By Kara Stewart, Purdue University Department of Animal Science, and Kyle Lovercamp, University of Central Missouri Department of Biology and Agriculture
Training boars for semen collection typically begins between 8 and 9 months of age; occurs over a two- to four-week period; and has important implications for the overall efficiency of semen production for the boar stud.
Previous studies indicate that this is a good strategy; the majority of boars successfully collect in the first one to two weeks; and the percentage of boars that never train for semen collection is typically quite small, between 3% and 5%. However, a recent survey of U.S. boar studs indicated that nearly one-third of studs were starting to train boars at younger ages with some beginning when boars were less than 7 months of age.
The impact on beginning the training period at younger ages has not been evaluated with modern genetic lines. Therefore, a study was conducted to evaluate training frequency in young “modern” boars on success in semen collection.
Six month-old boars were trained for semen collection either five days or two days per week, for a total of three weeks. Each training session was five minutes in length and only extended in time if the boar was actively engaged with the dummy. For each training session, the boar’s behavior was given a numerical score based on the following criteria.
0: No interest in dummy
1: Sniffs and rubs against the dummy, but does not chew, bite or charge it
2: Aggressively interacts with the dummy (bites, chews, charging)
3: Mounts dummy, but does not extend penis
4: Mounts dummy, extends penis, does not collect
5: Mounts and collects
Figure 1 indicates that 37.5% of the boars in the two-days-per-week training group were successfully trained for semen collection after the three-week training period compared with 88.9% of boars in the five-days-per-week regimen. Most of the boars that were not trained during the first three weeks in both treatments had scores of 2, 3 or 4, indicating that they were very interested in the collection dummy and their training period probably should be extended.
The results of this study indicate that young boars can be successfully trained for semen collection at young ages and increased training frequencies enhance the efficiency at which this occurs. It is important to remember that sexual maturity in boars is a gradual process that occurs over time and includes behavioral events such as the boar’s desire to mount as well as physiological ones associated with production of fertile sperm.
Studs that initiate training at 8 to 9 months of age likely have a large percentage of the boars mount and collect in the first week since both the behavioral and physiological aspects associated with puberty have occurred in the majority of the boars. However, it is possible that this management strategy results in possible loss of two to three months of semen production since most of these boars are capable of semen collection at younger ages. Given that most boars in studs remain in production for 12 to 16 months, this represents anywhere from 12.5% to 25% of their lifetime productivity and presumably a delay in turning over the genetics for the stud’s customers.
As a result, the age at which to begin training boars for semen collection is a decision that is stud specific and has to balance increased labor costs against improvements in lifetime productivity and genetic progress. Nevertheless, increasing the training frequency appears to improve the proportion of boars that can be successfully collected while reducing the time period over which this occurs.