Managing ewes for successful joining
Managing ewes for joining
Setting the time of joining for lambing is an important on-farm management decision. Where practical, aim to lamb about three to four months before the end of the growing season for a Merino enterprise. In a prime lamb enterprise, a decision based on the most profitable compromise between ewes joined per hectare, the likely reproduction rate and market price must be made.
Key points:
- The higher the condition of the ewe at joining, the higher the potential number of lambs and the lower the number of dry ewes.
- Ewes joined in the spontaneous breeding season have a greater chance of falling pregnant.
- It is cheaper to maintain ewe condition from weaning rather than let the ewes’ condition drop and then feed them supplements in the lead up to joining.
Oestrus activity in ewes increases after the longest day of the year, 22 December (fig 1). Most ewes have higher ovulation rates as days shorten and the peak is between March and May. The spontaneous cycling in Merinos, and to a lesser extent in breeds such as Poll Dorset, are least affected by day length. Breeds such as Border Leicesters and other British breeds are most affected by day length, as shown in the graph.
Figure 1. The proportion of ewes showing oestrus throughout the year for different breeds.
Joining ewes out of season?
To join ewes outside the spontaneous breeding season, the ‘ram effect’ can be used. For this to be effective, all ewes must be kept at least 1 km from any ram (including neighbouring property’s rams) for four weeks before the introduction of teasers or rams. The introduction of teasers/rams to the isolated ewes will induce them to start cycling. The major benefit of successfully using the ‘ram effect’ induced by teasers is to get a high proportion of ewes in lamb over a short period of time which results in a more compact lambing. Figure 2 shows the proportion of ewes coming into oestrus during the joining period following teasing.
Figure 2. The proportion of ewes coming into oestrus following teasing.
What condition should my ewes be in?
The higher the condition score or fat score of ewes at joining, the higher the potential number of lambs and the lower the number of dry ewes there will be in a flock. Remember it is cheaper to maintain condition rather than to feed supplements to put on weight. If joining is on dry feed, ewes will need to have reached optimum condition before the pastures deteriorate or stubbles are grazed out. Check out the optimum condition score profiles for Merino flocks in different regions of southern Australia at
www.lifetimewool.com.au for joining, pregnancy and weaning.
Merino ewes in condition score (CS) less than 2 will result in more than 20 per cent dry ewes, so draft these from the breeding flock. The condition of the ewes should be maintained over the joining period to ensure optimum conception and profitability. For more details on the impact of nutrition on reproductive rate visit the
conception rate page at lifetimewool. Maiden ewes must reach at least 85 per cent of their adult body weight prior to joining to maximise their chances of conception.
Figure 3.The probability of a ewe's pregnancy status at a particular condition score.
Understanding the responsiveness of your ewe flock’s reproductive rate (foetuses/100 ewes joined) can assist in making decisions about feeding ewes prior to joining. Figure 3 shows the average probability of a ewe bearing single or twin lambs or being dry for a given condition. To determine the responsiveness of your own flock follow the technique outlined at
www.lifetimewool.com.au or use the
conception response calculator (excel file - suitable for fat or condition score).
Depending on if your ewe flock is responsive (+30 lambs/CS) or less responsive (-10 lambs/CS) to improving condition at joining can effect the profitability of feeding ewes by $1 to $3 per ewe in a wool enterprise. It is also important to note that ewes joined just before the breeding season (late November/December) are likely to be in better condition normally than ewes joined in February.
How long should joining be?
The length of joining for an average flock should be 5 weeks. If your flock is mated outside the breeding season, join ewes for 6 to 7 weeks if unable to use teasers (see figure 2). Extending joining for a longer period of time is not recommended. The 2 to 4 per cent of extra lambs generated by a longer joining has the potential to hold up significant husbandry procedures such as marking and weaning, and contribute little to whole farm profit and makes pregnancyscanning less accurate. See figure 4 for the impact of joining period on survival to hogget age.
Delaying weaning for late winter/spring lambs can result in serious consequences, such as high worm burdens, leading to weight loss in both ewes and lambs. Merinos that lamb late generally have low survival rates over the summer period due to a lower body weight.
Figure 4. The impact of joining length on number of hoggets available (post 1st February) for a spring lamb flock.
Take home messages:
- Assess ewe and ram condition prior to joining and cull any unhealthy/thin ones.
- Know and understand the responsiveness of your ewe flock’s reproductive rate
- Tease ewes if joining before January to ensure a concise lambing
- Have ewes in good condition prior to joining using paddock feed – hand feeding to increase liveweight for joining is not often cost effective.
For more information:
CJ Hawkins Homestead, University of New England, Armidale NSW 2351