Predicting the Weight of Holstein-Friesian Males at Different Ages by some Body Measurements

This study was conducted in one of the private fields for breeding Holstein-Friesian calves in the village of Al-Hamad in Al-Diwaniyah Governorate, where 107 males were used, including 21 at the age of 1 year, 51 at the age of 2 years, and 35 at the age of 3 years. The animals were weighed with an electronic scale, and body measurements (height body, chest girth and hip girth in centimeters) and the study aims to find the best single or double size to estimate the body weight of Holstein Friesian males, and the results of the current study can be summarized as follows: It was found that age had a highly significant effect (p<0.01) on body weight and its measurements, as it increased with age, as the weights of Holstein Friesian males, aged 1, 2, and 3 years, for all ages reached 271.714, 359.627, 522.914, and 395.785 kg, respectively. Age also had a significant (p<0.01) effect on measurements of body length, chest and hip girths, and the correlation coefficients ranged between body measurements for males and for the sum of ages between 0.887 to 0.988. In this study, it was found that the best measure for estimating body weight is chest and hip girth, as the correlation coefficients between body weight and chest girth ranged between 0.845 to 0.965, and between weight and chest girth from 0.831 to 0.970. And that the best equation for estimating the body weight of bulls at the age of one year is the chest girth as a single measurement if the regression equation Y=-76.791+1.280GC. The coefficient of determination, R2 = 0.930, with a standard error of the estimate 5.59. As for the best equation for estimating the weight of bulls at the age of 2 years, it is based on the girth of the chest, as the determination reached R2 = 0.715, and the regression equation Y=-348.104+4.206CG. With a standard error of the estimate 25.625. And the girth of the hip, as the coefficient of determination was 0.753 = R2 and the regression equation y = - 431.986 + 4.647 CG. And with a standard error of the estimate 23.838. The best equation for estimating the weight of bulls at the age of 3 years is to rely on chest girth as a single measure and the regression equation. Y=-451.388+5.05 CG, And the determination equation is R2 = 0.877, with a standard error of the estimate 20.518. As for the regression equation to estimate the body weight of bulls and for all ages, the equation of dependence on the girth of the chest can be used Y=-610.582+5.813 CG. Where it was R2= 0.931 with a standard error of estimation was 27.936 or depending on the girth of the hip Y = -632.404 + 5.884 CG, where R2 = 0.941 HG and with a standard error of estimation was 25.725.


Introduction
The weight scale is considered the gold standard, if the scales used are of good calibration.In most rural areas, livestock markets, and private stations in Iraq, livestock is rarely weighed, as obtaining weighing tools is expensive, requires technical maintenance, and is difficult to transport to livestock farms.Especially in grazing systems, farmers and livestock dealers often rely on visual judgment in determining the live weight of animals, which is a self-method whose accuracy depends on the experience of the user.Since the accurate estimation of the body weight of farm animals determines the weight of the carcass, the appropriate level of nutrition, the nutritional status of the animals, the growth rate, the selling prices, and the dosage of the drug Correct and responses to genetic selection, and that evaluating the live weights of animals is necessary to determine the appropriate allowable levels of feed, grazing intensity, and stocking rates.Therefore, evaluating the live weight of animals is critical in implementing appropriate grazing management practices to achieve sustainability [1][2][3][4][5].And many researchers in cattle found that body weight is significantly related to different body measurements, especially chest girth as a single measure in estimating body weight, or two or multiple variables, and the correlation coefficients were between medium and strong, as they ranged between 0.24 to 0.98 [6][7][8][9][10].It was found that with age, body weight measurements increase [7,[11][12][13].

Materials and Methods
The experiment was conducted in one of the private fields located in the village of Al-Hamad in Al-Diwaniyah Governorate for the period from December to April 2023, where 107 Holstein-Friesian bulls, ages 1, 2, and 3 years old, which were raised for fattening and then slaughtered or for the purpose of sale, were used.These animals were weighed.With an accurate electronic scale installed in the field, and gradually from zero to 1000 kg, the bulls' body measurements body length (BL), chest girth(CH), and hip girth(HG) were also taken, which are the most closely related measurements to body weight, where different correlations were found for weight and body measurements for all ages and for each age separately and status Predictive equations for estimating weight based on single (single variable), binary and multiple measurements, and judging the best regression equations is the best, depending on the coeffficent of detrmination R 2 , the adjusted R 2 , and the standard error of the estimate.The results were analyzed by using one way classification to find the effect of Holstein-Friesian bulls, ages 1, 2, and 3 years old according to SPSS(14), Also regression equations to estimate weight of males at different ages by some body measurements and coefficient of determination and standard error of the estimate were estimated depending on the same statistical program [14].

Results and Discussion
Table (1) shows that the overall means weight of Holstein-Friesian calves, body length, chest girth, and hip girth were 395.785 kg, 130.682, 173.122, and 174.757 cm, respectively.Where the 3-year-old males outperformed males of 1-and 2-year-old in body weight by 215.200 and 163.287 kg, respectively, and 2-year-old males outperformed 1-year-old males by 88.113 kg.In this regard, (128) found in different breeds of calves that weight increases with age and is significantly related to chest girth.It was also found that age had a highly significant effect (p<0.01) on different body measurements, as males excelled in all body measurements (body length, chest girth, and hip) over females, and this result agrees with findings which was found (11).In the local buffaloes, where they mentioned that the age of the calf had a significant effect (p<0.01) or (p<0.05) in all different body measurements, as it increased with the age of the animal [12].Tables (2, 3, 4, and 5)appear that body weight is significantly (p<0.01)related to all body measurements (body length, chest girth, and hip girth).Between body weight and chest girth for ages 1, 2, and 3 years and for all ages between 0.618 for one year of age and 0.965 for all ages and for body weight and hip girth between 0.813 for one year of age and 0.970 for all ages.The two highest values of correlation between body measurements were 0.997 between chest and hip girth at 3 years of age and 0 .988between chest and hip girths for all ages, the lowest being 0.605 between body length and chest girth at the age of one year, and 0.750 also between body length and chest girth at the age of 2 years.The results of the current study explain that the best measure for estimating body weight is chest and hip girths, as the correlation coefficients between body weight and chest girth ranged from 0.845 to 0.965, and between weight and hip girth from 0.813 for one year of age to 0.970 for all ages.The best questions for estimating body weights for males at all ages was chest and hip girth (Table -3 The current results agreed with many of the results of [11], in the local buffaloes, where it was found that body weight was significantly (p<0.01)associated with chest and hip girths, and the correlation coefficients were 0.963 and 0.966, respectively.As [15], stated in different breeds of cows, the correlation coefficient between body weight and chest girth was 0.96, and with body length it was 0.92, and they indicated that the best measure for estimating cows' weight is chest girth.It also agreed with the results in the current study, [8] in the Nguni cow breed, where they showed that the correlation coefficient between body weight, chest girth, and body length is (0.90) (P<0.01) and (0.43) (P<0.05),respectively.Similar results were demonstrated by [7], in Nigerian cows, where they obtained a correlation coefficient between body weight and chest girth of 0.89.[12], also found that body weight was significantly associated with chest girth.[17], confirmed in different breeds of beef cattle that there are significant differences in weight and different body measurements, if they obtained significant correlation coefficients between body weight and its different measurements and it was between medium and high, if it ranged from 0.40 to 0.83, as were the correlation coefficients between Different body measurements between medium and high 0.22 to 0.81.0.295 HG ** means that the regression is significant at the probability level 0.01 ** .Table (6) shows that the best estimate of body weight for bulls at the age of one year is the chest girth as a single measurement.The regression equation for estimating body weight is y =-76.791+ 1.280 CG, with a coefficient of determination of R 2 = 0.930, and with a standard error of the estimate was 2.597.He also obtained the best regression equation for estimating body weight through the variables of chest girth and body length, where the coefficient of determination for this equation was R² = 0.944, with a standard error of the estimate was 2.378 .

Y=-247.196+3.645Bl+0.44GH
In this regard, many researchers found that chest girth is the best single measure for estimating body weight [4,6,15,18].Table (7)appears the regression equations for estimating the weight of Holstein-Friesian bulls by means of body measurements at the age of 2 years, where it obtained the highest determination coefficient for estimating body weight by means of chest girth or hip girth as a single measurement, reaching 0.715 and 0.753, respectively, with a standard error of the estimate was 25. 625 [12], found an approximate regression equation for estimating body weight by chest girth for twoyear-old Taita strain Lw = -3340 + 3.98 HG and with an accuracy of R² = 0.80.[13] found a regression equation for estimating body weight by chest girth Lw=-357.56+4.25 Hg with coefficient determination was 0.80.It is close to what was found in this study, and as a binary measure to estimate body weight, body length and chest girth were achieved better regression equation.Y = -1781.635+ 12.83 BL + 2.736 GC =0.782 with R ² [16] also found in Ethiopian working bulls several equations for estimating weight by chest girth7 y=-408+4.51,with an accuracy of R²=0.79 Table 6.Correlation coefficients between body weight and some body measurements for 2-year-old Holstein-Friesian males.

Conclusions
The correlation coefficients ranged between body measurements for males and for the all ages between 0.887 to 0.988.It was found in this study that the best measure for estimating body weight is chest and hip girths, as the correlation coefficients between body weight and chest girth ranged between 0.845 to 0.965 and between weight and chest girth from 0.831 to 0.9707 As for the regression equation to estimate body weight for males of all ages, the equation can be used to depend on the girth of the chest: Y=-610.582+5.813CG.Where it reached R 2 = 0.931 with a standard error of the estimate 27.936, depending on the girth of the hip Y=-632.404+5.884CG where R² = 0.941 NG with a standard error of 25.725.

Table 1 .
Means of body weight and some body measurewmenst at all ages.Different letters mean the differences among means are significant at probability level at 0.01.

Table 2 .
Correlation coefficients between body weight of Holstein-Friesian males and some body measurements for all ages.
**Chest girt means that the correlation is significant at the probability level 0.01 ** .

Table 3 .
Regression equations for estimating the weight of Holstein-Friesian males for all ages based on some body measurements.

Table 4 .
Correlation coefficients between body weight of Holstein-Friesian males and some body measurements at the age of one year.

Table 5 .
Regression equations for estimating the weight of Holstein-Friesian males by some body measurements at the age of one year.

Table 7 .
Regression equations for estimating the weight of 2-year-old Holstein-Friesian males based on some body measurements.

Table ( 8
[12]plains the estimation of the weight of Holstein-Friesian males at the age of 3 years, where it was found that the best regression equation for estimating body weight is through the chest girth as a And the estimates of standard error for two equations were 25.725 and 27.936 respectively .whofound the These results are close with results of[12], determination coefficient was 0.87 ² as well as in theTanzaniancows and in Zebue strain the equation regression was: Lw = -543.33+ 5.47 HG and with a determination coefficient of R ² = 0.93.

Table 8 .
Correlation coefficients between the body weight of Holstein-Friesian males and some measurements at the age of 3 years.

Table 9 .
Regression equations for estimating the weight of Holstein-Friesian males at the age of 3 years, according to some body measurements7