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• Crossbreeding requires more mating decisions than a traditional breeding program.
• The herd breed composition continually changes in a crossbreeding program.
• Each breed composition needs a specific breeding strategy.
• Sire selection continues to be the most important genetic decision for a producer.
• The most success from crossbreeding will result by choosing outstanding bulls from each breed.

Crossbreeding among dairy breeds has increased in recent years. Anticipated advantages to crossbreeding dairy cattle are reduced fluid carrier, i mproved fertility and greater productive life. Anticipated disadvantages to crossbreeding dairy cattle are potential loss of breed identity, short rather than long-term cure for inbreeding and difficulty to maintain performance with dynamically changing herd composition.

If you have primarily a Holstein herd and are considering crossbreeding, the following article will define some expected outcomes. First, crossbreeding is not easy. It requires more decisions than a traditional breeding program because the producer needs to decide which breeds to use in the crossbreeding program in addition to selecting the bulls within a breed. Of course, shortly after the breeds are chosen, the producer’s herd will have new breed combinations and the producer will need to make additional breed decisions.

Table 1. Age distribution for a dairy herd

Example 1: For the first example, I will start with an all Holstein herd. Table 1 shows the expected age distribution of animals in that herd. In order to simplify the example, I consider the oldest animal in the herd to be six years old and that death loss increases as the animals grow older. The third column identifies the percent of the milking herd in each age bracket. The last column indicates the number of females in each age bracket for a 100-cow milking herd. Sixty heifers are less than one year of age. Fifty heifers are less than two years old. Forty cows are expected to be between the ages of 2 and 3 years. Only 10 of the 100 cows that are milking are expected to be between 5 and 6 years of age.

This Holstein herd will enter into a two breed rotational crossbreeding program, which is the simplest crossbreeding program. Jerseys will be used as the second breed, but many other options exist. A typical mating decision would be to mate all Holsteins to Jerseys. This is the only breed decision that needs to be made for the first two years of the program. This decision can be followed as long as some animals in the herd are 100% Holstein. The next breed decision would be to mate the Holstein-Jersey crossbreds back to Holstein and create an offspring that is 75% Holstein and 25% Jersey ( HJ/HH). Note that this is the pattern for a two breed rotational crossbreeding program. The crossbreds that are 75% Holstein and 25% Jersey should be mated back to Jersey to maintain the two breed rotational crossbreeding system. The resulting offspring would be 37.5% Holstein and 62.5% Jersey ( HJHH/JJJJ).

Theoretically, it is easy to describe a two breed rotational crossbreeding program. Alternate breeding between two breeds. The difficulty comes in the application because the herd breed composition continually changes. After a number of years, an equilibrium breed composition will be achieved with two-thirds of one breed and one-third of the other. The next generation, the herd would have individuals that were one-third of the first breed and two-thirds of the second breed. The breed composition of the herd would vacillate between these extremes even after equilibrium is reached. Table 2 has the breed composition for the first seven years of a two breed rotational crossbreeding program. Equilibrium has not yet been reached. No 100% Holsteins would remain in the herd in the 7 th year, although the herd was only Holsteins in year 1. Year 6 has the most diversity in breed composition with four different breed compositions present. Each breed composition needs a specific breeding strategy. After year 3, semen from both breeds will be used in the breeding program.

Table 2. Number of cows or heifers by breed or breed combination

However, the semen needs will two-thirds Holstein and one-third Jersey one year and then the next generation the opposite semen distribution between breeds will be required. And to repeat, the most success from the program will result by choosing outstanding bulls from each breed. Using a crossbreeding program does not replace sire selection, which continues to be the most important genetic decision for a producer.

Example 2: In cattle, the average milk production of purebred Jersey and Holstein cows is 16,052 and 23,374 pounds, respectively. Crossbred cows from the mating of Holstein bulls and Jersey females may result in cows that have an average milk production of 21,624 pounds. The reciprocal cross may produce cows that average 21,744 pounds. Using these data, the heterosis of milk production would be 10%. The average of the Holstein-Jersey crossbred is expected to be better than the average of the purebred Holstein and purebred Jersey by 10%. Please note that even with this positive heterosis, the average Holstein is expected to outproduce the crossbreds for milk production. Figure 1 demonstrates that heterosis would need to be greater than 20% for the crossbreeds to exceed the purebred Holsteins for milk yield.

If a two-breed rotational crossbreeding program was followed, the heterosis would need to be

30% to match the Holsteins for milk performance because only two-thirds of the heterosis is captured. More of the heterosis would be captured in more complicated crossbreeding strategies. For example, a three-breed rotational crossbreeding program at equilibrium would capture 86% of the possible heterosis, but reaching equilibrium would require over 20 years. Crossbreeding is not an easy solution to improve dairy profitability.