Sheep Updates 2006 - part 4

This session covers seven papers from different authors: MANAGEMENT 1. Wool and meat traits in Merino flocks in different regions, K.G. Geenty, A.A. Swan, A.J. Smith, J.L. Smith, Sheep CRC and CSIRO Livestock Industries, Armidale 2. Fat score or Condition score? - It all depends on what you want to do! Chris Oldham, Department of Agriculture and Food Western Australia 3. Sheep worm control - the latest for Western Australia, RG Woodgate, RA Love, E Dobbe, HM Hoult, J Pearson, S Hill, A van Burgel and RB Besier, Department of Agriculture and Food Western Australia PASTURES 4. Rethinking pasture production - STEPS to greater productivity with perennials, R. Warburton, Farmer, Mobrup, WA, L. Mathwin, Farmer Kojonup WA, D. Rogers, E. Crossley, Department of Agriculture and Food Western Australia 5. Sheep Returnes from Saltland Pastures, Allan Herbert, Department of Agriculture and Food Western Australia 6. Pasture legumes and grasses from saline land, Phil Nichols, Tony Albertsen, Darryl McClements, Department of Agriculture and Food Western Australia, & Cooperative Research Centre for Plant-based Management of Dryland Salinity MERINO INNOVATION DAY 7. Towards \u27clean, green and ethical\u27 sheep production, Graeme Martin, Penny Hawken, Carolina Viñoles, Beth Paganoni and Dominique Blache, School of Animal Biology, Faculty of Natural & Agricultural Sciences, The University of Western Australi

Milk production and lamb growth in Dorset, Corriedale, and Romney sheep and carcass growth and development in lambs of the three breeds and crosses among them

The supply of milk to young lambs determines whether they survive and grow satisfactorily (Moule, 1954; Wallace, 1948a; Marnicoat, 1949a). Therefore the potential of the ewe to produce milk is important in the evaluation of breeds for selection and crossbreeding programmes, particularly where these programmes are aimed at increasing fecundity. This is particularly relevant with the recent importation of highly fecund sheep such as the Finnish Landrace. Since the objectives of increasing fecundity are presently being met, larger number of surplus male lambs will become available from breeding flocks for the export market in the future. Several breeds and crosses have been evaluated for this market but to keep abreast with changed which might occur, new and less popular breeds, particularly those with potential use in crossbreeding programmes, should also be evaluated. The objectives of the present experiments were to measure the lactation yields of 3 parent breeds and to study the compositional growth and development of their pure and crossbred progeny until they were weaned

Relationships between pasture availability, wool profiles and staple strength in different sheep grazing environments

Information on variation in fibre diameter during the wool growing season derived using optical fibre diameter analysis (OFDA2000) can be used to predict wool staple strength. Information on fibre diameter can also be used to initiate nutritional management strategies for preventing wool tenderness and the associated price reduction. However, OFDA2000 measurements involve costs associated with the collection of mid-side wool samples and laboratory analyses. In addition, the information is retrospective, as results are usually obtained too late for feeding and management interventions. We investigated the use of real-time pasture availability data obtained using satellite imaging to predict fibre diameter profile and staple strength. Correlations between pasture availability and changes in fibre diameter were strong, but varied between environments. In general, the rate of reduction in pasture availability was moderately correlated with the reduction in fibre diameter; on average it accounted for 28% of the variation in fibre diameter, and in some environments it accounted for up to 75% of the variation in fibre diameter. The decrease in pasture availability was positively correlated with staple strength and accounted for 26% of the variation in staple strength. The use of satellite-derived pasture availability estimates in feeding strategies designed to prevent wool tenderness is discussed, as is the potential of satellite data for predicting regional staple strength changes

Diet has minimal impact on Australian consumer palitability

This study tested the palatability of lamb meat derived from pasture versus grain finishing systems. The loin and topside muscles from 105 lambs were collected. Sensory scores were generated using untrained consumers who tasted 5 day aged grilled steaks, scoring tenderness, juiciness, flavour and overall liking. Consumer scores did not differ in female lambs fed grain or pasture diets. However in wether lambs palatability scores for overall liking, tenderness and juiciness were higher for those on grain compared to those on pasture. Correcting for intramuscular fat accounted for most of these differences. These results confirm that Australian consumers do prefer grain-fed lamb meat, but only in wether lambs

Genetics of lamb survival: Preliminary studies of the information nucleus flock

Poor lamb survival is recognised in Australia as a major contributor to reproductive inefficiency in the national flock. This paper provides preliminary estimates of phenotypic and genetic parameters on lamb survival and related traits for the 2007 and 2008 data from the CRC for Sheep Industry Innovation’s Information Nucleus. The paper focuses on the potential utility of measurements on related traits for achieving genetic improvement in lamb survival. Although timed lamb behaviour traits show consistently high genetic correlations with lamb survival to 3 days of age, no obvious candidates have yet been identified for commercial use as indicator traits to genetically improve lamb survival.F. D. Brien, M. L. Hebart, J. E. Hocking-Edwards, J. C. Greeff, K. W. Hart, G. Refshauge, G. Gaunt, R. Behrendt, K. Thomson, G. N. Hinch, K. G. Geenty and J. H. J. van der Werfhttp://www.aaabg.org/proceedings18/index.htmlhttp://trove.nla.gov.au/work/3642077

Opportunities for genetic improvement of lamb survival

Data on lamb survival and associated traits involving records from 15 192 lambs, 6308 dams and 284 sires from the Sheep CRC’s Information Nucleus were studied. Lamb survival to 3 days of age and to weaning was 85 and 80%, respectively, and heritability (±s.e.) was 0.014 ± 0.010 and 0.010 ± 0.010, respectively. Of the 14 traits recorded at birth, time taken for the lamb to bleat, rectal temperature and crown–rump length had the highest genetic correlations with lamb survival to weaning (–0.43 ± 0.32, 0.56 ± 0.33 and –0.38 ± 0.36, respectively). Under selection for a multi-trait objective including net reproduction rate (but not lamb survival), survival was predicted to decline genetically by 0.25 lambs weaned per 100 lambs born.year, although this was reversed to a gain of 0.20 lambs weaned per 100 lambs born.year by including the trait in the breeding objective and using 50 half-sib and 50 progeny records per selection candidate. Accuracy of selection for lamb survival was improved to 0.735 with a selection index of lamb survival to weaning, lamb ease, birth coat score, time taken to bleat, rectal temperature and crown–rump length, with the addition of 50 half-sibs and 50 progeny records per candidate. Our results suggest that unless actively incorporated into breeding objectives, lamb survival may genetically decline; however, gains are possible with direct selection using half-sib and progeny records. The addition of indirect selection criteria for lamb survival can further improve accuracy, up to 93.4%, but requires further investigation.F. D. Brien, M. L. Hebart, D. H. Smith, J. E. Hocking Edwards, J. C. Greeff, K. W. Hart, G. Refshauge, T. L. Bird-Gardiner, G. Gaunt, R. Behrendt, M. W. Robertson, G. N. Hinch, K. G. Geenty and J. H. J. van der Wer

Reproductive performance in the Sheep CRC Information Nucleus using artificial insemination across different sheep-production environments in southern Australia

The present paper covers reproductive performance in an artificial-insemination (AI) program of the Sheep CRC Information Nucleus with 24 699 lambs born at eight locations in southern Australia across five lambings between 2007 and 2011. Results from AI with frozen semen compared well with industry standards for natural mating. Conception rates averaged 72%, and 1.45 lambs were born per ewe pregnant for Merino ewes and 1.67 for crossbreds. Lamb deaths averaged 21% for Merino ewes and 15% for crossbreds and 19%, 22% and 20% for lambs from ewes that were mated to terminal, Merino and maternal sire types, respectively. Net reproductive rates were 82% for Merino ewes and 102% for crossbreds. From 3198 necropsies across 4 years, dystocia and starvation-mismothering accounted for 72% of lamb deaths within 5 days of lambing. Major risk factors for lamb mortality were birth type (single, twin or higher order), birthweight and dam breed. Losses were higher for twin and triplet lambs than for singles and there was greater mortality at relatively lighter and heavier birthweights. We conclude that reproductive rate in this AI program compared favourably with natural mating. Lamb birthweight for optimum survival was in the 4–8-kg range. Crossbred ewes had greater reproductive efficiency than did Merinos.K. G. Geenty, F. D. Brien, G. N. Hinch, R. C. Dobos, G. Refshauge, M. McCaskill, A. J. Ball, R. Behrendt, K. P. Gore, D. B. Savage, S. Harden, J. E. Hocking-Edwards, K. Hart and J. H. J. van der Wer