BY: BEN ALLOTT
The 2020 mating season in North Canterbury was a real challenge. A dry summer extended into a very dry autumn, leaving pasture covers very low, and feed quality very poor through the mating season. Grain trailers were widely utilised to flush ewes on pasture but despite this practice most North Canterbury farmers reported mixed age ewes scanning 10-15% down on their 2019 results.
With about 12kg of grain/ewe being fed out through this flushing and early mating period, at a feed cost of $5.40/ewe, a few farmers I regularly touch base with are looking around for other options that may provide more effective, more reliable results, at a lower cost.
Craig Tomlinson, who mates 1500 hoggets, 1400 two-tooths, and 3800 MA ewes between two North Canterbury farms had a different experience to most last season.
In 2019, MA ewes on his Omihi farm scanned at 172% and he saw a lift in the 2020 season with a scanning result of 178% in the same mob. These ewes were flushed and fed through the first cycle of the mating period on a kale crop sown specifically for this purpose. In preparation, all ewes receive a long-acting iodine injection (Flexidine) one month prior to tupping.
Then 17 days prior to the planned start of mating, Craig introduces entire ‘teaser rams’ to the mob for 48-72 hours. Ten days before mating, ewes are introduced to the crop for several hours a day before being left on it seven days out from the ram. The crop is offered as three-four-day breaks with the ewes staying in this system until the end of one full cycle of mating (17-20 days).
Hay is made available, but Craig’s comment is that very little supplement is used in this system. It costs 10c/kg drymatter (DM) for the kale crop and 90c/ewe for flexidine injection. The total $4.90/ewe cost with a break fence shift every three or four days, compares favourably to $5.40/ewe with the grain trailer being used every day.
In the brassica flushing system, as long as the kale crop has established well and grown through the summer you will have a high quality feed type, with no internal parasite challenge, and low fungal pressure in the autumn.
While the example above utilised kale, other brassica crops could be utilised in a similar fashion. Rape or leafy turnip could be grazed early in the season and then be locked up for mating feed. I would urge a little more caution with root crops e.g. turnips. The potential for acidosis is higher with a root crop and a well-managed transition will be that much more important to avoid potential issues close to mating.
With these ewes off pasture for four weeks it also creates a huge opportunity for summer stressed pasture to recover following the first autumn rains and to build some quality cover going into the winter.
Some cautionary points:
- The three-day introduction period Craig practices is on the brief side of my comfort zone. In my discussions with clients I encourage a more gradual transition of seven days. Introducing stock too quickly can result in nitrate toxicity, rumen acidosis, liver damage, and photosensitivity (scald) – none of which you want to occur one week before the ram.
- Don’t forget to adapt the rams to the new diet. You can do a great job of transitioning the ewes but if the ram gets over-cooked this could have a big impact on mating performance.
- Iodine is important – Craig has this covered well with flexidine. He could use a pre-tup oral iodine drench but he wants the longer cover due to wintering some ewes on brassica crops as well.
- Flystrike – fly pressure will be far higher if you get warm autumn rain while ewes are on the crop. Even small areas of strike have a huge impact on scanning performance.
- Flocks with existing foot-rot problems could see larger autumn outbreaks than usual following this type of mating management.
Body condition score is king
No matter what approach you take to flushing ewes and feeding them through mating, it is important to recognise that body condition score at mating is the most important driver of reproductive performance.
It is difficult to lift body condition through the summer in ewes and you do not have a large window between weaning and mating. The biggest ‘bang for buck’ action you should take immediately is to BCS every ewe and draft into summer management mobs based on body condition. Do not wait for a month after weaning. Get the ewes in several days later and get them sorted pre-Christmas.
High quality is key
There are a number of reasons why ewes flushed and mated on brassicas may out-perform those on pasture with supplementary grain. While grain is a consistently high-quality feed, it can only make up a relatively small proportion of the overall diet (about 25%). The rest of the diet is then being made up by the pasture you have on hand and this potentially brings with it:
- Low feed quality – making it difficult to get ewes on a rising plane of nutrition despite the grain.
- Fungal toxins – sporidesmin from facial eczema spores (North Island/Tasman), zearalenone and oestrogenic compounds from fusarium fungus. These can suppress ovulation rates and impact on dry rates dramatically.
- Internal parasite larvae – we often get our first good rainfall through the early autumn and this can cause a spike in parasite challenge from pasture. While ewes are more resistant to disease than lambs, this challenge will still have a production cost.
- Ben Allott is a North Canterbury veterinarian.
