Give bulls a helping hand

Sometimes empty cows are caused by bulls having performance issues or health problems. Joanna Grigg talked with two large animal vets to find out how to avoid this and get 90% in-calf cows.

A Marlborough study of 10,000 cows by Vet Marlborough, using client data, showed poor scanning rates were linked to confirmed bull problems.

Nine farms in 2020 had fewer than 50% of cows in the herd scanned in calf from cows put to the bull. Two cases were obvious bull failure, five had no bovine viral diarrhoea (BVD) vaccination history for bulls or cows and the last two had suspect low-libido bulls.
“Any exceptionally bad scanning results tend to be due to confirmed bull problems, not the cows,” said Trish Lipyeat, veterinarian with Vet Marlborough.

“I’ve seen up to 30 dry cows in a mob of less than one hundred and it’s heartbreaking, as it’s avoidable.”

Farms with 50% to 58% conception had issues relating to cows; light cow condition, suspected BVD or trace element issues, Trish said.
The two large animal vets at Vet Marlborough, Trish and Mary Bowron, pregnancy test about 10,000 beef cows annually between them. The 2020 average, for a three-cycle mating, was 92%. This is still higher than the New Zealand average but, in 2020, was pulled down by bull break downs, mainly in the East Coast of the South Island.

“It’s hard (for bulls) trying to stay safe whilst riding cows in that Ward wind,” Trish said.

Measure conception

The most telling way to measure conception is ‘cows in calf in the first cycle’ – which is 21 days. This standardised conception rate takes out any effect from an extended mating period. The NZ average range is 0.49 to 0.62 while the top 25% of herds have a 0.62 conception rate. Marlborough sub-region results in 2020 ranged from 0.53 for East Coast South, up to 0.62 for Seddon/Awatere.

Professor Steve Morris, Massey University, speaking in a Beef + Lamb NZ podcast on The NZ Beef Cow, said that a good target for mixed age cows is 0.50 conceived in the first 21 days and a mating period of no longer than 60 days.

“This is upwards of 50% of cows conceived in the first cycle of 21 days, and a concentrated calving.”

He describes this as the only way to lift the NZ average calving percentage from a “static” 82% towards 90%.

“If 100 cows go to the bull, then 95% should be pregnant and, of those 95 cows, then 95% should wean a calf – giving us a 90% weaning.”

Check your boys out

The good news is that bull failure is avoidable. Checking bulls properly before and during mating can spot problems early and allow a follow-up bull to be used. Conception may be delayed but at least they are in calf.

“Rough country isn’t an excuse for poor pregnancy rates – many have great results,” Trish said.

Mary suggests farmers visit the herd every five to seven days, if practical, and look for bull lameness, corkscrew penis issues or bulls standing alone, which may be a sign of a sore back.

“If the bulls mount but don’t do the wee jump at the end, getting their back feet off the ground, then they may not be firing.”

About one third of Vet Marlborough clients test bull performance using on-heat heifers and an artificial vagina.

“This is the best standard for animal welfare.”

Although bull studs should libido test bulls pre-sale, some don’t, she said.

“Rough country isn’t an excuse for poor pregnancy rates – many have great results . . .”

BVD is linked to suppressed bull and cow fertility. Mary suggests bulls get a yearly BVD booster. About 70% of her clients vaccinate heifers each year and some farms also vaccinate MA cows.

“BVD can show up as an early-death embryo, often meaning the cow doesn’t have a chance to get pregnant again.”

Trish said farmers with extended calving dates, into the third cycle and even fourth, need to consider to shorten the mating term.

“We definitely see more issues the following year if the farmer left the bull out for three or four cycles.”

“There will be more dries and a delayed conception again.”

“To remedy it, restrict the mating period and take the hit with potentially more dries but get a better conception the following year, and more even age of calves.”

Trish said the 2021 pregnancy scanning season (as of early April) is shaping up to be just another average year, with similar results to the previous season.

This is a good result given that spring feed allocations were tight in many places during mating, with a feed flush in December and then four months of diminishing quality and quantity. Despite the worsening conditions, cows have got back in calf, even at lighter condition scores, and carried on growing a calf at foot. This shows the value of a cow’s utility.

Vet Marlborough has provided regional and individual heifer and cow conception figures to clients since 1999.

Pregnancy scanning tips

Good planning can help speed up and smooth the cow pregnancy testing process.

Veterinarian Mary Bowron, Vet Marlborough, said having enough staff to load the backyard, push up cows and mark dries, is key to a smooth operation.

“I’d suggest a minimum of three.”

In danger of stating the obvious, separating calves off before the vet arrives is a good idea, she said.

“And have a side yard for cows scanned dry, that should be rechecked manually.”

Timing of scanning is important. Beyond six months of pregnancy the probe has to be inserted 900cm (full length) which is harder on the cow and takes longer. Between 42 and 120 days is ideal.

Having a good record of all joining dates with the bull helps the vet know what size foetus (and therefore the position) to be looking for.
“We also appreciate being forewarned if foetal aging is required.”

Bowron’s Marlborough clients are increasingly asking for this aging service, mainly to identify third cycle cows which are pulled out for potential sale. Cows have to be between six and 15 weeks in calf. Vet Marlborough has a head fixed monocular scanning system – this kit alone worth about $4500.

One thing the farmers have less control over is the state of the rectal matter.

“Dry feed makes for hard dry poo and compaction when using the probe – it’s just a bit slower.”

She says 2018 was a bad year as dry feed was combined with lighter cows, and 2021 is shaping up to be similar.

Heifers calve autumn, rest in spring 

Splitting mating dates and autumn calving heifers, works well for Paul and Muff Newton on their summer-moist Havelockfarm, Marlborough.
The heifers are mated in June at 22 months, scanned in November and they calve the following autumn. The 100 mixed-age cows calve on August 1. Paul likes the system as it means heifers are well-grown, reducing the chance of dystocia (difficult or obstructed labour).

“Calving in autumn also gives the heifers more time to get back in calf, as rising three-year-olds, from a November mating. “

The Newton’s Angus cows are larger-framed animals. Because the heifers are not put to the bull until they are almost rising-two, Paul doesn’t use a low-birth-weight EBV bull for heifers.

“They are all big enough.”

He pregnancy tests once a year (March for mixed age cows), accepting that any dry heifers will just grow on and be sold as prime beef.
This season his 103 mixed age cow herd scanned with 93.2% in calf, with one dry cow having an obvious hernia.

“I leave the bull out for at least 63 days and don’t worry about late calves.”

“Late calves are kept and fattened and if they are really late, they can go with autumn calving heifers.”

About 85% calves are weaned to cows mated. The cows stay on the very steep hills over winter and calve there too.

“Their job is prepping pastures for lambing.”

To keep conception rates up, Paul pays close attention to bull soundness during mating.

“I’ve had to cull two bulls over the past four years but was able to put in a replacement bull at an early stage.”

He admits he doesn’t BVD booster the bulls and probably should.

“We have vaccinated heifers and mixed-age cows in the past but not recently.”

Trace element supplementation includes annual copper bullets and selenium.

For his 120 cows he uses three bulls, with a spare back-up bull on hand at a ratio of 1:40 cows. Bulls have been sourced recently from Matariki (Hereford), Woodbank and Brackenfield (Angus).

The mixed-age cows’ job is to clean up rank feed off the hills for the higher-returning sheep. Last season Paul took on 50 extra cows from his brother’s farm in Nelson, to help control the November surplus.

All progeny are fattened and sold via the Aleph Contract with ANZCO. Prime cattle are sold from August onwards at 23 months with most going in November. Heifer carcass weights are 280kg+ and steers 310kg+.