If sheep are ‘doing the deed’ and ‘getting the job done’ in this heat, why are conception rates still low?
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Producers are beginning to question if and how the higher temperatures will affect the fertility and conception rates of their sheep.
Recently speaking at the Mumblebone Spring Field Day near Wellington on September 19, Russ Davis from Ceva Animal Health, said they are starting to see an impact and solid research in Australia about temperature response in sheep.
“The higher the temperature, the lower the fertilisation rate,” he said.
“What we are seeing, and the problem is, is there is not enough temperature differentiation between the day and the night.
“With a day time temperature of 32 [degrees] and there not being enough cool down, like a 10 degree spread at night.”
Mr Davis highlighted on a slide during his presentation that fertilisation rate is decreased from 81 to 95 per cent at 21 degrees to 56 to 60pc at 32 degrees.
“Lengthened oestrus, weaker/lowering of twins, lowering of conception – we are starting to see this occur due to temperature response,” he said.
Decreased feed availability in some areas, may cause nutritional stress that can result in embryonic loss following conception.
Ram fertility is also a factor to be considered. Lower semen values, semen quantity/quality or libido will result in lower conception.
It is important to remember rams are 50pc of the reproductive equation, managing both ewes and rams is fundamental.
Mr Davis questioned why producers put so much time into selecting their rams but so little effort into managing them outside of the eight weeks prior to joining.
“We put them in a paddock and keep them there the whole year. We devote eight weeks when we are going to use them, then we turn them out,” he said.
“Producers cannot correct a fault in a ram once you put it to joining or eight weeks prior as it takes eight weeks for them to produce semen.
“They need to prevent the problem before it occurs.”
The internal semen temperature in a ram only needs to change by one degree to render the semen less fertile or infertile – it is really sensitive, Mr Davis said.
“Rams are incredibly efficient in managing scrotal temperature. On hot days they stand with testes low to increase surface area and sweat to allow them to cool down,” he said.
“When testicles are distended and heat is radiated back, some cook off [of semen] may occur. Not saying it is a problem, but it may happen.”
This highlights the importance of providing shade to allow rams to be efficient in hot temperatures.
