Page 116 - NZ Herefords Magazine 2019 Edition

Industry Focus

Fine tuning heifer mating

WORDS REBECCA HARPER PHOTOGRAPHS SUPPLIED

GETTING HEIFERS IN CALF EARLY is key to setting them up for MANAGEMENT OF HEIFERS
successful lifetime performance in your herd. Driving weight and getting heifers as heavy as possible
In a Heifer Mating Carpool Karaoke video, produced for the before going to the bull is crucial.
Virtual Beef Breeder Forum in 2018, Max Tweedie from Beef + In the video, Tweedie and Archer discussed the ideal target
Lamb NZ Genetics and Dr Jason Archer, from AbacusBio, discuss weight for heifers to go to the bull and suggested the old
yearling heifer mating and what that means for the lifetime fertility standard mating weight of 280kg no longer applied.
of a cow and for breeding programmes. As well as exploring the Archer said genetics in cattle had changed markedly over
‘why’, they offer advice on ‘how’ to achieve successful outcomes. the past 20 to 25 years and, globally, people were questioning
Tweedie explained that the first mating is important for how that rule of thumb.
that heifer goes on to perform as a cow. In the Beef Progeny Test most heifers were being put to the
“Research shows if she performs well as a heifer and gets in bull, with good in-calf rates achieved, from anything weighing
calf early, that in successive matings she gets in calf early again 320kg and upwards.
and has a better reproductive lifetime. She is also more likely to “It’s about balance, what your priority stock units are and
wean a heavier calf; because she gets in calf early, that calf will what you are trying to feed and prioritise in your system. In
be heavier come weaning.” terms of driving reproduction and getting extra calves now and
Research from DairyNZ had looked at high fertility versus later, I would have thought getting maternal heifers to 320kg
low fertility cows within one herd. should be the benchmark, but that does depend on their final/
“They looked at what was different about those cows, based mature weight,” Tweedie said.
on their fertility as cows and, actually, the thing that stands out In terms of how many heifers to mate, Tweedie said he was
is high fertility cows go through puberty earlier as heifers and inclined to put as many to the bull as possible, for a restricted
get in calf earlier as heifers,” Archer said. mating period of 42 days, and then cull accordingly to the
Australian Beef CRC research also reinforced that required replacement rate.
finding, looking at genetically high fat versus low fat heifers. Research from the United States suggested heifers had
It found that heavier and fatter heifers achieved puberty and a longer postpartum anestrus interval than cows, so the time
conception earlier. taken to cycle again after having their first calf was about 70
“Interestingly, once that heifer is in calf and has gone through days, compared with a cow at 50 days. This gave some weight
the cycle and calved, whether she was high fat or low fat didn’t to the argument to mate heifers earlier than the main cow herd.
seem to make a difference for the subsequent calving. “Some people will say if you mate them three weeks earlier,
“As long as they got in calf, the cows that were lower fat you can’t feed them, because the grass isn’t growing yet. I
performed just as well, but there was a higher drop-out of them would argue, if that was a critical three weeks, to put some feed
at that first mating. It shows that getting in calf as a yearling, into them would be a great investment of feed,” Archer said.
and nice and early preferably, is really positive – both from a “Personally, I think that would be a strategic time to poke an
management and phenotype point of view. But also, they’re extra bit of feed into your heifers, as a mob, to try to get them back
probably genetically the ones you want.” up and back in calf as early as you can the second time around.”

DAIRY NZ HIGH V LOW LINE FERTILITY RESEARCH

Predicted & Actual calving pattern
300
Number of heifers calved 200 High Fertility_Predicted
250

150

100
High Fertility
50
Low Fertility
0 Low Fertility_Predicted
1-Jun 29-Jun 6-Jul 11-Jul 15-Jul 19-Jul 23-Jul 27-Jul 31-Jul 4-Aug 8-Aug 12-Aug 16-Aug 20-Aug 24-Aug 28-Aug 1-Sep 5-Sep 9-Sep 16-Sep 20-Sep 27-Sep 1-Oct 10-Oct

‘Heifers predicted to be more fertile reached puberty earlier and
conceived earlier.’
Heifer mating at Monymusk Polled Herefords stud.
114