Pelvic measuring puts spotlight on calving ease EBV

Obtaining pelvic measurements of heifers has alerted a Simmental and Charolais breeder to the potential dangers of the calving ease direct estimated breeding value (EBV). 

The minimum requirement is for his 150-head commercial herd of Simmental cross Stabiliser cross South Devon cattle to calve a 37kg calf at two years old. He says he will be watching four of his commercial heifers and four of his Charolais heifers “very closely”.

Adrian Ivory © Richard Stanton

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Beef and arable farmer Adrian Ivory, who breeds heifers to calve at two years old, will now select replacements on breeding, eye and pelvic measurements at Strathisla Farms, Meigle, Perthshire.

“I’m not as concerned about the pedigree animals with pelvises below 170 sq cm, as these calve at three years old,” explains Mr Ivory.

“These heifers have two or three generations of easy-calving sires in their lines and it is showing in their frame.

“I will still look at calving ease direct when making breeding decisions, but in a very different light.

“However, I didn’t cull anything on the back of the measurements, as I have nothing yet to benchmark against.”

Mr Ivory warns that while calving ease appears to be a helpful trait to aid bull selection on a terminal herd, systems aiming to use a closed herd or those with limited bull choice must be careful.

Along with new advice from Quality Meat Scotland, Mr Ivory warns that, while calving ease is suitable for terminal breeding, “continually selecting for easy-calving bulls could lead to smaller heifers being born that may not be easy calving themselves if used for breeding.”

Pelvimeter

• The pelvimeter is used in the rectum, guided by a hand. Veterinary instruction should be taken before using it
• Measurement is best taken at bulling age
• The vertical height is multiplied by the width to give an area
• The results can be used to remove heifers with small pelvises from the breeding programme
• Cost including delivery is about £195+VAT

© G Shepherd

Narrow pelvises

A total of 54 yearling heifers were measured following a steady rise in calving difficulty (dystocia, interventions, calves pulled) on Mr Ivory’s spring-calving unit.

Furthermore, observations made while performing AI on young cows and heifers suggested pelvises were getting tighter. The suspected cause was breeding replacements from bulls rated positively for the calving ease direct EBV.

Once measurements were taken, dimensions of heifers were then cross-referenced back to the sire and calving-ease credentials were assessed.

This confirmed that, as far as breeding for replacements was concerned, calving ease direct was resulting in narrow heifers.  

“If you are a purely using terminal bulls and heifers are fattened then this is no problem at all, but if you are keeping heifers for breeding, then I think you have to be aware,” stresses Mr Ivory, who requires 25 replacements heifers each year for his commercial herd.  

Measuring up

A horizontal and vertical measure was obtained from yearling heifers in April this year. 

Measuring took 20-30secs/heifer with the pelvimeter. Animals were restrained in a squeeze crush and averaged 500kg at the start of May.  

The two dimensions were multiplied together and adjusted for a 365-day size to cater for growth from yearling to two years of age. Pelvimeter instructions advise 0.25sq cm/day. 

Heifers age ranged from 397 days down to 337 days, with heifers selected born in the first eight weeks of a 10-week bulling period.

Calf size

Size and shape of calves are two important factors that Mr Ivory knows play a big role in calving heifers, as well as the pelvic area of the dam.

He aims for a 40kg newborn calf, with the lighter end of the average being about 38kg, although he does very occasionally have cows calving 50kg calves. 

However, Mr Ivory, along with veterinarians, stresses that calculations give a “ballpark figure” of future pelvic size, with the general advice being that pelvic measuring is a useful tool to minimise extremes.

Easy calving

Winter housing extends into the spring-calving block at Strathisla, where cows and calves can be monitored day and night. Easy calving is as much for cow productivity and the next calving as it is for labour.

“In my view it is the heifers or cows that don’t get back in calf that are often the ones that had something needed doing to them during or after calving – either a cleansing or a backwards calf.”

In terms of the “calving ease daughters” EBV, Mr Ivory does not pay much attention to this trait, instead looking at gestation length and calving ease on the maternal side. He also looks at fat depth, scrotal circumference and 400-day growth.

“I’m trying to keep things moderate and fairly consistent for breeding replacements,” he adds. “I am now looking to bull with a moderately positive direct easy calver one year and moderately negative one the following year, so calving ease stays around zero.”