Prediction of zebu cattle live weight using live animal measurements

O M A Abdelhadi and S A Babiker*

Department of Animal Production, Faculty of Natural Resources, University of Kordofan,P O Box 716, Khartoum, Sudan
Omer.abdelhadi@yahoo.com
* Department of Meat Production, Faculty of Animal Production, University of Khartoum, Sudan

Abstract

The present work was conducted to predict live weight of zebu cattle using external body measurements. A total of 247 Sudanese indigenous Baggara bulls were used for the study. Their live weights ranged from 170 to 390 Kg.

The study revealed that heart girth around the hump had the highest correlation coefficient with live weight (r = 0.83, p<0.001) compared with other body measurements. Grouping of data according to live weight indicated that heart girth around the hump in group B (medium weight) and C (heavy weight) had the closest correlation coefficient with live weight (r = 0.66 and 0.86, respectively). This gave more confidence in the use of the former measurement in prediction of live weight of humped cattle. The regression analysis of live weight on heart girth around the hump was highly significant (P<0.001), and the regression lines indicated that a linear relationship existed. The regression equations were also obtained to estimate the live weight of the “heavy”, “medium” and “light” weight bulls. However, the general equation for prediction of live weight of the humped cattle was as follows:

Y = 2.4573x – 92.472(± 0.36),

Where, Y = live weight (Kg), x = heart girth around the hump (cm).

Key words: Body measurements, heart girth, live weight, zebu

Introduction

Sudan has a large cattle population estimated as 41 million head (Ministry of Animal Resources and Fisheries 2007). These animals are maintained on natural grazing in open range conditions and seasonal migration. Under these conditions there are no weighing devices to determine live weight changes. Determination of live weight is necessary to calculate feed requirements, animal growth, marketing weight and estimation of animal’s cash value as well as conducting breeding studies, field experiments and estimation of dressed carcass weight (Payne 1990). At present, animal owners and cattle traders depend on eye judgment to live weight. The accuracy of such subjective method depends on individual experience. The importance of conformation as an indicator of commercial value is based on the assumption that carcasses with better conformation have advantages in terms of lean meat content, proportion of higher priced cuts and possibly greater muscle size or area (Kempster et al 1982 and Khogali 1999).

On the other hand, cattle weighing instruments are costly to obtain, heavy to transport and follow the nomadic herds and need technical maintenance which is also costly and beyond the means of many live stock breeders, especially in remote and rural areas. The available measuring tapes are designed for the temperate cattle which lack the hump.

The objective of this research is to find out a method for predicting zebu cattle live weight using body measurements.

Materials and methods 

Live animals from which the data used were obtained from Kuku Research Center (K.R.C) feedlot, Khartoum State – Sudan. Two hundred and forty seven bulls of western Baggara type were used (Photo 1). 

Live weights were taken using a weigh-bridge and recorded in kilograms. External body measurements were taken using a steel tape and a measuring stick; both of them were graduated in centimeters. The body measurements were taken according to the procedures reported by (Brown et al 1974 and Abdelhadi 2001).

Then the data were grouped in three groups (A, B and C) according to weight following frequency distribution curve (Figure 1).

Group A contained all the bulls weighing 229 kg or less and were termed “light weight animals”, while those ranging from 230 to 329 kg fell in group B and called “medium weight animals”, however, group C contained bulls weighing 330 kg or over and were termed “heavy weight animals”. 

Statistical analysis

Data were examined using Statistical Analysis System (SAS 1996) to give means, standard deviation, coefficient of variation and correlation coefficient. Regression technique was also used to obtain the relationship between live weight and external body measurements.

Results 

Live animal measurements

Table (1) shows overall body weights and external body measurements of Baggara bulls.

However, according to weight group these measurements were greater in group C, intermediate in group B and lower in group A which had the lightest live weight, Table (2).

Correlation coefficients

The correlation coefficients between live weight and the various body measurements of all bulls studied are shown in Table (3).

All the correlation coefficients between live weight and the various body measurements were significant except for abdominal circumference and neck length. A highly positive correlation coefficient was found between live weight and heart girth around the hump (r = 0.83, P< 0.001).

Table (4) shows the correlation coefficients of the different body measurements with live weight according to live weight group.

The heart girth around the hump, in group C, showed a highly positive correlation coefficient (r = 0.89, P<0.001), however, it was intermediate in group B and lower in group A. It was observed that for the heart girth around the hump the correlation coefficient increased as the live weight increased. Correlation coefficients for the other body measurements with live weight were low and inconsistent.

Regression analysis

Regression of live weight on heart girth around the hump for all bulls gave a straight line relationship (Figure 2).

The regression equation of live weight (y) on heart girth around the hump (x) for live weight groups indicated that an increase or a decrease of one cm of heart girth around the hump gave an increase or a decrease of 3.892 kg of live weight:

Y = 3.892 x – 259.93 (±0.3), R² = 0.69

The regression equation for the live weight groups were:

Group A:             Y = 0.953 x + 64.066 (±0.26), R² = 0.22.

Group B:             Y = 2.0475 x – 68.336 (±0.11), R² = 0.43

Group C:             Y = 2.4573 x – 92.472 (±0.36), R² = 0.79

The regression equation of group C gave a high coefficient of determination (R² = 0.79) which indicated the accuracy of using heart girth around the hump for estimation of live weight of humped cattle. A small variation was found between the actual and calculated live weight which was 2% in group C and 5% in both group A and B.

Discussion 

The mean values of external body measurements in the present work were lower from those reported by (Rahama 1994 and Khogali 1999) for the same breed of cattle. They were also lower than those reported by (Bailey et al 1986) for (Holstein X Friesian) bulls of 340 kg live weight (159.2 and 116.2 cm) for heart girth and height at wither, respectively. McGee et al (2007) also reported values of height at wither (132.3, 127.4, 122.5 cm) and back length (128.6, 123.9, 123.4 cm) for Holstein, Friesian and Charolais X Holstein-Friesian), respectively, which were higher than those in this study.  These differences might be due to the variation in live weight, degree of fatness and age of bulls used in these studies. In fact in this studies animals varied in their age and degree of finishing.

The calculation of the correlation coefficients showed that live weight and heart girth around the hump were highly correlated, however, the correlation coefficients increased with body weight increase, which clearly indicated that heart girth around the hump could be the most reliable measurement for prediction of live weight of zebu cattle (Abdelhadi 2001). This contrasted previous studies which reported high correlation coefficient between live weight and heart girth measurement (Branton and Salisbury 1946, Mullick 1950, Veiga 1939, El Khidir 1980 and Khogali 1999). This might be due to the fact that in the first three studies temperate type of cattle were used, however, the last two studies were conducted on Zebu cattle of equal initial weight.

According to live weight group, heart girth around the hump had the closest relationship with live weight, particularly for medium and heavy weight groups. The best correlation coefficient was found in the heavy group, which indicated that a high accuracy existed in the use of live weight of heavy humped cattle. Conformation to these findings were obtained by (Wanderstock and Salisbury 1946) who worked on temperate steers weighing 290 to 370 kg, which lack the hump and had the same live weight as the heavy group in this study.

The regression analysis for all live weight groups indicated that a linear relationship existed between live weight and heart girth around the hump. The information about live weight and heart girth around the hump is lacking as all the work done in this aspect concentrated on temperate cattle, which lack the hump. The regression equation Y = 3.1892x – 259.92 (±0.13), gave convenient results for estimation of live weight using heart girth around the hump. The mean variation between actual and estimated live weight was 4%, which was different from the percentage reported by (Mullick 1950) who found 7% variation. This variation might be due to the large number of animals used in the present study.

The regression of live weight on heart girth around the hump in each of group A, B, and C showed a straight line relationship. The regression equation, Y = 2.4573x – 92.472 (±0.36), gave an accurate estimate of live weight of heavy weight cattle (group C), when heart girth around the hump ranged from 156 to 197 cm. The R² value (0.79) was higher than in group A and B, which indicated that 79% of the variation in live weight was determined by heart girth around the hump. The mean variation in this group for the calculated live weight was very small (2%). When the data were grouped into “light”, “medium” and “heavy” weight bulls, the correlation coefficients between live weight and heart girth around the hump increased with live weight increase, indicating a greater accuracy of heart girth around the hump in predicting live weight of “heavy” bulls compared with “light” ones.

Acknowledgements 

Thanks are due to the Staff of Animal Research Center (Kuku) where this study was conducted, for assistance and provide of animals.

References 

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Received 4 May 2009; Accepted 15 May 2009; Published 5 August 2009

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