Introduction

Improvement in wool production of indigenous sheep in India was attempted through crossbreeding with exotic breeds like corriedale , Merino and Rambouillet. This resulted in the evaluation and development of new breeds/ strains viz., Hissardale, Kashmir Merino, Deccani Merino and some superior strains like  Avivastra, Avikalin, Bharath Merino, UAS- improved strain and Sandyno (Singh, 1990). Crossbreeding of native sheep with selected exotic breeds of sheep superior in body weight, growth rate, wool yield and multiple births seems to be the quickest way  of improving native breeds and their production potentials  Clean fleece weight 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. 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 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 clean fleece weight are presented in Table-1

Table-1:The Least Square Mean and Standard Error for Clean fleece weight.

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 clean fleece weight was 231.36 ± 3.44 c.m. The comparison of means among genetic groups revealed that the highest clean fleece weight  was recorded in UAS- Improved strain (394.06 ± 8.33g) followed by Rambouillet X Deccani (283.44 ± 11.14 g), Corriedale X Deccani (245.49 ± 8.98g), Bannur (165.46 ± 4.17g),  Deccani (158.20 ± 7.12g), and Corriedale X Bannur (133.51 ± 9.16g).

Genetic group differences in clean wool production were found to be significant (P ≤ 0.05). The clean fleece weight of Bannur sheep (165.46 ± 4.17g) was higher than its  crosses with Corriedale (133.51 ± 9.16g). Corriedale X Deccani sheep had higher clean fleece weight (245.49 ± 8.98g) as compared to purebred Deccani (158.20 ± 7.12g). The clean fleece weight in UAS- improved strain, Corriedale X Deccani and Rambouillet X Deccani were similar but higher than other genetic groups and the difference was significant. The mean values for clean fleece weight in Bannur , Deccani and Corriedale X Bannur were lower than those observed in other genetic groups and differences in clean fleece weight among these genetic groups were significant. Such genetic groups differences in clean fleece weight were also reported by Chougule et al.(1988) but, Singh et al.(2008) reported no significant effect of breed on clean fleece weight in Corriedale and South Down breed.

The least square mean of clean fleece weight of sheep aged above one-and-a-half to two-and-a-half years was the heaviest (312.88 ± 12.88g) and of sheep aged four-and-a-half to five-and-a-half years was the lightest (178.55 ± 6.82g). In this study, it was observed that effect of age on clean fleece weight wqas not significant. In contrast to this result, significant difference in clean fleece weight due to age was reported by Garcia and Alvarez (1992) in German Mutton Merinos.

The sheep shorn in period II had heavier clean fleece weight  (271.59 ± 6.56g) than those born in period I (207.35 ± 4.12g). The probable reason for the significant difference ( P ≤ 0.05) was attributable to climatic variation, apart from non-genetic factors.

The sheep shorn in the month of December and January yielded more clean fleece weight (236.58 ± 5.82g) than those  sheep shorn in the months of July and August (226.57 ±4.27g ). The difference was found to be  significant (P ≤ 0.05). This observation was supported by earlier reports of Sahani et al. (1980) who observed that the season of shearing significantly affected the clean fleece weight in Magra sheep.

The clean fleece weight recorded in female sheep was lower (226.59 ± 3.11g) than that of male sheep (262.44 ± 10.17 g). The difference was found to be significant  (P ≤ 0.05). This variation may be attributable to their hormonal differences.

Reference

Chougule BA, Deshmukh AP and Patil GD.  1988. Fleece production and quality of wool of Deccani and their halfbreds with Dorset and Merino. Indian Veterinary Journal. 65(3): 242-244

Garcia DG and Alvarez SP. 1992. Effect of age on on variation in body weight and some fleece characters in German Mutton Merinos. Simiente. 62(2): 97-102

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

Sahani MS, Dwivedi VK, Dubey SC and Arora CL. 1980. Note on body weight from birth to first breeding and fleece weight in native and crossbred (quarterbred) sheep production under field conditions in semi-arid areas of Rajasthan . Indian Journal of Animal Science. 50(7): 580-581.

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.

Singh VK. 1990. Breeding sheep for fine wool and carpet wool production. In: Proceedings of the Workshop-cum-Seminar on Recent Advances in Sheep Production and Utilization. 12-25, September, CSWRI, Avikanagar, Rajasthan.

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