Sheep farmers adopting fodder beet for winter grazing are being warned that it could result in serious under-nutrition in multiple-bearing ewes.
The study involved researchers from Uruguay, Australia’s Department of Primary Industries, Regional Development WA and the university.
They investigated the reproductive outcomes of 200 Merino ewes known to have either a calm or a nervous temperament. They found the ovulation rate and rate of successful pregnancies to be higher in the calm ewes.
Associate professor Dominique Blache from UWA’s School of Agriculture and Environment and Institute of Agriculture who led the study said temperament affects ovulation rate but not the occurrence of ovulation.
“Differences in reproductive outcomes between the calm and nervous ewes were mainly due to a higher ovulation rate in calm ewes,” she said.
“Even when the ovulation rate is maintained, some of the nervous ewes have problems in maintaining their pregnancy possibly because of the quality of the eggs and subsequent embryos, and perhaps the quality of the uterine environment during the first two weeks of pregnancy.”
The researchers say understanding why the reproductive outcome of these ewes is different will help to breed sheep better suited for the production system and improve their welfare.
The study found that behavioural reactivity affects ovulation rate, but not the occurrence of ovulation. Therefore, any differences in reproductive outcomes between the calm and nervous ewes were mainly due to a higher ovulation rate in calm ewes.
It also discovered that some of the nervous ewes, when the ovulation rate is maintained, have problems in maintaining their pregnancy. This is possibly because of the quality of the oocytes and subsequent embryos, and perhaps the quality of the uterine environment during the first two weeks of pregnancy.
As plasma concentrations of progesterone post-AI were not affected by temperament, but insulin and leptin concentrations were, the researchers suggest that reproduction in nervous ewes is compromised by factors leading up to ovulation and conception, or in the uterine environment during early pregnancy – that reflect differences in energy utilisation.
The paper, Calm Merino ewes have a higher ovulation rate and more multiple pregnancies than nervous ewes was published in the journal Animal. The research was supported by Meat and Livestock Australia.