Reproductive efficiency is a major factor for profitability in dairy herds. Artificial insemination (A.I.) is the most common practice used to breed dairy cows in the United States, accounting for approximately 78 percent of all services.
Accurate animal identification, semen handling, hygiene of the A.I. procedure and site of semen deposition are paramount to achieving acceptable reproductive outcomes over time.
Inseminators should review A.I. procedure on a regular basis (e.g., monthly), as well as their reproductive performance over time. Although the A.I. procedure (i.e., hygiene and site of semen deposition) is often overlooked, an appropriate and clean A.I. technique is recommended to optimize reproductive outcomes in dairy cows.
Protective A.I. cover sheaths, rigid PVC tubes of 30 cm in length and 0.7 cm in diameter, were developed to prevent vaginal contamination of the A.I. gun at the time of A.I., with the aim of improving reproductive outcomes.
The presence of manure around the vulva is common at the time of A.I. in lactating dairy cows. The contact of the tip of the A.I. gun with manure present on the vulvar skin must be avoided to reduce the likelihood of introducing external contaminants (e.g., E. coli) into the uterine lumen at the time of A.I.
The effectiveness of using cover sheaths (on top of the regular A.I. sheaths) at the time of A.I. on pregnancies per A.I. (PAI) was evaluated in three commercial dairy herds. The objectives of this study were to: evaluate the effectiveness of using disposable protective sheths to minimize vaginal contamination of the A.I. gun at the time of A.I. and assess pregnancies per A.I. in lactating dairy cows inseminated with or without the use of disposable protective sheaths.
Materials and methods
Lactating cows (primiparous = 1,158 and multiparous = 1,062) housed in freestall barns from three commercial dairy farms were used in this study. All cows were presynchronized with two injections of PGF2α (25 mg) given 14 days apart (starting at 26 ± 3 days postpartum) followed by Ovsynch OV; GnRH-7 d-PGF2α-56 h-GnRH-16 h-timed-AI(TAI) 12 days later.
Cows presenting signs of standing heat any time during the protocol received A.I., whereas the remaining animals were subjected to TAI 16 hours after second OV GnRH (100 μg). At the time of A.I., 2,843 services from lactating dairy cows were randomly assigned to one of the two groups; with (TRT, n = 1,405) or without (CON, n = 1,438) the use of sheaths.
In the TRT group, the AIC protected with a sheath was introduced into the vagina; once in the cranial portion of the vagina adjacent to the cervical os, the sheath was pulled back and only the A.I. gun was manipulated through the cervix into the uterine body for semen deposition.
In the CON group, cows received A.I. without the use of sheaths. Furthermore, sterile cotton swab samples were taken from the tip of the A.I. gun (n = 102) after A.I. from both the treatment and control groups for bacteriology. Pregnancy diagnosis was determined by ultrasonography 39 ± 3 days after A.I. Data analyses were performed using GLIMMIX (PAI) and FREQ (culture) procedures of SAS.
Results and discussion
Cultured swab samples revealed that the use of sheaths was effective in minimizing contamination of the A.I. gun (positive bacterial growth; TRT = 51.9 percent v. CON = 98.2 percent; P = 0.05). The most common bacteria isolated (49 percent) at the time of A.I. was E. coli.
Regarding the bacterial density growth, the majority (67 percent) of the samples from the TRT group (A.I. with the use of sheaths) had light or sparse bacterial growth compared with the CON group (A.I. without sheaths), in which the majority of the samples showed heavy colony growth (71 percent).
Although the potential detrimental effects of introduced bacteria into the bovine uterus at the time of A.I. has not yet been reported, the bacteria may colonize the uterine lining and trigger an inflammatory response, as shown in mares (post-breeding subclinical endometritis). At the time of A.I., not only semen but also bacteria and debris can be introduced into the uterine lumen and lead to chronic inflammation and decreased fertility in mares.
Under normal uterine conditions this physiological immune reaction, described as post-mating inflammatory response, is cleared within 48 hours. In lactating dairy cows, the proportion of PMN (greater than 15 percent), immediately before and four hours post-A.I., were associated with poor reproductive performance.
Previous studies (using the same sheaths as this study) reported no improvement on conception to first services in dairy cattle. These studies were conducted more than 20 years ago, using several A.I. technicians (and weekly randomization of sheaths), and only non-return rates to first service were evaluated.
The effectiveness of sheaths (assigned to every other cow) at the time of A.I. in one commercial dairy herd using one A.I. technician and the same reproductive management was investigated.
Lactating dairy cows that received A.I. with the use of sheaths had greater proportion of pregnancies per A.I. compared to cows receiving A.I. without the use of sheaths.
Furthermore, in this field study the proportion of cows pregnant (all services; summer and spring from three dairy herds) was greater for cows in TRT (30.1 ± 1.7 percent) compared with CON group (25.4 ± 1.9 percent).
According to these findings, lactating dairy cows may benefit from the use of sheaths at the time of A.I. by reducing the potential introduction of external contaminants such as E. coli (e.g., from perineum or vaginal origin) into the uterine lumen at the time of A.I.
In conclusion, results suggested that the use of sheaths at the time of A.I. reduced contamination of the A.I. gun and improved pregnancies per A.I. in lactating dairy cows. Performing a clean A.I. technique through the use of sheaths may be an effective strategy to improve reproductive outcomes in dairy cattle.
Cleanliness of the whole A.I. procedure must become a top priority for professional A.I. technicians and on-farm breeders to achieve consistent reproductive results over time.
References omitted due to space but are available upon request to firstname.lastname@example.org.
—Excerpts from 2011 SFT/ACT Annual Conference & Symposium