Litter weight weaned (LWW)
Electronic national livestock identification system (NLIS) sheep tags make it possible for sheep producers to measure the actual performance of an individual ewe in terms of lamb production. Pregnancy scanning data provides an indication of the potential lamb production from a ewe; however, many factors influence the actual production achieved due to lamb mortality and variations in lamb growth rates.
Measuring litter weight weaned (LWW) is not a new concept; however, in the past it has been restricted to use within the stud sector simply due to the labour involved in recording the pedigree information required.
Practical use of LWW in a commercial flock
The use of electronic (NLIS) sheep tags make it possible to assess the performance of an individual ewe based upon LWW in a low cost, low labour manner.
All ewes and lambs in a mob are tagged with electronic (NLIS) sheep tags and a process known as Pedigree Matchmaker used to establish which lambs belong to each ewe. Pedigree Match Maker is a walk-by system that uses electronic (NLIS) sheep tags to estimate associations between ewes and their lambs, which in turn enables traceability of an individual animal pedigree. Find out more about how to implement Pedigree MatchMaker.
With the pedigree known for each lamb, it is then a simple process of recording individual live weights for each lamb using electronic (NLIS) sheep tags at approximately 100 days of age. Some commercial contractors and consultants have developed a system that takes this data and calculates the kilograms of lamb produced by each ewe and ranks them. The result is a relative ranking of ewes within the mob, based upon the kilograms of lamb that each has weaned.
Demonstration property results
Various commercial consultants have conducted a number of litter weight weaned demonstration activities in recent years. These have illustrated enormous variation in the level of production achieved in relation to litter weight weaned per ewe. This variation simply cannot be identified without the use of electronic (NLIS) sheep tags, which then provides knowledge of lamb pedigree, and recording of individual weaning weights.
HM Prison Langi Kal Kal demonstration
Ewes in a mob were all scanned as multiple bearing, demonstrating their reproductive potential. All ewes were in condition score three or better, and feed quantity and quality in the paddock was excellent with approximately 2000kg/ha of phalaris and clover.
The most productive ewe in the mob reared a phenomenal 139.5kg of lamb (lambs at average age of 113 days). She reared 3 lambs with weights of 45kg, 45.5kg, and 49kg. The most efficient ewe in the mob weighed in at 73kg and reared 121.5kg of lamb. That is equivalent to 166 per cent of her body weight reared in lamb weight. A number of ewes only reared a single lamb with weights ranging from 42-50kg.
A mob of six hundred first cross ewes were used in the demonstration. The LWW recorded for ewes with lambs at an average age of 85 days ranged from 21.5kg to 115kg. The highest growth rates (based on assumed average birth date of one week into lambing period, and birth weight of 6kg for all lambs irrespective of rearing type) achieved was 560g/day up until day 85.
The highest three average growth rates achieved were all in excess of 540g/day. Of these three lambs, one was reared as a single, one as a twin, and one as a triplet. Twin and triplet lambs were found to be regularly out performing some single lambs based on average growth rates throughout the 85 day period.
LWW will now form the basis of ewe selection within the maternal flock at Shelburn.