Selection and judging of the breeding stock are the first and foremost steps to start with any breeding programme. Appearance of the animal alone is not is not always a reliable guide to its breeding value as its appearance depends on the inheritance it has received from its parents and on the environment in which it grows up. It is, therefore, necessary to correctly estimate the breeding value of the individual which depends on the accuracy in selecting the animals as per the defined objectives.
a) Selection and judging of sheep for fine wool production
It should be true to the characteristics of the breed chosen. examples of fine wool breeds : Hissardale, Deccani-Merino, Avivastra, Nali and Chokla synthetics, Bharat Merino, Nilgiri synthetic and other crossbred types available in J&K, HP and hilly regions of UP.
i) Density of fleece (no. of fibes/sq.cm of skin surface)
ii) Staple length (>75mm is superior quality)
iii) Completeness of the covering (i.e. uniformity)
i) Fineness of fibre (diameter) : measured only under protein microscope/lanometer; at the field level, one can differentiate between coarse and fine wool by spreading the fleece on the body of the sheep.
ISI standards : ≤ 34.4µ : A grade
34.4-37.0 µ : B grade
37.1-40.0 µ : C grade
≥ 40.0 µ : D grade
ii) Medullation percentage : can only be adjudged under a lanometer; no field-level visual method
Fine wool : no medullation
Carpet wool : 10-20% medullation
iii) Staple/fibre length : ≥ 3.5 cm can successfully be processed on the worsted system
iv) Soundness : healthy and uniform growth of wool on the skin surface
i) Purity : judged by the absence of hair, kemp, black and dark fibres; in selection of sheep for fine wool production, due care should be taken to ascertain presence of only pure fibres, esp. in breeding stock
ii) Presence of foreign matter : this is a disqualification in grading of wool. Classification based on the extent of vegetable matter content:-
< 3% : Light burr
3-5% : Medium burr
>15% : Heavy burr
Apart from vegetable matter, fleece may be contaminated with dust and other matter. Though the contamination is mostly related to faulty management practices, but all the same, these are to be kept in view while selecting the animals.
iii) Amount and distribution of yolk : A yellow wool fat "yolk" which accumulates on the wool fibres as a protective layer making the wool more resistant to water and snow, is important in determining the condition of wool.
iv) Colour of the fleece : The colour of the wool should be white and any deviation from it is regarded as disqualification except for the entire colours which are required for some specific purposes. In grading of wool, the colur is given the weightage as tinged white (TW), light yellow (LY), heavy yellow (HY) and other colours in order of merit.
The method of selection to be applied directly depends on the genetic parameters of the characters and the population concerned. As most of the characters related to fleece characterization are highly heritable, their weighted heritability estimates in Indian breeds of sheep are as follows:-
Greasy fleece weight : 0.210 ± .050
Average fibre diameter : 0.453 ± .447
Medullation percentage : 0.661 ± .556
Staple length : 0.400 ± .050
· Since the heritability of these traits are moderate to very high, individual selection of sheep based on their own performance should result into their genetic improvement.
· Open-faced ewes have been reported to produce more lambs than ewes whose faces are covered with wool
· Selection of open-faced ewes adds to their productivity
· Based on the estimates of heritability and genetic and phenotypic correlations among body weights at different ages, six months body weight perhaps seems to be the best selection criteria for improving market weight (9-12 months body weight) and adult body size.
· For improving the quantity and quality of wool, an emphasis on combining the greasy fleece weight with a positive weightage and medullation percentage with a negative weightage would improve both the yield and quality of carpet wool.
· At the Central Sheep & Wool Research Institute, Avikanagar, emphasis was laid on selecting animals with greasy fleece weight of 2.5 kg, 22 µ diameter & no medullation for Avivastra, and 2.0 kg, 27 µ diameter & upto 20% medullation for Avikalin.
· Under the project on improvement of indigenous breeds of sheep for carpet wool by selection at the Division of Carpet Wool & Karakul Pelt Production, Bikaner, emphasis was laid on improving the Marwari breed to produce 2.0 kg greasy fleece weight per annum of 30 µ diameter and 20% medullation.
· Since the body and fleece weights are positively genetically correlated, the selection for the former should also improve the latter. The same stands true for staple length and fleece weight.
b) Selection and judging of sheep for mutton
The mutton type in characterized by a deep, wide, blocky body with symmetry, balance, breed character, thick fleshing, a strong constitution and quality. In selection of the mutton quality animal one should actually look for the carcass characteristics which are defined by the tenderness and juiciness of the mutton, high proportion of lean to fat, higher proportion of meat to bone ratio etc. Since these characteristics may not be known till the animals are slaughtered, the animal breeder has to depend on indirect measurements of such qualities.
- clean-cut, well-shaped head covered with fine wool
- bone of ample size and clean joints
- firm and evenly distributed flesh
- good, light, dense fleece
- symmetrically balanced body
The breeder should supplement the information by indirect judging with the information on full-sibs, for utilization in selection. Progeny testing of rams may also be useful. As mutton traits are highly heritable, individual selection should be used for fat lamb production.
c) Selection and judging of sheep for pelt production
Till 1975, there was no organized programme for lamb pelt production in the country. After the import of 250 Karakul sheep in 1975, experimental work under hot and cold arid conditions was initiated at CSWRI, Bikaner and Kumbhathang, near Kargil in Ladakh Dist. (J&K). The ¾ crossbreds of Malpura, Sonadi and Marwari with Karakul have produced pelts comparable with those of purebred Karakuls. Mature purebred Karakul lambs weigh 80-105 kg and ewes 60-75 kg. Wool is of low quality, coarse, brown/black in colour, and grades as carpet wool. The pelts taken from the lambs are usually classified as Broad tail, Persian and Caucasian.
Grades of the pelt should be given a primary weight in selection.
Traits of economic importance
a) Prolificacy : includes both regularity of lambing and the frequency of twinning. Twinning in sheep is generally more desirable because ewes that wean twins produce 15-18 kgs more lambs than ewes that wean only one lamb. But in areas where grazing conditions are very poor, twins may be a disadvantage.
b) Birth weight : As such birth weight is of little value except that it is related to vigour at birth and rate of gain.
c) Weaning weight : The age at weaning can vary according to the conditions under which the animals are reared, but 120 days has been taken as the standard. This measure, though taken individually, can also be used to express lamb production of ewes on a per head basis or per 100 kg ewe-weight basis, depending on conditions. Lambs can be weighed at 120 days age or in case they are weaned earlier, the weaning weights are corrected to 120 days age. This is done by multiplying the daily average weight gain with 120 and adding the product to the birth weight. Similarly, adjustment has to be made for twins and triplets as their weaning weights are likely to be less than that of singles, due to less availability of milk ad maternal care. Weaning weight may be adjusted to single-lamb-basis by for the purpose of valid genetic studies by multiplying the adjusted 120 day weight by the factors 1.0529 for twins and 1.0923 for triplets. Ram lambs and lambs of mature dams have been observed to have higher weaning weight.
d) Post-weaning gain in body weight : This is medium to highly heritable. Therefore, mass selection based on this trait can be effective. Annual or semi-annual weights of breeding stock will be quite useful if they are used to evaluate productivity in relation to body weight.
e) Type and conformation : Type and finish of lams at weaning reflect market value to a great extent. With sheep, attention should be given to wool characteristics in addition to mutton production and rate and efficiency of gains. Subjective appraisals of type through a system of scoring remains still the most popular means of evaluating these traits. Animals with defects such as wool blindness, skin folds, over-shot jaws, under-shot jaws, black wool shallow bodies etc. should be culled from the flock.
f) Carcass traits : Tenderness juiciness and good flavour are traits relished universally. In advanced countries, there is a preference for greater proportion of lean to fat. As carcass quality can be tested at present only by slaughtering the animal (thus making it unusable for breeding), the next-best method will be to measure these traits in close relatives like twins, full-sibs or half-sibs.
Salient features of a good milch goat :-
a) Head : It should be long and of moderate width, with a full and well-developed muzzle and prominent nostrils. It should be naturally hornless or disbudded. The head in the doe should be well carried and should bear a feminine appearance. The eyes should be large and bright, set well apart, indicating docility and some capacity for understanding.
b) Neck & shoulders : The neck should be long and slim, and of good depth, with the tassels, if present, evenly hung. The withers and the shoulders should be fine in appearance, and connect the neck with the body with little break in continuity. A considerable thickness in the shoulders or a drop immediately between the shoulder blades is undesirable.
c) Chest : This should be moderately deep and of good width, giving the appearance of strength without coarseness.
d) Forelegs : They should be straight, strong and possess good bone.
e) Feet : The animal should stand well on its legs without the tendency to “turn toes” or “walk on its heels”. The hairy growth covering the hoof should be kept trimmed to the ‘sole’ of the foot, leaving the latter bare underneath.
f) Body : Good depth is an important feature. It should drop in a gradual curve from the point where the abdomen unites with the chest, i.e. a little way behind the forelegs, and then rise slightly again to meet the udder. The back should be level from the shoulders to the hips and then drop slightly at the tail region. The hips are often slightly higher than the shoulder, but this need not be regarded as a defect. An excessive dip in the back, however, is highly undesirable. Plenty of length from the head to the tail is a desirable feature.
g) Ribs : The ribs should be well sprung so as to give a barrel effect; flat sides are a common fault. The abdomen should not be protruding beyond the width of the ribs, so that its roundness is not affected.
h) Hind-quarters : There should be sufficient width across the hips and the rump, and between the pin bone and the hocks. The hind-legs should face straight forward and not outward; the latter tendency is one of the commonest defects in goats resulting in the so-called ‘cow hocks’. There should be a slight rise from the back to the hips and a gradual drop from the rump to the tail. A sharp drop from the hips to the tail is regarded as a defect.
i) Hind-legs : Bones should give the appearance of strength with the hocks slightly bent. The pastern should be short, its joint showing no sign of weakness that might result in dropped pastern.
j) Udder and teats : The udder should be carried well under the body. When viewed from the side it should be in front of the hind-legs. It should be large, but its size should be proportional to the size of the goat. The skin of the udder is usually covered partly with fine, soft and pliable hair. The texture of the udder should be reasonably soft. Heavy milk production is associated with the amount of milk-secreting tissue. The udder should undergo considerable shrinkage after milking. Milk ducts and teats should be entirely free from hard lumps (indicating chronic inflammation), these being sometimes discovered only after milking. The teats should be quite separate from the udder with a distinct line of demarcation, point downward and slightly forward, and be of moderate length and of suitable size to be conveniently held in the hand during milking. Large milk-veins should be present under the belly and lead to the udder. These veins, although usually better developed in old goats, indicate superior milch quality. The shape of the udder in the Indian breeds varies considerably. The occurrence of four milking quarters, all lending themselves to being used in milking, is not uncommon in Jamunapari goats.
k) Skin and hair : The skin should be soft, supple and loose. The coat varies in different breeds, but is generally glossy, with fine, short hair.
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Disclaimer : The information on this site is meant as an aid to students and fellow veterinarians and should be used for educational purposes only. The views expressed are solely that of the author and should not be construed to be that of his employer or any other organization.