Pregnancy scanning results from northern, central and southern NSW suggest that higher than normal dry ewes are being recorded but with producers also finding an increase in twin-bearing ewes it is hoped lambing averages will remain steady for the season.
A number of causes have been identified to affect the health of ewe mobs this year which are triggering lower conception rates and Sheep Solution’s Goeff Duddy said it can be broken down into three main areas.
He said it’s a combination of wet winter and spring which has caused health issues, in particular foot rot and abscesses, a decline in feed quality and the more unheard of threat, an abundance of mosquitoes.
Mr Duddy said across the board upwards of 10 to 15 per cent of ewes are scanning dry, with older ewe mobs accounting for the majority.
“Although we had a lot of feed, the bulk feed was high in structural components and low in energy, protein and digestibility,” he said.
“Feed test results for 30 per cent clover, rye pastures in mid-February came back with two per cent protein, five megajoules of energy and mid-50’s digestibility,” he said.
Also affected this season were rams during the joining period – with rams not actively pursuing ewes in the paddock because of foot diseases, anemia and fly strike.
Mr Duddy said the surge in mosquitoes has caused the transmission of bacterial diseases causing anemia. Recently a producer near Moulamein alerted Mr Duddy to his flock rams avoiding shady tree areas during joining because of mosquitoes, therefore the weakness and irritation caused a lack of want to pursue the ewe mobs.
Meridian Agriculture’s Richard Cannon said in Hay the story remains the same, with his dry Merino ewe numbers increasing to 12 per cent. He said at the time of joining late last year the quality of pasture, although there was a lot of bulk, had a falseness in its nutritional value.
“Our local scanner said multiple births are up but overall conception was back – hopefully the net results will remain stable because of this.”
“The rise in twinning could be because producers seem to be more objective in their classing and producing more sheep from twin lambs, so I would say the rate of fertility would be lifting in some flocks,” Mr Cannon said. “The tremendous spring and condition scores on sheep made it hard to know the condition of ewes during joining when the feed quality dropped off – so not all ewes had the extra condition to conceive.”
Feed quality double edge sword
Sheep Solution’s Geoff Duddy believes a food source too high in energy and protein could possibly contribute to the increased dry ewe numbers and twinning percentages.
Mr Duddy said it’s common for twinning rates to go up if sheep are in good condition however feed too high in nutrition can also have a detrimental affect on conception as well.
“There can be negative impact during the first week of conception – when insemination occurs and the egg is being fertilised, a really high quality energy and protein feed in that time can actually cause abortion in especially single bearing ewes,” he said.
“It’s to with progesterone production – the twin bearing ewes tend to be producing enough progesterone to maintain the pregnancy so under those sorts of conditions you will end up having a lot of single bearing ewes abort early on.”
“Those ewes may then come back and be joined later but I am not sure if this has been the pattern across properties this year – if we saw a lot of ewes joining later that would suggest the singles may have aborted and re-joined, which may explain the higher amount of twins too,” he said.
Cowra Agricultural Research and Advisory Station, NSW DPI research officer Dr Gordon Refshauge said currently dry ewes have risen to 40 per cent for some producers and in many cases the high dry rate occurs in conjunction with higher than normal numbers of twin-bearing ewes within the same mob.