Value of data from ram breeding flocks as an industry reference population for Australian sheep

This study examined the value of using carcass data from seedstock ram breeding flocks to build upon an industry sheep reference population in Australia. Data from 995 lambs managed in 15 commercial ram breeder flocks were collected between 2017 and 2020 for carcass and meat quality measurements: hot carcass weight, tissue depth on the 12th rib (GR site), eye muscle depth, fat between the 12th and the 13th rib (C - site), intramuscular fat and shear force. Industry data were cross-validated with and without reference data from the MLA Resource Flock. Industry data did not bias the estimation of breeding values when used in combination with the reference population (MLA Resource Flock). Therefore, industry data can be used to expand an industry reference population if data collection is accurate and consistent with industry standards

Using historic data to understand the cost of an extra condition score in sheep

Below optimum body condition in sheep is associated in its extreme with death due to malnutrition and at lesser levels with reduced reproduction and productivity. Producers who need to increase ewe body condition are forced to change their management practices to increase feed available, which comes at a cost. A long-term solution is to breed for a ewe that is better able to meet the body condition targets of the production system. An industry led desire within maternal and Merino based sheep operations is to increase genetic condition within the breeding objective and this requires an understanding of the bio-economic value of body condition in adult ewes specific to each production system

Evolution of sheep breeds within LAMBPLAN and the rise of the Composites

The LAMPLAN – Terminal and Maternal analysis are large and contain multiple breeds. Over the last 20 years there has been an increase in cross breeding in seedstock flocks and thus the number of composite animals in these analyses, especially in the Maternal analysis and an overall reduction in the number of breed pure animals. The increase in crossbred animals will require some development to ensure that breed and heterosis effects are being modelled accurately. Further use and reporting of breed composition via genomics and pedigree methods should be considered. However, composite animals provide the comparisons needed for an accurate multibreed LAMBPLAN analysis allowing selection of animals across breeds for the industries diverse needs

Fibre diameter variation as a measure of resilience in sheep

The ability to select sheep which have a greater capacity to overcome environmental fluctuations
 is topical given the severity of climatic events, labour shortages and increased productive demands
 (lamb, meat and wool). In this paper, we review the possibility of using variation in fibre diameter
 (FD), measured along the wool staple as an indicator of how sheep respond to the fluctuations of
 their environment

Improve your social license - Breed sheep for disease resistance

Consumer interests in the health and welfare of animals has increased as production systems become more transparent. This brings about a need for cultural change around how the industry approaches the long-term management of disease traits. Genetic tools have been used by leading sheep breeders for decades to bring about genetic gain in production traits. The same approach can also be applied to breeding for good health and welfare. This paper provides a summary of the steps required to develop long-term solutions to diseases outbreaks allowing sheep producers to breed for disease resistance and improve the social license for the agricultural industry

Genetic associations between ultrasound and carcase muscle dimension measures in sheep

This study investigated the genetic relationship between eye muscle width and depth recorded via ultrasound on live animals and on carcases in two populations of Australian and New Zealand sheep. Genetic correlations between ultrasound and carcase muscle dimensions were estimated within populations. Carcase eye muscle dimensions have sufficient genetic variation to be included in sheep breeding programs. Genetic correlations between carcase eye muscle depth (CEMD) and width (CEMW), and between CEMW and ultrasound eye muscle depth (PEMD) in Australian sheep were lower than expected. On the other hand, high genetic correlations were observed between ultrasound depth and width recorded in different ages on New Zealand Merinos. These differences indicate further research about CEMW is required and the implications of current selection practises has on carcase eye muscle dimensions

Season and reproductive status rather than genetics factors influence change in ewe weight and fat over time. 3. Analysis of Merino ewes

Published: 22 April 2014The profitability of southern Australian sheep production systems depends on the optimisation of stocking rates by meeting the nutritional demands of the breeding ewe while effectively utilising grown pasture. The aim of the study was to evaluate the genetic variation in liveweight and body condition of Merino ewes across their breeding life within a wool-based enterprise. The results were consistent with findings in crossbred ewes and showed that the genetic component of weight and body condition remained constant across the production cycle and age. The overall additive genetic effect accounted for 92% of the genetic variation in weight of Merino ewes bred across five production cycles. A genetic correlation of 0.85 suggested that ewes that were superior at maintaining their condition when rearing a single lamb would maintain this superiority when rearing multiple lambs. To improve weight and condition of Merino ewes during the ‘tough’ times, when nutrient requirements are not met by the pasture, selection can be made at any time and this will result in increased genetic condition at all times.S. F. Walkom, F. D. Brien, M. L. Hebart, N. M. Fogarty, S. Hatcher and W. S. Pitchfor

Is sex determination in Merinos heritable?

This paper investigates the ability of different linear mixed models to estimate the heritability of sex determination in a sub-set of the Australian Merino population. The dataset used was from Centre Plus Merinos in central-west New South Wales with 25 plus years of full pedigree collection and over 20,000 lambing events where the sex of the progeny were recorded. This study used sex of a lamb as a trait, (i.e. zero phenotype for female and one phenotype for male). We observed a significant, yet normal, amount of phenotypic variation in the sex ratio of progeny for dams, sires, maternal grand sires and maternal grand dams. However, no model was able to estimate significant genetic variation in sex determination and failed to return a heritability above 0.01. Consequently, it can be concluded within this dataset that it would not be possible to select to alter sex determination in Merinos