The use of plastic cover sheaths at the time of artificial insemination improved fertility of lactating dairy cows.

An adequate and clean artificial insemination (AI) technique is recommended to improve reproductive outcomes in dairy cattle. The objective of this study was to evaluate the effectiveness of using protective plastic sheaths (PS) to minimize contamination of the AI catheter (AIC) on pregnancies per AI (PAI) in lactating dairy cattle. Lactating cows housed in freestall barns on a commercial dairy farm were presynchronized with 2 injections of PGF(2α) given 14 d apart (starting at 26±3 d postpartum) followed by Ovsynch (GnRH-7 d-PGF(2α)-56 h-GnRH-16 h-timed-AI; TAI) 12 d later. Cows presenting signs of standing heat any time during the protocol received AI, whereas the remaining animals were subjected to TAI 16h after second Ovsynch GnRH. At the time of AI (1 AI technician), 996 services from 773 lactating dairy cows were randomly assigned to 1 of the 2 groups; with (TRT, n=487) or without (CON, n=509) the use of disposable PS. In the TRT group, the AIC protected with a PS was introduced into the vagina; once in the cranial portion of the vagina adjacent to the cervical os, the PS was pulled back and only the AIC was manipulated through the cervix into the uterine body for semen deposition. In the CON group, cows were inseminated without the use of PS. Samples were taken with a sterile cotton swab from the tip of the AIC (n=51) after AI from both treatment groups. Pregnancy diagnosis was determined by ultrasonography 39±3 d after AI. Cultured swab samples revealed that the use of PS was effective in minimizing contamination of the AIC (positive bacterial growth: TRT=61.53% vs. CON=100%). Overall, the proportion of cows pregnant was greater for cows in TRT (42.7) compared with the CON group (36.1). For first services postpartum, PAI did not differ between CON (43.01%, n=194) and TRT (43.8%, n=182) groups. However, PAI for second or greater services were greater in TRT (43.8%, n=305) than in CON cows (32.3%, n=315). Results from this study provided evidence that the use of PS during AI improved PAI for second or greater services in lactating dairy cows. Performing a clean AI technique through the use of PS may be an effective strategy to improve reproductive outcomes in dairy cattle.