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Comparison of the CIDR Select and 5-day Select Synch + CIDR protocols that included limited estrus detection and timed insemination for synchronizing estrus in beef heifers
The Professional Animal Scientist 27 (2011):141–146
©2011 American Registry of Professional Animal Scientists
Comparison of the CIDR Select and 5-day Select Synch + CIDR protocols that included limited estrus detection and timed insemination for synchronizing estrus in beef heifers G. A. Bridges*1,2 and S. L. Lake,† PAS *Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; and †Department of Animal Science, University of Wyoming, Laramie 82073
ABSTRACT The objective of this study was to compare AI pregnancy rates between the 5-d Select Synch + CIDR (5dCIDR; CIDR = controlled internal drug-release insert) and CIDR Select (CS) programs in replacement beef heifers with a limited period of estrus detection and AI followed by a timed insemination (TAI) of heifers not exhibiting estrus. Crossbred beef heifers (n = 318) were equally and randomly assigned to either the 5dCIDR or CS treatment. The 5dCIDR treatment consisted of gonadotropin-releasing hormone (GnRH) at CIDR insertion, followed 5 d later by CIDR removal and administration of two 25-mg doses of prostaglandin F2α (PGF) administered approximately 12 h apart. The CS treatment consisted of insertion of a CIDR for 14 d, Current address: University of Minnesota, North Central Research and Outreach Center, 1861 Highway 169 E, Grand Rapids, MN 55744. 2 Corresponding author: [email protected] 1
an injection of GnRH 9 d after CIDR removal, and administration of PGF 7 d following GnRH. In both treatments, heifers were detected for estrus for 52 h following PGF, and those exhibiting estrus were inseminated based on the AM/ PM rule. Heifers not observed in estrus were TAI 72 h after PGF, concurrent with GnRH administration. Ten days following TAI, bulls were placed with the heifers for approximately 45 d. Estrus response tended (P = 0.07) to be greater in the CS treatment than in the 5dCIDR treatment. However, conception rate of heifers exhibiting estrus, TAI conception rate, overall AI pregnancy rate, and breeding season pregnancy rate did not differ (P > 0.10) between treatments. In conclusion, 5dCIDR and CS protocols were equally effective at synchronizing estrus in replacement beef heifers. Key words: beef, controlled internal drug-release insert, estrus synchronization, heifer
INTRODUCTION Recently, 2 protocols, the 5-d COSynch + CIDR (controlled internal drug-release insert) and the CIDR Select (CS), have been developed to facilitate timed artificial insemination (TAI) in beef heifers. Both protocols have resulted in greater TAI pregnancy rates in beef heifers than has the 7-d CO-Synch + CIDR program (Busch et al., 2007; Wilson et al., 2007). With both of these estrus synchronization approaches, combining a limited (<60 h) period of estrus detection and AI followed by TAI of heifers failing to be observed in estrus may increase overall AI pregnancy rates in beef heifers. However, both protocols have practical limitations. The 5-d Select Synch + CIDR and TAI (5dCIDR) protocol requires animals to be handled twice in a single day to deliver 2 injections of prostaglandin F2α (PGF) 12 h apart on the day of CIDR removal, whereas the duration of the CS protocol (33
142 d) and the necessity to handle the animals 5 times may limit its broad implementation within the industry. Although both protocols have limitations, both represent viable options for beef producers wanting to use estrus synchronization and AI. However, a direct comparison between the 5dCIDR and CS protocols has not been reported, making it difficult to reliably make recommendations to producers as to which protocol will deliver the greatest pregnancy rate. Therefore, the objective of this experiment was to compare AI pregnancy rates between the 5dCIDR and CS protocols in replacement beef heifers in which estrus detection was performed for 52 h and followed by TAI in heifers failing to exhibit estrus.
MATERIALS AND METHODS Animals All animals were handled in accordance with procedures approved by the Purdue University Animal Care
Bridges and Lake
and Use Committee. Nulliparous yearling Hereford × Angus beef heifers at Heaton Land and Livestock (Alton, UT; n = 318) were used in this experiment. Heifers were maintained in a dry lot and fed a haylage-based diet that was formulated to achieve at least 0.7 kg/d gain. Although BCS of the heifers were not recorded, heifers were in appropriate body condition at the time of estrus synchronization.
Description of Treatments Heifers were randomly assigned to either the 5dCIDR or CS estrus synchronization program (Figure 1). Heifers assigned to the 5dCIDR protocol received an intravaginal progesteronereleasing insert (CIDR, Pfizer Animal Health, NewYork, NY) for 5 d as well as 100 μg of gonadotropin-releasing hormone (GnRH; Cystorelin, Merial, Duluth, GA; i.m.) at CIDR insertion. Five days following CIDR insertion, heifers were administered 25 mg of dinoprost tromethamine (PGF; Lutalyse, Pfizer Animal Health, NewYork,
NY; i.m.) and the CIDR inserts were removed. All heifers in the 5dCIDR treatment received a second 25-mg injection of PGF approximately 12 h after the initial injection to ensure luteal regression. Heifers assigned to the CS protocol (Figure 1) received a CIDR for 14 d. Nine days following CIDR removal, heifers received GnRH and were then administered 25 mg of PGF 7 d following GnRH. Due to the number of heifers at this location, the day of PGF administration was offset by 24 h between treatments to facilitate animal handling and management and to minimize the difference in time between the first heifer and last heifer through the chute. Hence, heifers in the CS treatment received PGF 1 d in advance of heifers in the 5dCIDR treatment. Estrus detection was performed for 1 h, at minimum, in the AM and PM and concluded 52 h following PGF. Heifers observed in standing estrus were sorted from herdmates into an adjacent pen and artificially inseminated approximately 12 h after being detected in estrus. Heifers not detected in behavioral estrus within 52 h after the initial PGF injection were TAI concurrent with GnRH administration (100 μg) at approximately 72 h (70 to 74 h) after the initial PGF administration. Four AI technicians and a single AI sire were used to inseminate all heifers. All heifers observed in estrus and sorted to be bred were comingled, regardless of treatment. Heifers were randomly worked through the breeding box and randomly bred by one of the 4 inseminators. The treatments of the heifers were not known to the inseminators at the time of AI.
Breeding Season and Pregnancy Diagnosis
Figure 1. Illustration of the 5-d Select Synch + CIDR and timed-AI (TAI) and CIDR Select protocols that included 52 h of estrus detection and AI following prostaglandin F2α (PGF2α) administration and TAI in heifers failing to exhibit estrus at 72 h after PGF2α administration. CIDR = controlled internal drug-release insert; GnRH = gonadotropin-releasing hormone.
Ten days after TAI, intact bulls that were tested by a trained veterinarian for disease and fertility were placed with the heifers for 45 d. Pregnancy diagnosis was performed 35 d after TAI using transrectal ultrasonography (variable megahertz linear array transducer, MicroMaxx, Sonosite, Bothell, WA) to determine conception
5-day Select Synch + CIDR versus CIDR Select in beef heifers
during the synchronization period. Following pregnancy diagnosis to determine AI pregnancy rate, heifers and bulls were moved to summer range. To determine breeding season pregnancy rate (overall pregnancy rate during the season), pregnancy diagnosis was performed again 35 d following bull removal via transrectal ultrasonography. Six heifers in the 5dCIDR treatment and 9 in the CS treatment were not available for final pregnancy diagnosis due to an inability to locate these females following gathering from summer range. These heifers were included in the estrus response and first-service conception rate data; however, they were excluded from the final pregnancy diagnosis analysis.
Data and Statistical Analysis Estrus response was defined as the percentage of all females treated that were detected in estrus within 52 h of PGF administration. Conception rate was calculated as the number of heifers that were detected in estrus during the 52-h period following PGF, inseminated, and determined to be pregnant, divided by the number of heifers detected in estrus and inseminated during the synchronization period. Pregnancy rate to TAI was defined as the percentage of heifers treated that were not observed in estrus within 52 h of PGF and were TAI and became pregnant. Pregnancy rate to AI was defined as the number of heifers that were determined to be pregnant to either estrus detection and AI or TAI divided by the number of heifers treated. Breeding season pregnancy rate was defined as the percentage of all treated animals that were pregnant at the end of the breeding season. Estrus response, conception rate, TAI pregnancy rate, pregnancy rate to AI, and breeding season pregnancy rate were analyzed using the GLIMMIX procedure of SAS (SAS Inst. Inc., Cary, NC). For dependent variables, the statistical model included treatment. Differences were considered to be statistically significant
when P ≤ 0.05. Artificial insemination technician was initially included in all analyses. However, differences were not detected for technician and interactions with treatments were not detected; therefore, this term was removed from the final analyses.
RESULTS AND DISCUSSION Estrus synchronization and AI offers numerous advantages to beef producers. These advantages include an increased proportion of females bred early in the breeding season, increasing calf uniformity, and stimulation of puberty in prepubertal heifers (Short et al., 1976; Larson et al., 2006). Similarly, AI allows producers to use genetically superior sires and select for production traits important for their operation such as calving ease, weaning weight, and carcass quality (Lamb et al., 2006). The present study was conducted to compare the efficacy of the 5dCIDR and CS estrus synchronization protocols to facilitate AI in virgin beef heifers. Both approaches involved a period of estrus detection in combination with TAI, thereby maximizing conception rates by breeding heifers that exhibit estrus while also allowing all females to receive AI regardless of expression of estrus. In recent years, numerous estrus synchronization programs have been developed for use in replacement virgin beef heifers. Many of these programs, including the 5dCIDR and CS, include a progestin source, either melengestrol acetate or a CIDR insert, and the administration of GnRH. The progestin serves to prevent the expression of estrus and ovulation (Patterson et al., 1989) and assists in stimulating the attainment of puberty in prepubertal females (Hall et al., 1997), and GnRH is used to control follicular wave development (Geary et al., 1998). A deficiency of estrus synchronization programs that use GnRH is the ineffectiveness of GnRH at inducing ovulation or luteinization of the dominant follicle and thus controlling follicular wave dynamics. Response to GnRH is dependent on stage of
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the estrous cycle when administration occurs (Moreira et al., 2000; Atkins et al., 2008), and in randomly cycling beef or dairy heifers, GnRH is only effective in synchronizing follicular wave in 43 to 60% of the heifers treated (Macmillan and Thatcher, 1991; Pursley et al., 1995; Moreira et al., 2000; Atkins et al., 2008). Thus, in a proportion of heifers, follicular wave dynamics are not controlled, which is detrimental to the success of a TAI protocol. Although not completely effective in controlling follicular wave dynamics, in a large, multistate trial, Lamb et al. (2006) demonstrated that including GnRH administration at the initiation of a 7-d CO-Synch + CIDR program was necessary to reduce variation in pregnancy rates across locations. Two estrus synchronization programs for beef heifers that may improve the management of follicular dynamics and promote the ovulation of a more physiologically mature follicle at the time of insemination as compared with previous approaches are the 5dCIDR (Bridges et al., 2008) and the CS (Busch et al., 2007; Leitman et al., 2008) programs. However, the current study is the first to compare the reproductive performance of replacement beef heifers enrolled in these 2 protocols. The present study included a finite period, 52 h, of estrus detection. The proportion of heifers detected in estrus by 52 h after PGF (Table 1) tended (P = 0.07) be greater in the CS than in the 5dCIDR treatment. It is important to note that in the present study, estrus detection was concluded at 52 h after PGF administration, thus limiting overall expression of estrus in this group of females. The distribution of estrus in the 52 h following PGF between treatments is presented in Figure 2. The reasons behind the tendency for reduced expression of estrus in the 5dCIDR treatment are not clear. Previous reports using these protocols have indicated that the interval to estrus is either similar or slightly greater in the CS compared with the 5dCIDR protocol (Busch et al., 2007; Wilson et al., 2007; Leitman et al., 2008, 2009).
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Bridges and Lake
Table 1. Estrus response rate, conception rate, timed-AI (TAI) pregnancy rate, AI pregnancy rate, and breeding season pregnancy rate for beef heifers in which estrus was synchronized with either the 5-d Select Synch + CIDR1 and TAI (5dCIDR) or CIDR Select (CS) protocol Treatment 5dCIDR CS a,b
Estrus rate,2 %
Conception rate,3 %
TAI conception rate,4 %
AI pregnancy rate,5 %
Breeding season pregnancy rate,6 %
85/159 = 53.5%a 101/159 = 63.5%b
65/85 = 76.5% 76/101 = 75.2%
47/74 = 63.5% 36/58 = 62.1%
112/159 = 70.4% 112/159 = 70.4%
132/150 = 88.0% 141/153 = 92.2%
Estrus response rate tended (P = 0.07) to be greater in the CS compared with the 5dCIDR treatment.
1
CIDR = controlled internal drug-release insert.
2
Proportion of heifers that were observed in estrus within 52 h of prostaglandin F2α administration.
3
Proportion of heifers that were detected in estrus, artificially inseminated, and conceived.
4
Proportion of heifers that were not detected in estrus, were TAI 72 h following prostaglandin F2α, and conceived.
5
Proportion of heifers that conceived to AI after being detected in estrus or TAI.
6
Proportion of heifers pregnant at the end of the breeding season.
Therefore, it was anticipated that the proportion of heifers exhibiting estrus before TAI would be similar between treatments if not marginally greater for the 5dCIDR protocol. Wilson et al. (2007) reported that the average interval from PGF to estrus in heifers treated with the 5dCIDR protocol, which were TAI at 72 h post-PGF, was 51 h. In the CS protocol the average interval from PGF to estrus has been reported as 52 h (Leitman et al., 2008) but as great as 68 h (Leitman et al., 2009) in heifers that did not receive TAI. In addition, Busch et al.
(2007) evaluated expression of estrus in beef heifers synchronized with the CS protocol that received TAI at 72 h after PGF, and the average interval to estrus was 65 h. Of the heifers that exhibited estrus, conception rates did not differ between the synchronization treatments (Table 1). Moreover, conception rates in the present study were greater in both the 5dCIDR (76.5%) and CS (75.2%) treatments than those reported previously by other investigators using these programs. Helser et al. (2006) reported conception rates
Figure 2. Distribution of estrus following prostaglandin F2α (PGF2α) administration between 5-d Select Synch + CIDR and timed-AI (5dCIDR) or CIDR Select (CS) treatments. CIDR = controlled internal drug-release insert.
of 66.2% in beef heifers synchronized with the 5-d Select Synch + CIDR protocol. However, in this study heifers only received a single 25-mg dose of PGF at the time of CIDR removal, whereas in the present study heifers in the 5dCIDR treatment received two 25-mg doses of PGF 12 h apart. In 2 groups of heifers synchronized with the CS protocol and inseminated based on observed estrus, Leitman et al. (2009) reported conception rates of 65 and 61%. However, unlike the present study, Helser et al. (2006) and Leitman et al. (2009) did not combine a period of estrus detection and AI followed by TAI of heifers not observed in estrus. To our knowledge, the present study is the first to use the 5dCIDR and CS protocols in this manner in either beef heifers or cows. Timed-AI conception rates did not differ between treatments (Table 1). However, because a period of estrus detection and AI was combined with TAI in the present study, it cannot be inferred that both protocols would result in similar TAI pregnancy rates if strict TAI was used. Both the CS and 5dCIDR protocols have been investigated as strict TAI programs for beef heifers and have been demonstrated to result in greater TAI pregnancy rates than the 7-d CO-Synch + CIDR (Busch et al., 2007; Wilson et al., 2007). Busch et al. (2007) observed similar TAI pregnancy rates (62%) as
5-day Select Synch + CIDR versus CIDR Select in beef heifers
reported in this study, in beef heifers synchronized with the CS protocol and inseminated strictly by TAI at 72 h after PGF. Wilson et al. (2007) observed lesser TAI pregnancy rates (57.8%) compared with the present study, in beef heifers synchronized with the 5-d CO-Synch + CIDR. When pregnancy response from estrus detection and AI and TAI were combined, overall pregnancy rates did not differ between treatments (Table 1). In both treatments, overall AI pregnancy rates (70.4%) were greater than those observed in most other reports, regardless of estrus synchronization protocol used. With strict TAI, Wilson et al. (2007) reported pregnancy rates of 57.8% using the 5-d CO-Synch + CIDR in replacement beef heifers. Busch et al. (2007) reported TAI pregnancy rates of 62% when using the CS protocol with strict TAI. Contributing to the high overall pregnancy rates and the improved AI pregnancy rates compared with previously reported data is the combination of a period of estrus detection followed by TAI used in this study. Such an approach ensures that heifers that exhibit estrus greater than 24 h before TAI are inseminated, and the TAI in heifers not exhibiting estrus ensures all heifers receive an opportunity to conceive to AI. Breeding season pregnancy rates (Table 1) and the percentage of heifers that experienced embryonic loss between the initial and final pregnancy diagnosis (3.6%) did not differ (P > 0.10) between treatments. In the current study, heifers in the 5dCIDR treatment received two 25-mg doses of PGF at a 12-h interval. Due to the 5-d interval between GnRH administration, causing the potential development of an accessory corpus luteum, and PGF administration, it was unclear if a single 25-mg dose of PGF would be sufficient to induce complete luteal regression. In mature beef cows it has been demonstrated that a single 25-mg injection of PGF is not sufficient to induce luteolysis in all females (Souto et al., 2009) and consequently TAI pregnancy rates are reduced (Kasimanickam
et al., 2009). Having to administer 2 separate doses of PGF increases the labor required to conduct the 5dCIDR protocol and may limit its use in the beef industry. Similarly, the long duration of the CS protocol makes this approach undesirable to some producers. However, recent research has demonstrated that administering 2 separate doses of PGF to heifers enrolled in the 5dCIDR may not be a necessity. In dairy heifers synchronized with the 5-d CO-Synch approach, TAI pregnancy rates were similar between heifers that received one or 2 doses of PGF (Rabaglino et al., 2010). However, before PGF delivery to beef heifers in the 5dCIDR protocols is modified from 2 separate doses to a single dose, additional research is warranted.
IMPLICATIONS Although estrus response tended to be greater in the CS treatment than in the 5dCIDR treatment, both treatments resulted in similar AI pregnancy rates. Moreover, with AI pregnancy rates greater than 70% in both treatments, both treatments appear to be effective methods to synchronize estrus and facilitate AI in beef heifers. Therefore, both the 5dCIDR and CS protocols are effective protocols for synchronizing estrus and facilitating AI in replacement beef heifers when a period of estrus detection is combined with TAI.
ACKNOWLEDGMENTS Appreciation is expressed to Select Sires, Plains City, Ohio, for funding provided to support this research. Gratitude is extended to Pfizer Animal Health (New York, NY) for donation of Lutalyse and CIDR. The assistance of the Heaton family of Heaton Land and Livestock is also recognized.
LITERATURE CITED Atkins, J. A., D. C. Busch, J. F. Bader, D. H. Keisler, D. J. Patterson, M. C. Lucy, and M. F. Smith. 2008. Gonadotropin-releasing
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hormone-induced ovulation and luteinizing hormone release in beef heifers: Effect of day of the cycle. J. Anim. Sci. 86:83. Bridges, G. A., L. A. Helser, D. E. Grum, M. L. Mussard, C. L. Gasser, and M. L. Day. 2008. Decreasing the interval between GnRH and PGF2α from 7 to 5 days and lengthening proestrus increases timed-AI pregnancy rates in beef cows. Theriogenology 69:843. Busch, D. C., D. J. Wilson, D. J. Schafer, N. R. Leitman, J. K. Haden, M. R. Ellersieck, M. F. Smith, and D. J. Patterson. 2007. Comparison of progestin-based estrus synchronization protocols before fixed-time artificial insemination on pregnancy rate in beef heifers. J. Anim. Sci. 85:1933. Geary, T. W., J. C. Whittier, and D. G. Lefever. 1998. Effect of calf removal on pregnancy rates of cows synchronized with the Ovsynch or CO-Synch protocol. J. Anim. Sci. 81(Suppl. 1):278. (Abstr.) Hall, J. B., R. B. Staigmiller, R. E. Short, R. A. Bellows, M. D. MacNeil, and S. E. Bellows. 1997. Effect of age and pattern of gain on induction of puberty with a progestin in beef heifers. J. Anim. Sci. 75:1606. Helser, L. A., G. A. Bridges, D. E. Grum, M. L. Mussard, C. L. Gasser, D. M. Lantz, and M. L. Day. 2006. Effect of decreasing the interval from GnRH to PGF2α and lengthening proestrus on reproductive performance in GnRH-CIDR-PGF2α synchronization programs. J. Anim. Sci. 84(Suppl. 1):432. (Abstr.) Kasimanickam, R., M. L. Day, J. S. Rudolph, J. B. Hall, and W. D. Whittier. 2009. Two doses of prostaglandin improve pregnancy rates to timed-AI in a 5-day progesteronebased synchronization protocol in beef cows. Theriogenology 71:762. Lamb, G. C., J. E. Larson, T. W. Geary, J. S. Stevenson, S. K. Johnson, M. L. Day, R. P. Ansotegui, D. J. Kesler, J. M. DeJarnette, and D. G. Landblom. 2006. Synchronization of estrus and artificial insemination in replacement beef heifers using gonadotropinreleasing hormone, prostaglandin F2α, and progesterone. J. Anim. Sci. 84:3000. Larson, J. E., G. C. Lamb, J. S. Stevenson, S. K. Johnson, M. L. Day, T. W. Geary, D. J. Kesler, J. M. DeJarnette, F. N. Schrick, A. DiCostanzo, and J. D. Arseneau. 2006. Synchronization of estrus in suckled beef cows for detected estrus and artificial insemination and timed artificial insemination using gonadotropin-releasing hormone, prostaglandin F2α, and progesterone. J. Anim. Sci. 84:332. Leitman, N. R., D. C. Busch, J. F. Bader, D. A. Mallory, D. J. Wilson, M. C. Lucy, M. R. Ellersieck, M. F. Smith, and D. J. Patterson. 2008. Comparison of protocols to synchronize estrus and ovulation in estrous-cycling and prepubertal beef heifers. J. Anim. Sci. 86:1808. Leitman, N. R., D. C. Busch, D. A. Mallory, D. J. Wilson, M. R. Ellersieck, M. F. Smith,
146 and D. J. Patterson. 2009. Comparison of long-term CIDR-based protocols to synchronize estrus in beef heifers. Anim. Reprod. Sci. 114:345. Macmillan, K. L., and W. W. Thatcher. 1991. Effects of an agonist of gonadotropin-releasing hormone on ovarian follicles in cattle. Biol. Reprod. 45:883. Moreira, F., R. L. de la Sota, T. Diaz, and W. W. Thatcher. 2000. Effect of day of the estrous cycle at the initiation of a timed artificial insemination protocol on reproductive responses in dairy heifers. J. Anim. Sci. 78:1568. Patterson, D. J., G. H. Kiracofe, J. S. Stevenson, and L. R. Corah. 1989. Control of the
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Pursley, J. R., M. O. Mee, and M. C. Wiltbank. 1995. Synchronization of ovulation in dairy cows using PGF2alpha and GnRH. Theriogenology 44:915.
Souto, L. A., M. Maquivar, M. L. Mussard, G. A. Bridges, D. G. Grum, and M. L. Day. 2009. Fertility and luteal regression with the 5-d CIDR synchronization program in postpartum beef cows using differing luteolytic treatment. J. Anim. Sci. 87(Suppl. 1):465. (Abstr.)
Rabaglino, M. B., C. A. Risco, M. J. Thatcher, I. H. Kim, J. E. Santos, and W. W. Thatcher. 2010. Application of one injection of prostaglandin F (2alpha) in the five-day CO-Synch + CIDR protocol for estrous synchronization and resynchronization of dairy heifers. J. Dairy Sci. 93:1050. Short, R. E., R. A. Bellows, J. B. Carr, R. B. Staigniller, and R. D. Randel. 1976. Induced
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©2011 American Registry of Professional Animal Scientists
Comparison of the CIDR Select and 5-day Select Synch + CIDR protocols that included limited estrus detection and timed insemination for synchronizing estrus in beef heifers G. A. Bridges*1,2 and S. L. Lake,† PAS *Department of Animal Sciences, Purdue University, West Lafayette, IN 47907; and †Department of Animal Science, University of Wyoming, Laramie 82073
ABSTRACT The objective of this study was to compare AI pregnancy rates between the 5-d Select Synch + CIDR (5dCIDR; CIDR = controlled internal drug-release insert) and CIDR Select (CS) programs in replacement beef heifers with a limited period of estrus detection and AI followed by a timed insemination (TAI) of heifers not exhibiting estrus. Crossbred beef heifers (n = 318) were equally and randomly assigned to either the 5dCIDR or CS treatment. The 5dCIDR treatment consisted of gonadotropin-releasing hormone (GnRH) at CIDR insertion, followed 5 d later by CIDR removal and administration of two 25-mg doses of prostaglandin F2α (PGF) administered approximately 12 h apart. The CS treatment consisted of insertion of a CIDR for 14 d, Current address: University of Minnesota, North Central Research and Outreach Center, 1861 Highway 169 E, Grand Rapids, MN 55744. 2 Corresponding author: [email protected] 1
an injection of GnRH 9 d after CIDR removal, and administration of PGF 7 d following GnRH. In both treatments, heifers were detected for estrus for 52 h following PGF, and those exhibiting estrus were inseminated based on the AM/ PM rule. Heifers not observed in estrus were TAI 72 h after PGF, concurrent with GnRH administration. Ten days following TAI, bulls were placed with the heifers for approximately 45 d. Estrus response tended (P = 0.07) to be greater in the CS treatment than in the 5dCIDR treatment. However, conception rate of heifers exhibiting estrus, TAI conception rate, overall AI pregnancy rate, and breeding season pregnancy rate did not differ (P > 0.10) between treatments. In conclusion, 5dCIDR and CS protocols were equally effective at synchronizing estrus in replacement beef heifers. Key words: beef, controlled internal drug-release insert, estrus synchronization, heifer
INTRODUCTION Recently, 2 protocols, the 5-d COSynch + CIDR (controlled internal drug-release insert) and the CIDR Select (CS), have been developed to facilitate timed artificial insemination (TAI) in beef heifers. Both protocols have resulted in greater TAI pregnancy rates in beef heifers than has the 7-d CO-Synch + CIDR program (Busch et al., 2007; Wilson et al., 2007). With both of these estrus synchronization approaches, combining a limited (<60 h) period of estrus detection and AI followed by TAI of heifers failing to be observed in estrus may increase overall AI pregnancy rates in beef heifers. However, both protocols have practical limitations. The 5-d Select Synch + CIDR and TAI (5dCIDR) protocol requires animals to be handled twice in a single day to deliver 2 injections of prostaglandin F2α (PGF) 12 h apart on the day of CIDR removal, whereas the duration of the CS protocol (33
142 d) and the necessity to handle the animals 5 times may limit its broad implementation within the industry. Although both protocols have limitations, both represent viable options for beef producers wanting to use estrus synchronization and AI. However, a direct comparison between the 5dCIDR and CS protocols has not been reported, making it difficult to reliably make recommendations to producers as to which protocol will deliver the greatest pregnancy rate. Therefore, the objective of this experiment was to compare AI pregnancy rates between the 5dCIDR and CS protocols in replacement beef heifers in which estrus detection was performed for 52 h and followed by TAI in heifers failing to exhibit estrus.
MATERIALS AND METHODS Animals All animals were handled in accordance with procedures approved by the Purdue University Animal Care
Bridges and Lake
and Use Committee. Nulliparous yearling Hereford × Angus beef heifers at Heaton Land and Livestock (Alton, UT; n = 318) were used in this experiment. Heifers were maintained in a dry lot and fed a haylage-based diet that was formulated to achieve at least 0.7 kg/d gain. Although BCS of the heifers were not recorded, heifers were in appropriate body condition at the time of estrus synchronization.
Description of Treatments Heifers were randomly assigned to either the 5dCIDR or CS estrus synchronization program (Figure 1). Heifers assigned to the 5dCIDR protocol received an intravaginal progesteronereleasing insert (CIDR, Pfizer Animal Health, NewYork, NY) for 5 d as well as 100 μg of gonadotropin-releasing hormone (GnRH; Cystorelin, Merial, Duluth, GA; i.m.) at CIDR insertion. Five days following CIDR insertion, heifers were administered 25 mg of dinoprost tromethamine (PGF; Lutalyse, Pfizer Animal Health, NewYork,
NY; i.m.) and the CIDR inserts were removed. All heifers in the 5dCIDR treatment received a second 25-mg injection of PGF approximately 12 h after the initial injection to ensure luteal regression. Heifers assigned to the CS protocol (Figure 1) received a CIDR for 14 d. Nine days following CIDR removal, heifers received GnRH and were then administered 25 mg of PGF 7 d following GnRH. Due to the number of heifers at this location, the day of PGF administration was offset by 24 h between treatments to facilitate animal handling and management and to minimize the difference in time between the first heifer and last heifer through the chute. Hence, heifers in the CS treatment received PGF 1 d in advance of heifers in the 5dCIDR treatment. Estrus detection was performed for 1 h, at minimum, in the AM and PM and concluded 52 h following PGF. Heifers observed in standing estrus were sorted from herdmates into an adjacent pen and artificially inseminated approximately 12 h after being detected in estrus. Heifers not detected in behavioral estrus within 52 h after the initial PGF injection were TAI concurrent with GnRH administration (100 μg) at approximately 72 h (70 to 74 h) after the initial PGF administration. Four AI technicians and a single AI sire were used to inseminate all heifers. All heifers observed in estrus and sorted to be bred were comingled, regardless of treatment. Heifers were randomly worked through the breeding box and randomly bred by one of the 4 inseminators. The treatments of the heifers were not known to the inseminators at the time of AI.
Breeding Season and Pregnancy Diagnosis
Figure 1. Illustration of the 5-d Select Synch + CIDR and timed-AI (TAI) and CIDR Select protocols that included 52 h of estrus detection and AI following prostaglandin F2α (PGF2α) administration and TAI in heifers failing to exhibit estrus at 72 h after PGF2α administration. CIDR = controlled internal drug-release insert; GnRH = gonadotropin-releasing hormone.
Ten days after TAI, intact bulls that were tested by a trained veterinarian for disease and fertility were placed with the heifers for 45 d. Pregnancy diagnosis was performed 35 d after TAI using transrectal ultrasonography (variable megahertz linear array transducer, MicroMaxx, Sonosite, Bothell, WA) to determine conception
5-day Select Synch + CIDR versus CIDR Select in beef heifers
during the synchronization period. Following pregnancy diagnosis to determine AI pregnancy rate, heifers and bulls were moved to summer range. To determine breeding season pregnancy rate (overall pregnancy rate during the season), pregnancy diagnosis was performed again 35 d following bull removal via transrectal ultrasonography. Six heifers in the 5dCIDR treatment and 9 in the CS treatment were not available for final pregnancy diagnosis due to an inability to locate these females following gathering from summer range. These heifers were included in the estrus response and first-service conception rate data; however, they were excluded from the final pregnancy diagnosis analysis.
Data and Statistical Analysis Estrus response was defined as the percentage of all females treated that were detected in estrus within 52 h of PGF administration. Conception rate was calculated as the number of heifers that were detected in estrus during the 52-h period following PGF, inseminated, and determined to be pregnant, divided by the number of heifers detected in estrus and inseminated during the synchronization period. Pregnancy rate to TAI was defined as the percentage of heifers treated that were not observed in estrus within 52 h of PGF and were TAI and became pregnant. Pregnancy rate to AI was defined as the number of heifers that were determined to be pregnant to either estrus detection and AI or TAI divided by the number of heifers treated. Breeding season pregnancy rate was defined as the percentage of all treated animals that were pregnant at the end of the breeding season. Estrus response, conception rate, TAI pregnancy rate, pregnancy rate to AI, and breeding season pregnancy rate were analyzed using the GLIMMIX procedure of SAS (SAS Inst. Inc., Cary, NC). For dependent variables, the statistical model included treatment. Differences were considered to be statistically significant
when P ≤ 0.05. Artificial insemination technician was initially included in all analyses. However, differences were not detected for technician and interactions with treatments were not detected; therefore, this term was removed from the final analyses.
RESULTS AND DISCUSSION Estrus synchronization and AI offers numerous advantages to beef producers. These advantages include an increased proportion of females bred early in the breeding season, increasing calf uniformity, and stimulation of puberty in prepubertal heifers (Short et al., 1976; Larson et al., 2006). Similarly, AI allows producers to use genetically superior sires and select for production traits important for their operation such as calving ease, weaning weight, and carcass quality (Lamb et al., 2006). The present study was conducted to compare the efficacy of the 5dCIDR and CS estrus synchronization protocols to facilitate AI in virgin beef heifers. Both approaches involved a period of estrus detection in combination with TAI, thereby maximizing conception rates by breeding heifers that exhibit estrus while also allowing all females to receive AI regardless of expression of estrus. In recent years, numerous estrus synchronization programs have been developed for use in replacement virgin beef heifers. Many of these programs, including the 5dCIDR and CS, include a progestin source, either melengestrol acetate or a CIDR insert, and the administration of GnRH. The progestin serves to prevent the expression of estrus and ovulation (Patterson et al., 1989) and assists in stimulating the attainment of puberty in prepubertal females (Hall et al., 1997), and GnRH is used to control follicular wave development (Geary et al., 1998). A deficiency of estrus synchronization programs that use GnRH is the ineffectiveness of GnRH at inducing ovulation or luteinization of the dominant follicle and thus controlling follicular wave dynamics. Response to GnRH is dependent on stage of
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the estrous cycle when administration occurs (Moreira et al., 2000; Atkins et al., 2008), and in randomly cycling beef or dairy heifers, GnRH is only effective in synchronizing follicular wave in 43 to 60% of the heifers treated (Macmillan and Thatcher, 1991; Pursley et al., 1995; Moreira et al., 2000; Atkins et al., 2008). Thus, in a proportion of heifers, follicular wave dynamics are not controlled, which is detrimental to the success of a TAI protocol. Although not completely effective in controlling follicular wave dynamics, in a large, multistate trial, Lamb et al. (2006) demonstrated that including GnRH administration at the initiation of a 7-d CO-Synch + CIDR program was necessary to reduce variation in pregnancy rates across locations. Two estrus synchronization programs for beef heifers that may improve the management of follicular dynamics and promote the ovulation of a more physiologically mature follicle at the time of insemination as compared with previous approaches are the 5dCIDR (Bridges et al., 2008) and the CS (Busch et al., 2007; Leitman et al., 2008) programs. However, the current study is the first to compare the reproductive performance of replacement beef heifers enrolled in these 2 protocols. The present study included a finite period, 52 h, of estrus detection. The proportion of heifers detected in estrus by 52 h after PGF (Table 1) tended (P = 0.07) be greater in the CS than in the 5dCIDR treatment. It is important to note that in the present study, estrus detection was concluded at 52 h after PGF administration, thus limiting overall expression of estrus in this group of females. The distribution of estrus in the 52 h following PGF between treatments is presented in Figure 2. The reasons behind the tendency for reduced expression of estrus in the 5dCIDR treatment are not clear. Previous reports using these protocols have indicated that the interval to estrus is either similar or slightly greater in the CS compared with the 5dCIDR protocol (Busch et al., 2007; Wilson et al., 2007; Leitman et al., 2008, 2009).
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Bridges and Lake
Table 1. Estrus response rate, conception rate, timed-AI (TAI) pregnancy rate, AI pregnancy rate, and breeding season pregnancy rate for beef heifers in which estrus was synchronized with either the 5-d Select Synch + CIDR1 and TAI (5dCIDR) or CIDR Select (CS) protocol Treatment 5dCIDR CS a,b
Estrus rate,2 %
Conception rate,3 %
TAI conception rate,4 %
AI pregnancy rate,5 %
Breeding season pregnancy rate,6 %
85/159 = 53.5%a 101/159 = 63.5%b
65/85 = 76.5% 76/101 = 75.2%
47/74 = 63.5% 36/58 = 62.1%
112/159 = 70.4% 112/159 = 70.4%
132/150 = 88.0% 141/153 = 92.2%
Estrus response rate tended (P = 0.07) to be greater in the CS compared with the 5dCIDR treatment.
1
CIDR = controlled internal drug-release insert.
2
Proportion of heifers that were observed in estrus within 52 h of prostaglandin F2α administration.
3
Proportion of heifers that were detected in estrus, artificially inseminated, and conceived.
4
Proportion of heifers that were not detected in estrus, were TAI 72 h following prostaglandin F2α, and conceived.
5
Proportion of heifers that conceived to AI after being detected in estrus or TAI.
6
Proportion of heifers pregnant at the end of the breeding season.
Therefore, it was anticipated that the proportion of heifers exhibiting estrus before TAI would be similar between treatments if not marginally greater for the 5dCIDR protocol. Wilson et al. (2007) reported that the average interval from PGF to estrus in heifers treated with the 5dCIDR protocol, which were TAI at 72 h post-PGF, was 51 h. In the CS protocol the average interval from PGF to estrus has been reported as 52 h (Leitman et al., 2008) but as great as 68 h (Leitman et al., 2009) in heifers that did not receive TAI. In addition, Busch et al.
(2007) evaluated expression of estrus in beef heifers synchronized with the CS protocol that received TAI at 72 h after PGF, and the average interval to estrus was 65 h. Of the heifers that exhibited estrus, conception rates did not differ between the synchronization treatments (Table 1). Moreover, conception rates in the present study were greater in both the 5dCIDR (76.5%) and CS (75.2%) treatments than those reported previously by other investigators using these programs. Helser et al. (2006) reported conception rates
Figure 2. Distribution of estrus following prostaglandin F2α (PGF2α) administration between 5-d Select Synch + CIDR and timed-AI (5dCIDR) or CIDR Select (CS) treatments. CIDR = controlled internal drug-release insert.
of 66.2% in beef heifers synchronized with the 5-d Select Synch + CIDR protocol. However, in this study heifers only received a single 25-mg dose of PGF at the time of CIDR removal, whereas in the present study heifers in the 5dCIDR treatment received two 25-mg doses of PGF 12 h apart. In 2 groups of heifers synchronized with the CS protocol and inseminated based on observed estrus, Leitman et al. (2009) reported conception rates of 65 and 61%. However, unlike the present study, Helser et al. (2006) and Leitman et al. (2009) did not combine a period of estrus detection and AI followed by TAI of heifers not observed in estrus. To our knowledge, the present study is the first to use the 5dCIDR and CS protocols in this manner in either beef heifers or cows. Timed-AI conception rates did not differ between treatments (Table 1). However, because a period of estrus detection and AI was combined with TAI in the present study, it cannot be inferred that both protocols would result in similar TAI pregnancy rates if strict TAI was used. Both the CS and 5dCIDR protocols have been investigated as strict TAI programs for beef heifers and have been demonstrated to result in greater TAI pregnancy rates than the 7-d CO-Synch + CIDR (Busch et al., 2007; Wilson et al., 2007). Busch et al. (2007) observed similar TAI pregnancy rates (62%) as
5-day Select Synch + CIDR versus CIDR Select in beef heifers
reported in this study, in beef heifers synchronized with the CS protocol and inseminated strictly by TAI at 72 h after PGF. Wilson et al. (2007) observed lesser TAI pregnancy rates (57.8%) compared with the present study, in beef heifers synchronized with the 5-d CO-Synch + CIDR. When pregnancy response from estrus detection and AI and TAI were combined, overall pregnancy rates did not differ between treatments (Table 1). In both treatments, overall AI pregnancy rates (70.4%) were greater than those observed in most other reports, regardless of estrus synchronization protocol used. With strict TAI, Wilson et al. (2007) reported pregnancy rates of 57.8% using the 5-d CO-Synch + CIDR in replacement beef heifers. Busch et al. (2007) reported TAI pregnancy rates of 62% when using the CS protocol with strict TAI. Contributing to the high overall pregnancy rates and the improved AI pregnancy rates compared with previously reported data is the combination of a period of estrus detection followed by TAI used in this study. Such an approach ensures that heifers that exhibit estrus greater than 24 h before TAI are inseminated, and the TAI in heifers not exhibiting estrus ensures all heifers receive an opportunity to conceive to AI. Breeding season pregnancy rates (Table 1) and the percentage of heifers that experienced embryonic loss between the initial and final pregnancy diagnosis (3.6%) did not differ (P > 0.10) between treatments. In the current study, heifers in the 5dCIDR treatment received two 25-mg doses of PGF at a 12-h interval. Due to the 5-d interval between GnRH administration, causing the potential development of an accessory corpus luteum, and PGF administration, it was unclear if a single 25-mg dose of PGF would be sufficient to induce complete luteal regression. In mature beef cows it has been demonstrated that a single 25-mg injection of PGF is not sufficient to induce luteolysis in all females (Souto et al., 2009) and consequently TAI pregnancy rates are reduced (Kasimanickam
et al., 2009). Having to administer 2 separate doses of PGF increases the labor required to conduct the 5dCIDR protocol and may limit its use in the beef industry. Similarly, the long duration of the CS protocol makes this approach undesirable to some producers. However, recent research has demonstrated that administering 2 separate doses of PGF to heifers enrolled in the 5dCIDR may not be a necessity. In dairy heifers synchronized with the 5-d CO-Synch approach, TAI pregnancy rates were similar between heifers that received one or 2 doses of PGF (Rabaglino et al., 2010). However, before PGF delivery to beef heifers in the 5dCIDR protocols is modified from 2 separate doses to a single dose, additional research is warranted.
IMPLICATIONS Although estrus response tended to be greater in the CS treatment than in the 5dCIDR treatment, both treatments resulted in similar AI pregnancy rates. Moreover, with AI pregnancy rates greater than 70% in both treatments, both treatments appear to be effective methods to synchronize estrus and facilitate AI in beef heifers. Therefore, both the 5dCIDR and CS protocols are effective protocols for synchronizing estrus and facilitating AI in replacement beef heifers when a period of estrus detection is combined with TAI.
ACKNOWLEDGMENTS Appreciation is expressed to Select Sires, Plains City, Ohio, for funding provided to support this research. Gratitude is extended to Pfizer Animal Health (New York, NY) for donation of Lutalyse and CIDR. The assistance of the Heaton family of Heaton Land and Livestock is also recognized.
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