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Fertility after implementation of long- and short-term progesterone-based ovulation synchronization protocols for fixed-time artificial insemination in beef heifers
Theriogenology 83 (2015) 1226–1232
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Fertility after implementation of long- and short-term progesterone-based ovulation synchronization protocols for fixed-time artificial insemination in beef heifers R. Kasimanickam a, *, S. Schroeder a, J.B. Hall b, W.D. Whittier c a
Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington, USA Department of Animal and Veterinary Science, Nancy M Cummins Research Extension and Education Center, University of Idaho, Carmen, Idaho, USA c Department of Large Animal Clinical Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 August 2014 Received in revised form 5 January 2015 Accepted 5 January 2015
Two experiments were conducted to evaluate the effect of long-term (LT; a 14-day controlled internal drug release insert [CIDR]–PGF2a [PGF]–GnRH) and short-term (ST; 5-day CO-Synch þ CIDR) progesterone-based protocols on pregnancy rate to fixed-time artificial insemination (FTAI) in beef heifers. In experiment 1, Angus cross beef heifers (N ¼ 1887) at nine locations received a body condition score and a reproductive tract score (RTS). Within the herd, heifers were randomly assigned to LT-72 and ST-56 protocol groups. Heifers in the LT-72 group received a CIDR from Days 0 to 14, followed by 25 mg of PGF 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 mg of gonadorelin hydrochloride (GnRH) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group, and all heifers were given GnRH (100 mg, intramuscular) at the time of AI. In experiment 2, Angus cross beef heifers (N ¼ 718) at four locations received a body condition score and an RTS. Within the herd, heifers were randomly assigned to LT-72 and ST-72 protocol groups. The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both LT-72 and ST-72 groups. In experiment 1, no difference in AI pregnancy rates between the LT-72 and ST-56 groups was observed (54.5% [489 of 897] and 55.5% [549 of 990], respectively; P ¼ 0.92) after accounting for the RTS. The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 52.6%, 53.6%, and 59.9%, respectively (P < 0.05). In experiment 2, controlling for the RTS, no difference in AI pregnancy rates was observed between the LT-72 and ST-72 groups, 56.9% (198 of 347) and 57.8% (214 of 371), respectively (P ¼ 0.87). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 49.3%, 58.4%, and 62.1%, respectively (P < 0.05). In conclusion, heifers synchronized for fixed-time AI with LT and ST protocols resulted in a similar AI pregnancy rate. Approximately, 55% of the herd was pregnant to one insemination in 33 days with the LT protocol compared with just 8 days with the ST protocol. Ó 2015 Elsevier Inc. All rights reserved.
Keywords: Beef heifer 5-Day CIDR 14-Day controlled internal drug release insert Estrous synchronization Insemination Pregnancy rate
1. Introduction * Corresponding author. Tel.: þ1 509 335 6060; fax: þ1 509 335 0880. E-mail address: [email protected] (R. Kasimanickam). 0093-691X/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.theriogenology.2015.01.004
Estrous synchronization and artificial insemination (AI) provide producers with management tools to maximize
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the reproductive potential of their herd by incorporating superior genetics into their beef operations. In addition, the use of fixed-time artificial insemination (FTAI) is attractive to many beef cattle producers as it eliminates the time and labor required for estrous detection. Recent improvements in our understanding of methods for synchronizing the time of estrus and ovulation in replacement beef heifers create the opportunity to significantly increase the use of AI [1]. Technology with many options now exists to successfully inseminate heifers at predetermined fixed times with pregnancy rates comparable with those achieved with estrous detection. Selection of a desirable protocol should consider evaluation of available resources and assessment of heifers intended for estrous synchronization. Consideration should also include the length of the protocol [2], number of times animals are handled [3], facility type [4], experience of operators, cost involved in the implementation of the protocol [5], and the ability to successfully deliver treatments. Currently two estrous synchronization protocols, the 5-day CO-Synch þ controlled internal drug release insert [CIDR] and the 14-day CIDR–PGF2a (PGF)–GnRH, have been recommended to implement for FTAI in beef heifers. Both protocols have resulted in greater AI pregnancy rates in beef heifers than have the 7-day CO-Synch þ CIDR protocols [6– 10]. However, both these protocols have practical limitations. The 5-day CO-Synch þ CIDR (short term [ST]) protocol requires animals to be handled twice on Day 5 of the protocol to deliver two injections of PGF on the day of CIDR removal, whereas the duration of the 14-Day CIDR–PGF–GnRH (longterm [LT]) protocol (33 days) and the requirement to handle the animals five times may restrict its use. Although both protocols have limitations, both represent viable options for beef producers wanting to use estrus synchronization and AI. However, a direct comparison between these 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 study was to evaluate the effect of LT (14-day CIDR–PGF– GnRH) and ST (5-day CO-Synch þ CIDR) protocols on pregnancy rate to FTAI in beef heifers. 2. Materials and methods 2.1. Experiment 1 In experiment 1, Angus cross beef heifers (N ¼ 1887) at nine locations included in 2012 fall and 2013 spring breeding seasons received a body condition score (BCS; 1–9; 1: emaciated; 9: obese) and a reproductive tract score (RTS; 1–5; 1: under developed; 5: cycling; N ¼ 1639; heifers were not given the RTS in two locations). Within the herd, heifers were randomly assigned to LT-72 (n ¼ 897) and ST-56 (n ¼ 990) estrous synchronization protocol groups (Fig. 1A). Heifers in the LT-72 group received a CIDR (Eazi-Breed CIDR Cattle Insert; Pfizer Animal Health, New York, NY, USA) from Days 0 to 14, followed by 25 mg of PGF (dinoprost; 5 mL intramuscular [im]; Lutalyse sterile solution; Pfizer Animal Health) 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 mg of gonadorelin hydrochloride (GnRH; 2 mL, im; Factrel; Pfizer Animal
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Health) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group. All heifers were given GnRH (100 mg, im) at the time of insemination. Artificial insemination sires differed among locations and were selected and assigned to heifers on the basis of sire traits and to avoid inbreeding. In six locations, the ranch used technicians from breeding companies, and in the other three locations, one clinician performed the inseminations. Experienced clinicians or trained veterinary students assigned the BCS and RTS for each heifer. The timing of CIDR insertion, CIDR withdrawal, interval to the second PGF injection, and timed AI were recorded for each animal. 2.2. Experiment 2 In the 2013 spring breeding season, Angus cross beef heifers (N ¼ 718) at four locations were randomly assigned to LT-72 (n ¼ 350) and ST-72 (n ¼ 368) protocols within the herd (Fig. 1B). The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both ST-72 and LT-72 groups. Additionally, each heifer received a BCS and an RTS (N ¼ 499; heifers were not given the RTS in two locations). Artificial insemination sires differed among locations and were selected and assigned to heifers on the basis of sire traits and to avoid inbreeding. In all locations, the ranch used technicians from stud companies. The BCS and RTS were assigned by experienced clinicians or by trained DVM students. Two weeks later, intact Angus bulls were placed with heifers (approximately1:40–1:50), across treatments, for the remainder of the 60 to 70 days of the breeding season. 2.3. Pregnancy diagnosis Heifers were examined for pregnancy status approximately 70 days after FTAI by ultrasonography (Aloka-500; Sysmed Lab Inc., Chicago, IL, USA) of the uterus and its contents to differentiate heifers bred by AI or natural service sires. The criteria considered were the size of the amniotic vesicle, fetus, and placentomes. The AI pregnancy rate was calculated as the number of heifers pregnant to AI divided by the total number of heifers inseminated. 2.4. Statistical analyses Data were analyzed with a statistical software program (SAS Version 9.3 for Windows; SAS Institute, Cary, NC, USA). Differences in the mean BCS between the treatments were analyzed using one-way ANOVA (PROC GLM of SAS). Differences in the mean interval (hour) from CIDR insertion to CIDR withdrawal and the interval from CIDR removal to the time of insemination between the groups were analyzed by ANOVA; the Bartlett test was used to assess homogeneity of variance (PROC GLM of SAS). Because variances for the mean interval were heterogeneous, a log10 transformation was performed. The values are presented with nontransformed values.
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Fig. 1. Schematic presentation of a synchronization protocol. (A) Angus cross beef heifers (N ¼ 1887) at nine locations received a body condition score (BCS) and a reproductive tract score (RTS) and within the herd were randomly assigned to LT-72 and ST-56 protocol groups. Heifers in the LT-72 group received a controlled internal drug release insert (CIDR) from Days 0 to 14, followed by 25 mg of PGF2a (PGF) 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 mg of gonadorelin hydrochloride (GnRH) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group, and all heifers were given GnRH (100 mg, intramuscularly) at the time of artificial insemination (AI). (B) Angus cross beef heifers (N ¼ 718) at four locations received a BCS and an RTS and within the herd were randomly assigned to LT-72 and ST-72 protocol groups. The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both the treatment groups, and all heifers were given GnRH (100 mg, intramuscularly) at the time of AI. FTAI, fixed-time AI.
The data were analyzed using PROC GLIMMIX of SAS to determine the difference in AI pregnancy rate between the ST and LT protocols. The data were analyzed separately for experiments 1 and 2. In experiment 1, the variables
included in the model were treatment (LT vs. ST), BCS categories (4, 5 and 6, and 7), RTS (3, 4, and 5; RTS 1, 2, and 3 were grouped together), treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS
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categories interactions. Year (location), AI sires, and AI technicians were included as random variables in the model. In experiment 2, the variables included in the model were treatment (LT vs. ST), BCS categories (4, 5 and 6, and 7), RTS (3, 4, and 5; RTS 1, 2, and 3 were grouped together), treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS categories interactions. Location, AI sires, and AI technicians were included as random variables in the model. A P value of 0.05 was considered significant. For model reduction, the P value was set at 0.1 or less for inclusion and greater than 0.1 for exclusion until the model contained only significant main and interaction effects. After model reduction, the final models in both experiments had only treatment and RTS categories. 3. Results 3.1. Experiment 1 The mean standard error of the mean BCS for the ST group is 5.77 0.07 (range, 5.26–5.92) and for the LT group is 5.65 0.09 (range, 5.17–5.81). Within locations, mean BCS did not differ between the ST and LT groups (P > 0.1). The time intervals (hour) from CIDR removal to AI were 55.75 0.09 and 71.40 0.06 for the ST and LT groups, respectively. The time interval (hour) between two PGF injections on Day 5 in the ST group was 5.83 0.05. Within locations, mean time intervals did not differ between the ST and LT groups (P < 0.01). Accounting for RTS categories (P ¼ 0.02), there was no difference in AI pregnancy rates between the LT (54.5% [489 of 897]) and ST (55.5% [549 of 990]) groups (P ¼ 0.92; Table 1). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 52.8% (162 of 307), 53.5% (214 of 400), and 59.9% (558 of 932), respectively. The BCS, treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS categories interactions did not influence AI pregnancy (P > 0.1). The AI pregnancy rates for BCS categories 4, 5 and 6, and 7 were 52.1%, 55.9%, and 58.4%,
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respectively (P ¼ 0.64). The AI pregnancy rates differed (49.4%–67.5%) among locations (P < 0.01). Within location, there was a significant difference in AI pregnancy between the treatment groups (P < 0.05). Mean AI pregnancy differences between the treatment groups for different locations are depicted in Figure 2. 3.2. Experiment 2 The mean standard error of the mean BCS for the ST group is 5.94 0.07 (range, 5.37–6.12) and for the LT group is 5.77 0.12 (range, 5.43–6.13). Within locations, mean BCS did not differ between the ST and LT groups (P > 0.1). The time intervals (hour) from CIDR removal to AI were 71.42 0.11 and 72.10 0.14 for the ST and LT groups, respectively. The time interval (hour) between the two PGF injections on Day 5 in the ST group was 6.10 0.09. Within locations, mean time intervals did not differ between the ST and LT groups (P < 0.01). Accounting for RTS categories (P ¼ 0.04), there was no difference in AI pregnancy rates between the LT and ST groups, 56.9 (198 of 347) versus 57.8% (214 of 371), respectively (P ¼ 0.62). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 49.3 (71 of 144), 58.4 (87 of 149), and 62.1% (128 of 206), respectively. The BCS, treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS categories interactions did not influence AI pregnancy (P > 0.1). The AI pregnancy rates for BCS categories 4, 5 and 6, and 7 were 51.0 (50 of 98), 59.8 (259 of 433), and 55.6% (104 of 187), respectively (P ¼ 0.11). The AI pregnancy rates ranged from 54.4% to 61.0% among locations (P < 0.01). Within location, there was significant difference in AI pregnancy between the treatment groups (P < 0.05). Mean AI pregnancy differences between the treatment groups for different locations are given in Figure 3. 4. Discussions The 5-day CO-Synch þ CIDR and 14-day CIDR–PGF– GnRH estrous synchronization protocols evaluated in the
Table 1 Explanatory variable, synchronization protocol, and reproductive tract score influencing pregnancy to artificial insemination (AI) in Angus cross beef heifers (N ¼ 4041). Effect Experiment 1a Synchronization protocolb Reproductive tract scorec Experiment 2d Synchronization protocole Reproductive tract scorec
Degrees of freedom
F value
P value
1 2
0.01 4.16
0.92 0.02
1 2
0.06 3.22
0.62 0.04
a Fit statistics: Bayesian information criterion (BIC) ¼ 1224.78; 2 Res Log Likelihood ¼ 1217.87; covariate parameter estimates: year (locations) ¼ 0.004057; AI sires ¼ 0.000175; AI technicians ¼ 0.001918; residual ¼ 0.2418. b Refer Figure 1A for protocol. c Reproductive tract score: 1, immature and anestrus to 5, mature and cyclic. d Fit statistics: BIC ¼ 767.43; 2 Res Log Likelihood ¼ 754.73; covariate parameter estimates: locations ¼ 0.003257; AI sires ¼ 0.000115; AI technicians ¼ 0.000992; residual ¼ 0.1723. e Refer Figure 1B for protocol.
Fig. 2. Mean artificial insemination (AI) pregnancy difference (mean AI pregnancy difference ¼ mean AI pregnancy for the ST-56 group mean AI pregnancy for the LT-72 group) between the ST-56 (5-day COSynch þ controlled internal drug release insert [CIDR]) and LT-72 (14-day CIDR–PGF–GnRH) treatment (refer Figure 1A for protocol) groups in different locations. The ST-56 protocol resulted in greater AI pregnancy in five locations (dark-colored bar), and the LT-72 protocol resulted in greater AI pregnancy in four locations (light-colored bars).
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Fig. 3. Mean artificial insemination (AI) pregnancy difference (mean AI pregnancy difference ¼ mean AI pregnancy for the ST-72 group mean AI pregnancy for the LT-72 group) between the ST-72 (5-day COSynch þ controlled internal drug release insert [CIDR]) and LT-72 (14-day CIDR–PGF–GnRH) treatment (refer Figure 1B for protocol) groups in different locations. The ST-72 protocol resulted in greater AI pregnancy in two locations (dark-colored bars) and the LT-72 protocol resulted in greater AI pregnancy in two locations (light-colored bars).
present study have proven to be successful methods to facilitate FTAI in beef heifers but had never been directly compared in a large multilocation field study. Despite the fact that each protocol varies in its approach to facilitate a synchronous ovulation at FTAI, results from the present study support that FTAI pregnancy rates in beef heifers did not differ when using these protocols. It should be noted that even though these protocols did not affect FTAI pregnancy rate, prepubertal heifers (based on the RTSs) at protocol initiation had a reduction in FTAI pregnancy rates. This outcome validates the importance of proper heifer development programs to ensure that puberty is attained before initiation of the breeding season [11]. Numerous estrous synchronization protocols are available for facilitating AI in beef cattle. Although some of these protocols rely on estrous detection, several recently developed protocols facilitate breeding of all females at a predetermined time. These programs synchronize the time of ovulation and thus eliminate estrus detection. Recently, several FTAI approaches have been developed for beef heifers. Among these include the 5-day CO-Synch þ CIDR protocol and 14-day CIDR–PGF protocols with or without GnRH [10]. The LT protocol uses an LT progestin treatment to facilitate a tight synchrony of estrous expression after PGF administration [12,13], and thus, the LT protocol does not rely on GnRH to control follicular dynamics during estrous synchronization. Administration of GnRH to initiate a new wave of ovarian follicular development was not required with the LT CIDR approaches, and removal of GnRH administration resulted in a tight synchrony of estrus [14] and showed a similar [14] tendency to improve FTAI pregnancy rates compared to when GnRH was administered [10,14]. In the present study, this longer approach without GnRH resulted in acceptable FTAI pregnancy rates (54.5% and 56.9%) but did not improve FTAI pregnancy rates when compared to the ST protocol (P > 0.1). The ST protocol was developed on the principle that reducing the interval from CIDR insertion and GnRH to
CIDR removal and PGF from 7 to 5 days would allow the interval from CIDR removal to FTAI to be extended to 72 hours, thus maximizing preovulatory estradiol concentrations [6]. In cattle, it has been found that maximizing preovulatory estradiol concentrations during the preovulatory period increases the probability of becoming pregnant [15,16]. In the recent study, however, there was a greater pregnancy rate after 56 hours of interval from CIDR removal to FTAI proving that 56 hours of interval is sufficient to maximize preovulatory estradiol concentrations [7]. This protocol relies on GnRH to reset follicular development at CIDR insertion, which has been reported to have limited [17] and significant [18] effectiveness in beef heifers. However, the 5-day interval from GnRH to PGF may limit asynchronous follicular development in females that fail to respond to the initial GnRH administration [15]. In the present study, the AI pregnancy for ST treatment did not differ from the LT treatment. Although FTAI pregnancy rates were not impacted by treatment, pubertal status at protocol initiation affected FTAI pregnancy rates. The proportion of pubertal heifers at the start of the breeding season, however, can vary dramatically across herds [11] and is influenced by numerous factors, including age, weight, body condition, and breed [19–21]. Given the extended duration of the LT treatment and the necessity to initiate this protocol earlier to allow for similar days of AI among protocols, it was expected and observed that fewer heifers in this treatment group would be pubertal at protocol initiation across all locations. Heifers that failed to attain puberty before protocol initiation had reduced FTAI pregnancy rates, emphasizing the importance of proper heifer development before the initiation of the breeding season. Although providing progesterone can stimulate pubertal attainment in previously prepubertal heifers [22,23], it does not negate the importance of having a high proportion of heifers pubertal at the initiation of the breeding season to maximize pregnancy success [11]. Similar to results in the present study, other studies in beef heifers have reported improved AI pregnancy rates in heifers that were pubertal or postpubertal at the time of treatment initiation to induce or synchronize the time of estrus, respectively [11,23–25], yet others have observed that pubertal status at the onset of the breeding season does not affect pregnancy success to AI [26]. The interval from PGF injection to FTAI for the LT protocol used in the present study was 72 hours. In previous studies, the insemination was performed between 66 and 72 hours. Those studies [12–14] reported that the peak estrous response occurred from 48 to 60 hours after the PGF treatment assessed by a heat watch system. The optimal time to AI in the beef heifers is 4 to 20 hours after the detection of estrus by using the HeatWatch system [27]. On the basis of this information, acceptable AI pregnancy can be achieved if the beef heifers are inseminated between 52 and 80 hours after the PGF injection. The intervals from CIDR removal (from the first PGF injection) to FTAI for the ST protocol used in the present study were 56 and 72 hours. Insemination at 56 hours after CIDR removal when the ST protocol was used resulted in greater AI pregnancy rates than with insemination at 72 hours [7]. In the present study, both 56 and 72 hours of
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insemination timings for the ST protocol were compared with insemination at 72 hours for the LT protocol to determine the difference in AI pregnancy rates; insemination was performed at the same time (72 hours) for both ST and LT protocols and compared with insemination at different periods (56 vs. 72 hours). There was no difference in AI pregnancy between the ST and LT protocols irrespective of the difference in the timing of insemination for the ST protocol. In a previous study, it was reported that there was dominant follicle regression and a new wave of ovarian follicle development occurring after Day 25, and the variance in follicle diameter on Day 30 was less in heifers treated using the LT protocol indicating the presence of a dominant follicle [10]. Similarly, the presence of a dominant follicle occurs by 56 hours after CIDR removal [7,15,16]. Elevated estradiol concentrations before estrus are important for follicular and oocyte maturation and uterine function [16]. Therefore, when using protocols to synchronize the time of ovulation in cattle, maximizing the proportion of females with a dominant follicle before FTAI is critical even if estrus is not exhibited. It should be noted that in experiment 1, four locations had greater AI pregnancy for the ST protocol and three locations had greater AI pregnancy for the LT protocol. Similarly, in experiment 2, two locations had higher AI pregnancy for the ST protocol and two locations had higher AI pregnancy for the LT protocol. This variability in the AI pregnancy rate, noted in this study, may not have been caused by the synchronization treatment per se but by other problems inherent in the AI programs in which large numbers of animals are inseminated in a short time span [28]. When selecting a program to synchronize the time of estrus and ovulation in cattle, however, attention should be focused on its monetary advantage compared with natural service and its benefit over other synchronization protocols in an individual herd. Utilization of protocols to synchronize estrus and ovulation as compared with the use of natural service in beef heifers provides for an advantage of enhanced pregnancy rates [29] and lifetime revenue [30]. The probability of conception early in the first breeding season is increased in beef heifers that have experienced multiple estrous cycles before the onset of the breeding season [31,32]. The most effective method to induce puberty in heifers involves administration of a progestin [33–35]. Although progesterone supplementation before the beginning of the breeding season helped prepubertal and peripubertal beef heifers in achieving greater AI pregnancy rates [36], studies [23–25] have reported improved AI pregnancy in pubertal compared with prepubertal beef heifers after progesterone-based synchronization protocol as noted in this study. This warrants detailed investigation on the role of progesterone supplementation in improving AI pregnancy in prepubertal heifers. 4.1. Conclusions Heifers in which the time of estrus and ovulation is synchronized for FTAI with LT and ST protocols had similar AI pregnancy rates. Approximately, 55% of the herd is pregnant to one insemination in 33 days with the LT protocol compared with just 8 days with the ST protocol.
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Heifers that failed to attain puberty before protocol initiation had reduced FTAI pregnancy rates, highlighting the importance of proper heifer development before the initiation of the breeding season. Acknowledgments The authors thank cattle producers in Washington, Idaho, Wyoming, and Virginia states. The authors also thank Pfizer Animal Health for the donation of Eazi-Breed CIDR Cattle Insert, Lutalyse, and Factrel. S. Schroeder, Doctor of Veterinary Medicine (DVM) class of 2016, was supported by DVM Students Summer Research Experience Program, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA. References [1] Patterson DJ, Kojima FN, Smith MF. A review of methods to synchronize estrus in replacement heifers and postpartum beef cows. J Anim Sci 2003;81(Suppl.2):E166–77. [2] Nash JM, Mallory DA, Ellersieck MR, Poock SE, Smith MF, Patterson DJ. Comparison of long-term controlled internal drug release-based protocols to synchronize estrus and ovulation in postpartum beef cows. J Anim Sci 2013;91:3168–76. [3] Nash JM, Mallory DA, Ellersieck MR, Poock SE, Smith MF, Patterson DJ. Comparison of long- versus short-term CIDR-based protocols to synchronize estrus prior to fixed-time AI in postpartum beef cows. Anim Reprod Sci 2012;132:11–6. [4] Kasimanickam R, Schroeder S, Assay M, Kasimanickam V, Moore DA, Gay JM, et al. Influence of temperament score and handling facility on stress, reproductive hormone concentrations, and fixed time AI pregnancy rates in beef heifers. Reprod Dom Anim 2014;49:775–82. [5] Johnson SK, Jones RD. A stochastic model to compare breeding system costs for synchronization of estrus and artificial insemination to natural service. Prof Anim Scientist 2008;24:588–95. [6] Bridges GA, Helser LA, Grum DE, Mussard ML, Gasser CL, Day ML. Decreasing the interval between GnRH and PGF2alpha from 7 to 5 days and lengthening proestrus increases timed-AI pregnancy rates in beef cows. Theriogenology 2008;69:843–51. [7] Kasimanickam R, Asay M, Firth P, Whittier WD, Hall JB. Artificial insemination at 56 h after intravaginal progesterone device removal improved AI pregnancy rate in beef heifers synchronized with fiveday CO-Synch þ controlled internal drug release (CIDR) protocol. Theriogenology 2012;77:1624–31. [8] Peterson C, Alkar A, Smith S, Kerr S, Hall JB, Moore D, et al. Effects of one versus two doses of prostaglandin F2alpha on AI pregnancy rates in a 5-day, progesterone-based, CO-Synch protocol in crossbred beef heifers. Theriogenology 2011;75:1536–42. [9] Busch DC, Wilson DJ, Schafer DJ, Leitman NR, Haden JK, Ellersieck MR, et al. Comparison of progestin-based estrus synchronization protocols before fixed-time artificial insemination on pregnancy rate in beef heifers. J Anim Sci 2007;85:1933–9. [10] Mallory DA, Nash JM, Ellersieck MR, Smith MF, Patterson DJ. Comparison of long-term progestin-based protocols to synchronize estrus before fixed-time artificial insemination in beef heifers. J Anim Sci 2011;89:1358–65. [11] Gutierrez K, Kasimanickam R, Tibary A, Gay JM, Kastelic JP, Hall JB, et al. Effect of reproductive tract scoring on reproductive efficiency in beef heifers bred by timed insemination and natural service versus only natural service. Theriogenology 2014;81:918–24. [12] Bridges GA, Mussard ML, Burke CR, Day ML. Influence of the length of proestrus on fertility and endocrine function in female cattle. Anim Reprod Sci 2010;117:208–15. [13] Bridges GA, Day ML, Geary TW, Cruppe LH. Deficiencies in the uterine environment and failure to support embryonic development. J Anim Sci 2013;91:3002–13. [14] Atkins JA, Busch DC, Bader JF, Keisler DH, Patterson DJ, Lucy MC, et al. Gonadotropin-releasing hormone-induced ovulation and luteinizing hormone release in beef heifers: effect of day of the cycle. J Anim Sci 2008;86:83–93. [15] Kasimanickam RK, Firth P, Schuenemann GM, Whitlock BK, Gay JM, Moore DA, et al. Effect of the first GnRH and two doses of PGF2a in a
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R. Kasimanickam et al. / Theriogenology 83 (2015) 1226–1232 5-day progesterone-based CO-Synch protocol on heifer pregnancy. Theriogenology 2014;81:797–804. Leitman NR, Busch DC, Mallory DA, Wilson DJ, Ellersieck MR, Smith MF, et al. Comparison of long-term CIDR-based protocols to synchronize estrus in beef heifers. Anim Reprod Sci 2009;114: 345–55. Leitman NR, Busch DC, Wilson DJ, Mallory DA, Ellersieck MR, Smith MF, et al. Comparison of controlled internal drug release insert-based protocols to synchronize estrus in prepubertal and estrous-cycling beef heifers. J Anim Sci 2009;87:3976–82. Mallory DA, Wilson DJ, Busch DC, Leitman NR, Ellersieck MR, Smith MF, et al. Comparison of long-term progestin-based estrus synchronization protocols in beef heifers. J Anim Sci 2010;88: 3568–78. Lammoglia MA, Bellows RA, Grings EE, Bergman JW, Bellows SE, Short RE, et al. Effects of dietary fat and sire breed on puberty, weight, and reproductive traits of F1 beef heifers. J Anim Sci 2000; 78:2244–52. Barcellos JO, Pereira GR, Dias EA, McManus C, Canellas L, Bernardi ML, et al. Higher feeding diets effects on age and liveweight gain at puberty in crossbred Nelore Hereford heifers. Trop Anim Health Prod 2014;46:953–60. Lardner HA, Damiran D, Hendrick S, Larson K, Funston R. Effect of development system on growth and reproductive performance of beef heifers. J Anim Sci 2014;92:3116–26. Grings EE, Hall JB, Bellows RA, Short RE, Bellows SE, Staigmiller RB. Effect of nutritional management, trace mineral supplementation, and norgestomet implant on attainment of puberty in beef heifers. J Anim Sci 1998;76:2177–81. Lucy MC, Billings HJ, Butler WR, Ehnis LR, Fields MJ, Kesler DJ, et al. Efficacy of an intravaginal progesterone insert and an injection of PGF2alpha for synchronizing estrus and shortening the interval to pregnancy in postpartum beef cows, peripubertal beef heifers, and dairy heifers. J Anim Sci 2001;79:982–95. Leitman NR, Busch DC, Bader JF, Mallory DA, Wilson DJ, Lucy MC, et al. Comparison of protocols to synchronize estrus and ovulation in estrous-cycling and prepubertal beef heifers. J Anim Sci 2008;86: 1808–18. Wood-Follis SL, Kojima FN, Lucy MC, Smith MF, Paterson DJ. Estrus synchronization in beef heifers with progestin-based protocols. I.
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Differences in response based on pubertal status at the initiation of treatment. Theriogenology 2004;62:1518–28. Lamb GC, Larson JE, Geary TW, Stevenson JS, Johnson SK, Day ML, et al. Synchronization of estrus and artificial insemination in replacement beef heifers using gonadotropin-releasing hormone, prostaglandin F2alpha, and progesterone. J Anim Sci 2006;84: 3000–9. Dorsey BR, Kasimanickam R, Whittier WD, Nebel RL, Wahlberg ML, Hall JB. Effect of time from estrus to AI on pregnancy rates in estrous synchronized beef heifers. Anim Reprod Sci 2011;127:1–6. Wishart DF, Young IM, Drew SB. A comparison between the pregnancy rates of heifers inseminated once or twice after progestin treatment. Vet Rec 1977;101:230–1. Rodgers JC, Bird SL, Larson JE, Dilorenzo N, Dahlen CR, Dicostanzo A, et al. An economic evaluation of estrous synchronization and timed artificial insemination in suckled beef cows. Anim Sci 2012;90: 4055–62. Fench J. Evaluation of pregnancy rates following timed AI in beef heifers after synchronization of follicular waves using 14-d controlled internal drug release insert, and the lifetime productivity of beef heifers conceiving to, or sired by, AI. MS thesis. Colorado, USA: Colorado State University; 2012. p. 73–88. Byerly DJ, Staigmiller RB, Berardinelli JG, Short RE. Pregnancy rates of beef heifers bred either on puberal or third estrus. J Anim Sci 1987;65:645–50. 1987. Bagley CP. Nutritional management of replacement beef heifers: a review. J Anim Sci 1993;71:3155–63. Patterson DJ, Corah LR, Brethour JR, Higgans JJ, Kiracofe GH, Stevenson JS. Evaluation of reproductive traits in Box taurus and Bos indicus crossbred heifers: relationship of age at puberty to length of the postpartum interval to estrus. J Anim Sci 1992;70: 4018–35. Gonzalez-Padilla E, Ruiz R, LeFever D, Denham A, Wiltbank JN. Puberty in beef heifers. III. Induction of fertile estrus. J Anim Sci 1975;40:1110–8. Short RE, Bellows RA, Carr JB, Staigmiller RB, Randel RD. Induced or synchronized puberty in heifers. J Anim Sci 1976;43:1254–8. Lamb GC, Nix DW, Stevenson JS, Corah LR. Prolonging the MGA-prostaglandin F2a interval from 17 to 19 days in an estrus synchronization system for heifers. Theriogenology 2000;53:691–8.
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Fertility after implementation of long- and short-term progesterone-based ovulation synchronization protocols for fixed-time artificial insemination in beef heifers R. Kasimanickam a, *, S. Schroeder a, J.B. Hall b, W.D. Whittier c a
Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington, USA Department of Animal and Veterinary Science, Nancy M Cummins Research Extension and Education Center, University of Idaho, Carmen, Idaho, USA c Department of Large Animal Clinical Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 1 August 2014 Received in revised form 5 January 2015 Accepted 5 January 2015
Two experiments were conducted to evaluate the effect of long-term (LT; a 14-day controlled internal drug release insert [CIDR]–PGF2a [PGF]–GnRH) and short-term (ST; 5-day CO-Synch þ CIDR) progesterone-based protocols on pregnancy rate to fixed-time artificial insemination (FTAI) in beef heifers. In experiment 1, Angus cross beef heifers (N ¼ 1887) at nine locations received a body condition score and a reproductive tract score (RTS). Within the herd, heifers were randomly assigned to LT-72 and ST-56 protocol groups. Heifers in the LT-72 group received a CIDR from Days 0 to 14, followed by 25 mg of PGF 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 mg of gonadorelin hydrochloride (GnRH) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group, and all heifers were given GnRH (100 mg, intramuscular) at the time of AI. In experiment 2, Angus cross beef heifers (N ¼ 718) at four locations received a body condition score and an RTS. Within the herd, heifers were randomly assigned to LT-72 and ST-72 protocol groups. The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both LT-72 and ST-72 groups. In experiment 1, no difference in AI pregnancy rates between the LT-72 and ST-56 groups was observed (54.5% [489 of 897] and 55.5% [549 of 990], respectively; P ¼ 0.92) after accounting for the RTS. The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 52.6%, 53.6%, and 59.9%, respectively (P < 0.05). In experiment 2, controlling for the RTS, no difference in AI pregnancy rates was observed between the LT-72 and ST-72 groups, 56.9% (198 of 347) and 57.8% (214 of 371), respectively (P ¼ 0.87). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 49.3%, 58.4%, and 62.1%, respectively (P < 0.05). In conclusion, heifers synchronized for fixed-time AI with LT and ST protocols resulted in a similar AI pregnancy rate. Approximately, 55% of the herd was pregnant to one insemination in 33 days with the LT protocol compared with just 8 days with the ST protocol. Ó 2015 Elsevier Inc. All rights reserved.
Keywords: Beef heifer 5-Day CIDR 14-Day controlled internal drug release insert Estrous synchronization Insemination Pregnancy rate
1. Introduction * Corresponding author. Tel.: þ1 509 335 6060; fax: þ1 509 335 0880. E-mail address: [email protected] (R. Kasimanickam). 0093-691X/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.theriogenology.2015.01.004
Estrous synchronization and artificial insemination (AI) provide producers with management tools to maximize
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the reproductive potential of their herd by incorporating superior genetics into their beef operations. In addition, the use of fixed-time artificial insemination (FTAI) is attractive to many beef cattle producers as it eliminates the time and labor required for estrous detection. Recent improvements in our understanding of methods for synchronizing the time of estrus and ovulation in replacement beef heifers create the opportunity to significantly increase the use of AI [1]. Technology with many options now exists to successfully inseminate heifers at predetermined fixed times with pregnancy rates comparable with those achieved with estrous detection. Selection of a desirable protocol should consider evaluation of available resources and assessment of heifers intended for estrous synchronization. Consideration should also include the length of the protocol [2], number of times animals are handled [3], facility type [4], experience of operators, cost involved in the implementation of the protocol [5], and the ability to successfully deliver treatments. Currently two estrous synchronization protocols, the 5-day CO-Synch þ controlled internal drug release insert [CIDR] and the 14-day CIDR–PGF2a (PGF)–GnRH, have been recommended to implement for FTAI in beef heifers. Both protocols have resulted in greater AI pregnancy rates in beef heifers than have the 7-day CO-Synch þ CIDR protocols [6– 10]. However, both these protocols have practical limitations. The 5-day CO-Synch þ CIDR (short term [ST]) protocol requires animals to be handled twice on Day 5 of the protocol to deliver two injections of PGF on the day of CIDR removal, whereas the duration of the 14-Day CIDR–PGF–GnRH (longterm [LT]) protocol (33 days) and the requirement to handle the animals five times may restrict its use. Although both protocols have limitations, both represent viable options for beef producers wanting to use estrus synchronization and AI. However, a direct comparison between these 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 study was to evaluate the effect of LT (14-day CIDR–PGF– GnRH) and ST (5-day CO-Synch þ CIDR) protocols on pregnancy rate to FTAI in beef heifers. 2. Materials and methods 2.1. Experiment 1 In experiment 1, Angus cross beef heifers (N ¼ 1887) at nine locations included in 2012 fall and 2013 spring breeding seasons received a body condition score (BCS; 1–9; 1: emaciated; 9: obese) and a reproductive tract score (RTS; 1–5; 1: under developed; 5: cycling; N ¼ 1639; heifers were not given the RTS in two locations). Within the herd, heifers were randomly assigned to LT-72 (n ¼ 897) and ST-56 (n ¼ 990) estrous synchronization protocol groups (Fig. 1A). Heifers in the LT-72 group received a CIDR (Eazi-Breed CIDR Cattle Insert; Pfizer Animal Health, New York, NY, USA) from Days 0 to 14, followed by 25 mg of PGF (dinoprost; 5 mL intramuscular [im]; Lutalyse sterile solution; Pfizer Animal Health) 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 mg of gonadorelin hydrochloride (GnRH; 2 mL, im; Factrel; Pfizer Animal
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Health) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group. All heifers were given GnRH (100 mg, im) at the time of insemination. Artificial insemination sires differed among locations and were selected and assigned to heifers on the basis of sire traits and to avoid inbreeding. In six locations, the ranch used technicians from breeding companies, and in the other three locations, one clinician performed the inseminations. Experienced clinicians or trained veterinary students assigned the BCS and RTS for each heifer. The timing of CIDR insertion, CIDR withdrawal, interval to the second PGF injection, and timed AI were recorded for each animal. 2.2. Experiment 2 In the 2013 spring breeding season, Angus cross beef heifers (N ¼ 718) at four locations were randomly assigned to LT-72 (n ¼ 350) and ST-72 (n ¼ 368) protocols within the herd (Fig. 1B). The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both ST-72 and LT-72 groups. Additionally, each heifer received a BCS and an RTS (N ¼ 499; heifers were not given the RTS in two locations). Artificial insemination sires differed among locations and were selected and assigned to heifers on the basis of sire traits and to avoid inbreeding. In all locations, the ranch used technicians from stud companies. The BCS and RTS were assigned by experienced clinicians or by trained DVM students. Two weeks later, intact Angus bulls were placed with heifers (approximately1:40–1:50), across treatments, for the remainder of the 60 to 70 days of the breeding season. 2.3. Pregnancy diagnosis Heifers were examined for pregnancy status approximately 70 days after FTAI by ultrasonography (Aloka-500; Sysmed Lab Inc., Chicago, IL, USA) of the uterus and its contents to differentiate heifers bred by AI or natural service sires. The criteria considered were the size of the amniotic vesicle, fetus, and placentomes. The AI pregnancy rate was calculated as the number of heifers pregnant to AI divided by the total number of heifers inseminated. 2.4. Statistical analyses Data were analyzed with a statistical software program (SAS Version 9.3 for Windows; SAS Institute, Cary, NC, USA). Differences in the mean BCS between the treatments were analyzed using one-way ANOVA (PROC GLM of SAS). Differences in the mean interval (hour) from CIDR insertion to CIDR withdrawal and the interval from CIDR removal to the time of insemination between the groups were analyzed by ANOVA; the Bartlett test was used to assess homogeneity of variance (PROC GLM of SAS). Because variances for the mean interval were heterogeneous, a log10 transformation was performed. The values are presented with nontransformed values.
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Fig. 1. Schematic presentation of a synchronization protocol. (A) Angus cross beef heifers (N ¼ 1887) at nine locations received a body condition score (BCS) and a reproductive tract score (RTS) and within the herd were randomly assigned to LT-72 and ST-56 protocol groups. Heifers in the LT-72 group received a controlled internal drug release insert (CIDR) from Days 0 to 14, followed by 25 mg of PGF2a (PGF) 16 days later (Day 30). Heifers in the ST-56 group received a CIDR and 100 mg of gonadorelin hydrochloride (GnRH) on Day 25 followed by 25 mg of PGF at CIDR removal on Day 30 and a second dose of PGF 6 hours later (Day 30). Artificial insemination was performed at 56 hours (Day 32) after CIDR removal for the ST-56 group and at 72 hours (Day 33) after CIDR removal for the LT-72 group, and all heifers were given GnRH (100 mg, intramuscularly) at the time of artificial insemination (AI). (B) Angus cross beef heifers (N ¼ 718) at four locations received a BCS and an RTS and within the herd were randomly assigned to LT-72 and ST-72 protocol groups. The protocol was similar to experiment 1 except that AI was performed at 72 hours after CIDR removal for both the treatment groups, and all heifers were given GnRH (100 mg, intramuscularly) at the time of AI. FTAI, fixed-time AI.
The data were analyzed using PROC GLIMMIX of SAS to determine the difference in AI pregnancy rate between the ST and LT protocols. The data were analyzed separately for experiments 1 and 2. In experiment 1, the variables
included in the model were treatment (LT vs. ST), BCS categories (4, 5 and 6, and 7), RTS (3, 4, and 5; RTS 1, 2, and 3 were grouped together), treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS
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categories interactions. Year (location), AI sires, and AI technicians were included as random variables in the model. In experiment 2, the variables included in the model were treatment (LT vs. ST), BCS categories (4, 5 and 6, and 7), RTS (3, 4, and 5; RTS 1, 2, and 3 were grouped together), treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS categories interactions. Location, AI sires, and AI technicians were included as random variables in the model. A P value of 0.05 was considered significant. For model reduction, the P value was set at 0.1 or less for inclusion and greater than 0.1 for exclusion until the model contained only significant main and interaction effects. After model reduction, the final models in both experiments had only treatment and RTS categories. 3. Results 3.1. Experiment 1 The mean standard error of the mean BCS for the ST group is 5.77 0.07 (range, 5.26–5.92) and for the LT group is 5.65 0.09 (range, 5.17–5.81). Within locations, mean BCS did not differ between the ST and LT groups (P > 0.1). The time intervals (hour) from CIDR removal to AI were 55.75 0.09 and 71.40 0.06 for the ST and LT groups, respectively. The time interval (hour) between two PGF injections on Day 5 in the ST group was 5.83 0.05. Within locations, mean time intervals did not differ between the ST and LT groups (P < 0.01). Accounting for RTS categories (P ¼ 0.02), there was no difference in AI pregnancy rates between the LT (54.5% [489 of 897]) and ST (55.5% [549 of 990]) groups (P ¼ 0.92; Table 1). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 52.8% (162 of 307), 53.5% (214 of 400), and 59.9% (558 of 932), respectively. The BCS, treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS categories interactions did not influence AI pregnancy (P > 0.1). The AI pregnancy rates for BCS categories 4, 5 and 6, and 7 were 52.1%, 55.9%, and 58.4%,
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respectively (P ¼ 0.64). The AI pregnancy rates differed (49.4%–67.5%) among locations (P < 0.01). Within location, there was a significant difference in AI pregnancy between the treatment groups (P < 0.05). Mean AI pregnancy differences between the treatment groups for different locations are depicted in Figure 2. 3.2. Experiment 2 The mean standard error of the mean BCS for the ST group is 5.94 0.07 (range, 5.37–6.12) and for the LT group is 5.77 0.12 (range, 5.43–6.13). Within locations, mean BCS did not differ between the ST and LT groups (P > 0.1). The time intervals (hour) from CIDR removal to AI were 71.42 0.11 and 72.10 0.14 for the ST and LT groups, respectively. The time interval (hour) between the two PGF injections on Day 5 in the ST group was 6.10 0.09. Within locations, mean time intervals did not differ between the ST and LT groups (P < 0.01). Accounting for RTS categories (P ¼ 0.04), there was no difference in AI pregnancy rates between the LT and ST groups, 56.9 (198 of 347) versus 57.8% (214 of 371), respectively (P ¼ 0.62). The AI pregnancy rates for heifers with RTS 3 or less, 4, and 5 were 49.3 (71 of 144), 58.4 (87 of 149), and 62.1% (128 of 206), respectively. The BCS, treatment by RTS categories, treatment by BCS categories, and RTS categories by BCS categories interactions did not influence AI pregnancy (P > 0.1). The AI pregnancy rates for BCS categories 4, 5 and 6, and 7 were 51.0 (50 of 98), 59.8 (259 of 433), and 55.6% (104 of 187), respectively (P ¼ 0.11). The AI pregnancy rates ranged from 54.4% to 61.0% among locations (P < 0.01). Within location, there was significant difference in AI pregnancy between the treatment groups (P < 0.05). Mean AI pregnancy differences between the treatment groups for different locations are given in Figure 3. 4. Discussions The 5-day CO-Synch þ CIDR and 14-day CIDR–PGF– GnRH estrous synchronization protocols evaluated in the
Table 1 Explanatory variable, synchronization protocol, and reproductive tract score influencing pregnancy to artificial insemination (AI) in Angus cross beef heifers (N ¼ 4041). Effect Experiment 1a Synchronization protocolb Reproductive tract scorec Experiment 2d Synchronization protocole Reproductive tract scorec
Degrees of freedom
F value
P value
1 2
0.01 4.16
0.92 0.02
1 2
0.06 3.22
0.62 0.04
a Fit statistics: Bayesian information criterion (BIC) ¼ 1224.78; 2 Res Log Likelihood ¼ 1217.87; covariate parameter estimates: year (locations) ¼ 0.004057; AI sires ¼ 0.000175; AI technicians ¼ 0.001918; residual ¼ 0.2418. b Refer Figure 1A for protocol. c Reproductive tract score: 1, immature and anestrus to 5, mature and cyclic. d Fit statistics: BIC ¼ 767.43; 2 Res Log Likelihood ¼ 754.73; covariate parameter estimates: locations ¼ 0.003257; AI sires ¼ 0.000115; AI technicians ¼ 0.000992; residual ¼ 0.1723. e Refer Figure 1B for protocol.
Fig. 2. Mean artificial insemination (AI) pregnancy difference (mean AI pregnancy difference ¼ mean AI pregnancy for the ST-56 group mean AI pregnancy for the LT-72 group) between the ST-56 (5-day COSynch þ controlled internal drug release insert [CIDR]) and LT-72 (14-day CIDR–PGF–GnRH) treatment (refer Figure 1A for protocol) groups in different locations. The ST-56 protocol resulted in greater AI pregnancy in five locations (dark-colored bar), and the LT-72 protocol resulted in greater AI pregnancy in four locations (light-colored bars).
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Fig. 3. Mean artificial insemination (AI) pregnancy difference (mean AI pregnancy difference ¼ mean AI pregnancy for the ST-72 group mean AI pregnancy for the LT-72 group) between the ST-72 (5-day COSynch þ controlled internal drug release insert [CIDR]) and LT-72 (14-day CIDR–PGF–GnRH) treatment (refer Figure 1B for protocol) groups in different locations. The ST-72 protocol resulted in greater AI pregnancy in two locations (dark-colored bars) and the LT-72 protocol resulted in greater AI pregnancy in two locations (light-colored bars).
present study have proven to be successful methods to facilitate FTAI in beef heifers but had never been directly compared in a large multilocation field study. Despite the fact that each protocol varies in its approach to facilitate a synchronous ovulation at FTAI, results from the present study support that FTAI pregnancy rates in beef heifers did not differ when using these protocols. It should be noted that even though these protocols did not affect FTAI pregnancy rate, prepubertal heifers (based on the RTSs) at protocol initiation had a reduction in FTAI pregnancy rates. This outcome validates the importance of proper heifer development programs to ensure that puberty is attained before initiation of the breeding season [11]. Numerous estrous synchronization protocols are available for facilitating AI in beef cattle. Although some of these protocols rely on estrous detection, several recently developed protocols facilitate breeding of all females at a predetermined time. These programs synchronize the time of ovulation and thus eliminate estrus detection. Recently, several FTAI approaches have been developed for beef heifers. Among these include the 5-day CO-Synch þ CIDR protocol and 14-day CIDR–PGF protocols with or without GnRH [10]. The LT protocol uses an LT progestin treatment to facilitate a tight synchrony of estrous expression after PGF administration [12,13], and thus, the LT protocol does not rely on GnRH to control follicular dynamics during estrous synchronization. Administration of GnRH to initiate a new wave of ovarian follicular development was not required with the LT CIDR approaches, and removal of GnRH administration resulted in a tight synchrony of estrus [14] and showed a similar [14] tendency to improve FTAI pregnancy rates compared to when GnRH was administered [10,14]. In the present study, this longer approach without GnRH resulted in acceptable FTAI pregnancy rates (54.5% and 56.9%) but did not improve FTAI pregnancy rates when compared to the ST protocol (P > 0.1). The ST protocol was developed on the principle that reducing the interval from CIDR insertion and GnRH to
CIDR removal and PGF from 7 to 5 days would allow the interval from CIDR removal to FTAI to be extended to 72 hours, thus maximizing preovulatory estradiol concentrations [6]. In cattle, it has been found that maximizing preovulatory estradiol concentrations during the preovulatory period increases the probability of becoming pregnant [15,16]. In the recent study, however, there was a greater pregnancy rate after 56 hours of interval from CIDR removal to FTAI proving that 56 hours of interval is sufficient to maximize preovulatory estradiol concentrations [7]. This protocol relies on GnRH to reset follicular development at CIDR insertion, which has been reported to have limited [17] and significant [18] effectiveness in beef heifers. However, the 5-day interval from GnRH to PGF may limit asynchronous follicular development in females that fail to respond to the initial GnRH administration [15]. In the present study, the AI pregnancy for ST treatment did not differ from the LT treatment. Although FTAI pregnancy rates were not impacted by treatment, pubertal status at protocol initiation affected FTAI pregnancy rates. The proportion of pubertal heifers at the start of the breeding season, however, can vary dramatically across herds [11] and is influenced by numerous factors, including age, weight, body condition, and breed [19–21]. Given the extended duration of the LT treatment and the necessity to initiate this protocol earlier to allow for similar days of AI among protocols, it was expected and observed that fewer heifers in this treatment group would be pubertal at protocol initiation across all locations. Heifers that failed to attain puberty before protocol initiation had reduced FTAI pregnancy rates, emphasizing the importance of proper heifer development before the initiation of the breeding season. Although providing progesterone can stimulate pubertal attainment in previously prepubertal heifers [22,23], it does not negate the importance of having a high proportion of heifers pubertal at the initiation of the breeding season to maximize pregnancy success [11]. Similar to results in the present study, other studies in beef heifers have reported improved AI pregnancy rates in heifers that were pubertal or postpubertal at the time of treatment initiation to induce or synchronize the time of estrus, respectively [11,23–25], yet others have observed that pubertal status at the onset of the breeding season does not affect pregnancy success to AI [26]. The interval from PGF injection to FTAI for the LT protocol used in the present study was 72 hours. In previous studies, the insemination was performed between 66 and 72 hours. Those studies [12–14] reported that the peak estrous response occurred from 48 to 60 hours after the PGF treatment assessed by a heat watch system. The optimal time to AI in the beef heifers is 4 to 20 hours after the detection of estrus by using the HeatWatch system [27]. On the basis of this information, acceptable AI pregnancy can be achieved if the beef heifers are inseminated between 52 and 80 hours after the PGF injection. The intervals from CIDR removal (from the first PGF injection) to FTAI for the ST protocol used in the present study were 56 and 72 hours. Insemination at 56 hours after CIDR removal when the ST protocol was used resulted in greater AI pregnancy rates than with insemination at 72 hours [7]. In the present study, both 56 and 72 hours of
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insemination timings for the ST protocol were compared with insemination at 72 hours for the LT protocol to determine the difference in AI pregnancy rates; insemination was performed at the same time (72 hours) for both ST and LT protocols and compared with insemination at different periods (56 vs. 72 hours). There was no difference in AI pregnancy between the ST and LT protocols irrespective of the difference in the timing of insemination for the ST protocol. In a previous study, it was reported that there was dominant follicle regression and a new wave of ovarian follicle development occurring after Day 25, and the variance in follicle diameter on Day 30 was less in heifers treated using the LT protocol indicating the presence of a dominant follicle [10]. Similarly, the presence of a dominant follicle occurs by 56 hours after CIDR removal [7,15,16]. Elevated estradiol concentrations before estrus are important for follicular and oocyte maturation and uterine function [16]. Therefore, when using protocols to synchronize the time of ovulation in cattle, maximizing the proportion of females with a dominant follicle before FTAI is critical even if estrus is not exhibited. It should be noted that in experiment 1, four locations had greater AI pregnancy for the ST protocol and three locations had greater AI pregnancy for the LT protocol. Similarly, in experiment 2, two locations had higher AI pregnancy for the ST protocol and two locations had higher AI pregnancy for the LT protocol. This variability in the AI pregnancy rate, noted in this study, may not have been caused by the synchronization treatment per se but by other problems inherent in the AI programs in which large numbers of animals are inseminated in a short time span [28]. When selecting a program to synchronize the time of estrus and ovulation in cattle, however, attention should be focused on its monetary advantage compared with natural service and its benefit over other synchronization protocols in an individual herd. Utilization of protocols to synchronize estrus and ovulation as compared with the use of natural service in beef heifers provides for an advantage of enhanced pregnancy rates [29] and lifetime revenue [30]. The probability of conception early in the first breeding season is increased in beef heifers that have experienced multiple estrous cycles before the onset of the breeding season [31,32]. The most effective method to induce puberty in heifers involves administration of a progestin [33–35]. Although progesterone supplementation before the beginning of the breeding season helped prepubertal and peripubertal beef heifers in achieving greater AI pregnancy rates [36], studies [23–25] have reported improved AI pregnancy in pubertal compared with prepubertal beef heifers after progesterone-based synchronization protocol as noted in this study. This warrants detailed investigation on the role of progesterone supplementation in improving AI pregnancy in prepubertal heifers. 4.1. Conclusions Heifers in which the time of estrus and ovulation is synchronized for FTAI with LT and ST protocols had similar AI pregnancy rates. Approximately, 55% of the herd is pregnant to one insemination in 33 days with the LT protocol compared with just 8 days with the ST protocol.
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Heifers that failed to attain puberty before protocol initiation had reduced FTAI pregnancy rates, highlighting the importance of proper heifer development before the initiation of the breeding season. Acknowledgments The authors thank cattle producers in Washington, Idaho, Wyoming, and Virginia states. The authors also thank Pfizer Animal Health for the donation of Eazi-Breed CIDR Cattle Insert, Lutalyse, and Factrel. S. Schroeder, Doctor of Veterinary Medicine (DVM) class of 2016, was supported by DVM Students Summer Research Experience Program, College of Veterinary Medicine, Washington State University, Pullman, Washington, USA. References [1] Patterson DJ, Kojima FN, Smith MF. A review of methods to synchronize estrus in replacement heifers and postpartum beef cows. J Anim Sci 2003;81(Suppl.2):E166–77. [2] Nash JM, Mallory DA, Ellersieck MR, Poock SE, Smith MF, Patterson DJ. Comparison of long-term controlled internal drug release-based protocols to synchronize estrus and ovulation in postpartum beef cows. J Anim Sci 2013;91:3168–76. [3] Nash JM, Mallory DA, Ellersieck MR, Poock SE, Smith MF, Patterson DJ. Comparison of long- versus short-term CIDR-based protocols to synchronize estrus prior to fixed-time AI in postpartum beef cows. Anim Reprod Sci 2012;132:11–6. [4] Kasimanickam R, Schroeder S, Assay M, Kasimanickam V, Moore DA, Gay JM, et al. Influence of temperament score and handling facility on stress, reproductive hormone concentrations, and fixed time AI pregnancy rates in beef heifers. Reprod Dom Anim 2014;49:775–82. [5] Johnson SK, Jones RD. A stochastic model to compare breeding system costs for synchronization of estrus and artificial insemination to natural service. Prof Anim Scientist 2008;24:588–95. [6] Bridges GA, Helser LA, Grum DE, Mussard ML, Gasser CL, Day ML. Decreasing the interval between GnRH and PGF2alpha from 7 to 5 days and lengthening proestrus increases timed-AI pregnancy rates in beef cows. Theriogenology 2008;69:843–51. [7] Kasimanickam R, Asay M, Firth P, Whittier WD, Hall JB. Artificial insemination at 56 h after intravaginal progesterone device removal improved AI pregnancy rate in beef heifers synchronized with fiveday CO-Synch þ controlled internal drug release (CIDR) protocol. Theriogenology 2012;77:1624–31. [8] Peterson C, Alkar A, Smith S, Kerr S, Hall JB, Moore D, et al. Effects of one versus two doses of prostaglandin F2alpha on AI pregnancy rates in a 5-day, progesterone-based, CO-Synch protocol in crossbred beef heifers. Theriogenology 2011;75:1536–42. [9] Busch DC, Wilson DJ, Schafer DJ, Leitman NR, Haden JK, Ellersieck MR, et al. Comparison of progestin-based estrus synchronization protocols before fixed-time artificial insemination on pregnancy rate in beef heifers. J Anim Sci 2007;85:1933–9. [10] Mallory DA, Nash JM, Ellersieck MR, Smith MF, Patterson DJ. Comparison of long-term progestin-based protocols to synchronize estrus before fixed-time artificial insemination in beef heifers. J Anim Sci 2011;89:1358–65. [11] Gutierrez K, Kasimanickam R, Tibary A, Gay JM, Kastelic JP, Hall JB, et al. Effect of reproductive tract scoring on reproductive efficiency in beef heifers bred by timed insemination and natural service versus only natural service. Theriogenology 2014;81:918–24. [12] Bridges GA, Mussard ML, Burke CR, Day ML. Influence of the length of proestrus on fertility and endocrine function in female cattle. Anim Reprod Sci 2010;117:208–15. [13] Bridges GA, Day ML, Geary TW, Cruppe LH. Deficiencies in the uterine environment and failure to support embryonic development. J Anim Sci 2013;91:3002–13. [14] Atkins JA, Busch DC, Bader JF, Keisler DH, Patterson DJ, Lucy MC, et al. Gonadotropin-releasing hormone-induced ovulation and luteinizing hormone release in beef heifers: effect of day of the cycle. J Anim Sci 2008;86:83–93. [15] Kasimanickam RK, Firth P, Schuenemann GM, Whitlock BK, Gay JM, Moore DA, et al. Effect of the first GnRH and two doses of PGF2a in a
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