B-3296 [1-6] Indian J. Anim. Res., Print ISSN:0367-6722 / Online ISSN:0976-0555
AGRICULTURAL RESEARCH COMMUNICATION CENTRE
www.arccjournals.com/www.ijaronline.in
Morphological structuring using principal component analysis of RampurBushair sheep under transhumance production in western Himalayan region, India *Varun Sankhyan*, Y.P Thakur, Sanjeet Katoch, P.K Dogra and Rakesh Thakur1 Department of Animal Genetics and Breeding, College of Veterinary & Animal Science, CSKHPKV Palampur-176 062, India Received: 30-08-2016 Accepted: 28-04-2017
DOI:10.18805/ijar.B-3296
ABSTRACT Principal component analysis (PCA) was employed on 12 biometric traits of Rampur-Bushair sheep of Himachal Pradesh. Morphological and biometrical observations were recorded on 162 young and 566 adult animals. Multivariate statistics and principal component analysis revealed that body measurements except for peripheral traits were mostly positively and significantly correlated. The correlation among conformation traits ranged from -0.08 to 0.79 and “0.18 to 0.71 in young and adult sheep respectively. Three and four factors were extracted in young and adult sheep respectively, which accounted for 57% and 61% of variation. The principal component extracted contributed effectively to explain general body conformation. The regression analysis suggested that use of principal component was more appropriate than the use of original correlated variable in estimating body weights. Therefore, factor extracted could be helpful in breeding programme with sufficient reduction in the number of biometric traits to be recorded to explain the body conformation. Key words: Biometrical traits, Phenotypic characterization, Principal component analysis, Rampur-Bushair sheep. INTRODUCTION Over the last few years greater efforts had been diverted to characterize and document indigenous breed as an important prerequisite for focusing on their conservation and sustainable utilization. FAO has recommended that a global strategy should involve identifying and understanding a unique genetic resource in a particular region and developing the proper use of associated diversity (FAO, 2012). Rampur-Bushair is an important dual purpose breed of North temperate Himalayan state of Himachal Pradesh, India predominately reared under migratory/transhumance production system (Verma, 1996). Tribes rearing this sheep breed follows Alpiwirtscaft type of strategy, associated with movement of people and animal in vertical space, community control of pastures combined with individual control of plots/ haying fields and social institution that schedule the complex movement in space and time (Bhasin, 2013). There is decline in the population of this breed due to introduction of crossbreeding program long back in the state. In spite of its connotation with tribal community and cultural heritage breed has not attracted much attention from researchers. Though breed standards and morphological evaluation do exists but lacks comprehensive evaluations compared to other breeds of region. Preliminary studies (Dixit et al., 2005) have used only few body measurements (body height, body length and heart girth) to describe this breed. Morphological *Corresponding author’s e-mail & address:
[email protected] 1 SMS Animal Science, Krishi Vigyan Kendra Sundernagar, CSKHPKV
conformational appraisal of livestock is probably the oldest way of information collection and it played central role in many breeding associations and has been used with great success over the years (Janssens and Vandepitte, 2004). Phenotypic characteristics are important in breed identification and classification. The first step of the characterization of local genetic resources is to assess variation of morphological traits (Delgado et al., 2001). A combination of linear body measurements along with weight of animal describes more completely an individual rather than the conventional method of weighing and grading (Riva et al., 2004; Salako, 2006). Analysis of variance and correlation are widely used to characterize phenotypic and genetic relationship among body measurements of animals (Dietl et al., 2005; Taye et al., 2010; Ogah, 2011; Patoo et al., 2016). However factor analysis using principal component analysis (PCA) is a valuable refinement statistical tool in multivariate methodology that is of use when characteristics are correlated (Yak abu and Ayodae, 2009). PCA is interdependence technique whose primary purpose is to define the underlying structure among the variables in the analysis (Yunusa et al., 2013). The purpose of present investigation is to define the biometric structure of Rampur-Bushair sheep and to develop latent factors to examine percentage contribution of various body measurements towards total dimensional variation of the breed.
2
INDIAN JOURNAL OF ANIMAL RESEARCH
MATERIALS AND METHODS Study area: The study was carried out in breeding tract (Figure. 1) of Rampur- Bushair breed (Figure. 2-3) of sheep. The area is located in western Himalayan ranges and at latitude 30o22’-34o12’ and longitude 75o47’-79o40’E, at altitude varying from above 1500 meters above mean sea level (MSL) to as high as 3800 meters above MSL. The age of the animal was identified through dentition and a total of 162 young (up to 6 month) and 566 adult sheep from the flocks of 21 migratory farmers from three districts (Shimla, Kinnaur, Lahaul and Spiti) were included in the study.
Figure 1: Map depicting the study area
Figure 2: Adult Rampur-Bushair Ram
Data collection: Farmers migrating through various migratory route, camping site and stationary flocks from villages were randomly selected and 10-25 sheeps per farmer (as per flock size) used for different body measurements. A fabricated weighing balance was designed especially to be used in far flung migratory location. Animals were weighed and various linear body measurements were recorded in the morning to avoid post-prandial variation. The pregnant, crossbred and diseased animals were excluded from the study. Body dimension was taken with tape after holding the animal in unforced condition on levelled ground. Twelve (12) morphometric traits were measured on each animal. Body measurements recorded include body weight (BW), wither height (WH), heart girth (HG), paunch girth (PG), body length (BL), neck length (NL), face length (FL), face width (FW), ear length (El), ear width (EW), tail length (TL) and horn Length (HL). Statistical analysis: Statistical analysis was carried out by Statistical Analysis Software, SAS 9.3. Data collected were analysed using fixed effect model, by considering district effect as fixed so as to adjust the data for significant effect of district if any as per the following statistical model. Y= µ+Di+eij Where, Y is the phenotypic observation for one of the 12 biometric traits, µ is the overall mean; Di is the fixed effect of district, while eij is the random residual error associated with each observation which is normally and independently distributed with mean zero and unit variance. Descriptive statistics (mean, standard error and coefficient of variation) were determined for every parameter Principal components (PC) were generated using correlation matrix. The PC analysis was verified for adequate determinant factor, sample adequacy using Kaiser-Meyer-Olkin test and sphericity using Bartlett’s test. Procedure of varimax rotation was applied to enhance the interpretability of principal components. The stepwise multiple regression procedure was adopted to obtain models for predicting body weight from body measurement (1) and principal components (2) BW = a + BiXi+…………+ BkXk (1) BW = a + BiPCi+………...+ BkPCk
(2)
Where BW is the body weight, a is the regression intercept and Bi is the ith partial regression coefficient of ith linear body measurements, Xi or the ith principal component (PC).
Figure 3: Adult Rampur-Bushair Ewe
RESULTS AND DISCUSSION Descriptive analysis: Means, Standard error and coefficient of variation and significance of age and sex effects on each morphological trait are presented in Table 1. Body measurements revealed comparatively more variability in young sheep compared to adult sheep for all measurement included in the study. In young animals face width (FW), horn length (HL), body weight (BW), and tail length (TL)
Vol. Issue , () Table 1: Descriptive statistics on morphological traits in young and adult Rampur-Bushair sheep. Traits Body weight (Kg) Wither height(cms) Heart girth (cms) Paunch girth(cms) Body length(cms) Neck length(cms) Face length(cms) Face width(cms) Ear length (cms) Ear width(cms) Tail length(cms) Horn length (cms)
Mean 8.66±0.31 44.67±0.52 48.84±0.65 54.76±0.77 42.23±0.64 21.68±0.49 14.65±0.24 23.82±1.27 11.00±0.17 6.00±0.08 11.42±0.36 9.38±0.52
Young sheep (n=162) SD 3.80 6.38 8.07 9.53 7.88 6.10 3.01 15.75 2.12 1.05 4.41 4.78
were the most variable measurements as depicted by coefficient of variation ranging(CV) between 38 and 66. In adult animal horn length (HL), ear length (EL), ear width (EW) and body weight (BW) were the most variable measurement with CVs between 14 to 64. Whereas wither height (WH), body length (BL) and heart girth (HG), revealed comparatively more homogeneity with CVs between 6.8 to 8.3. Large variation shown by some measurement could be attributed to either due to absence of selection or the body part may be subjected to more environmental variation. Coefficient of variation for body weight (14.80) could be important for selection and improvement. In an earlier study of Zulu sheep (Mavule et al., 2013) also reported similar pattern with BW, TL and EL as the most variable and HG, WH and BL as homogenous measurements. While in adult hill goat of Assam (Khargharia et al., 2015) the body weight showed the maximum variation (14.99) followed by paunch girth (9.63) and rump width (9.55). The coefficient of variation found in the present investigation is also in accordance with the results of other studies in sheep and goats (Janssens and Vandepitte, 2004; Herrera et al., 1996). While comparatively lower coefficient of variation was reported in studies (Legaz et al., 2011) in Spanish sheep. Higher
CV 40.87 14.29 16.52 17.41 18.67 28.15 20.56 66.12 19.28 17.47 38.55 50.95
Mean±SE 25.72±0.16 58.10±0.17 70.05±0.24 76.70±0.30 57.67±0.20 29.06±0.24 20.67±0.10 30.59±0.12 11.88±0.08 6.65±0.04 11.61±0.08 14.82±0.41
Adult sheep (n=566) SD CV (%) 3.81 14.80 3.92 6.76 7.01 7.99 7.09 9.14 4.79 8.31 5.68 19.54 2.45 11.83 2.81 9.21 2.10 17.74 1.05 15.80 1.93 16.62 9.77 65.94
heterogeneity in Rampur-Bushair sheep might be due to reason that not much scientific selection is practiced since the breed is maintained under transhumance system with traditional system. Phenotypic correlation: Phenotypic correlations between various morpho-metric measurements are presented in Table 2. A total of 66 correlations were estimated in young and adult sheep. In young Rampur-Bushair sheep 47 out of 66 were positively and significantly (p
