Introduction

The rural economy of developing countries will be improved only by breeding and development of superior breeds of sheep for wool and mutton. Wool production in India is inadequate. Hence, to meet the increase in demand for apparel wool India imports more than 20 million kg of wool every year. This predisposes an increase in the production of fine wool as well as carpet wool from the indigenous sheep.

The wool quality determines the use of wool for various purposes by the industry, as the properties of the yarn or fabric depend on a complex interrelation between the fibre arrangements and fibre properties (Chopra, 1990).

Shrinkage percentage is an important trait determining wool quality in sheep. This trait is affected, both by genetic and non- genetic factors with varying degree. Hence, an attempt was made to determine the effect of breed group, age, period of birth, season of shearing and sex on staple length.

Materials and Methods

Wool samples were collected from Bannur (n=68) and UAS-improved strain (n=120) maintained at UAS campus, Bangalore. Wool samples(n =608) were also collected from Bannur(n=69), Rambouillet X Deccani (n=56), Corriedale X Bannur(n=76), Corriedale X Deccani (n= 122) and  Deccani(n=97) before shearing at the left side region at Large Scale Sheep Breeding and Training Centre, Kudapura, Chellakere of Chithradurga district of Karnataka.

Samples were collected from one square inch area in left mid side region using curved scissors . The samples collected were packed in labeled plastic bags.

Greasy fleece weight of each animal was recorded immediately after shearing, to the nearest gram.Clean fleece weight was estimated by weighing the samples after scouring as per the techniqur of Johnston (1934) as described here under.  Four scouring units with scouring solutions of the following concentration and temperature were used.

Tub 1: One per cent soap solution and 0.5 per cent washing soda at 48 to 50˚C.

Tub 2: 0.5 per cent soap solution at 45 to 47˚C

Tub 3: Clean tap water at 42 to 43˚C

Tub 4: Clean tap water at 40˚C

The samples were kept in each scouring unit. The samples when transferred from one tub to the next were squeezed manually. The samples were passed sequentially from first to fourth tub. After removal from the last tub the samples were squeezed completely and dried by placing it in an incubator for 24 hours at 37˚C. After ensuring complete drying of the samples, other extraneous materials like burr were removed from the sample manually. The samples were then weighed and clean fleece weight of the samples recorded. The difference between greasy fleece weight and clean fleece weight of the sample was expressed in terms of percentage.

The Least squares analysis of variance technique was adapted to detect the significant sources of non-genetic variation if any( Harvey, 1987).

The following mathematical model was adapted.

Y_ijklmn = µ + G_i +A_j + Y_k + S_l +X_m +e_ijklmn             

Where, Y_ijklmn  is the record of the n^th individual belonging to i^th genetic group,  j^th age group, k^th period of birth, shorn at l^th season belonging to m^th sex.

µ is the population mean

G_i is the fixed effect of i^th genetic group ( i=1,2,3 … 6)

A_j is the fixed effect of j^th age group (j=1,2,3 … 7)

Y_k is the fixed effect of k^th period of birth (k=1,2)

S_l  is the fixed effect of l^th season of shearing (l=1,2)

X_m is the fixed effect of m^th sex group (m=1,2)

e_ijklmn is the random error associated with   Y_ijklmn and assumed to be identically,   independently and normally distributed with mean zero and unit variance and interaction between various effects was assumed to be zero.

The Least Square means of different groups within each of the factors were compared by computing the Least Significant Difference (LSD) (Snedecor and Cochran, 1968).

Results

The least square mean and standard error computed for shrinkage percentage are presented in Table-1

Table-1:The Least Square Mean and Standard Error for shrinkage percentage.

R X D : Rambouillet X Deccani; C X B : Corriedale    X Bannur; C X D : Corriedale   X  Daeccani

UAS  :  UAS improved strain; Column-wise means with atleast one common superscript do not differ significantly.

Discussions 

The overall least square mean of shrinkage percentage was 28.51 ± 0.21 c.m. The comparison of means among genetic groups revealed that the highest in Corriedale X Bannur (31.84 ± 0.64) followed by Deccani (29.69 ± 0.49), Rambouiller X Deccani (29.14 ± 0.72), Corriedale X Deccani (28.43 ± 0.43), Bannur (27.43 ± 0.43) and the least in UAS-improved strain (27.89 ± 0.38).

Differences in shrinkage percentage due to genetic groups were found to be significant (P ≤ 0.01). In case of indigenous purebreds, Bannur had significantly lower shrinkage percentage (27.43 ± 0.43), as compared to Deccani (29.69 ± 0.49). Amongst the crossbred sheep, UAS-improved strain had the least shrinkage percentage (27.89 ± 0.38) differing significantly from those of Deccani crossed with Rambouillet (29.14 ± 0.72) and Corriedale (28.43 ± 0.43) and Bannur with Corriedale (31.84 ± 0.64).The difference in shrinkage percentage among different breeds may be attributed to impurities like grease and dust particles adhering to the wool fibres. However, Umrikar et al (1992) had reported that genetic groups did not reveal significant effect on shrinkage percentage in Nilgiri (55.8 ± 1.11) and Merino X Nilgiri (52.7 ± 1.27) and Singh et al(2008) did not find any significant effect  of breed group on shrinkage percentage in his studies with Corriedale, Poll Dorset and South Down.

The least squares mean of shrinkage percentage of fleece of sheep aged half to one-and-a-half years was the least (27.67 ± 0.69) and sheep aged five-and-a-half to six-and-a-half was the highest (29.17 ± 0.40). In this study, it was observed that effects of age , period of birth, season of shearing and sex on shrinkage percentage were not significant. In contrast to this observation, Lopez and Ulloa (1988) observed a significant effect of age on shrinkage percentage. Figueiro and Candido (1987) reported significant effect on age and sex on shrinkage percentage. The probable reason for this might be associated with the management of the flock including grazing practice. If the managemental practices are good enough, the dirt, burrs and other materials likely to be adhering to fleece can be minimized and this reduces the shrinkage percentage which will be considered as the most favourable one as far as the wool textile business is concerned.

References

Chopra SK. 1990. Wool quality evaluation and tactile apparisan. In: Proceedings of Workshop-cum-Seminar on Recent Advances in Sheep Production and Utilization. September, CSWRI, Avikanagar, Rajasthan. Pp. 12-25

Harvey  WR. 1987. Least Squares Analysis of Data with Unequal Subclass Numbers  ARS, 20ARS, USDA.

Johnston  A. 1934. A quick method of scouring small samples of wool. Pastoral Review. 44: 5-6

Figueiro PRP and Candido JG. 1987. Some factors affecting clean wool yield in Polwarth sheep. Animal Breeding Abstracts. 57(2): 929.

Lopez GCA and Ulloa AR. 1988. A study of factors associated with wool traits. Animal Breeding Abstracts. 56 (8): 4992

Singh PK, Banik S, Ganai TAS and Sarkar TK. 2008. Comparative performance of different breeds of sheep on wool production and quality traits in Kashmir valley.  Indian Journal  of Animal Research. 42(1):63-65.

Snedecor  GW and Cochran W.G. 1968. Statistical methods. 6^th Edn., Oxford and IBH Pub. Co., New Delhi.

Umrikar UD, Natarajan N, Kanakaraj P and  Thangaraju P.(1992). Influence of genetic groups and pregnancy on wool characters in sheep.  Indian Veterinary Journal 69(2): 136-140.