Comparison between 7 vs 9 Days of Controlled Internal Drug Release Inserts Permanency on Oestrus Performance and Fertility in Lactating Dairy Cattle

Abstract

The objective was to evaluate the reproductive performance after oestrus synchronization using controlled internal drug release (CIDR) maintained into the vagina either 7 or 9 days. A controlled randomized block design was performed. Cows (n=255) were blocked by lactation number and days in milk and then randomly divided into 2 groups. In the first group, CIDR was maintained for 7 days (CIDR-7; n=127), and in the second group, CIDR was maintained for 9 days (CIDR-9; n=128). Both groups received Prostaglandin-F2α at CIDR removal. Oestrus response, oestrus onset, oestrus duration, conception rate, and pregnancy at days 28 and 45 were evaluated. Cows were oestrus detected 4 times a day for 120 h after CIDR removal, and only cows in standing oestrus were artificially inseminated between 6 and 12 h after oestrus detection. Oestrus response for both groups was 79.5% and 87.5% for CIDR-7 and CIDR-9, respectively (P=0.09). The oestrus onset (mean ± SD) for the same groups was 56.3±17.2 h and 59.4±17.9 h, respectively (P=0.19). Oestrus duration was 11.3±7.3 h and 11.7±7.8 h for groups CIDR-7 and CIDR-9, respectively (P=0.71). At day 28, the conception rates for the groups CIDR-7 and CIDR-9 days were 51.5% and 45.5% (P=0.39), and the pregnancy rates were 40.9% and 39.8% (P=0.89) for the same groups, respectively. No differences in oestrus performance and fertility in lactating cows’ oestrus synchronized by using CIDR maintained in the vagina either 7 or 9 days were detected.

KeyWords:

• Cattle
• Controlled internal drug release
• Oestrus synchronization
• Oestrus performance
• Fertility

Introduction

In the United States, only 10% of all dairy operations surveyed used protocols of oestrus synchronization with artificial insemination (AI) at a fixed time at the first service postpartum, and around 15% used such protocols at the second service or later (USDA, 2009). Therefore, oestrus detection was a frequent activity for most of the AI programs. The most common method to detect oestrus on dairy operations is by visual observation of standing to be mounted (93%; USDA, 2009). Visual observation to detect oestrus was used in a higher percentage of small operations (≤100 animals, 93%) and medium operations (≥101 to ≤500 animals, 95.5%) than in large operations (≥501 animals, 77.7%; USDA, 2009). In summary, oestrus detection by visual observation continues to be an essential component in many of the AI programs for dairy cattle.

Progesterone intravaginal devices are satisfactory means of controlling oestrus and ovulation in cattle (Roche, 1976; Hansel and Beal, 1979). Their efficacy is dependent on their ability to release adequate concentrations of progesterone in peripheral plasma for a sustained period of time (Munro and Moore, 1985, 1986; Savio et al., 1993). At present, the two most common used devices containing progesterone are the progesterone-releasing intravaginal devices (PRID; Webel, 1976) and the controlling internal drug release (CIDR; McMillan et al., 1991). Currently, CIDR is the only product marketed in the United States. It contains 1.38 g of progesterone and is maintained in the vagina for only 7 days (Chenault et al., 2003). In the last US Department of Agriculture (USDA) survey, 32.4% of the dairy operations used CIDR insert at least 1 time during 2007 (USDA, 2009). The main reasons reported for the use of CIDR were: to induce oestrus in animals in anoestrus (65.7%), treatment of ovarian cysts (43.5%), and as part of an oestrus synchronization program (34.3%; USDA, 2009).

Different climatic factors were reported to affect onset and oestrus duration. An extended period of high temperatures shortens the duration of oestrus and reduces the intensity of behaviour (Gangwar et al., 1965). Moreover, heavy rain, strong winds, and high humidity reduce or suppress oestrus behaviour (Hurnik et al., 1975; Kilgour et al, 1977). In the authors’ practice, farmers in some instances, for different reasons, such as climatic conditions, crop situations, or labor circumstances, did not pull out the CIDRs at the recommended seventh day but 1 or 2 days later. These females showed oestrus and were pregnant, but no comparative evaluation on these reproductive parameters for those cases was performed. This additional permanency could affect the oestrus performance and fertility of this synchronized oestrus. In cattle, subluteal circulating progesterone induces an increase in the frequency of luteinizing hormone (LH) pulses, prolonged growth of the dominant follicle, increased peripheral estradiol, and reduced fertility (Savio et al., 1993; Bridges and Fortune, 2003). Earlier studies showed that the use of intravaginal devices maintained longer than 12 days was characterized by reduced fertility (Maurer et al., 1975; Macmillan and Peterson, 1993; Gordon, 1999). Previous information from another type of CIDR (CIDR-B), which contained higher concentrations of progesterone (1.90 g per device) than the present CIDR insert (1.38 g per device) and is recommended to be maintained in the vagina for 10 to 12 days with no detrimental effects on the fertility were noticed (Maurer et al., 1975; Broadbent et al., 1993; Gordon, 1999). However, no studies were found on the effect on oestrus performance and fertility of the present CIDR insert maintained 9 days in the vagina.

The main goal of the present study was to evaluate the oestrus performance and fertility in lactating dairy cows oestrus synchronized with CIDR maintained in the vagina either 7 or 9 days.

Materials and methods

Study conditions

This study included Holstein and crossbred cows from a single farm from December 2006 to May 2008 at the Dairy Cattle Teaching and Research Center at the University of Minnesota, USA. Lactating cows were housed in a covered tie stall barn, milked twice daily, and fed a total mixed ration of corn or grain sorghum, soybean meal, alfalfa, and corn silage formulated to meet National Research Council requirements (National Research Council, 2001). Mineral salt and water were offered ad libitum. The females were in the 2.3 lactation (range: 1-7) with an average of 98 days in milk (range: 41-415 days). The rolling herd milk production of the cows was 9500 kg per cow. The study was performed in compliance with established standard operating procedures and guidelines for animal care and use at the University of Minnesota.

Cattle

Two hundred sixty lactating Holstein and crossbred cows were used. As a part of the authors’ reproductive herd health preventive program, the females had their first reproductive examination after 25 days post-partum. In addition, at this time the body condition score was evaluated and the cows received a postpartum vaccination. The protocol of vaccination has been reported elsewhere (Romano et al., 2011). Cattle were Holstein, Holstein-Jersey crossbred, and Holstein-Montbéliard crossbred animals. Beginning at day 55 postpartum, the cows were enrolled in an oestrus synchronization program for subsequent AI. The cows were first stratified by lactation number (1 vs ≥2) and days in milk, and then were randomly divided into 2 groups. In the first group, CIDR (1.38 gr, Pharmacia & Upjohn Co., New York, NY, USA) was maintained for 7 days in the vagina (CIDR-7 group; n=130), and the second group, CIDR was maintained for 9 days in the vagina (CIDR-9 group; n=130). The CIDR was inserted in unknown stages of the estrous cycle and removed in both groups at the same time. At this time, each cow received an administration of prostaglandin F_2a (Lutalyse, 25 mg, Pharmacia & Upjohn Co.). The females were released from the tie stall for evaluation of sexual behaviour in a temperature-controlled indoor place with rubber mats covering the floor. A cow was considered to be in oestrus when she was observed standing to be mounted by another cow. Detection of oestrus was performed 2 times a day from the first day of CIDR insertion to 24 h after CIDR removal and then 4 times a day (at 1 a.m., 7 a.m., 2 p.m., and 8 p.m.) for 30 to 45 min until day 5 day after CIDR removal. All the AI was done 6 to 12 h after oestrus was first noted (oestrus=day 0) by 1 person by using different frozenthawed bull semen. The following parameters were evaluated: oestrus response, oestrus onset, oestrus duration, fertility (pregnancy at days 28 and 45). This experiment was performed in 10 replicates containing from 13 to 38 females per replication.

Transrectal ultrasonography

The transrectal ultrasonography (TRUS) examinations were conducted as described (Romano et al., 2006), and all were performed by the same operator, who scanned the same area twice before making a diagnosis. A portable ultrasound (Tringa linear, Esaote, Maastricht, The Netherlands) with a 7.5 MHz linear transducer was used. A diagnosis of pregnancy was made if nonecho dense fluid in the uterine lumen and a corpus luteum in the ipsilateral ovary plus an embryo were visualized at day 28 after AI. When an embryo was seen, its heartbeat was evaluated. In the absence of an allantochorion and/or an embryo, the female was considered not pregnant. All the females were examined by TRUS at days 28 and 45 to determine the percentage of pregnancy rate during the embryonic period (Committee on Bovine Reproductive Nomen clature, 1972). To facilitate TRUS, cows were examined in their stalls with dim ambient light. The diagnosis of pregnancy loss was made when an embryo with no heart beat was detected, signs of embryo degeneration were observed, or complete absence of positive signs of pregnancy in a previously diagnosed pregnant cow by TRUS (Romano, 2004). Cows diagnosed as not pregnant by TRUS from day 28 were included in a new oestrus synchronization program. Cows were used until 3 times. No repeat breeder was detected in the project.

Oestrus performance and fertility calculations

Oestrus response was considered as the total females showing oestrus within 5 days after CIDR removal from the total number of females that received CIDR. Oestrus onset was considered as the interval from the CIDR removal and the first accepting mount by another cow. Oestrus duration was defined as the interval between the first and last accepting mount. Conception rate was defined as the number of females pregnant at day 28 from the total number of females that were artificially inseminated. Pregnancy rate was considered as the total number of pregnant females at days 28 and 45 from the total number of females in the synchronization program.

Statistical analysis

The null hypothesis was that oestrus performance and fertility were not different between CIDR permanencies in the vagina of either 7 or 9 days in lactating dairy cattle. The sample size required for a 2-sided alternative hypothesis to be able to detect a difference of 20% among groups with a conception rate of 50% using α-error of 5% and β-error of 0.20 was 96 animals for each group (Browner et al., 2001). The continuous variables (oestrus onset and oestrus duration) were analyzed by using Student’s t- test for independent variables. The categorical variables (oestrus response, conception rate, and pregnancy rate) were analyzed by using χ² analysis or Fisher Exact Test as appropriate (Devore and Peck 1993). In addition, a binary logistic regression analysis was performed with the main outcome of oestrus response. In the model, the main effects of replicate, lactation, permanency of CIDR, bred and days in milk were included. A difference was considered significant when P≤0.05. A software program was used to statistically analyze all the results (Minitab 15, Minitab Inc., State College, PA, USA).

Results and discussion

During the experiment, 5 females were excluded (3 from CIDR-7 and 2 from CIDR-9) from the trial due to different ailments (teat problem, uterine infection, and mastitis) between the time of oestrus synchronization and day 45 of pregnancy. The final total number of females analyzed was 255. None of the CIDR inserted were lost. A summary of the results can be seen in Table 1. The binary logistic regression showed that the oestrus response was affected by replicate (P=0.04), with a tendency in the effect of CIDR permanency (P=0.09). The bred (P=0.20), days in milk (P=0.32), and lactation number (P=0.60) did not show significant differences. The overall average oestrus response was 83.5%, with a range from 68.4% to 100% among replicates. Oestrus response between CIDR-7 and CIDR-9 was 79.5% and 87.5%, respectively (P=0.09). None of the cows showed signs of oestrus during the period of maintenance of CIDR in the vagina. The oestrus onset (mean ± SD) for CIDR-7 and CIDR-9 was 56.3±17.2 h and 59.4±17.9 h, respectively (P=0.19). Oestrus duration was 11.3±7.3 hours and 11.7 ± 7.8 hours for groups CIDR-7 and CIDR-9, respectively (P=0.71). Overall oestrus duration lasted from 6 to more than 24 h (Figure 1). Conception rates for the groups CIDR-7 and CIDR-9 were 51.5% and 45.5%, respectively (P=0.39). Pregnancy rates at day 28 were 40.9% and 39.8% (P=0.89), and pregnancy rates at day 45 were 40.9% and 37.5% (P=0.61) for the same groups, respectively.

The present results showed no differences in oestrus performance and fertility when CIDR was maintained into the vagina either 7 or 9 days. None of the females in the oestrus synchronization program lost the CIDR insert; this outcome was in contrast with the average of 98% of retention from previous experiences in this farm as well as in other dairy operations in the authors’ practice. A previous investigation reported CIDR retention between 91.9% and 100%, with a mean of 97.3% when 8 different farms were analyzed (Chenault et al., 2003a). When CIDR-B was compared with PRID, the retention in the vagina was higher and the percentages of vaginitis lower for the CIDR-B (Broadbent et al., 1993).

The average oestrus response is considered very good compared with the average from 50% to 74% of oestrus detection for nonsynchronized oestrus (Stevenson and Britt, 1977; Williams et al., 1981). The probable reasons of this high rate of oestrus detection were the combination of several factors working together, such as trained personnel, frequency, duration, time, and conditions of oestrus detection. The personnel in charge of oestrus detection have several years of experience detecting oestrus, good knowledge in recognizing primary and secondary signs of oestrus, and keep adequate records that permit a careful followup of animals that were closed to showing oestrus. Additionally, the personnel were willing to detect oestrus this week because in the previous week, all eligible cows for AI had an inserted CIDR, and such intense activity was not required. The frequency of oestrus detection was another crucial factor that influenced the results, because it showed clearly that approximately 50% of the females in oestrus had oestrus duration of 6 hours. This is in agreement with a previous report that used a radio telemetric oestrus detection system in which 58.4% of the females had an oestrus duration of around 7 hours or less (Dransfield et al., 1998). In a recent US survey, only 31% of the dairy operations observed for oestrus three or more times daily (USDA, 2009). In the present study, each period of oestrus detection lasted between 20 and 45 min. However, more than 50% of operations reported visually observing cows for oestrus 20 min or less at each visual observation period (USDA, 2009), and this could be another contributing factor to reduce oestrus detection efficiency, as previously reported (Hurnik et al., 1975). Oestrus detection was not performed coincident with other activities such as feeding and milking, as these activities have been shown to interfere with oestrus expression (Hurnik et al., 1975). Only the animals eligible for oestrus detection were released, creating special social conditions to form rapidly sexually active groups (Williamson et al., 1972; Kilgour et al., 1977). Moreover, the exclusion of animals not oestrus synchronized decreased not only the possible interference of this group of females with the oestrus synchronized group but also reduced the number of females to be released and observed by the personnel. It was shown that the rates of oestrus detection improved as the proportion of cows in pro-oestrus and oestruses in a group increased (Hurnik et al., 1975; Helmer and Britt, 1985). Oestrus response could have been higher than the one reported here for several reasons. Some animals could have had shorter oestrus duration than the frequency used for oestrus detection, and some females could have been low in the social hierarchy ranking to express oestrus or were in oestrus after the fifth day of oestrus detection as previously reported (Hurnik et al., 1975; Kilgour et al., 1977; Helmer and Britt, 1985; Walker et al., 1996; Dransfield et al., 1998).

The interval from CIDR removal to oestrus onset is in conformity with previous studies that used CIDR-B and CIDR insert (Broadbent et al., 1993; Chenault et al., 2003). The percentage of oestrus response shows a tendency to augment when CIDR was maintained 9 versus 7 days that is in agreement with previous studies showing that oestrus response and synchrony was improved when the CIDR was maintained longer periods; however, this resulted in an oestrus of low fertility (Maurer et al., 1975; Macmillan and Peterson, 1993; Gordon, 1999).

Oestrus duration was in accordance with previous reports that used continual video recording or radiotelemetric oestrus detection system (Hurnik et al., 1975; Vailes and Britt, 1990; Walker et al., 1996) and longer than 7.1 h reported in a further description that used the same last method (Dranfield et al., 1998) or 8.2 h, when CIDR-B was used in cows that were oestrus detected 4 times per day (Broadbent et al., 1993). It is interesting to note that oestrus duration varied with the number of females in oestrus, increasing from 7. 1 to 10.1 h, when the number of cows in oestrus ranged from 1 to 3 cows in oestrus at one time, respectively (Hurnik et al., 1975). Cows in the present study spend the majority of the time on mats on concrete flooring. Nevertheless, all the cows were released to an indoor area covered with rubber mats for oestrus detection. Concrete floor was reported to influence the duration of oestrus (Britt et al., 1986; Vailes and Britt 1990). Rubber mats were reported to improve the expression of oestrus (Platz et al., 2008). Cattle in stanchions when put outdoors mounted more frequently than cows housed in free stalls or cows that run freely on pasture (De Silva et al., 1981; Gwazdauskas et al., 1983). The releasing and locking of each animal from the tie stall was additional work at each time of oestrus detection. However, this was well-adjusted with the previous week in which no such intense oestrus detection was required. It is interesting to note that a high percentage of females, as mentioned previously, have duration of oestrus of 6 hours. Based on the present as well as past investigations on oestrus duration (Hurnik et al., 1975; Helmer and Britt, 1985; Vailes and Britt, 1990; Broadbent et al., 1993; Walker et al., 1996; Dransfield et al., 1998) detecting oestrus twice a day seems could not be an adequate valid recommendation for efficient oestrus detection. In the current study, if this approach had been used, a high percentage of females in oestrus would have been missed.

The fertility rate obtained was similar, as was previously reported (Fonseca et al., 1983). Comparable conception rate results (45.3%) were obtained when 1616 lactating cows from 17 different dairy farms were artificially inseminated with frozen-thawed semen at natural or induced oestrus by prostaglandin F-2α (Dransfield et al., 1998). An initial concern in this investigation was the potential negative effect of keeping the CIDR for 2 additional days on fertility results. The permanency of CIDR beyond the recommended 7 days could produce low peripheral progesterone levels. In cattle, subluteal circulating progesterone increased the frequency of LH pulses, prolonged growth of the dominant follicle, increased levels of peripheral estradiol, and reduced fertility (Savio et al., 1993; Bridges and Fortune, 2003). However, when CIDR-B (containing 1.9 g P₄) was compared with CIDR insert (1.38 g P₄) maintained for 7, 10, or 20 days were bioequivalent in daily progesterone release based on peripheral progesterone levels using ovariectomized nonlactating Friesian cows (Ogle, 1999). The present results showed no differences in the reproductive parameters evaluated. Therefore, this investigation expands our knowledge that the permanency of CIDR insert for 2 extra days does not affect oestrus performance or fertility of lactating dairy cows.

Figure 1. Percentage of lactating cows with different oestrus duration detected four times a day by visual observation.

Table 1. Oestrus performance and fertility in lactating dairy cows oestrus synchronized with controlled internal drug release maintained 7 or 9 days in the vagina.

	CIDR-7	CIDR-9	Significance
Number of animal	127	128
Days in milk	100.1	95	P= 0.32
Lactation number	2.4	2.3	P= 0.60
Oestrus response, %	79.5	87.5	P= 0.09
Oestrus onset, h	56.3	59.4	P= 0.19
Oestrus duration, h	11.4	11.7	P= 0.71
Conception rate, %	51.5	45.5	P= 0.39
Pregnancy rate at 28 days, %	40.9	39.8	P= 0.89
Pregnancy rate at 45days, %	40.9	37.5	P= 0.61

CIDR, controlled internal drug release.

Conclusions

The use CIDR as a tool for reproductive management offers several advantages. Its insertion is independent of the oestrus cycle stage as compared with the use of luteolytic agents alone. During the week that CIDR was in place, no females’ exhibited oestrus. This is of practical importance, because all the eligible breeding females do not require observation for oestrus, giving time off to the personnel in charge of this critical task. Oestrus response showed to be compact. More than 80% of the females showed oestrus between days 2 and 5 after CIDR removal. Finally, the progesterone offers an additional advantage, because it is natural hormone that is present in the milk (Chenault et al, 2003a), and its level in milk from cows with a CIDR insert is lower than from pregnant cows (Chenault et al., 2003b). It is necessary to remark, that even though the present results did not show any differences between the 2 permanencies on the reproductive parameters evaluated, the authors do not recommend maintaining CIDR insert in the vagina for 9 days. In addition, this permanency will be considered as an extra label use of CIDR insert based on the present regulations. It is concluded that the use of CIDR for oestrus synchronization maintained for 9 days in the vagina was an adequate alternative when the removal could not be performed at day 7. No differences in oestrus performance and fertility parameters were detected.

Acknowledgments

The authors thank Dr. Jim Linn and William Hansen for technical assistance and all the personnel of the Dairy Cattle Teaching and Research Unit. In addition, they thank the assistance of Mrs. Lisa Chamberlain for reviewing the manuscript.

This research was supported by the Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA.