It is a proven fact some sheep breeds selected narrowly for muscling have poorer maternal care. This is according to research by sheep behaviour specialist Professor Cathy Dwyer, with Scotland’s Rural College. Although United Kingdom-based, the research is relevant to the intensive farming style in this country.
New Zealand’s three main farming types are best categorised by how lambing is undertaken, which also tends to be a reflection of the type of country farmed, but intensive operations, which also have a strong focus on muscle and growth, are coming under the research spotlight.
Work done in the UK shows selection for any narrow set of production traits, such as muscle and growth, without including some assessment of fitness traits, is not a good idea. Fitness traits include maternal behaviour.
Dwyer’s research shows sheep can become a product of their environment but it isn’t all to do with how they are handled, although this does play a role.
The crucial factor has a lot to do with key traits and heritability, with ram selection playing a vital part in future maternal behaviour of the flock.
Like many NZ farmers, Dwyer said UK farmers also tended to believe that a ewe needing assistance in one lambing was highly likely to need assistance in the future.
Her research showed this was incorrect and that only 10% of ewes studied, over four lambings, needed help again.
The crucial point was that of the ewes needing help over any of the four lambings, a major contributing factor was lamb behaviour at birth, which comes down to sire selection.
“The genetics of the lamb is a significant contributor to (the ewe) needing assistance so it would be a mistake to cull/get rid of everything that has needed lambing assistance as there are many reasons why this might occur, including which ram you have used.
“You may be getting rid of good ewes who have needed assistance through no fault of their own.
“I advise that farmers keep a record of ewes that were assisted in each pregnancy, and if it occurs again for a particular ewe then that is the time to take action and not use her or her daughters again.
“Personally I think we have considered lamb mortality as a fault of the ewe for far too long, and this has probably hindered our ability to make progress on reducing lamb mortality.”
Dwyer suggests that lamb traits, in terms of easy delivery and its ability to “get up and go”, are as important as how the ewe behaves.
“Personally I think we have considered lamb mortality as a fault of the ewe for far too long, and this has probably hindered our ability to make progress on reducing lamb mortality.”
Research shows these lamb traits are directly related to heritability and ram genetics.
Whatever the ewe does from birth, in terms of expressing maternal behaviour, will not be enough if the lamb has inherited poorer genetics from both the ewe and the ram.
Apart from sire selection to ensure good maternal traits are there to begin with, on-farm management plays a big role in how maternal behaviour is expressed.
Farmers of intensive operations will be well versed on how maternal bonds can break down between a ewe and her lamb/s, but they may not realise the science behind why it occurs.
For instance, it is not uncommon for a maiden ewe, inexperienced in maternal behaviour, to not want her lamb immediately after an assisted lambing.
Farmer intervention can hinder the release of the oxytocin hormones – in humans this is sometimes referred to as the “hormone of love”. It contributes to maternal behaviour and bonding.
The hormone can also be released during suckling, which explains why bonding in assisted births of maiden ewes can sometimes be triggered by latching lambs on to feed.
The highest levels of the maternal hormone are achieved in situations where no interference of birth has taken place and lambs are vigorous and quick to suckle.
ifferent breeds of sheep are also genetically programmed to express different levels of maternal hormones, explaining why some breeds are considered better mothers than others.
There are two distinctive foundations to maternal behaviour, even though they are interlinked.
The first is the release of hormones as discussed, and the second is in how the ewe builds her selective memory towards her own lamb/s, which occurs immediately after birth and over the next six hours. How a maiden ewe is allowed to behave during this time sets in motion how she is likely to perform at further lambings.
This is where Dwyer’s research shows incorrect sire selection has the most impact.
Difficult birth and mismatched behavioural or vigour traits can quickly lead to a breakdown in bonding, which risks further damage if farmer intervention or interruption is needed.
Maiden ewes develop better maternal behaviour for life if in her first lambing she has:
• Maintained good nutrition,
• Lambs unassisted at her chosen birth site,
• Remains uninterrupted with her lambs for at least six hours following birth and her lamb/s are quick to stand and suckle.
Correct feed management during pregnancy, well-matched sire genetics and, where possible, avoiding interruption from birth to six hours afterwards, are three key factors in nurturing strong maternal behaviour.
