Sheep Production

Original Version

This module includes 22 topics.

Associated PPT files are available and can be download as a compressed archive – WOOL-412-512-08.

Topic 01: Profile of the Australian Sheep Industry

This topic will introduce the key factors that characterise the Australian sheep industry including the environments in which wool is produced, the different enterprises responsible for wool production and their relative contributions to the industry, historical and current trends in sheep population and wool production and state and regional differences in sheep and wool production. On completion should be able to:

  • articulate your understanding of the Australian environments in which wool production is undertaken, specifically rainfall patterns and how these influence pasture growth and composition;
  • describe the range of Australian wool-producing enterprises, including the difference between specialist woolgrowers and mixed enterprises, the determinants of farm income from wool, the major production costs and the variation that exists in farm productivity and profitability between individual farms within a district; and
  • use your understanding of the productivity of the Australian wool-growing industry in terms of product quantity and quality, including state and regional differences as well as features of the national sheep population (genotypes, spatial distribution and age structure) to analyse information and justify informed decisions.

Topic 02: Fleece Weight and its Component Traits

This topic will give you an understanding of the factors that contribute to fleece weight and yield and how the contribution of each differs within and between fleeces as well as discussing how some of the component traits are measured. On completion you should be able to:

  • describe and quantify the relationships between fleece weight, washing yield and the non-fibre components of the fleece;
  • explain the relationship between clean fleece weight and its component traits;
  • describe the sources of variation and within-fleece gradients in the fibre and non-fibre components of the fleece;
  • justify the merits of the mid-side region of the fleece for flock testing purposes; and
  • identify non-genetic factors that may introduce bias into selection decisions based on fleece weight and its component traits.

Topic 03: Fibre Diameter, Staple Strength, Style, Handle and Curvature

This topic will discuss the economic importance of and sources of variation in fibre diameter, staple strength, style; handle and curvature. On completion of this topic you should be able to:

  • demonstrate an understanding of fibre diameter and the economic importance of fibre diameter;
  • explain and calculate the difference between the standard deviation of diameter and the coefficient of variation of diameter;
  • define the relationship between mean diameter, diameter variation and “coarse edge” or “prickle”;
  • measure staple strength and describe its economic importance;
  • explain the sources of variation in staple strength within a mob of sheep;
  • describe localised vs generalised fibre weakness as determinants of staple strength;
  • define and quantify the relationship between staple strength and each of minimum diameter, along-staple diameter variation, rate of change in diameter, fibre length variation and intrinsic fibre strength;
  • relate raw wool style including the main component traits to economic importance;
  • explain the influence of fibre diameter and fibre crimp on wool handle; and
  • describe fibre curvature and the value of curvature.

Topic 04: Wool Colour and Fleece Rot

This topic describes greasy colour of fleece wool on the sheep in the context of two types of unscourable discolourations that develop under certain conditions of moisture, temperature and bacterial activity, namely yellow discolouration and fleece rot. The economic impact of unscourable colour on fleece value is presented. The processes involved in the development and the measurement of yellow discolouration and fleece rot are described, with factors associated with resistance to yellow discolouration and fleece rot identified.

On completion of this topic you should be able to:

  • explain the economic importance of wool colour and measurement of wool discolouration and fleece rot;
  • articulate and document the processes involved in the development of yellow wool discolouration; and
  • discuss the importance of factors associated with resistance to yellow wool discolouration describe the development of fleece rot and discuss the factors associated with resistance to fleece rot.

Topic 05: Contamination – Dark and Medullated Fibres and Vegetable Matter

Dark fibres can be a fault in white or pale dyed products while medullated fibres can be objectionable in dyed products, with such faults leading to the rejection of or costly repairs to the product.

Vegetable fault (or vegetable matter – VM – contamination) refers to any particles of plant material present within greasy wool. When present, vegetable fault incurs a price penalty in the market place. The price discounts imposed depend on the amount and type of VM present.

On completion of this lecture you should be able to:

  • discuss the relevance of dark and medullated fibre contamination in wool;
  • describe some of the procedures used to detect and describe these fibres in white wool;
  • document the main origins of dark and medullated fibres and the economic implications;
  • justify practices implemented to prevent or control occurrences of dark and medullated fibres and the opportunities for improvement;
  • document the causes of Vegetable Contamination (VM);
  • calculate how VM is measured;
  • describe the effect of VM on wool processing;
  • describe the economic importance of VM;
  • list and describe the plant species causing VM problems;
  • illustrate your understanding of the strategies which can be employed to reduce VM; and
  • plan management strategies in a sheep management system to reduce VM problems.

Topic 06: Lamb and Mutton Markets

The lamb industry in the 21st century is a modern, versatile and ‘trendy’ industry that has undergone major changes in the last decade to provide consumers with a quality product that offers versatility, value for money and an enjoyable eating experience.

On completion of this topic you should be able to:

  • Understand the significance of the Australian sheepmeat industry;
  • Improve your knowledge and skills in producing lambs and sheep to market specifications;
  • Incorporate new knowledge and skills into your sheepmeat production system;
  • Understand the reasons why Australia has a live sheep trade with other countries and why at various times this is controversial;
  • Recognise customer requirements dictate the existence of the trade in parallel with the export carcase trade;
  • Explain why feeder lamb systems are being developed;
  • Recognise the benefits of breeding feeder lambs;
  • Know how to breed feeder lambs;
  • Be aware of the benefits for the specialist lamb finisher;
  • Understand the benefits of breeder/finisher alliances;
  • Appreciate the difficulties in developing alliances;
  • Know the different specifications required for a grass and feedlot finishing system;
  • Have skills in describing live weight and fat score of the live animal and how they meet a market specification;
  • Be able to calculate dressing percentage of sheep and lambs;
  • Understand how improving quality assurance in production systems increases the number of sheep and lambs meeting market specifications; and
  • Gain an understanding of the management factors that will improve returns from lamb and sheep skins.

Topic 07: Sheep Health

Disease is one of the major environmental factors, like nutrition or climate, which markedly influences the efficiency of sheep production for wool or meat. This lecture introduces you to the major disease challenges facing sheep and the mechanisms by which they influence sheep productivity and welfare. The lecture will then consider internal and external parasitic disease of sheep in considerable detail.

On completion of this topic you should be able to:

  • describe the major disease challenges faced by sheep during their lifecycle and the reasons why these challenges occur when they do;
  • discuss the impact of disease on sheep productivity and underlying mechanisms for this; and
  • describe and quantify the impact and discuss the management of disease caused by internal and external parasites of sheep.

Topic 08: Managing Weaners and Breeding Ewes

It is well documented that young sheep produce less wool, often of higher quality, than adult animals. The higher quality is associated with finer fibres but there are also other aspects of the fleece that need to be considered. In many environments around Australia young Merino sheep are also perceived to be extremely sensitive to environmental effects on fleece quantity and quality; this being particularly true in the Mediterranean environments. In these environments patterns of food availability and quality appear to impact on young animals in a way that is not so apparent in the temperate areas.

Wool growth and staple strength has also been reported to decline as a result of pregnancy and lactation and this has been associated with both the high nutritional demands of this physiological state and also with hormonal changes. The impact on farm income of this decline could be considerable particularly due to changes in wool quality associated with loss in staple strength. It has been estimated that of the ‘tender’ combing wool (<30 N/ktex) produced in WA, over 40% is derived from the breeding ewes; the impact being somewhat less in temperate climate zones.

On completion of this topic you should be able to:

  • demonstrate a clear appreciation of the extent of the impact of age, season, pregnancy and interactions with nutrition on liveweight and fibre growth;
  • explain how hormonal mechanisms contribute to the effects of age, pregnancy and lactation on wool;
  • describe and justify management strategies that can be used to minimise the impact of age, pregnancy and lactation on wool growth and quality; and
  • compare and contrast management choices that can be made to modulate wool production and quality in young and/or pregnant sheep.

Topic 09: Managing – Finishing

Growing lambs require a balance of energy and protein in their diet for optimal growth. In some situations lambs will have to be fed supplements with the intention of maximizing lamb growth to achieve target market specifications.

Sometimes it may be more economic to allow slower growth rates and have lambs reach target weights when prices are higher.

At the end of this module the learner will be able to:

  • Understand why protein and energy requirements change during life of the lamb;
  • Explain the difference between supplementation, substitution and complementation when feeding lambs;
  • Describe non-nutritional issues that affect lamb performance and their management; and
  • Discuss finishing options for lambs used in the Australian lamb industry.

Topic 10: Husbandry Calendars, Precision Sheep Management and Benchmarking

Setting up a profitable husbandry calendar is not a simple task. It involves assessing the resource base of the farm and juggling management events to get the optimum compromise between conflicting needs of pastures, animals, financial resources and labour. There is no one right answer as to what would be the most profitable husbandry calendar, however there are some guiding principals that will allow the manager to set up that calendar within the resources allocated.

Other topics within the course will deal with specific issues within the whole system, however the focus of this topic is to provide a framework by which new and existing technologies can be assessed, and then either accepted or rejected in designing the system for the farm in question. In order to do this the manager must be able to prioritise the different components of the production system according to those that have the most influence on profit. These have been identified through benchmarking.

On completion of this topic you should be able to:

  • define what drives profitability in sheep enterprises;
  • use the key principals that will enable prioritisation and organisation of management events in order to achieve the most profitable compromise for a farm; and
  • describe the role of technologies that allow precision sheep management.

Topic 11: Genetics of Fleece Weight and Fibre Diameter

This topic provides a background on Merino breeding including the structure of the ram breeding industry and a summary of the history of Merino breeding research in Australia. You will also be introduced to some basic animal breeding principles and definitions as well as relevant genetic parameters. Students with no prior knowledge of this material should access a basic text on the subject.

The second half of the topic is devoted to the specific issue of genetically improving the quantity and fibre diameter of wool produced by Merino sheep to achieve increased profits from wool production enterprises.

On completion of this topic you should be able to:

  • demonstrate a broad understanding of the history of Merino breeding and genetics research in Australia;
  • apply knowledge of the repeatability and heritability of a range of economically-important production traits, as well as the genetic correlations between some of these traits;
  • explain the breeding objectives and selection strategies employed within the stud industry;
  • explain the roles of WOOLPLAN and RAMPOWER in design and implementation of industry genetic improvement programs;
  • describe the economic importance of fleece weight and fibre diameter and explain why these two traits should be given high priority within breeding objectives;
  • explain the potential for identifying individual bloodlines to achieve genetic improvement in fleece weight and fibre diameter, even though these two traits are genetically antagonistic at the bloodline level;
  • explain the potential for identifying individual animals within a flock to deliver genetic improvement in fleece weight and fibre diameter, even though these two traits are genetically antagonistic at the within-flock level;
  • describe the value of performance records, pedigree information, adjustments for environmental ‘penalties’ and index selection in improving the accuracy of selection; and
  • describe the Trangie QPLU$ selection lines, demonstrating simultaneous improvements in fleece weight and fibre diameter.

Topic 12: Genetics of Staple Strength, Style and Skin-based Selection

Fleece weight and fibre diameter are the two most important wool production traits affecting income. However, secondary wool quality traits such as staple length, staple strength and style also contribute to the commercial value of wool, especially for producers of fine and superfine wool types.

This topic focuses on the potential to make genetic improvements in staple strength and style. Different methods of selection that are used to achieve genetic potential, such as objective measurement, traditional classing and skin-based selection, will be discussed in the last section on breeding methods.

On completion of this topic you should have:

  • an understanding of inheritance of staple strength in both young and mature Merino sheep in different environments;
  • an understanding of potential consequences for staple strength of breeding programs emphasising a reduction in fibre diameter;
  • an understanding of potential for the coefficient of variation of fibre diameter as cost effective and indirect selection criterion for improving staple strength;
  • an understanding of inheritance of measured and visually assessed style traits;
  • an understanding of potential consequences for style traits of breeding programs emphasising improvement of fleece weight and fibre diameter;
  • an understanding of skin-based traits and how they correlate with economically important production traits;
  • an understanding of the potential value of incorporating skin-based traits into a breeding program;
  • an understanding of soft rolling skin type and its potential value as a selection criterion; and
  • an awareness of the South Australian Merino Selection Demonstration Flocks.

Topic 13: Genetics of Disease Resistance

This topic describes the genetics of the major diseases that affect Merino sheep production in Australia and approaches to breeding for resistance to these diseases: nematodiasis (the effects of gastrointestinal roundworms), flystrike (and its major precursor fleece rot) and footrot. Other diseases are significant, such as Johnes disease and brucellosis, due to substantial effects in individual sheep flocks that may occur and restrict movement and trade in livestock and their products. However, due to a lack of genetic studies, these diseases are not covered in this lecture.

On completion of this topic you should be able to:

  • define measures of resistance to sheep diseases: disease resistance, resilience, reduced treatment costs approach;
  • explain the heritability of resistance to some major sheep diseases in Australia: gastrointestinal roundworms, flystrike, fleece rot and footrot;
  • describe the genetic relationships among disease resistance traits and between the disease resistance traits and production traits • articulate the considerations involved in incorporating disease resistance traits into a breeding objective;
  • describe the potential to use variation in disease resistance between strains and bloodlines within the Merino breed; and
  • explain the potential use and benefits of genetic markers to identify disease resistant sheep.

Topic 14: Genetics of Bodyweight and Reproduction

The genetics of bodyweight and reproduction is core information necessary for anyone wishing to genetically improve their flock for either meat or wool production. This topic outlines the key animal characteristics associated with body size and reproductive events, and the genetic parameters (heritability and genetic correlations) for these traits. There is also some discussion of the primary environmental effects likely to be of significance and then finally a section dealing with the application of this information in industry.

On completion of this topic you should be able to:

  • explain the inheritance of body weight and reproductive characteristics in sheep;
  • describe the main environmental factors likely to alter the ranking of the main reproductive and growth characteristics; and
  • demonstrate how inheritance information can be applied in sheep selection indices such as EBVs and explain what responses are possible through appropriate selection.

Topic 15: Genetics of Growth and Carcase Specifications

This topic outlines the importance of growth, fat and muscle to lamb profitability and in meeting carcase specifications for target markets. Variation between breeds and crossbreeding types is illustrated. The concept of heritability and genetic variation for growth and carcase traits is introduced. Genetic evaluation of animals and the national program (LAMBPLAN) are outlined together with the concept of estimated breeding values (EBVs) and indexes for evaluating the genetic merit of animals. Research results are presented that show EBVs really do work with high EBV rams producing on average higher performing progeny. The use of EBVs to select appropriate rams to produce lambs for which a high proportion will meet varying target market carcase specifications is illustrated. While the focus is on selection of the best ram it is important to remember that the sire only contributes half the genes to the lamb for growth and carcase traits and the dam contributes the other half. The genetic merit of the ewe flock can have a large impact on growth and carcase traits of lambs which is highlighted by recent research results. Finally, the factors affecting the additional value of a ram with high EBVs are outlined along with an example of the calculation of the $ value.

On completion of this topic you should be able to:

  • describe the importance and genetic variation of growth and carcase traits in lamb production;
  • explain LAMBPLAN and justify the traits with genetic information available;
  • compare estimated breeding values (EBVs) and LAMBPLAN indexes;
  • discuss how this information can be used to select rams to achieve improved growth and carcases in commercial lambs;
  • describe the genetic contribution of the ewe flock to growth and carcase of lambs; and
  • explain the calculation of the $ value of EBVs.

Topic 16: Grazing Management

There are principles of grazing management and, because grazing management usually has linkages to virtually every aspect of farm management, the inter-relationships are complex. This topic highlights those principles which have been discovered in research and also applied by graziers. There is no absolute answer to questions about grazing management. The central conundrum of grazing management is, “how do you match the conflicting needs of a pasture which grows variably in response to climate with the more or less constant needs of the grazing animal without destroying the natural plant and soil resources which support livestock enterprises” .

On completion of this topic you should be able to:

  • demonstrate a thorough understanding of grazing management concepts and the science behind grazing management principles;
  • discuss relevant literature relating to grazing management and sustainability;
  • access and utilise recent research and extension efforts describing sustainable grazing systems and recognise the difference between anecdotal claims and objective evidence; and
  • Understand some of the important differences in the capacity of different pasture species to support sustainable wool production and the important influences of fertiliser, stocking rate and grazing management.

Topic 17: Lamb and Wool Production from Perennial and Annual Pastures

Pasture management (i.e. how to improve pasture productivity and sustainability) and grazing management (i.e. how to improve the efficiency of utilisation of pastures to achieve sustainable animal production targets) are critical considerations in the strategies underpinning a profitable wool production enterprise and both topics have been dealt with in Topic 16 – Grazing Management.

As the strategies available to woolgrowers depend on the environment, a distinction is usually made between perennial and annual pastures but both will be discussed in this topic emphasising particularly the impact of the different systems on wool production.

On completion of this topic you should be able to:

  • understand the dynamics of annual pastures and the implications for sheep production;
  • understand of the influence of stocking rate on the productivity of annual pastures and on the sheep grazing them;
  • understand the potential value for grazing strategies such as autumn deferment, intensive spring grazing and strip grazing to accommodate the seasonality of annual pastures used for wool production;
  • understand of the influence of stocking rate on wool production per head and per hectare;
  • understand the role of native and introduced perennial grass species in sheep production in Northern NSW;
  • understand the focus given to stocking rate and fertiliser application rate for perennial pastures used for sheep production in southern Victoria; and
  • appreciate the different approaches to pasture and grazing management used by sheep producers.

Topic 18: Sheep Production in Semi-arid Rangelands

Rangelands are semi-natural ecosystems in which woolgrowers seek to obtain a productive output by simply adding sheep to a natural plant community in which native animal populations, although modified, intermingle with sheep. Management is therefore predominantly ecological in nature, of a low energy input and involves actions that seek to modify, rather than control, the natural forces operating on the system. Climatic forces exert a greater influence on productivity compared to management.

Selection of stocking rate is the most important rangeland management decision for the sheep enterprise. Managers can maintain or improve the condition of pastures by adjusting stocking rates at critical times although other remedies such as fire, or mechanical disturbance, may be available. The appropriateness of various management strategies depends on the rangeland community to be managed. This requires a specific knowledge of the species to be managed.

On completion of this topic you should be able to:

  • describe the diverse nature of the rangelands utilised for sheep production;
  • analyse and discuss the impact of grazing pressure on botanical stability of rangeland communities;
  • justify the need to manage the total grazing pressure exerted by sheep and other competing herbivores within the rangelands environment;
  • explain the importance of maintaining the botanical stability of specific rangelands communities and the role of various management tools; and
  • describe the differences that exist between various rangelands communities in their response to grazing pressure and other systems of manipulating botanical composition.

Topic 19: Sheep Production in Mediterranean Environments

The ‘classic’ Mediterranean environment is one characterised by wet cool winters and dry hot summers. Autumn and spring are transitional between these extremes. Rainfall, although in many cases low by annual comparisons with others sheep producing regions, is relatively reliable and largely (of the order of 85%) confined to the cooler months. The net outcome of this, with lower evaporation, is the potential for a considerably more effective rainfall, and hence the growth of a range of adapted pasture grass and legume species. The distinctive features of such an environment and the agricultural systems commonly practised are discussed in some detail in this topic.

On completion of this topic you will, for Mediterranean climatic regions in Australia:

  • Understand the distribution and characteristics;
  • Be aware of the pasture growth characteristics;
  • Be aware of whole-farm considerations of key farming systems;
  • be aware of eed sources for sheep other than pastures, in particular those associated with crop residues; and
  • Understand the impact of these factors on wool growth.

Topic 20: Dry Year Management and Supplementary Feeding

Regular seasonal supplementary feeding is relatively easy to manage and various principles and options are discussed as part of this topic. The challenges and planning are far more difficult when dry periods are longer than expected and when pastures and conserved feed starts to run out – a condition referred to ‘drought’. Drought can be defined as a period of below average rainfall that exceeds expectation and planning. However drought occurs sufficiently often in most parts of Australia for regular appraisal by policy-makers as to whether it is an exceptional condition, inappropriate land use or poor planning. This topic deals with strategies for planning for, and managing, ‘drought’.

By completing this topic, you should have an understanding of the following aspects of drought management and supplementary feeding. You should be able to:

  • discuss planning and managing sheep production in expected and unexpected dry periods;
  • justify your selection of strategies for the sheep producer in times of drought;
  • explain your design and implementation of a program of supplementary feeding;
  • discuss animal welfare and productivity;
  • evaluate using crop residues for animal production; and
  • apply your knowledge to practical aspects of supplementary feeding – what nutrients are needed and when to start feeding, selecting the most appropriate supplement, how much to feed, feeding methods and when to stop.

Topic 21: Diet Selection and Feeding Behaviour

What motivates animals to eat and dictates what it eats and how much it consumes is a growing area of science and involves complex interactions between animals and with animals and their environment. In this topic we cover some of the principles that determine the choices of foods sheep make and the factors influencing how much is consumed. Essentially we can summarise these under broad headings namely: where to eat, what to eat, when to eat and how much to eat.

On completion of this topic you should be able to:

  • explain the key factors influencing feeding areas chosen by sheep;
  • describe the factors contributing to diet selection;
  • compare and contrast factors limiting total feed consumed; and
  • explain the processes that determine choices between pasture species and between pastures and other feeds (supplements).

Topic 22: Mineral Nutrition

The focus of this topic is the dietary mineral requirements of sheep. About 20 minerals are ‘essential’ for the animal, i.e. they must be ingested or the animal will not survive.

A mineral deficiency (generally due to sub-optimal gut uptake of a particular mineral) can lead to reduced production before any clinical signs appear and it is often the worry that a hidden problem could be eroding profitability that motivates producers to use mineral supplements.

it is important to weigh up the evidence carefully before providing sheep with mineral supplements. You should base your decision on experimental results from grazing trials (not pen-feeding studies) under soil and fertiliser conditions that are likely to apply to your situation. In practice, only a few of the 20 or so essential minerals are likely to affect sheep production. This topic focuses on the minerals most likely to be important in the nutrition of sheep in Australia.

On completion of this topic you should be able to:

  • articulate the macro-and micro-minerals of importance in sheep production;
  • describe the major roles of each mineral associated with nutritional disorders of sheep;
  • explain how the animal, plant and soil factors alter mineral requirements of sheep;
  • explain which minerals are most likely to limit wool production in grazing or grain-supplemented sheep and justify your explanation;
  • calculate and explain the characteristics of the animal response curve to tissue mineral supply;
  • explore alternative hypotheses when analysing whether or not mineral deficiencies or toxicities are likely to be affecting sheep production;
  • articulate why mineral supplementation is likely to be justified economically; and
  • justify your recommendations for practical solutions to overcoming identified mineral deficiencies or toxicities.