Introduction

Body measurements have been widely used for estimating animals live weight especially when weighing equipments are not readily available. The various lengths, heights and girths of live animals are measured to assess the relationship between these variables and the live weight, in cattle (Dineur and Thys 1986; Goe et al., 2001; Mekonnen and Biruk 2004; Abdelhadi and Babiker 2009), in sheep (Valdez et al., 1997; Atta and El khidir 2004; Sowande and Sobola 2008; Kunene et al., 2009; Oke and Ogbonnaya 2011, and Agamy,2015) or goat (Mohammed and Amin 1997; Nsoso et al., 2004; Adeyinka and Mohammed 2006; Singh and Mishra 2004., Abdel-Mageed and Ghanem, 2013; Abd-Alla, 2014), and in pig and poultry (Lawrence and Fowler, 1997, Ojedapo et al., 2012). In practice, external measurements of body have been used to estimate the development of the skeleton and/or soft tissues of the body. Standford et al., 1982 and Suleiman et al., 1990, reported that, Body length is described as distance between the scapula and pin bones or the distance between tip of scapula and ischium, though the measurement of body length can be used to estimate the weight of animals, Sulieman et al., 1990 reported that measurements of body length and height at withers were less valuable than use of body weight using appropriate weighing instruments. Lawrence and Fowler, (1997) added that the coefficient of determination of multiple regression of heart girth and any other linear measurement on body weight was slightly higher than that of the simple regression of heart girth on body weight. Curvilinear relationship has been reported between live weight and heart girth (Thys and Hardouin, (1991): Lawrence and Fowler, 1997), cubed heart girth, (Brody, 1945), and based on y=0.0001668×2.867 for males of Nilotic sheep, where y and x are body weight and heart girth respectively has been reported by Atta and ElKhidir, (2004). Moreover, significant positive correlations between live weight, heart girth, live weight and height at withers were reported in goat kids of Philippine goats, (Galeon, 1951), Singh et al., (1975). In the last few years, the demand for goat meat increased progressively in Sudan. Weight determination is of major concern for Goat kids buyers in the markets of Khartoum state.

Objectives

To develop an easy-to-use method that could provide more precise and meaningful description of live body weight of goat kids in Khartoum state markets; to establish a prediction formula based on non-linear body measurements; to investigate the relationship among various measures to determine the value of using more than one body measure to predict live weight in goat kids.

Materials and Methods

Seventy-eight Sudanese indigenous kids were used in this study. An attempt was made to keep the kids age close to the kids brought to Khartoum state markets. The kids were between 4 to 8 months old and had live weight of 8 to 15 kg. All the
kids were apparently healthy. Live body weight was measured by 50 kg spring balance, height at the highest point of the hip and at the spine were in centimeters using pocket- tape. Scale tape according to Standford etal, (1982), and Sulieman etal, (1990).

Data analyses

The data from the measurements was used to predict body weight based on a simple regression analysis to describe the relationship, y=ax^b, where y is the body weight, x is the body measurements, (Heart girth, body length, withers height and height at back). The data were analyzed using SAS package program (SAS. 2008). Simple correlation coefficients of various body measurements with each of body weight were calculated and tested for significance. The coefficient of determination (R2) assessed the accuracy of the equations. Values of probability <0.05 were considered as a significant level.

Results

Relationships between body weights, height at back, wither height and body length of indigenous goats breed kids are shown in Table 1. Study showed that, body weight was equal to the heart girth raised to exponential 2.58, height at back raised to exponential of 1.29, wither height raised to exponential of 1.34 and body length raised to exponential of 1.34. The coefficient of determination (R²) which measured the proportion of the variation of the dependent variable (body weight) that could be explained due to the independent variable (heart girth) revealed that 68%, 33%, 32% and 27%, of the variation in body weight was due to the heart girth, wither height, body length and height at back respectively.(Figure,1).

Figure 1: Regression of body weight on heart girth. (Y= Body weight in kg; X= Heart girth; R= Coefficient of determination)

Table 1: Regression equations of body weight (kg) on heart girth (cm) wither height (cm) body length (cm) and height at back (cm) for kits in Khartoum state markets

Y= Dependent variable (body weight in kg); R²= Coefficient of determination; x₁= Heart girth; x₂= Wither height; x₃= Body length; x₄= Height at back; Significant when P< 0.05.

Predicted values of body weight from heart girth, height at back, wither height, and body length with the residual values is shown in figure 1 and 2. Results showed that, body weight of kids was predicted from heart girth, height at back, wither height, and body length, the predicted weights were valid when the weight of kids ranged between 10 to 13 kg, underestimation and overestimations were observed when the body weight was above 14 kg ,in addition, less than 9 kg respectively.(Figure, 2 and 3).

Figure 2: Predicted values of body weight from heart girth and height at back (Hg= Heart girth; H= Height)

Figure 3: Predicted Values of Body Weight from wither height and Body Length

Discussion

Body weight is a significant economic trait in animal that reared for meat. The prediction of body weight from body measurements is best method of weighing animals in Ethiopian sheep without a scale,,( Edea et al. (2009), and in Barbari goats, (Singh and Mishra (2004).In the present study, heart girth was found to be the most precise and easy to apply for non-linear body measurement and was found highly correlated with the body weight; this proves that the heart girth is reliable of body mass prediction. However, similar results were obtained by other authors , in goat and kids , (Khan et al., 2006; Mahieu,etal 2011: Abdel-Mageed and Ghanem, 2013; Abd-Alla, 2014),and in sheep (Atta and El-Khidir, 2004; Afolayan et al., 2006: Agamy,2015). Heart girth in the present study, was the best monitor for estimation body weight, with coefficient of determination (R2) being 68% in body weight of Sudanese kits, these results are in a line with that obtained by Nigm et al. (1995) who reported that heart girth was the best single predictor and accounted alone for 77% of the variation in body weight of Merino males, and with Abdel-Moneim (2009b) who showed that heart girth accounted for 86% in body weight of Barki lambs..Withers height in this study, could predict body weight of Sudanese kids with an accuracy of 33%, this finding agreed with that obtained by Agamy ,etal (2015), who reported that weights of live body, can predicted by measuring body length.Body length in this study, could predict body weight of Sudanese kids with an accuracy of 32%, This finding is is in the line of results reported by Abdel-Moneim (2009b) who reported that length of the body of Egyptian lambs could predict body weight with an accuracy of 64%. However, the accuracy was elevated (0.88) when the prediction equation including heart girth and body length in subtropical goat kids (Abdel-Mageed and Ghanem, 2013). This results are less than the finding obtained by Agamy ,etal (2015), who reported that weights of live body, can predicted by measuring body length, which represented 60% of the variation in body weight of Ossimi ram-lambs.In this study, regression of body weight on height at back, showed positive correlation but not significant. However, wither height, height at back, and body length all reflect a skeletal girth, are equally important to consider because body dimensions are often influenced by body condition or degree of fitness. (Wickersha and Schuiltz, 1963).The change of body weight in this study was equal to cubed heart girth, these findings are similar to those reported by Brody, (1945) and Atta and ElKhidir, (2004) who concluded that body weight of cattle and Nilotic sheep were changed with the cubed heart girth.The results obtained from this study provide a prediction variable which explains 43% of the variation of body weight in kids. Thys and Hardouin, (1991) in a study to predict the weight of sheep in Cameroon markets, found that heart girth explained 96% of the variation of body weight in rams. The body measurements (wither height, height at back, and body length) explain 8%, 10% and 15% respectively.

Conclusions

Equations presented here can be used to estimate body weight in local goats breed kids in Khartoum state markets or field studies from body measurements including heart girth, wither height, and body length specially when the body weights of these kids range between 9 kg and 13 kg live body weight.

Acknowledgement

The authors acknowledge to Mr. Adam Yahia for providing the scales.

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