The pasture sward in New Zealand is predominantly made up of ryegrass and white clover. In some regions of New Zealand, the summer dry conditions can reduce pasture growth and cause a decline in pasture quality. The summer period is generally when most of the lambs are finished and a decline in feed quality in summer can result in feed requirements not being met.
Individually, herbs such as plantain and chicory, and red clover can be more productive and produce a better quality sward in the summer period than a ryegrass/white clover sward. This increased herbage quality can enhance lamb production.
Chicory and plantain mixes have greater lamb growth rates than ryegrass and white clover pasture.
The chicory and plantain mixes had higher herbage quality than pasture.
Either chicory and/or plantain mixes can be used to increase lamb growth rates during summer in the lower North Island.
There were 2 experiments conducted in the Manawatu over two consecutive summer periods (Trial 1; 2011-2012 and Trial 2; 2012-2013) with three herbage treatments to compare the impacts on lamb production.
Pasture mix (perennial ryegrass and white clover)
Plantain mix (plantain, white clover and red clover)
Chicory mix (plantain, chicory, white and red clovers)
216 Romney cross male lambs aged approximately 3.5 months (32.8 ± 0.23 kg) were selected for this experiment. They were allocated to each treatment based on maintaining ad-lib feeding conditions with a herbage allowance of three times their predicted intake of 1.5 kgDM per head per day. The number of lambs allocated to each treatment were 48, 84 and 84 to the pasture, plantain and chicory mixes respectively. The different number of lambs was due to the different yields of each herbage across the trial period. This trial was run across 7 weeks.
The same experimental design was repeated the following year with 168 Romney cross male lambs aged approximately 4 months (35.8 ± 0.16 kg). The number of lambs allocated to each treatment were 48, 48 and 66 to the pasture, plantain and chicory mixes respectively. This trial was run across a 4 week period.
There were 2 enclosed cages placed in each herbage treatment to enable collection of a sample of the herbage that the lambs were eating. This was used to determine herbage quality and the botanical composition in each herbage treatment.
Lamb live weights, carcass weights and GR soft tissue depth were measured.
Figure 1 shows the metabolisable energy (ME) of the pasture (blue), plantain (purple) and chicory (grey) mixes. In both trial 1 and trial 2 the ME was greater in the plantain and chicory mixes compared to the pasture mix.
The crude protein (CP) in trial 1 was greatest in the plantain mix of 24.2% and no different between the chicory and pasture mixes of 20.1% and 18.7% respectively.
The CP in trial 2 was greatest in both the chicory and plantain mixes of 17.2% and 18.8% respectively, compared with the pasture (11.5%)
Overall, the CP is generally higher in the plantain and chicory mixes but varied in value depending on the seasonal variation.
Combined the ME and CP showed that the herbage mixes of plantain and chicory have greater nutritive value than the pasture over the summer period.
The herbage composition of each herbage treatment is shown below in Figure 2. Ryegrass was the predominant species in the pasture mix, while plantain was the predominant species in the plantain mixes and the chicory mix in trial 1. Chicory was the predominant species in the chicory mix in trial 2. There was a similar amount of dead matter in all herbage treatments.
Figure 3 below shows the average growth rate for each herbage treatment. Both the plantain mix and chicory mix lambs had greater liveweight gains compared with pasture mix lambs in both trial 1 and 2.
In trial 2, there was a greater difference in growth rate with the chicory and plantain mix lambs compared with the pasture mix lambs. This can be explained by the differences in the length of trial 1 (49 days) and trial 2 (26 days). This resulted in a greater difference in the final live weight between the herbage treatments for trial 2 compared with trial 1.
Lambs grazing the Plantain mix and Chicory mix had greater carcass weights compared to the lambs grazing the Pasture mix.
This is perhaps due to the higher quality herbage of the chicory and plantain mixes resulting in the lambs being able to use more energy for growth rather than maintenance compared to the lambs grazing the pasture mix during summer.
The studies were based on all the lambs being finished to the same date for each trial, therefore, carcass weight is highly related to the final live weight of the lambs. The lambs with the greatest live weight at the end of each trial were the Chicory and Plantain mix lambs.
Therefore, these results indicate that the farmers can utilise herb/legume mixes comprising of plantain and/or chicory, white and red clovers to improve lamb production in comparison to the ryegrass/white clover sward during the summer period.
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