Prediction of body weight using body measurements in some sheep and goats in Qatar

Figures & data

Table 1. Distribution of experimental animals according to type, breed and sex.

Type	Breed	Male	Female	Totals
Goats	Shami	54	132	186
	Aaridi	27	48	75
	Total	81	180	261
Sheep	Erbi	12	37	49
	Awassi	81	149	230
	Najdi	15	30	45
	Total	108	217	324
All groups		189	397	585

Table 2. Distribution of sensitivity testing animals according to type, breed and sex.

Type	Breed	Female	Male	Total
Goats	Shami	24	26	50
	Aaridi	49	20	69
	Total	73	46	119
Sheep	Najdi	30	16	46
	Erbi	28	14	42
	Awassi	43	40	83
	Total	101	70	171
All groups		174	116	290

Table 3. Correlation coefficients of weight with body measurements.

	Pooled	Sheep	Goats	Males	Females
HG	0.9292	0.9104	0.9424	0.9409	0.9301
HW	0.8787	0.8103	0.9011	0.8916	0.8705
BL	0.8208	0.7896	0.9138	0.8401	0.8082

HG is the heart girth.

HW is the height at wither.

BL is the body length.

Table 4. Parameters of the different mathematical models of regression of body weight (y) on heart girth (x) for the pooled data.

	Linear	Exponential	Logarithmic	Power
Formula	y = a + b*x	y = a*e^(b*x)	y = a + b*ln(x)	y = a*x^b
R^2	0.8633	0.8185	0.8875	0.9129
Error of estimate	7.5494	7.9603	8.6993	7.4208
A	−60.5737	2.8499	98.3380	0.0006
B	1.3321	0.0333	−383.0900	2.5608

R² is the coefficient of determination.

a is the regression intercept.

b is the regression coefficient.

Table 5. Parameters and statistical analysis of Power regressions of body weight (y) on heart girth (x) for the different animals’ groups (type, sex and breeds).

	N	A	b	R^2	SE b	SE D	Calculated t-value	df	Critical t-value at 5%	Critical t-value at 1%
Goats	777	0.0003	2.7694	0.9278	0.0365	0.2973	−0.4621	862	1.96	2.59
Sheep	973	0.0001	2.9068	0.9068	0.0519
Male	564	0.0003	2.7286	0.9329	0.0364	0.2597	0.9461	762	1.96	2.59
Female	1186	0.0008	2.4829	0.9150	0.0310
Sheep female	650	0.0001	2.9494	0.9320	0.0563	0.3345	−0.1387	430	1.96	2.59
Sheep male	323	0.0001	2.9958	0.9387	0.0556
Awassi	690	0.0001	2.9507	0.9289	0.0472	0.4046	1.3429	239	1.97	2.6
Erbi	146	0.0011	2.4074	0.7380	0.1165
Awassi	690	0.0001	2.9507	0.9289	0.0472	0.3690	0.4702	227	1.97	2.6
Najdi	137	0.0002	2.7772	0.9012	0.0890
Erbi	146	0.0011	2.4074	0.7380	0.1165	0.4534	−0.8157	139	1.98	2.62
Najdi	137	0.0002	2.7772	0.9012	0.0890
Goat female	536	0.0006	2.5702	0.9210	0.0466	0.3137	−1.3325	330	1.97	2.6
Goat male	241	0.0001	2.9882	0.9359	0.0518
Aaridi	224	0.0006	2.5777	0.9269	0.0700	0.3347	−0.8070	317	1.97	2.6
Shami	553	0.0002	2.8478	0.9344	0.0420

N is the number of observations.

R² is the coefficient of determination.

a is the regression intercept.

b is the regression coefficient.

SE b is the standard error of the regression coefficient.

SE d is the standard error of the difference of regression coefficient.

The calculated t-value is the calculated t-test value.

Critical t-value at 5% is tabulated critical t-test value at the probability of error 5%.

Critical t-value at 1% is tabulated critical t-test value at the probability of error 1%.

Table 6. Parameters of stepwise multiple regression of body weight on the linear body measurements.

	Step 1	Step 2	Step 3	Step 4
Adjusted R^2	0.8633	0.8852	0.8785	0.8874
Error of estimate	7.5494	6.9172	7.1147	6.8501
A	−60.5737	−69.2164	−70.4738	−71.9270
b of HG	1.3321	1.0633	0.9978	0.9666
b of BL		0.4196		0.3256
b of WH			0.5100	0.2394

R² is the coefficient of determination.

a is the regression intercept.

HG is the heart girth.

HW is the height at wither.

BL is the body length.

Figure 1. Plotting of body weight predicted by the power regression model on its residue values.

Figure 2. Plotting of body weight predicted by the multiple regression model on its residue values.

Table 7. Statistical examination of the difference between measured and estimated body weights of sensitivity testing population.

	Measured weight (Kg)	Estimated weight (kg)
No. of observations	290	290
Mean	51. 7	52.5
Standard deviation	19.42	18.28
Calculated t-value	0.527
P	0.598
Difference (kg)	0.8
Percentage of difference (%)	1.5%

The calculated t-value is the calculated t-test value.

P is the probability of error.

Data availability statement

Raw data were generated at the Animal Research Station, Department of Agricultural Researches, Ministry of Municipalities – Qatar. Derived data supporting the findings of this study are available from the corresponding author [M. Atta] on request.