Dr. Brady Campbell, Assistant Professor, OSU State Small Ruminant Extension Specialist
Tim Barnes, OSU Extension Educator ANR, Marion County
Dr. Alvaro Garcia-Guerra, Assistant Professor, OSU Reproductive Physiology
Whether it’s at the state fair or local livestock auction, a conversation that commonly occurs among producers revolves around the success rate of their breeding programs. In New Zealand during the late 1980s, a controlled internal drug release (CIDR) was developed and released for intravaginal release of progesterone (P4). Since then, estrous synchronization has improved on-farm production efficiencies that can assist in grouping lambing dates, breeding ewes out-of-season, or can serve as a crucial step in the implementation of artificial insemination.
Let’s Review the Basics
- Progesterone (P4) is the major hormone used in most reproductive livestock protocols. In females, P4 is produced by the corpus luteum (CL) and is required to maintain pregnancy. In addition, P4 suppresses estrus (“heat”) and ovulation, making it an important tool for estrous synchronization. So, the ewe’s reproductive system responds as if she is pregnant, and she will not show signs of estrus until progesterone levels diminish.
- A CIDR is an intravaginal insert impregnated with P4 (0.3 g). Depending upon the protocol used, CIDRs are maintained within the female for 5 to 14 days before removal. When removed, a rapid drop in concentration of systemic P4 occurs, thus allowing the animal to express estrus approximately 48 hours after removal.
- Synchronization of estrus is accompanied by administration of a single dose of pregnant mare serum gonadotrophin (PMSG) at the time of CIDR removal for inducing estrus and increase prolificacy (lambs/pregnant ewe), primarily during out-of-season breeding. Furthermore, this practice is particularly useful when performing timed artificial insemination (TAI), both in and out-of-season to increase synchrony. Currently, PMSG alone is not available in the US, instead PG600®, which contains both PMSG and human chorionic gonadotrophin (hCG), is routinely used as an off-label substitute (refer to the comment about VCPR under the warning section below). In addition, using CIDRs for short periods (i.e., 6 days) requires, primarily in season, the administration of a luteolytic dose of prostaglandin (PGF2α) at CIDR removal to control the endogenous source of P4 and thus improve estrus response.
CIDR Design and Use
The CIDR is an intravaginal, plastic, T-shaped nylon insert molded with a silicone rubber “skin” impregnated with P4. The P4 is released at a controlled rate by diffusion and absorbed through the vaginal mucosa into the bloodstream after placement. As a result, P4 increases rapidly in the blood stream after CIDR placement and also drops rapidly after CIDR removal, allowing for precise control of circulating P4.
Traditionally, synchronization of estrus in small ruminants involved insertion of CIDRs for prolonged periods (12 to14 days). However, several reports indicate that fertility after prolonged periods could be reduced compared to natural estrus due to low levels of P4 towards the end of treatment, which in turn affects follicle development and oocyte quality (Gonzalez-Bulnes et al. 2020). As a result, short-term CIDR treatments (5 to 7 days) have been developed to overcome the negative effects of exposure to low P4 (Menchaca and Rubianes 2004). In fact, insertion of a CIDR for 5 days is the recommendation provided on the label for the EAZI-BreedTM CIDR® sheep insert sold in the US.
The use of CIDR inserts in short-term protocols, coupled with the physical characteristics of these inserts that allow them to be washed and disinfected, has fueled interest in their potential for reuse. Anecdotal evidence suggests that this is a common practice performed in the cattle industry, and thus multiple studies have investigated the implementation of this practice in cattle (Colazo et al. 2004; Sales et al. 2015; Melo et al. 2018; Sala et al. 2020). Similarly, the implementation of this practice has been extensively investigated in sheep and goats and therefore poses the question: can CIDRs be reused in small ruminant production?
Can CIDRs be Reused?
The cost of CIDRs may vary slightly regionally, but for the purpose of this discussion, a price of $6.00 per unit will be used. At this price, a single unit may not seem expensive, but when synchronizing an entire flock, herd, or multiple breeding groups, having the ability to reduce costs by reusing these inserts may be economical. Nevertheless, assessment of the effectiveness of CIDR reuse needs to be carefully considered in the context of breed, season (in or out-of-season), breeding method (natural mating vs. artificial insemination), and length of the synchronization protocol, as well as the method for cleaning and disinfecting.
Several studies have explored the practice of reusing CIDRs in sheep (Cox et al. 2012; Pinna et al., 2012; Bazzan et al. 2013; Ungerfeld et al. 2013; Vilariño et al. 2013; Silva et al. 2014; Swelum et al. 2018; Biehl et al. 2019; Swelum et al. 2019) and goats (Vilariño et al. 2011; Alvarez et al. 2013; Swelum et al. 2018). When evaluating CIDR reutilization, consider its impact on multiple parameters, including the amount of P4 provided, CIDR retention rate, estrous response, pregnancy rates, prolificacy, and animal health. For example, circulating P4 declines with CIDR reuse as observed in multiple studies in sheep (Cox et al. 2012; Pinna et al., 2012; Ungerfeld et al. 2013; Vilariño et al. 2013). The concentration of P4 obtained during treatment with an intravaginal P4 insert, however, is dependent upon several factors including insert surface area, initial P4 load, and physiologic status of the animal. Reuse of a CIDR modifies the initial P4 load, which will vary depending on the number and length of time the device was used previously. Furthermore, retention of CIDRs during treatment is critical for optimizing an estrous synchronization program. Interestingly, reuse of CIDRs does not affect retention rate, which is usually greater than 90 to 95%, regardless of the length of treatment and number of uses (Cox et al. 2012; Pinna et al. 2012; Biehl et al. 2019; Swelum et al. 2018; Swelum et al. 2019).
Estrous response (percentage of animals detected in heat) is a primary outcome of synchronization protocols, particularly when used in combination with natural mating or artificial insemination after estrous detection. Results of multiple studies performed both in and out-of-season in a large variety of breeds indicate that the percentage of ewes displaying estrus is not affected when CIDRs are used up to three times in short intervals (5 to 7 days) in combination with PMSG and PGF2α at CIDR removal (Cox et al. 2012; Pinna et al. 2012; Bazzan et al. 2013; Silva et al. 2014; Swelum et al. 2018; Biehl et al. 2019). Typically, 70–100% of ewes will exhibit estrus at an average of 32 to 48 hr. after CIDR removal. On the other hand, reuse of CIDRs during long-term protocols may result in reduced estrous response (Ungerfeld et al. 2013, Swelum et al. 2019). For example, mature Corriedale crossbred ewes bred out-of-season using an 8-day CIDR protocol with twice-used CIDRs (previously used for 10 and 12 days) expressed estrus at a lower rate (26.7%) than those treated with a new CIDRs (56.7%; Ungerfeld et al. 2013). Similarly, Awassi ewes synchronized with new CIDRs for 12 days and PMSG at CIDR removal had a greater estrous response than ewes treated with reused (previously used once or twice for 12 days each) CIDRs and PMSG (Swelum et al. 2019).
The overarching goal of an estrous synchronization program is to achieve high pregnancy rates in a relatively short period of time. The use of CIDRs up to three times during short-term protocols (5 to 6 days) in combination with PMSG and PGF2α at CIDR removal resulted in similar pregnancy rates using natural mating in ewes bred out-of-season (Pinna et al. 2012; Silva et al. 2014). Likewise, pregnancy rates in Awassi ewes were similar between new and once-used CIDRs using a 6-day protocol in combination with PMSG; however, pregnancy rates decreased dramatically after the third use (Swelum et al. 2018). Conversely, utilization of previously used CIDRs (22 days total) in an 8-day protocol resulted in reduced pregnancy rates in ewes bred out-of-season using natural mating (Ungerfeld et al. 2013).
Reuse of CIDRs during synchronization for TAI in ewes has also been evaluated. Pinna et al. (2012) found that CIDRs could be used up to three times in a short-term (5 days) estrous synchronization protocol with PMSG and PGF2α without compromising pregnancy rates after laparoscopic TAI. Additionally, Biehl et al. (2019) reported similar pregnancy rates using transcervical TAI after synchronization with a new or used (11 days) CIDR during a short- (6 days) or long- (11 days) term protocol using PMSG and PGF2α followed by transcervical TAI. Alternatively, Vilariño et al. (2013) reported lower pregnancy rates in Merino ewes synchronized with CIDRs used three times compared with a new CIDR using a 6-day protocol with PMSG and PGF2α. Prolificacy (lambs/treated ewes) is not often reported; however, reuse of CIDRs has not been associated with a decrease in fecundity (Vilariño et al. 2013; Swelum et al. 2018; Swelum et al. 2019).
In dairy goats, using CIDRs up to three times during a short-term (6 days) protocol in either timed artificial insemination (TAI) (Llanes et al. 2019) or natural mating (Souza et al. 2011; Souza-Fabjan et al. 2015) did not affect pregnancy rates. Conversely, cross-bred dairy goats treated with CIDRs used three times during a 5-day protocol had lower pregnancy rates after TAI when compared with those treated with new CIDRs, while those treated with CIDRs used two times had intermediate pregnancy rates (Vilariño et al. 2011). However, the authors also noted that pregnancy rates were still considered “acceptable” (> 60%) given that the does were bred out-of-season.
Although used CIDRs are efficient at synchronizing estrus in ewes and does, the duration of previous usage and length of time the CIDR is used can negatively affect reproductive parameters and thus economic profit. According to the current literature, new CIDRs and those previously used for a combined total of 12 days or fewer may provide the best fertility rate—and net profit—when implemented in a short-term protocol. However, maintaining flocks and herds that are free of reproductive disease is a must when considering the practice of recycling CIDRs. Currently, there is a lack of information on the potential risk for disease transmission when reusing CIDRs, and the effectiveness of different cleaning methods. Cleaning of CIDRs typically involves rinsing with water followed by disinfection. The challenge for most producers in moving forward with this management plan will be the ability to properly clean and store used CIDRs. Economically, it is not advisable to use CIDRs that have been previously used for more than 12 days (Souza et al. 2011; Pinna et al. 2012; Silva et al. 2014; Souza-Fabjan et al. 2015; Swelum et al. 2019). To ensure the greatest probability of reproductive success, be sure to consult with your veterinarian on which CIDR management program best fits your operation. Don’t let upfront costs of reproductive technologies allow you to make poor decisions that may cost far more in the long run when it comes time to market lambs and kids.
The authors of this article do not support nor endorse the practice of reusing CIDRs in the reproductive management of sheep or goats. The intent of the current article is to present a summary of the current literature that investigates the practice of reusing CIDRs. The practice of reusing CIDRs is considered extra label use and therefore requires the approval of a licensed veterinarian. Producers are encouraged to establish a working veterinarian-client-patient relationship (VCPR) with their local veterinarian.
Editors Note: For a full list of references, please refer to the original Factsheet in Ohioline.