Economic evaluation of artificial insemination of sex‐sorted semen on a Brown Swiss dairy farm—A case study

Abstract Artificial insemination using sex‐sorted semen is employed to efficiently increase the number of female dairy calves born. Previous studies have determined that using sex‐sorted semen is beneficial to improve the management, but the mechanism by which it increases cattle numbers through objective indices of breeding remains unclear. This study focused on a Brown Swiss cattle herd in which frozen female sex‐sorted semen was systematically employed to increase the number of cattle. We analyzed the correlation between the increase in the number of cattle and the screening accuracy of sex‐sorted semen, measuring indices such as pregnancy rate and birth rate of female calves. Study revealed that: (1) production cost for female calves is influenced by the pregnancy rate, rate of female calves, and using sex‐sorted semen is less expensive than using nonsorted semen; (2) improvements in screening accuracy nearly doubled the number of cows and tripled the number of heifers in 5 years; and (3) use of sex‐sorted semen improved milk quality. The pregnancy rate was lower when sex‐sorted semen was used, but the birth rate of heifers was improved. Results suggest that artificial insemination using sex‐sorted semen is beneficial because it economically produces offspring to increase the herd.


| INTRODUC TI ON
Japan has introduced policies to prioritize efficient breeding methods and high productivity in commercial dairy farms, and the number of cattle has rapidly expanded to 80.7 individuals per farm (Arai, 1989;Ministry of Agriculture, Forestry and Fisheries, 2017).
Meanwhile, as feeder calf prices have soared, dairy farmers in many prefectures have begun to choose hybrid production, using semen from Japanese Black cattle rather than dairy cattle semen in artificial insemination or producing Wagyu though embryo transfer (Osada, Ushijima, & Ozawa, 2017). Although offspring production of dairy cattle has been guaranteed, the price of first-pregnancy dairy cows in Hokkaido has skyrocketed along with the price of beef cattle, with first-pregnancy dairy cows regularly commanding prices in excess of 1 million yen per head in 2017 (Ozawa, Lopez-Villalobos, & Blair, 2005). There is concern that the current guaranteed state of offspring will worsen as trends such as individual and cooperative farming become more popular Osada, Ushijima, & Ozawa, 2015) (Figure 1).
Securing guaranteed offspring is an important aspect of dairy farming, and the use of sex sorting technology for semen has prompted a number of studies of efficient methods for securing heifer calves

Economic evaluation of artificial insemination of sex-sorted semen on a Brown Swiss dairy farm-A case study
Masahiro Osada 1 | Hitomi Iwabuchi 1 | Toru Aoki 2 | Kika Sasaki 2 | Hitoshi Ushijima 1 | Takeyuki Ozawa 1 1 (Hamano, 2015;Kataoka et al., 2015;Kawano, Toma, & Sembokuya, 2014;. The utilization of domestic sex-sorted semen has increased to 12.9% (AIAJ, 2017), and its effectiveness has been confirmed, as the birth rate of female calves exceeded that of bull calves in 2015 ( Figure 2). Osada (2017) noted that the intended use of female sex-sorted semen is not to increase the overall number of female cows nationwide, but rather to secure the necessary number of female calves to maintain personal herds through efficient heifer calf production. Therefore, it is possible to receive tax exemptions on profits from beef sales in industries aimed at increasing the numbers of first-pregnancy heifers. These exemptions have expanded from dairy cattle sales to industries raising cattle for beef, including the production of crossbreeds and selective transfer of Japanese Black embryo. Although sex screening technologies have advanced from the diffusion stage to the practice/effect verification stage, to date there is no analysis of the process by which this technology affects the production of female calves, through objective indices of breeding technology.
At the 193rd Ordinary Diet session, draft legislation was revised to amend part of the law concerning livestock management stability. As of 2018, Japan will abolish the provisional aspect of laws such as the Act on Temporary Measures Concerning Compensation Price for Producers of Milk for Manufacturing Use, making the system permanent, and will expand the targets for tariff elimination restricting partial consignments and supplementary milk producers in order to promote distinctive dairy farming systems. As part of these revisions, a "premium trading system" was introduced in 1998 focusing on the elasticity of raw milk consignment sales, enabling farmers to negotiate prices for individual collections of distinctive raw milk or to add premiums to regular milk prices. The distinctive raw milk produced by Brown Swiss cattle is sold as milk and as other dairy products. As the size of herds has increased in recent years, so have expectations for boosting the diversity of raw milk trading.
This study focuses on cases where female sex-sorted semen was used to increase the production of Brown Swiss cattle (Endo, Kuroki, & Tanaka, 2017), in order to better understand the mechanism by which female sex-sorted semen affects the increase in cattle population in terms of objective indices of breeding technology. In addition, we consider the guaranteed offspring policy associated with using sex selection technology, and consider its implications for sustainable dairy farming.

| MATERIAL S AND ME THODS
The Ozasa Farm Dairy Farming Cooperative in Tochigi prefecture is located at an altitude of 1,300 m, at the northern end of Nikko Furthermore, the insemination rates of frozen female sex-sorted semen and nonsorted semen were compared, female production efficiency was calculated based on the sex of offspring, and the effect of using female sex-sorted semen was analyzed. Also, heifers were younger than 14-month-old nonpregnant cows, and were over 14-month-old pregnant cows.

| Fertility of female sperm
Changes in the number of and pregnancy rate for heifers/dairy cows according to type are indicated in Table 1. Although the use of frozen female sex-sorted semen fluctuates from year to year, from 2013 to 2016, artificial insemination using frozen female sex-sorted semen was used 231 times, a utilization rate of 49.3%. The pregnancy rate from female sex-sorted semen was 83/231 inseminations (35.9%); the rates for dairy cows and heifers were 32.4% and 41.6%, respectively, with heifers 9.2 points higher, which is not significantly different from the results of previous studies (Nakao, 2005). Studies have noted that the number of heifer calves produced increases with specific use of sex selection technology (Kataoka et al., 2015), and as heifer pregnancy rates are higher than dairy cow pregnancy rates, specific use of sex selection technology is particularly recommended for heifers. Although the use of female sex-sorted semen does not increase the rate of abnormalities (teratogenicity), the sperm survive only a short time, and the concentration of sperm is typically 3,000,000-6,000,000 sperm per ejaculate (less than one tenth of nonsorted semen), which is said to contribute to lower conception rates (Karakaya et al., 2014).

| The cost of producing female offspring
The cost to produce a female calf using frozen female sex-sorted semen was calculated, taking into consideration the results of using sex-sorted semen and pregnancy rates. The cost is based on a number of variable factors, such as the price of artificial insemination, the price of frozen sex-sorted semen, the pregnancy rate, and the female production ratio. Therefore, the expenses were calculated using the formula (compound rate + raw material)/rate of pregnancy/female Note. In case of multiple artificial insemination sessions per cycle, the number was recorded as "once." probability ( Table 2). This price represents the production cost of a single female calf and does not include the loss of milk revenue due to declining pregnancy rates or expenses incurred from prolonged fertility treatments. The rate of female calf production from nonsorted semen is approximately 48% (Hamano, 2015); in the case of artificial insemination, with a pregnancy rate of 40%, the cost of a female calf equals 46,875 yen. The pregnancy rate when female sexsorted semen is inseminated is 10% lower; however, the female production rate is 90%, bringing the price per female calf to 44,444 yen.
Thus, the use of female sex-sorted semen is an efficient method of producing female offspring.
Of note, all female sex-sorted semen of Brown Swiss on the market in 2015 was imported, and the sorting accuracy of imported semen may be less than 90% (Ushijima, Geshi, Akagi, Izaike, & Yoshiaki, 2018). If the probability of producing female offspring from imported sorted semen is only 80%, each female calf produced will cost 50,000 yen, making the process less cost-effective for dairy farmers.
Production costs per female calf were estimated based on the pregnancy rates of Ozasa Farm between 2013 and 2016, and from the female production rate of both nonsorted frozen semen and frozen female sex-sorted semen. With regard to the pregnancy rate of nonsorted semen, 2015 appeared to be an outlier with a 100% pregnancy rate, much higher than the average 53.5%, but the accuracy of female sex-sorted semen was 73.8%, unusually low. Based on 2016 pregnancy rates and the probability of producing female offspring, the price per head for nonsorted semen fertilization is 38,851 yen, and that for female sex-sorted semen is 45,293 yen, which is higher. However, the rate of production of female calves cannot be determined by the dairy farms, and responsibility lies solely with semen suppliers. As current frozen female sex-sorted semen on the market must meet a screening purity rate of 90% or more, the rate of female offspring produced should be 90%. In the trial calculation for average pregnancies from 2013 to 2016, the rate was 35.9%, indicating a cost of 37,140 yen per cow. The cost of producing calves using frozen female sex-sorted semen with a low pregnancy rate is equivalent to the rate of production using nonsorted frozen semen. Figure 4 and  As for the increased number of calves conceived in 2015, while there were slight improvements due to the use of female sex-sorted semen, pregnancy rates were as low as 38.1%. According to these results, the factors that determine pregnancy rate are the number of heifers who were unable to conceive in the previous year and the utilization rate of female sex-sorted semen that year, as well as the female sex-sorted semen fertilization rate for inseminations occurring two or more times (Table 4).

| Improvements to cattle production and breeding technologies
We must endeavor to improve the rate of conception using frozen female sex-sorted semen by paying attention to the method of insemination and semen characteristics. In an analysis that simulated an increase in the use of sex selection technology, when frozen female sex-sorted semen was used under conditions of low conception rate, it became difficult to guarantee offspring, leading to a reduction in profitability due to the increase in operational expenses and delays in conception rates. For the strategy to be effective, the conception rate must be at least 45%, and female sex-sorted semen must be used at least 50% of the time (Kawano et al., 2014).
The pregnancy rate for nonsorted semen at Ozasa Farm is 45% or lower. While the rate of pregnancy resulting from at least two uses of female sex-sorted semen has gradually decreased from its 2014 peak of 45.9%, the utilization rate exceeds 60%, from which it can be inferred that the rate of pregnancy has decreased. As pointed out in previous simulation analyses, the pregnancy rate deteriorated and reproductive performance worsened, with issues such as an increase in the number of empty placentas or an increase to the number of dry days. In response to these problems, the use of female sex-sorted semen was reduced after 2015, in an effort to improve pregnancy rates. Although the decline in conception rate is a concern, the average number of female calves produced between which has risen to 60% (Kataoka et al., 2015).
In an effort to expand processing and sales, Ozasa Farm achieved a female delivery rate of 65.7% after 4 years of thorough use of sexsorted insemination techniques, increasing the number of cattle in the herd. Both herd replacement rate and milk quality improved, making more high-quality milk and dairy products available to consumers, and demonstrating a successful sustainable dairy farming model.
Utilization of sex screening technology was confirmed to be an economical and efficient strategy for in-farm production of cattle while increasing the size of the herd . However, when using frozen female sex-sorted semen, it is necessary to maintain cattle rearing standards so that the rate of pregnancy does not decrease.