Determination of Breeding Target and Marginal Benefit Calculation of New Type of

Wei WANG, Yi SHI, Fang HE, Jia GAN, Donghui FANG, Maozhong FU, Xiaodong DENG, Suqun ZHAN, Zhimin LIAO, Cheng GUI, Bin WANG, Jun YI*

1. Sichuan Key Laboratory of Sichuan Province, Sichuan Animal Science Academy, Chengdu 610066, China; 2. Xuanhan County livestock and Poultry Breeding and Improvement Station, Xuanhan 636150, China; 3 Enyang Animal Disease Control and Prevention Center, Enyang 636046, China

Abstract [Objectives] To make targeted breeding of new type of Shuxuan beef cattle, study and determine the breeding target traits of new type of Shuxuan beef cattle. [Methods] The difference method was used to calculate the marginal benefit of each target trait, and the economic weight of the corresponding breeding target trait was obtained. [Results] The marginal benefits of weaning weight, fattening daily gain, 18-month weight, carcass quality, dressing percentage, pure meat percentage, age at first calving, calving interval and stay group time were 35.86, 13.76, 13.05, 421.96, 375.55, 22.58, -4.45, -27.53, and 1 555.24, respectively. The relative economic weight ratio of growth traits, carcass traits, and reproductive traits was close to 4∶1∶5. Through marginal benefit analysis, the economic benefits obtained by improving carcass quality, dressing percentage and stay group time were significantly higher than other traits. [Conclusions] It is expected to provide a theoretic basis for establishing the target trait selection indicators for the new type of Shuxuan beef cattle.

Key words Shuxuan beef cattle, Breeding target, Marginal benefits, Economic weight

1 Introduction

The method of determining the breeding target is to determine the target of obtaining the maximum economic benefit of animal production, and the selection of economically significant traits as the breeding target traits. It is necessary to determine the production traits in the comprehensive breeding value and calculate the marginal benefits of the traits. The marginal benefit of a trait reflects the influence of the trait on the economic benefits of the population and the breeding benefits that can be obtained through genetic improvement. The greater the marginal benefit, the higher breeding benefits can be obtained. Generally, the difference method is used to investigate the actual value of the marginal output and the marginal input of breeding, and carry out economic evaluation and calculation. The successful breeding of new type of Shuxuan beef cattle has effectively alleviated the demand for animal protein such as beef and milk in southern China. In recent years, with the changes in market demand in breeding areas, the economic value of Shuxuan beef cattle has become higher and more in line with the needs of the market and industry. On the basis of Shuxuan beef cattle population, our team screened individuals with excellent beef performance to form a breeding population, and carried out the selection and breeding of new beef groups. In addition, by establishing the profit function of the new type of Shuxuan beef cattle, we calculated the economic value and economic weight of the target traits, in the hope of providing a theoretical basis for the establishment of the target trait selection indicators for the new type of Shuxuan beef cattle.

2 Materials and methods

2.1 Parameter source

The production performance parameters and breeding technical parameters necessary for calculating the marginal benefit were obtained from the performance measurement and survey results of 2 300 new type of Shuxuan beef cattle in Xuanhan County, Sichuan Province from 2018 to 2019. We determined market economics parameters through surveying the benefits of cattle farms in Sichuan and market economics parameters. With reference to the relevant standards of Shuxuan Beef Cattle, we determined the nutritional parameters, and the specific parameters are shown in Table 1-5.

Table 1 Average production performance parameters for new type of Shuxuan beef cattle

Table 2 Breeding technical parameters for new type of Shuxuan beef cattle

Table 3 Market economic parameters in Sichuan

ItemCodeParameterCosts of building and repairing barn for each adult bull yuan K68 000.00Costs of grassland construction for each grazing cattle yuanK7500.00Travel, labor and consultation costs for breeding of each adult cow∥yuanK810.50Costs for beef performance measurement of each fat-tening cattle∥yuanK930.00Cost of each insemination∥yuanK10150.00Increase of beef price for one grade increase of car-cass quality∥yuanK111.50Annual interest on fundsK120.05Number of laborers for each calf per day∥personA10.015Number of laborers for each grazing young cattle per day∥personA20.02Number of laborers for each grazing adult cow per day person A30.02Number of laborers for each feeding young cattle per day∥personA40.015Number of laborers for each feeding adult cow per day person A50.02Number of laborers for each feeding adult bull per day person A60.015Number of laborers for each fattening cattle per day person A70.01Daily wage∥yuanA8120

Table 4 Nutritional parameters of Shuxuan beef cattle

ItemCodeParameterAverage energy for 1 kg weight gain of bull during fattening period/MJB1527.69Average energy for 1 kg weight gain of cow during fattening period/MJB1617.84Daily net energy for 1 kg weight gain of 18-month bull MJ B170.111Daily net energy for 1 kg weight gain of 18-month cow/MJB180.089Daily net energy for each adult bull∥MJB1959.79Daily net energy for each adult cow∥MJB2041.80Daily net energy for each cow during first mat-ing MJ B2132.97Energy contained in 1 kg starters∥MJB228.46Energy contained in 1 kg hay∥MJB234.04Energy contained in 1 kg corn silage∥MJB241.85Energy contained in 1 kg concentrates for fatte-ning cattle∥MJB257.28Energy contained in 1 kg concentrates for heifer and young cattle∥MJB267.29Energy contained in 1 kg concentrates for adult cattle MJ B277.63Average supplementary feeding time for each young cow and adult cow in supplementary feeding area∥dF1210Proportion of grazing and supplementary feeding∥%F215Proportion of entire barn feeding∥%F385Proportion of grazing cattle that can meet the nutritional needs∥%F490Energy for grazing cattle walking to metabolize 1 kg weight per day∥MJF50.419Proportion of concentrates, hay, and corn si-lage for lactating cowsH1C∶H1G∶H1S18∶16∶66Proportion of concentrates, hay, and corn si-lage for heiferH2C∶H2G∶H2S16∶21∶63Proportion of concentrates, hay, and corn si-lage for young cattleH3C∶H3G∶H3S13∶17∶70Proportion of concentrates, hay, and corn si-lage for fattening cattleH4C∶H3G∶H3S30∶20∶50

Table 5 Constant table for new type of Shuxuan beef cattle

2.2 Selection of breeding target traits for new type of Shuxuan beef cattle

The ultimate target of breeding is to obtain the maximum economic benefits, so it is necessary to solve the problem of how to measure and express the breeding target. According to modern breeding methods, when determining breeding target, we used the formula of comprehensive breeding value:

A

=∑

W

A

(1)

where

W

=

W

n

,

A

is the comprehensive breeding value,

W

is the economic weighting factor of trait

i

,

A

is the general breeding value of trait

i

,

W

is the marginal benefit of trait

i

,

n

is the discounted standardized performance value of trait

i

.

2.3 Calculation of the marginal benefit of breeding target traits

The marginal benefit is the difference between the marginal output and the marginal input when the target trait value exceeds the group mean by one unit. The greater the marginal benefit of a trait, the greater the contribution of the trait to the group’s economic benefits. We used the difference method to construct the calculation of the marginal benefit and the relationship between the cost and the benefit related to the trait under the current production management level. The calculation formula is as follows:

(2)

where

V

is the marginal benefit of trait

i

,

ΔR

is the

j

-th output component of trait

i

,

ΔC

is the

j

-th output component of trait

i

.

3 Results and analysis

3.1 Selection of breeding targets

In this study, we made a systematic analysis of the growth traits, carcass traits, and reproductive traits of the new type of Shuxuan beef cattle. The growth traits mainly include birth weight, weaning weight, year-old weight, 18-month weight, 24-month weight, adult weight, fattening daily gain, and feed conversion rate and other major traits that reflect economic benefits. In the Shuxuan beef cattle production system, the weaning weight not only reflects the growth of the calf before weaning, but also plays a decisive role in the growth trend of the calf after weaning. Thus, weaning weight is used as one of the breeding target traits. Because there is a linear relationship between weaning weight and birth weight, the birth weight is regarded as the selective trait of weaning weight. 18-month weight is an important evaluation standard for evaluating the future growth trend of breeding populations and commercial herds. The 18-month weight is used as a candidate target trait. Because 18-month weight is related to 24-month weight and adult weight, the 24-month weight and adult weight are regarded as selective traits for the 18-month weight traits. In view of the lack of data on the feed conversion rate of Shuxuan beef cattle, we selected the fattening daily gain of fattening cattle as the breeding target trait. Carcass quality traits mainly include carcass quality, marbling grade, back-fat thickness, thigh thickness, fat coverage, eye muscle area, shear force, water holding capacity, dressing percentage, and pure meat percentage. Carcass quality is the result of comprehensive evaluation of marbling grade, fat coverage, eye muscle area, shear force and water holding capacity. Thus, we selected the carcass quality as the breeding target traits, and took eye muscle area and the marbling grade as the selective traits of the carcass quality. The dressing percentage and meat percentage directly reflect the relative carcass quality and production performance of beef cattle, thus we selected dressing percentage and meat percentage as the breeding target traits. Reproductive traits are an important comprehensive trait and exert a long-term effect on breeding benefits. In this study, we took the age at first calving, calving interval and stay group time as the breeding target traits, and took feedlot record, first conception rate, and holding power as the selective traits of the above breeding target traits. Finally, we selected 9 breeding target traits, as shown in Table 6.

Table 6 Breeding target traits for new type of Shuxuan beef cattle

3.2 Construction of profit function for new type of Shuxuan beef cattle

Combining with the breeding, production and market system of Shuxuan beef cattle, and with reference to the research on income and cost functions abroad in recent years, we separately constructed the profit functions of 9 target traits.

The marginal benefit of weaning weight (WWT):

When the weight gain of the weaned bull is 1 kg, the corresponding weight gain of the cow is h=W2b/W2a=0.902.

V

=P5×Q3×(1+h)-P5×182×Q6×(B5+B6×B3×h)/[(B2+B3+B4)×B22]-P5×182×Q10×(B5+B6×h)×B4/[(B2+B3+B4)×B23]-P5×182×Q1×(B5+B6×h)×B2/[(B2+B3+ B4)×B1]

(3)

The marginal benefit of fattening daily gain (FDG):

V

=[(H4C×Q7+H4G×Q10+H4S×Q11)/100]×[P6×D9a/(100×D4a/D4b)+P7×D9b/100]×(1-P9+1)/2×[(H4C×B25+H4G×B23+H4S×B24)/100]+[K3×D8a×P6/(100×D4a/D4b)+K3×D8b×p7/100]×(1-p9+1)/(20×365)+[A7×A8×D8a/(100×D4a/D4b)]×P6×(1-P9+1)/2+(A7×A8×D8b/100)×P7×(1-P9+1)/2+(D8a×P6+D8b×P7)×Q15×[(1-P9+1)/2]/365

(4)

The marginal benefit of 18-month weight (WT18):

When the weight gain of the 18-month bull is 1 kg, the corresponding weight gain of the cow is h=W4b/W4a=0.806.

V

=(P5-P6+P8×h)×(1-P10)×Q4-[(P5-P6)×P10×365×B17+P8×P10×365×B18]×(H2C×Q8+H2G×Q10+H2S×Q11)/(H2C×B26+H2G×B23+H2S×B24)

(5)

The marginal benefit of carcass quality (CQ):

V

=(P6×D1a+P7×D1b)×K11×(1-P9)

(6)

The marginal benefit of dressing percentage (DP):

When the dressing percentage of slaughtered bull increases by 0.01, the corresponding increase in the dressing percentage of cow is h=W10b/W10a=0.009 12.

V

=[0.01×D1a+(0.01×0.00912)×D1b]×0.84×Q2×(1-P9)

(7)

The marginal benefit of pure meat percentage (PMP):

When the pure meat percentage of slaughtered bull increases by 0.01, the corresponding increase in the pure meat percentage of cow is h=W11b/W11a=0.009 34.

V

=[0.01×D1a+(0.01×0.00934)×D1b]×Q2×(1-P2)

(8)

The marginal benefit of age at first calving (AFC):

V

=0-F3×P8×[(H3C×Q8+H3G×Q10+H3S×Q11)/100]×B21/[(H3C×B26+H3G×B23+H3S×B24)/100]-P8×K2/(20×365)-(P8×F2×A2×A8+P8×F3×A4×A8)-P8×W8×Q4×(K12/365)-(P8×Q12+F2×P8×K7/365)

(9)

The marginal benefit of calving interval:

V

=0-[F2×(B20+F5×W6b)+F3×B20]×(H1C×Q9+H1G×Q10+H1S×Q11)/(H1C×B27+H1G×B23+H1S×B24)-K5/(20×365)-(F2×A3×A8+F3×A5×A8)-P8×(W6b×Q4+Q5)×K12/365-K10/21

(10)

The marginal benefit of stay group time (GT):

When the stay group time of adult cows increases from 7.9 years to 8.9 years, it is equivalent to increasing the lact from 6 to 7 and the average number of rejected cows sold per calving cycle dropped from 0.157 to 0.143. Due to the prolong of stay group time, the number of cow calves for breeding is reduced, and the feed consumption is reduced during 6-month weaning and 24-month. During this period, the breeding cows mainly experience the growth period (6-18 months old) and young period (18-24 months old), the average weight of the cows during the growth period is 310 kg, and the average weight of the cows during the young period is 450 kg.

V

=P1×P4×[W1a+(365-T7)×W7a+W1b+(365-T7)×W7b]×Q3×(365-T7)/182+(0.157-0.143)×Q3×W6b+(0.157-0.143)×(1-F4×F5)×[(230×B16+365×310×0.322)+(50×B16+182×450×0.322)]×(H3C×Q8+H3G×Q10+H3S×Q11)/(H3C×B26+H3G×B23+H3S×B24)-(0.157-0.143)×W6b×Q4-K5/20-(F2×A3+F3×A5)×A8×365-(F2×K7+Q13)

(11)

3.3 Economic weight of breeding target traits for new type of Shuxuan beef cattle

According to the calculation of the above functions, the marginal benefits of weaning weight, fattening daily gain, 18-month weight, carcass quality, dressing percentage, pure meat percentage, age at first calving, calving interval and stay group time were 35.86, 13.76, 13.05, 421.96, 375.55, 22.58, -4.45, -27.53, and 1 555.24, respectively. It is found that the marginal benefit values of improving carcass quality, dressing percentage and stay group time are the most significant, indicating that improving the genetic progress of these traits can achieve greater economic benefits. The marginal benefit value of age at first calving and calving interval is negative, indicating that as the age at first calving increases and calving interval prolongs, the economic benefit decreases. The marginal benefits of different units are standardized by the genetic standard deviation of each target trait, and the economic weight of each breeding target trait is obtained. Among the three types of traits, the economic weight ratio of growth traits, carcass traits, and reproduction traits is about 4∶1∶5, as indicated in Table 7.

Table 7 Selection importance of breeding target traits for new type of Shuxuan beef cattle

4 Conclusions

In this study, we determined the breeding targets of 9 economic traits in 3 traits of the new type of Shuxuan beef cattle. The relative economic weight ratio of growth traits, carcass traits, and reproductive traits was close to 4∶1∶5, Through marginal benefit analysis, the economic benefits obtained by improving carcass quality, dressing percentage and stay group time are significantly higher than other traits.