Written By: Amanda Minton, M.S. – Associate Director of Reproductive Technology with Acuity Genetics
The US swine industry regularly uses data platforms to measure and benchmark economic and production metrics across the sow and wean-to-market space but boar performance is left undefined. The reason for this gap is understandable – a small population of animals, a limited number of studs, etc. Because of pooling, we also don’t know individual fertility for most boars. Yet how boar studs operate and the fertility of boars has a profound impact across the entire industry. Research estimates 20 to 30% of the boar population is sub or infertile (Dyck et al., 2009) and the boar is responsible for 5-8% of the variation in farrowing rate and litter size (Broekhuijse, 2012). This not only affects sow farm wean pig volume but finisher efficiency and the ability to meet customer commitments.
Commercial sow farms receive pooled terminal semen from boars with relatively unknown fertility. Pooled semen has historically been used as a protection mechanism – to protect the sow farms from low fertility boars and protect the boar stud from losing business. If we look beyond our borders, there are countries like The Netherlands that only use single sire AI doses at 1.5 billion total sperm and sows average 27.5 weaned per year (Kemp et al, 2011, Broekhuijse, et al., 2015). While pooling creates a perceived safety net, there has to be a better way to minimize or take advantage of the fertility potential of a boar.
Boar studs use various types of technology for conventional semen analysis. Computer-assisted semen analysis (CASA) systems are used to subjectively determine ejaculate concentration and motility. Morphological abnormality evaluation is either done manually or automatically by a CASA to identify proximal and distal cytoplasmic droplets and bent tails. Boar studs rely on these parameters to make decisions on when to extend an ejaculate to include in a pool. But even when ejaculates pass based on motility and gross morphology, fertility isn’t guaranteed. There are still boars with poor conception rates (Figure 1) and low total born (Figure 2).
Figure 1. Each bar represents an individual boar. The graph depicts boar fertility vs. motility and morphology. Data were collected using single sire matings on multiple commercial sow farms (The Maschhoffs, unpublished).
Figure 2. Relationship between morphological abnormal cells and the total number of pigs (TNB) born per litter (Feitsma, 2009)
If our traditional semen quality parameters don’t adequately predict what we see in the field, what should we be measuring? Predicting the fertility of an individual boar requires taking a deep dive into complex functional and molecular sperm traits. A tool used to measure these traits is flow cytometry. Flow cytometry has been used in research for several years but hasn’t been widely adapted by boar studs for routine analysis. Reasons for this include cost as well as the inability to get results soon enough to make production decisions. Assays measuring sperm chromatin structure, cell viability, membrane and acrosome characteristics and a variety of biomarkers express varying levels of significance with fertility (Didion et al., 2009, Gillen, 2005, Sutovsky, 2015). To summarize the research, no single variable is an all-in-one indicator but a combination tells the best story of a boar’s fertility.
Boar fertility is complex and the model used to elucidate fertility potential must be holistic in nature. In the near term, boar studs will be able to manage boars and semen doses based on a deeper set of sperm parameters. No longer will studs need to pool semen but rather sow farms will be able to receive single sire doses from boars with known fertility potential.
Editor’s Note: We at The Real P3 reached out to our trusted experts in the industry to learn more about boar fertility and genetics. To hear more from Amanda Minton and Acuity listen now!
Acuity is a swine genetics company that was created in response to a need for genetic improvement with a systems-based focus. For nearly a decade, our technical team has worked to develop a platform capable of delivering solutions that increase profitability throughout the supply chain. Our focus is different: commercially-derived data supports decisions that enable value realization.