ANIMAL HUSBANDRY - Replacement Stock and Fattening Lambs Flashcards
What are the two methods that can be used to replace sheep stock?
Purchased stock
Homebred stock
What are the pros of purchasing replacement stock?
- Genetic diverisity as buying from different breeders can introduce fresh genetics into the farm which can increase hybrid vigour within the flock
- Less time and effort as you don’t have to manage breeding, lambing and rearing replacements so you don’t have to worry about genetics, health, or development of lambs
- High quality animals if you buy from high health status flocks
What are the cons of purchasing replacement stock?
- Higher initial cost
- Risk of introducing disease and parasites
- Limited control over genetics as the sheep have been reared by someone else
- Less familiarity with flock as replacements could have different health or behaviour profiles that you’re not prepared for
What are the pros of homebred replacement stock?
- Lower long term cost as once you have your breeding stock, producing replacements generally costs less than buying in animals every year
- Full control over genetics, allowing you to select for desirable traits which can help improve the overall quality of the flock
- Reduced risk of introducing disease and parasites
- Better flock familiarity as you know the health, behaviour, and productivity of your ewes
What are the cons of homebred replacement stock?
- Breeding management takes more time and effort as you need to track breeding schedules, manage the lambing process etc.
- Limited gene pool so inbreeding can become a problem over time
- Potential for poor quality replacements as there is a risk that the genetics don’t produce the qualities you are aiming for
- Frequently purebred so lack of hybrid vigour
Why is the risk of bringing in disease higher for purchasing replacement sheep compared to replacement cattle?
There is a higher risk of bringing in disease when bringing in purchased replacements compared to cattle as farmers tend to purchase larger numbers of sheep each year compared to cattle, so there is an increased probability of introducing disease to the flock each year
What are the three main catergories farmers are looking for in purchasing replacement stock?
Profitability
Health
Output
Which factors should be assessed to determine the profitability of replacement ewes?
Ewe mature weight
Number of live lambs sold
Growth rate of lambs
What is the ideal ewe mature weight?
Farmers are aiming for at least 20kg carcass weight when they sell their lambs for meat, and to achieve this the ewes producing the lambs need to be 60-65kg
If ewes weight less it will be more challenging to get the lambs up to 20kg ready for market, but if they weight more, the ewes will need to be fed more which increases costs
Why is it important to assess the number of live lambs sold when assessing profitability of replacement ewes?
If replacement ewes consistently produce a high number of live lambs that can be sold, this leads to higher income and better financial returns
Why is it important to assess the growth rate of lambs when assessing profitability of replacement ewes?
Lamb growth rate determines how quickly lambs reach market weight. If ewes are producing faster-growing lambs, these can be sold earlier so they will be sold at higher value and they spend less time on farm which reduces feed and care costs, increasing profitability
What are some of the key components of homebreeding replacement stock?
- Select your tups appropriately
- Nucleus flock with the rest of the flock being bred with terminal sires to allow for both genetic improvement and meat production for economic output
- Consider epigenetics
- Consider whether you should breed as ewe lambs or gimmers
- Never keep the tail end lambs for breeding and avoid keeping singles as they are born to ewes with lower fetility compared to twins etc.
What is a nucleus flock?
A nucleus flock is a core group of ewes and rams that are specifically selected and managed to improve the overall genetic quality of the flock over time. The nucleus flock usually a smaller, highly productive group which is typically responsible for producing the replacement ewes for the rest of the flock
What is ‘breeding to terminal sires’
Breeding to terminal sires is where ewes are bred to terminal sire tups with the goal of producing lambs that are raised for meat rather than breeding
If the farmer breeds the ewes that they don’t want to contribute to the genetics within the flock with terminal sires, they still get an economic output from that ewe
What are epigenetics?
Epigenetics refers to how environmental infleunces affect how genes are expressed, without changing the genetic code itself
What are the pros of breeding from ewe lambs?
Female lamb less than a year old
- Lifetime productivity increases by 10% as by breeding ewe lambs, they have a longer productive lifespan as they produce lambs earlier and thus can potentially produce more lambs throughout their lifespan
- They potentially will be better mothers at 2 years old compared to gimmers
What are the cons of breeding from ewe lambs?
- Physically immature, so breeding them early can put lots of stress on their bodies and increase the risk of complications at lambing - because of this they will have to be vigilantly managed to reduce the long term complications
- Will require more feeding during pregnancy and lactation compared to gimmers
- Ewe lambs don’t have the capacity to raise twins, so if they produce twins one should be taken off them or there is a risk that they will be less fertile in the subsequent lambing season
- Can be difficult mothers in their first year (but so can gimmers and with gimmers the relative cost will be more)
Which factors should you consider when selecting ewe lambs for breeding?
Select ewe lambs from the smallest ewes that have produced twin lambs, at the earliest point in the lambing season, with the best production history and least interventions required. Furthermore, the ewe lambs you select needs to be health, 60% of their mature weight at tupping with a BCS 3
Which maternal traits should be assessed when selecting ewes for breeding?
Number of lambs born (ideally twins)
Number of lambs surviving
Weight of progeny lambs at 8 weeks
Mature size of the ewe
This info cannot be gained by eye, long term data is required
Why is it important to assess the weight of the progeny at 8 weeks?
The weight of the progeny lambs at 8 weeks correlates to the milk production by the ewe. If the lambs are at target weight at 8 weeks, this indicates the ewe milk production was good
Why is it important to assess the mature size of the ewe?
You’re aiming to select the smallest ewes that still produce the quality of lambs you need, as the smaller the ewe the less she will need fed so the more profitable she will be
Why should you avoid flushing ewe lambs at tupping?
You should avoid flushing ewe lambs at tupping as this will promote twins which ewe lambs don’t have the capacity for in their first lambing season
What can be done to minimise the decline in growth rate seen at weaning?
If there is plenty of good quality grass for both the ewes and lambs, weaning can be delayed which will allow the lambs to continue suckling energy dense milk in addition to eating good quality grass. This also reduces parasite challenge for the lambs. Furthermore, when you do wean the lambs, you should keep the lambs on the same pasture and more the ewes. Both delayed weaning and keeping the lambs on familiar pasture helps to minimise the decline in growth rate seen at weaning
