Pursuit of a method for single administration of pFSH for superstimulation in cattle: What we have learned

A single dose protocol of FSH for superstimulation in cattle may improve compliance and superovulatory response. A single subcutaneous (sc) administration of pFSH was efficacious, but response depended on body condition and injection site; the adipose tissue pad behind the shoulder was most efficacious. Inconsistent results in Holsteins were partially overcome by sc administration of 75% of the total pFSH dose behind the shoulder on the first day followed by 25% 48 h later. An alternative would be to combine FSH with polymers that cause it to be released slowly over several days. Hyaluronan is found normally in most animal tissues and is nonreactive when administered parentally. A single intramuscular (im) administration of pFSH in a 2.0% hyaluronan induced a superovulatory response that did not differ from twice daily im administration over 4 d. However, 2.0% hyaluronan was viscous and difficult to mix with FSH. Although solutions of 1.0 and 0.5% hyaluronan were less viscous, they lacked efficacy as a single im administration. However, superovulatory response was high when either 1.0 or 0.5% hyaluronan was used in a two-dose im protocol; two-thirds on the first day and one-third 48 h later. A single im administration of FSH in 0.5% hyaluronan effectively induced superstimulation for OPU in cattle. Successful superovulation in the cow was associated with circulating FSH levels that were similar to endogenous FSH levels prior to follicular wave emergence; however, levels must be maintained above baseline for at least 72 h, or 36 h for OPU. Circulating FSH levels following a single sc administration of 400 mg NIH-FSH-P1 behind the shoulder in beef cows increased to 1.0 or 1.2 ng/mL at 12 h and were back near baseline in approximately 60 h, while FSH levels following im administration of 200 mg NIH-FSH-P1 in 0.5% hyaluronan into Holstein donors reached 1.5 ng/mL at 12 h and returned to baseline in approximately 36 h.