By Holly Phillips, BSc (Hons), Forage Agronomist PGG Wrightson Seeds and PhD Student Massey University 

Key Points

• Fully replicated farmlet trial looking at lamb growth and meat quality of lambs finished on different summer forages
• This is the second year of trialling, narrowed down to three key forages: Pallaton Raphno, Puna II chicory and perennial ryegrass/white clover
• Information collected included dry matter yields, stocking rates, lamb growth rates and lamb carcass weights as well as a meat sample for later analysis. This information is crucial to identify not only how a forage may be able to deliver meat with favourable attributes, but be profitable in a farm system given we are currently paid for meat on a yield basis
• All forages provided high quality feed for early summer, however with the very dry conditions experienced across the North Island in 2020, there was vast differences in regrowth, with Pallaton continuing to grow and provide quality feed right through summer and autumn
• The total carcass weight produced off Pallaton was 390kg/ha over the trial period, compared to 276kg/ha on chicory and 195kg/ha on pasture. That’s 41% more carcass weight on Pallaton compared to chicory, and 100% more than on pasture. Multiplying the carcass weight produced by the prime lamb price (and subtracting establishment costs) resulted in a profit of $1,679 per hectare on Pallaton, a $629 per hectare advantage over chicory

IMAGE 1: Holly Phillips and study lambs at Massey University 

Study Background

This is the second experiment of Holly Phillips PhD research, investigating live weight gain and meat quality characteristics of lambs on different summer forages. During the first trial in 2018/19 Pallaton Raphno impressed everyone with its performance in a very dry summer. All other forages including chicory, ryegrass, leafy turnip and red clover struggled carrying significantly lower stocking rates. Holly and the team recognised the potential of Pallaton in this dry season and initial meat quality results encouraged further investigation of the relationship between finishing diet and meat quality. Lambs finished on chicory were the heaviest (fastest growth rate per head) while Pallaton had the greatest carrying capacity (overall more weight gained per hectare). A key aspect of this years trial was to determine the increased forage yields, stocking rates and red meat yield per hectare associated with drought tolerant Pallaton when compared to chicory or perennial ryegrass/white clover pastures. Finishing systems must not only deliver meat with favourable attributes, but also work practically and sustainably for a lamb finishers business.

The farm

The trial was run at Massey University’s Keebles Farm – a drystock research farm in Palmerston North. The trial was set up as a replicated farmlet design, to represent a commercial lamb finishing system. Lambs were individually EID tagged and grazed on the forages, then followed through to the abattoir. Data collected included live weight gain, carcass weight, and dry matter grown per hectare. Striploin samples were taken from each lamb at the abattoir to test for meat quality and fat characteristics.  

The crops

The three forages chosen for this years trial were Pallaton Raphno, Puna II chicory and a ryegrass/white clover control. Each plot was 0.8 ha, and with three replicates of each totalled 3.4 ha for each forage. The forages were established in late spring 2019, and the trial began on the 17^th of January 2020 (53 days after sowing). A total of 436 male lambs were weighed and allocated to the different forages, the number based on a feed budget for each plot. Each plot was split into 4 cells and the lambs were managed on a rotational grazing system. These lambs were finished (slaughtered) over two dates, one 35 days after starting on crop, the second 67 days after starting on crop. A new line of lambs was started on the Pallaton and ryegrass/white clover treatments on the 25^th of March, then slaughtered on the 1^st of May. The forages continued to be grazed after the conclusion of the trial and will be regrassed in spring.

IMAGE 2: Chicory treatment (left) and Raphno treatment (right) 

The lambs diet

The feed budgets were done based on an allowance for 7% of lamb liveweight – this was about 2.7kg offered per lamb per day. The lambs were also offered hay for the first 10 days of the trial period, this was ad lib and replenished as required. Yield assessments were completed pre grazing and post grazing to determine lamb intakes and crop utilisation.

Lamb measurements

Lambs were EID tagged and weighed prior to the start of the trial. They were allocated to a plot based on their live weight so that each mob had the same average starting weight. All lambs were weighed fortnightly once on the trial so that individual per head performance could be monitored. Prior to being sent to the abattoir, a final live weight was collected so that dressing out percentages could be calculated. Lambs were followed through the abattoir, and carcass weight and yields were collected, as well as a strip loin sample from each lamb to be later tested for meat quality and fat characteristics.

The season

Manawatu had a very wet spring, and with the trial being on heavy clay soils, the forages were sown later than anticipated. Establishment was good, and all three forages had a good bank of quality feed at the beginning of the trial. Early 2020 brought very hot and dry conditions, similar to what was experienced right across the North Island. The rainfall data is shown in the table below, with rainfall being 30% below the 10 year average throughout the trial period. Both chicory and ryegrass struggled under these tough conditions, with regrowth of both forages slowing considerably along with a significant decline in ryegrass quality. Pallaton Raphno was the standout in the dry, continuing to grow despite the lack of rain. Pallaton held more lambs throughout the trial and pushed quality feed further into summer to fill the feed gap.

FIGURE 1: Rainfall data from AgResearch Grasslands. Data shown for crop establishment, through to the trial period of January - May

Crop feed supply

Both Pallaton Raphno and Puna II chicory were quick to establish, providing a bank of high quality feed 50 days after sowing. Regrowth of Pallaton was faster than chicory, and it continued to grow right through the drought conditions experienced in February and March. Despite low stocking rates, the slow growth of chicory meant that it was grazed down to a low residual and took a long time to recover post rain. It was for this reason that no new lambs were started on chicory in March (see Figure 1). All plots were yielded at the end of the trial so that the feed remaining on Pallaton and ryegrass, as well as the chicory regrowth could be accounted for.

Lamb performance

Similar to the first years trial, the lambs on chicory had the highest live weight gain per head (301g/day) vs Pallaton (202g/day) and pasture (187g/day). The chicory lambs did not appear to ‘check’ on transitioning to from pasture to chicory – growing well right from day 1 of the trial, compared to the Pallaton lambs, which did need time to transition before maximising their live weight gain. However, as shown above in the stocking rate diagram, Pallaton had a significantly higher stocking rate throughout the trial, resulting in a higher live weight gain per hectare over the length of the trial. All forages provided quality feed early in the season, but the superior regrowth ability of Pallaton meant that it provided quality feed later into summer and early autumn, when there was minimal other feed available on farm. These factors mean chicory lends itself to being well suited to ‘A’ lambs; your most forward lambs that don’t require much finishing. They can be grazed on chicory, having minimal transition and high live weight gains to get them out the gate quickly, thus taking advantage of early season prices. Pallaton, on the other hand is best suited to ‘B’ lambs, those medium lambs that will take a bit longer to finish. This way they can transition onto Pallaton (like any brassica) and stay on crop for longer, keeping them moving forward and on quality feed during summer when pasture quality and quantity is declining. Additionally, grazing lambs on crop provides a dressing out percentage advantage.

Carcass weight gained

Carcass weight gained was the main measure used to determine the farm systems benefits of the three forage options studied. Live weight can be misleading, as it is affected by forage type and time off feed, whereas carcass weight provides a more complete picture. Because the lambs were individually EID tagged, we could collect individual carcass weight data from the abbatoir for all the meat quality lambs. This, combined with the final liveweight figure which was measured prior to the lambs being loaded out, meant that we had individual dressing out percentages, that could be modelled on the spare lambs that weren’t tracked through the abbatoir.

FIGURE 2: Net carcass weight gained on Raphno, PunaII and Pasture over the trial period

The total carcass weight produced off Pallaton was 390kg/ha over the trial period, compared to 276kg/ha on chicory and 195kg/ha on pasture. That’s 41% more carcass weight on Pallaton compared to chicory, and 100% more than on pasture. Multiplying the carcass weight produced by the prime lamb price (and subtracting establishment costs) resulted in a profit of $1,679 per hectare on Pallaton, a $629 per hectare advantage over chicory.