GM-CSF treatment of frozen bovine sperm improves function, fertilization, and subsequent embryo development

In vitro embryo production (IVP) is used in the cattle industry to increase the rate of genetic gain. IVP uses semen that has been frozen and thawed, a process that renders sperm less viable than sperm from fresh semen. Granulocyte macrophage colony stimulating factor (GM-CSF) is present in bovine seminal plasma, while its receptor is present on bovine sperm. The present study aimed to determine if GM-CSF could improve the function and quality of frozen-thawed bovine sperm and embryo development following in vitro fertilization. Thawed bovine sperm (n = 3 bulls with 3 replicates per bull) was incubated with 0, 0.1, 1, 2 or 10 ng/ml of recombinant bovine GM-CSF in buffered wash media for 45 min and assessed for motility, glucose uptake, mitochondrial activity, intracellular calcium, capacitation, DNA integrity, and in vitro embryo development. The addition of 1, 2, and 10 ng/ml GM-CSF increased total motility (P = 0.02, P = 0.007, P = 0.01), progressive (P = 0.02, P = 0.03, P = 0.01), and rapid motility (P = 0.01, P = 0.01, P = 0.01), while 10 ng/ml increased glucose uptake (P = 0.003), and 1, 2, and 10 ng/ml increased capacitation (P = 0.003, P = 0.001, P = 0.0003). There was no difference between groups for mitochondrial activity, intracellular calcium, or DNA integrity. GM-CSF treatment of sperm prior to in vitro insemination increased fertilization rate (P = 0.01), hatching blastocyst rate (P = 0.05), and blastocyst inner cell mass cell number (P = 0.03) compared with control. In conclusion, GM-CSF treatment of frozen-thawed bovine sperm improves sperm function and quality resulting in increased fertilization capacity and subsequent embryo development, suggesting it may improve cattle IVP efficiencies.