In this summary we will look at two papers, the first one looks at the potential benefits of grazing lucerne on reproductive performance, and the second at the potential limitations around using lucerne over the breeding period.
For the summer dry areas of New Zealand (NZ), the grass species often grown in NZ have poor growth and quality. Lucerne is a perennial forage that has a deeper rooting system than grass, therefore, has better growth and quality in these drier conditions.
We have previously looked at selecting replacements born from hoggets, but can lucerne be used to ensure that the ewes bred as hoggets successfully get in lamb.
Grazing lucerne prior to breeding had no effect on the reproductive rate of hoggets.
The twinning rate increased in hoggets fed lucerne prior to breeding compared to those fed ryegrass based pasture.
Ewes grazing lucerne containing large amounts of fungal infected stem and dead herbage had 18 fewer foetuses per 100 ewes joined.
Lucerne can be utilised as a feed to increase live weight prior to the breeding period.
Feeding hoggets lucerne prior to breeding
This study was repeated across two years in 2015 and 2016.
Pasture (ryegrass and white clover)
The hoggets in each group had similar live weights. Hoggets were offered the herbage from 42 to 11 days before breeding. Then they were all managed on ryegrass and white clover until and during the breeding period.
In the first year (2015), there were no differences found between the number of hoggets diagnosed as non-pregnant for ewes grazing lucerne (27 hoggets) and pasture (33 hoggets) as shown in the graph below. However, there was an increase in twin-bearing hoggets in the group that were fed lucerne prior to breeding.
This could be a result of the hoggets grazing lucerne being heavier (50.9kg) on average at the start of breeding than those grazing pasture (49.1kg). The difference in live weight was probably due to the lucerne group eating more as the herbage quality was similar between groups (~8.0 MJME/kgDM).
In the second year (2016), there were no differences in pregnancy rate and there were also no increases in the twinning rate that was found in the previous year as shown in the graph below.
In the 2016 trial the hoggets were no different in live weight at the start of the breeding period, 42.4 vs 42.0kg for the lucerne and pasture groups, respectively.
The authors concluded that the difference in twinning rate in the first year is most likely due to the hoggets grazing lucerne being heavier on average. There have been previous studies of hoggets grazing pasture in which the twin-bearing hoggets were between 1.1-1.8kg heavier than the single-bearing hoggets (Kenyon et al. 2006; Kenyon et al. 2010). This indicates that perhaps live weight has a greater effect on twinning rate than type of herbage fed.
Therefore, the feeding treatment did not effect the pattern of hogget breeding, it is more important to have hoggets at adequate live weight (40kg) for breeding.
Feeding mature ewes lucerne for 14 days at breeding time
Pasture (ryegrass and white clover)
The ewes grazed the lucerne or pasture 7 days prior to breeding and for the first 7 days of the breeding period. Following this, both groups grazed pasture.
The lucerne and pasture were both of low quality (~7.8 MJME/kgDM) with high quantities of dead matter due to a drier than normal March in 2016 in the Wairarapa.
The lucerne had high levels of phyto-oestrogen (coumestrol, 107 mg/kgDM). As a result, the lucerne group had a lower proportion conceiving in the first 17 days of the breeding period which can be seen in Figure 3. The lucerne group that did not conceive in the first breeding period, mostly conceived in the second breeding period (Figure 3).
Even though there were a lower number of the lucerne group bred in the first breeding period, there was no difference on the proportion of non-pregnant ewes (2% lucerne group vs 1% pasture group). This is probably because by the second breeding period, any negative effects of the high phyto-oestrogens grazed in the first 7 days of breeding had gone away and the hoggets still managed to successfully get in lamb in the second breeding period.
There were no negative effects of hoggets grazing lucerne prior to breeding in the first study, however, were moved to pasture 12 days prior to breeding which could have alleviated any negative effects of the phyto-oestrogens.
The graph below shows the number of foetuses per ewe joined. There were 0.18 lambs per ewe or, over 100 ewes, this would be 18 more lambs in the pasture group compared with the lucerne group. So even though a similar number of ewes were pregnant, the lucerne group had their ovulation rate negatively impacted by grazing lucerne.
Hogget reproduction can be improved by offering lucerne for one month prior to breeding if it results in increased liveweight gains compared with those offered old pasture. Care must be taken, however, to ensure there is a period off lucerne prior to breeding to negate any potential negative effect of phyto-oestrogens.
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Corner-Thomas R, Panns J, Kemp P, Morris S, Kenyon P 2017. The effect of grazing ewe lambs on lucerne (Medicago sativa) prior to breeding on aspects of reproductive performance Proceedings of the New Zealand Society of Animal Production No. 77. p 55-60, Rotorua.
Cranston L, Kenyon P, Fields R, Moot D, Corner-Thomas RA, Kemp P, Morris S. (2017). Lucerne with a high coumestrol content is not a suitable feed for ewes just before and during the early breeding period. Journal of New Zealand Grasslands, 79, 55-60.