RESULTS from this month’s Brisbane Show 100-day Grainfed Performance classes, judged on a combination of feedlot and chiller carcase data, have for the first time allowed for a direct comparison between HGP-implanted and non-implanted steers.
Two separate classes have always been run for 100-day grainfed steers during the Ekka – one for HGP-implanted and the other for non-implanted cattle.
The difference this year was that for the first time, through an agreement reached with software service provider Blackbox, averages were provided for each trait, in both classes.
Both implanted and non-implanted groups were judged on feedlot weightgain performance, carcase quality and MSA eating quality. Meat yield was also part of the judging process, assessed by proxy through a formula using eye muscle area, carcase fatness and carcase weight.
All four traits can be influenced, either positively or negatively, by the use of implants, animal science has shown over countless research projects.
First some background, to ensure we’re ‘comparing apples with apples.’
Both 100-day classes this year worked on base specifications before penalties apply:
- 0-4 teeth
- 5-22mm of P8 fat
- Carcase weights 320-400kg
- Muscling A-C
- Meat colour 1B-2, fat colour 0-2.
The sample sizes weren’t insignificant, with 34 pens of seven (238 steers) entered into this year’s HGP-implanted class, and 29 pens (203 steers) in the HGP-free class.
A clear majority of entries in both classes were crossbreds.
British and British crosses were common in both, as were stabilised tropically adapted composites like Santas and Charbrays, Euro crosses and some composite x British entries. ‘Charolais’ or ‘Charbray’ were mentioned in the sire or dam pedigrees of 14 of the 34 implanted class entries (either crosses or purebreds), while in the HGP-free class, Angus were mentioned ten times, Santas nine and Charolais eight.
All cattle received host feedlot Beef City’s induction protocol including Bovillis MH+IBR on-property, followed by a second Bovillis plus Rhinohard at feedlot entry. The HGP class received an Elanco Component TE200 implant.
Feedlot induction weights were reasonably similar, at 415kg (implanted) and 428kg. The organisers set a lower upper limit on entry weights (480kg) on implanted cattle than free cattle (500kg), because of the risk of implanted cattle blowing-out on upper weight limits at slaughter.
The cattle had a five-day settling in period on hay, prior to feedlot entry. Both pens received identical number of days on feed.
So how did the two classes measure up, in terms of economically important traits?
There were a few surprises, despite the deep industry knowledge about likely HGP impact on meat quality, yield and feedlot performance.
To keep things simple, the figures below show implanted class average for each trait first, followed by HGP-free, sometimes in brackets.
Feedlot exit liveweights were 660kg (627kg), a 33kg or 5pc variance, due to the implant effect. This delivered average daily gains of 2.45kg/day for the implanted steers, and 1.99kg/day for the free steers.
Hot standard carcase weights were 369kg (353kg) a 16kg or 4.3pc variance – fairly typical differences for cattle like this, when the lighter starting weights for the implanted steers this year is taken into account. Unlike past years, not one beast exceeded the 400kg carcase weight upper limit this year, because of tighter starting weight rules.
P8 fat averaged 17mm (14mm), while rib fat measured 9mm (8mm), This went against conventional wisdom, where implanted steers typically express less surface fat than non-implanted.
Eye muscle area averaged 94sq cm (93sq cm). While the advantage this year was narrow, data over the past four years of similar competitions shows an EMA variance averaging 6sq cm in favour of the implanted steers, or 6.3pc. A handful of poor performance in the implanted class this year may have been responsible for the marginal difference.
A lean meat yield figure was calculated from EMA, fat cover and carcase weight data for all entries, producing an average of 55.87pc for the implanted steers, and 56.43pc for the HGP-free cattle – an 0.56pc advantage to the free class. Again, this went against industry convention, which typically shows an 0.5pc meat yield advantage in implanted steers due to greater muscling and leanness.
AusMeat marbling assessment during grading produced an average score of 0.96 for the implanted steers, and 1.06 on the free cattle. An expected result, although high rates of feedlot weight gain may have curbed marbling in the implanted steers.
Ossification scores (HGP-treated steers inevitably ossify faster than non-implanted at the same age) showed the treated steers at 164, versus 140 on the free cattle.
The combination of more favourable oss scores, better marbling and the HGP penalty built into the MSA model saw a sizeable gap in MSA Eating Quality Index scores – 53.7 for the implanted steers versus 60.43 for the free steers.
There was no significant difference between meat colour (both averaging score 2) or fat colour.
Antagonisms between eating quality and yield
Chief RNA beef steward Gary Noller said this year’s 100-day performance class results basically supported the view that yield and eating quality were antagonistic.
“If you are looking for high meat yield, you are going to affect your eating quality, and if you’re looking for meat eating quality, you’ll lose meat yield,” he said.
“In simple terms, there’s more meat in this year’s treated steers, and more marbling in the non-implanted ones.”
“Ossification definitely is a big factor in this year’s eating quality index figures, but when you add in hump height penalties, that was a huge factor when it came to eating quality,” he said.
“The other one that made a really big difference on MSA index score was marbling,” Mr Noller said.
Individual steers this year ranged from 0 marbling scores all the way to 5, after just 100 days on grain. Team averages for marbling ranged from 0.14 (mostly 0’s) to as much as 3.57 (all score 3s, 4s and 5s – shared by Don McRae’s Angus pens in the free class, and also in the implanted class).
“But there were some anomalies in results this year,” Mr Noller said. “While HGP-free cattle typically have more P8 and rib fat than implanted cattle (all other things being equal), that was not the case this year.”
“HGP inevitably increases muscle mass, but this year the entries displayed almost as much, or even more fat cover than the non-implanted class. Why that happened this year, we’re not quite sure. They were fed the same, so it looks like being breed related.”
“The primary reason why this competition is run is about education,” Mr Noller said.
“Anything that can be dragged out of the data and highlighted, like this, has got to be a good thing,” he said.
“The Blackbox software we got access to this year helped highlight those traits that really had an impact on eating quality and performance, across all entries.”
Without taking any JBS grid price premium for HGP-free cattle into consideration, the HGP-treated cattle this year produced a price premium over the non-implanted class of about $103 a head. That was due primarily to heavier carcase weight. The result was based on basic grid formulas only – it did not take meat yield results into account.
Forward contract rates at the time the steers went onto feed from JBS were 650c/kg on implanted grainfed export ox, and 660c on HGP-free. At those rates, the HGP-treated steers with average carcase weight of 369kg averaged $2398.50, while the free steers, with average carcase weight averaged $2329.80.