, all rounder bulls with moderate growth rate values. Our aim is to produce calves from heifers that can compete with the calves from our proven cows at our annual auction. It does not make financial sense to loose out on most of the calves from the heifers when they cannot compete in appearance and quality with the calves from the rest of the cow herd. During 2008 and 2009 we did not manage to produce any good enough quality bull calf from the heifer herd to present at the auction. With our breeding philosophy that changed, we presented 4 heifer calves at our 2010 auction and 16 at our 2011 auction. Our aim is to present an even higher number of heifer calves at the 2012 auction.

Pelvic measurement and the use thereof is not an exact science. We have not and neither will you have a 100% hit rate and success. There are many factors involved in calving ease and you will always get the exceptions. Some heifers in the top group with high pelvic index scores may present with calving difficulty whereas some heifers in the low pelvic index score group may calve without any problems.


Measuring pelvic areas will allow early identification of potential problem heifers and the breeder can plan accordingly. It makes financial sense to reduce calving difficulties, allow for better conception and most importantly to sell off the potential “heifer casualties” to the butcher beforehand.

At Hartebeestloop we will continue with the early mating of young heifers making use of the data we get from pelvic measurements.


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