Genetics of fibre production and fleece characteristics in small ruminants, Angora rabbit and South American camelids

Nowadays, the fibre diameter (FD) is considered the main selection objective in alpaca populations all over the world. International Committee for Animal Recording recommendations define the FD and its CV as the first two traits to be considered in breeding programmes for this specie. In addition to these main criteria, other selection criteria of economic value used are comfort factor (CF) or standard deviation (s.d.); also other less important traits being used as selection objectives are these morphological traits: density (DE), crimp (CR) or lock structure (LS) for, respectively, Huacaya (HU) and Suri (SU) ecotypes, head (HE), coverage (CO) and balance (BA). The goal of this study was to establish how to implement a combined selection index starting from genetic parameters and to study the expected correlation between genetic trends by considering different alternative procedures of weighting all the involved traits, and the consequences of a wrongly proceeding way. Heritabilities and genetic and phenotypic correlations were estimated from the data set belonging to the PACOMARCA experimental farm for SU and HU. Two approaches were used to check the consequences of a set of subjective weights essayed. The coefficients of selection indexes were obtained for two sets of reference weights. In addition, equivalent weights were drawn if applied those reference values as coefficients of hypothetical selection indexes directly on phenotypes; relative expected genetic responses were computed in different cases. Results showed that almost in all cases for both ecotypes, the weight applied to CF should be surprisingly negative. Concerning genetic responses, only CO was compromised in some cases for the HU ecotype. The essayed methodology allowed explaining the differences between ecotypes in the genetic trends. The proposed methodology was shown to be effective to study the relative importance of the traits granted by the manager of a breeding scheme.

Section: Introductionmentioning

confidence: 99%

Weighting fibre and morphological traits in a genetic index for an alpaca breeding programme

Gutiérrez

Cervantes

Pérez-Cabal

et al. 2014

“…For example, pelage secondary follicles of Merino sheep or Angora goats, which are essentially single-coated, may retain activity for 2 years or longer which contrasts with 6 months or less for the doublecoated cashmere-bearing animal (e.g. Allain and Renieri, 2010). Anagen is followed by a short catagen phase which features cessation of proliferation, apoptosis of the lower portion and shortening of the follicle and retention of the hair in a keratinised 'club end'.…”

Section: General Properties Of Integumental Tissuesmentioning

confidence: 99%

“…The numbers, types and activities of hair follicles and physical characteristics of fibres in different genotypes of South American Camelids have been described (Antonini, 2010). In addition, the paper of Allain and Renieri (2010) has evaluated aspects of quantitative and molecular genetics relating to properties of follicles and fibre. Traits of economic importance considered included yield, quality and colour.…”

Section: General Properties Of Integumental Tissuesmentioning

confidence: 99%

Fundamental hair follicle biology and fine fibre production in animals

Galbraith

2010

Hair 'fine' fibre is an important commercial product of farmed and certain wild animal species. The fibre is produced in follicles embedded in skin. These have properties in common with other tissues of the integument and have importance in determining yield and quality of fibre. Means of understanding and improving these characteristics are informed by knowledge of integumental and follicle biology. This paper reviews contemporary information that identifies the major fibre-producing species and their production characteristic. It surveys knowledge describing fundamental biology of the integument and considers information derived for the hair follicle from studies on a number of species including genetically modified mice. It identifies the composition of the follicle and describes components and interrelationships between epidermal hair-fibre producing epidermis and fibroblastand connective tissue-containing dermis. The structure of different primary and secondary follicle types, and associated structures, are described. Focus is given to the alterations in anatomy and in behaviour from active to inactive state, which occurs during the hair follicle cycle. Information is provided on the anatomical substructures (hair medulla, cortex, cuticles and supporting sheaths and dermal papilla), cellular and extracellular composition, and adhesion and chemical signalling systems, which regulate development from the early embryo to post-natal state and subsequent cycling. Such signalling involves the dermis and its specialist fibroblasts, which secrete signalling molecules, which along with those from local epidermis and systemic sources, largely determine structure and function of epidermal cells. Such chemical signalling typically includes endocrine-, paracrine-, autocrine-and juxtacrine-acting molecules and interactions with their receptors located on cell membranes or intracellularly with transduction of message mediated by transcription factors at gene level. Important hormones and growth factors and inhibitors regulating morphogenic and/or mitogenic activity are identified. These mediate mechanisms associated with presence or absence in skin and development of patterning for primary or secondary follicles. Reference is made to deposition of individual keratins and keratin-associated proteins in follicle sub-structures and to fibre properties such as length, diameter, medullation, crimp and lustre. Pre-and post-natal regulation of pigmentation by melanocytes is reviewed. Brief attention is given to genomic and non-genomic variation and impact on the phenotypes expressed and the role of regulatory gene products as potential molecular markers for selection of superior animals. The importance of nutrients in providing substrates for follicular structures and enzymes and in molecules facilitating gene expression is also considered.

“…In SAC, artificial selection has produced domestic genotypes differing in hair follicle morphology (Allain and Renieri, 2010). These include the Suri and Huacayo genotypes of alpaca that differ in follicle number, the ratio of primary/secondary follicles and the occurrence of natural shedding (Antonini, 2010).…”

Section: Artificial Selectionmentioning

confidence: 99%

“…goats, camels, South American camelids (SACs) and yak). The artificial selection resulted in marked changes with regard to follicle number, type, distribution, growth and even natural shedding (Allain and Renieri, 2010;Antonini, 2010;Galbraith, 2010a). The impact of these genetic manipulations on the adaptation and acclimatisation of the animals is not completely understood.…”

Section: Introductionmentioning

confidence: 99%

Relationships between integumental characteristics and thermoregulation in South American camelids

Gerken

2010

Hair fibre is regarded as a unique mammalian feature with an important role for endothermy. Artificial selection for hair characteristics resulted in marked changes with regard to follicle number, type, distribution, growth and natural shedding. This review focuses on the fine fibre-producing South American camelids (SACs) and the relationship between their hair coat and thermoregulation. SACs have developed several special integumental characteristics. While the hair coat of the wild lamoids vicuñ a (Vicugna vicugna) and guanaco (Lama guanicoe) is formed by two types of hair (the coarse outer guard hairs and a finer undercoat), the domesticated llamas (Lama glama) and alpaca (Lama pacos) exhibit variably double coat and predominantly single coat, respectively. The distribution of the hair coat across the body is not homogenous. Thermal windows with shorter hair or thinner skin can be identified at the ventral abdomen, axillary space and inside of the thighs (about 20% of the skin), thus allowing to modulate heat dissipation. In contrast to sheep wool, lamoid fibres are mainly medullated. The thermal conductance of summer pelage was higher than that of the winter fleece and highest for the axillar and lower flanks. Lamoids have developed behavioural strategies to modify heat loss by adopting specific postures according to ambient conditions by closing or opening the thermal windows. Energy savings of 67% attributed to posture were calculated. SACs have shown to be able to adapt to a broad range of different climatic conditions. The specific integumental characteristics of SACs indicate that they have developed adaptation mechanisms particularly suited for cooler climates. Accordingly, hyperthermia might become a problem in hot, humid areas outside of their original habitat. Several studies showed the beneficial effect of shearing against heat stress. In particular, fertility in males exposed to heat stress may be improved by shearing. Infrared thermography reveals that in shorn animals the heat is radiated across the entire body surface and is not restricted to the thermal windows. However, shearing also changes the conditions of the protective layer, resulting in a loss of thermal conductance that may result in adverse effects when animals are kept under cold temperatures. The length of residual fibre appears to be crucial in avoiding excessive heat loss in a cold environment, as demonstrated by shearing experiments with different shearing machines. There is, therefore, potential for welfare considerations to conflict with industrial demands for fibre length or homogenous quality.