THE breeding ewe is the engine room of flock production and ewe nutrition, particularly during pregnancy and it affects several areas of the production system, according to Northam-based DAFWA livestock development officer Katherine Ayres.
Ms Ayres said this included wool production in the ewe and its progeny, lamb survival rates, reproduction and effective use of feed.
Ms Ayres focused on the influence condition score has on breeding ewe and lamb productivity and tools to manage nutrition when she spoke at an informative on-property open day at the Wilkinson family’s Challara Merino stud at Badgingarra last week.
She used an example of 100 ewes with a condition score of three had the potential to produce an extra 20 lambs per joining compared to ewes with a condition score of two.
"This is due to the increase in the number of twins," Ms Ayres said.
"At 120 per cent scanning, about 60pc of the lambs conceived will be one of a twin."
Ms Ayres said a number of processes could be influenced by ewe nutrition during the gestation period including wool follicle development which determined fibre diameter and clean fleece weight.
"The lamb's primary follicles develop between days 60-90 and its secondry follicles from day 90-100 until lambing," Ms Ayres said.
"The secondary wool follicles is one of the most important mechanisms in wool production and by lambing, the wool follicle development is permanent and can't be influenced any further by nutrition."
Ms Ayres said it was obvious that ewes in better condition would have a heavier lamb which was important for lamb survival and condition changes during pregnancy could also affect birthweight.
"The average birthweight for a 50kg Merino ewe is 4.9kg for a single lamb and 3.7kg for a twin and a 10kg increase in mature ewe condition can be associated with 200-400 gram increase in birthweight," she said.
"A score condition change of one prior to day 90 during placental development can affect the birthweight by about 300 grams either way but in the later stages of pregnancy, a score change can change birthweight by about 500 grams."
Ms Ayres said around 70pc of lamb mortality occurred in the first 48 hours of its life and could be directly related to birthweight.
She said lightweight lambs in multiple litters were at greater risk of hyperthermia, exposure, lower body fat reserves and ability to regulate their body temperature.
"The optimum birthweight for lamb survival is between 4.5 and 5.5kg but it can be affected by lambing time and environmental conditions," Ms Ayres said.
"If a twinning ewe lamb's average birthweight drops by 500 grams, mortalities increase by up to 20pc."
Ms Ayres said poor nutrition during pregnancy can also affect the mother's maternal behaviour which is associated with colostrum and milk production.
"Ideally the ewe should stay with the lamb for about six hours following birth so disruptions during this period should be avoided such as hand feeding," she said.
Ms Ayres said ewe mortality mainly occurred late in the pregnancy and increased sharply when the ewe's condition score was less than two.
She said twin bearing ewes were at higher risk due to the high energy demands of the two foetuses which could cause pregnancy toxaemia and milk fever.
"If the condition score is lifted by half on a condition score two ewe, the mortality rate of single bearing ewes drops from 4pc to 1.4pc and from 6.2pc to 3.6pc for twin bearing ewes," Ms Ayres said.