The nuts and bolts of adding value to non-replacement calves

Strategic use of sexed cross-bred semen and beef semen, as well as low birthweight Hereford bulls, helped Dairy Trust Taranaki drop the number of bobby calves on one of its farms from 20 per cent to just five percent last season.

Now it’s refining the system to continue reducing the number of replacement calves born to low BW cows, and increasing the value of non-replacement calves.

The Trust has joined Beef and Lamb New Zealand’s Dairy Beef Progeny Testing (DBPT) program, which aims to identify beef sires that benefit both dairy and beef producers; has incorporated semen from DBPT sires into this season’s mating, and has also adjusted its sexed semen policy to get the best possible value out of these genetics.

Dairy Trust Taranaki general manager Diego Gomez says cutting bobby numbers so significantly in 2023/24 was a great achievement, and his team is keen to keep making gains in this direction.

Mags Bremer, head of science at Dairy Trust Taranaki, says the bobby calf situation in NZ is unique with a high dairy to beef ratio and a cross-sector approach is needed to develop new systems and products to rear the extra calves.

The bobby calf work has been done on the Trust’s Kavanagh farm, the largest of its four research properties, which is NZ’s Net Zero Pilot Farm, and run in collaboration with Nestle and Fonterra.

“At DTT Kavanagh this season we calved 538 Friesian/Friesian-cross cows with a stocking rate of 2.6 cows/ha,” Bremer explains.
“The cows were in-calf to either a cross-bred replacement calf (from sexed semen) or a beef breed non-replacement calf.”

Kavanagh heifers were in-calf to cross-bred calves (conventional, non-sexed semen) or Hereford calves from natural mating.

Twenty percent of calves born in spring 2024 were reared for replacement; 69 per cent were sold, and five per cent left the system as bobbies.

The majority of replacement calves came from mixed aged cows from sexed semen and only a small number from the heifers.

Of the calves sold, 9.5% were sired by a Hereford, and the rest by a Charolais. They went to a large-scale calf rearing business when they were five to 10 days old.

Of the five per cent of calves that were bobbied, most were Hereford bull calves from the R2 heifers that the Trust was not able to sell, with the rest being cross-bred bull calves also from the R2s.

Bremer says this result came from two strategies.

The first was using cross-bred sexed semen on the top 50 per cent BW cows, while the bottom BW cows received beef semen, mostly Charolais with some Hereford also used.

“This helps us get better replacement calves, thereby increasing the genetic merit of the herd while also significantly reducing the number of low-value, cross-bred bull calves.”

The second strategy saw R2 heifers synchronised, and inseminated with conventional, non-sexed cross-bred semen.

Low birthweight Hereford bulls joined the heifers a week after insemination to service any heifer that did not conceive.

“This allowed for breeding replacement calves from the R2 heifers to speed up the genetic gain of the herd as this usually is the group with the highest genetic merit.”

“This strategy also reduces the number of bobby calves as R2 heifers are mainly mated to jersey bulls resulting in low value calves.”

For mating in spring 2024, the DTT Kavanagh team reduced the number of sexed semen straws used per day, but increased the period of use by one week, from three weeks to four weeks.

“When using sexed semen, you are required to use a set number of sexed semen straws every day. This means on days when there are not enough top BW cows on heat those straws are used on lower BW cows to not waste them - they are expensive!”

Using fewer straws per day, for more days, cut the amount of sexed semen used on lower genetic merit cows.

Instead of generic Charolais and Hereford sires, the bottom 50 per cent BW cows at Kavanagh were mated in 2024 to sires of several different beef breeds selected by the Dairy Beef Progeny Testing programme.

These have been picked for short gestation, low birthweight and the ability to produce progeny that finish well with high value carcass characteristics.

Previous work by the DBPT has shown that the individual sire potential has significantly more impact on the performance of the calf than just the breed of the sire or the dam, with significant variance between the birth weight of a calf and its 600 day weight.

In terms of economics, Bremer says sexed semen is about 55 per cent more expensive than non-sexed.

“However a big part of the extra cost is offset by using fewer straws than what we would require if we were only using non-sexed (only 50:50 chance of getting a replacement heifer from non-sexed semen). Beef semen currently is about 20 per cent cheaper than non-sexed dairy replacement semen.

DBPT proven semen is not yet commercially available but we would expect it to have a premium over ordinary beef semen.

However, over time, as the rearer and finisher will gain confidence in the quality and performance of the stock, progeny from DBPT bulls should achieve higher sale prices.”