Comparative estrus induction in indigenous Sahel goats using two progestagens (CIDR and FGA) and eCG

B O Omontese, P I Rekwot*, I U Ate, J S Rwuaan and H J Makun**

Department of Theriogenology and Production, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
drbobwealth@hotmail.com
* Animal Reproduction Research Programme, National Animal Production Research Institute, Ahmadu Bello University, Zaria, Nigeria
** Small Ruminant Research Programme, National Animal Production Research Institute, Ahmadu Bello University, Zaria, Nigeria

Abstract

The objective of this study was to compare the efficacy of two different progestagens (EAZI-BREED™ CIDR^® and FGA-30^®) in combination with equine chorionic gonadotrophin (eCG) for synchronizing estrus in goats. Sahel does (n=110) were allocated initially into two groups and treated with progestagens containing natural progesterone (CIDR group; n = 50) and fluorogestone acetate (FGA group; n = 60) for 15 days. At the end of progestagen treatment, does that retained the intravaginal sponge (FGA) and devices (CIDR) were further divided into two groups per progestagen type with one half treated with 400 IU eCG intramuscularly concurrent with progestagen removal (CIDR group; n = 17, CIDReCG; n = 16) and (FGA group; n = 23, FGAeCG; n = 23). Does in estrus were identified twice daily (07.00 – 10.00 and 15.00 – 18.00 h) during a 120 h observation period using sexually active bucks. Thirty days after estrus and natural mating, pregnancy was determined by trans-cutaneous ultrasonography.

Retention rate (RR) was 66 % (CIDR) and 76 % (FGA), respectively. There were differences (p<0.05) among treatments for does in estrus (CIDR: 47 %, CIDReCG: 100 %, FGA: 57 %, FGAeCG: 74 %). The average time interval (mean ± SE) from withdrawal of progestagen to onset of estrus were 45.5±5.7, 35.9±3.6, 45.6±4.6 and 37.7±2.4 h while duration of estrus were 25.1±3.3, 53.9±3.0, 33.8±0.2 and 64.8±4.2 h in the CIDR, CIDReCG, FGA and FGAeCG groups, respectively. Pregnancy rates (CIDR: 75 %, CIDReCG: 88 %, FGA: 62 %. FGAeCG: 100 %) did not differ significantly (p>0.05) between treatments. It was concluded that both progestagens in combination with eCG were efficient in synchronizing estrus in Sahel goats.

Keywords: estrus response, fertility rate, gestagens, gonadotrophin, Sahel

Introduction

Several methods have been developed to induce estrus in goats allowing farmers to raise and provide kids to meet market demands. Intravaginal devices containing natural and synthetic types of progestagens, maintained in situ during 14–21 days, associated with gonadotrophin administration have been used (Ungerfield and Rubaines 2002; Whitley and Jackson 2004; Wildeus 2008; Omontese et al 2010; Albecia et al 2011; Abecia et al 2012; Omontese et al 2012a; 2012b). In the tropics, estrus synchronization enables kidding over a limited period thereby allowing producers breed their goats so they can kid at the time of the year when pasture is more abundant. The Sahel bred of goat accounts for the third largest population of goats in Nigeria and is one of potential livestock to be developed (Igbokwe et al 1998; Maina et al 2006). However, there is a dearth of information on their response following estrus synchronization using progestagens and gonadotrophins. The use of intravaginal progestagens followed by administration of pregnant mare's serum gonadotrophin (PMSG) to synchronize estrus has been reported for various breeds of sheep and goats (Greyling and Van Niekerk 1990; Pandleton et al 1992; Menegatos et al 1995; Karatzas et al 1997).

However, responses to gonadotrophins are equivocal, inconsistent and variable being influenced by factors such as treatments and breed (De Roover et al 2005).  The use of estrus synchronization for small ruminant livestock production in Nigeria is still predominantly under investigation and information on estrus synchronization using different progestagens in combination with eCG in goats is scanty (Voh Jr et al 2003; Omontese et al 2010).  Information regarding estrus synchronization efficiency and fertility in Sahel breed of goats induced by hormonal treatment (progestagens and gonadotrophin) will be useful in the design of an intensive and cost-effective breeding programme. The objective of the present study was to compare the effectiveness of two different intravaginal progestagens (CIDR and FGA) with or without eCG administration on estrus response and pregnancy rates in SH goats.

Materials and methods

The experiment was conducted at the National Animal Production Research Institute (NAPRI), Ahmadu Bello University, Zaria, Nigeria.  NAPRI is located in the Northern Guinea Savannah zone of Nigeria between latitude 11 ⁰N and 12 ⁰N and between longitude 7 ⁰E and 8 ⁰E at an elevation of 650 m above sea level with an average annual maximum and minimum temperature of 31.0 ± 3.2 ⁰C and 18.0 ± 3.7 ⁰C respectively. The region has an average annual rainfall of 1100 mm usually lasting from May to October with a mean relative humidity of 72 % while the dry season lasts from November to April with mean daily temperatures ranging from 15 – 36 ⁰C and mean relative humidity of between 20 – 37 %. One hundred and ten (n=110) apparently healthy Sahel does weighing 18 – 21 kg with body condition scores (BCS range 1 - 5) 2.5 – 3.5 (Spahr 2005), and aged between 2 - 3 years were used for this study. The does were identified by means of plastic ear tags. Does were allowed to graze within large paddocks, fed Digitaria smutsii (wooly finger grass) hay; concentrate supplement (0.5 kg/day), and water provided ad libitum. At the start of the experiment, Sahel does received EAZI-BREED^® CIDR, a vaginal progesterone releasing device (0.3 g of progesterone, InterAg, Hamilton, New Zealand; n = 50) and FGA-30^®, a vaginal sponge (30 mg, Chronogest, Intervet, The Netherlands; n = 60) for 15 days after which the retention rate of progestagens were recorded. Does that retained the progestagen were further subdivided into two groups, one half received 400 IU eCG i.m. (PMSG-Intervet, Ireland) concurrent with progestagen withdrawal while the other half received nothing (CIDR, n=17; CIDReCG, n=16; FGA, n=23; FGAeCG, n=23). Does were placed with sexually experienced Sahel bucks in the ratio 1 buck to 10 does. Does were observed visually for behavioral estrus manifestation twice (0700-1000 and 1500-1800 hours) daily for 5 days after sponge withdrawal. Standing to be mounted was the cardinal sign used to determine estrus response. Time interval to onset of estrus, duration of estrus and mounts per estrus periods was evaluated. Thirty days after mating, pregnancy status was determined by transcutaneous ultrasonography using a Real-time B-mode trans-abdominal ultrasound equipment (Aloka 500 V with a 3.5 MHz transducer, Corometrics Medical Systems, Wallingford, CT, USA).   

Data and statistical analyses

Retention, estrus response and pregnancy rates were expressed in percentages. Data on time to initiation of estrus, estrus duration and mounts per estrus periods were expressed as mean ± s.e.m. ANOVA and post hoc Tukey’s test were used to compare means between groups. Values of p < 0.05 were considered significant. Data were analyzed using Graphpad Prism^® data package for windows (2003). Values of p < 0.05 were considered significant.

Results

Retention rates of progestagens were 66 % and 76 % for the CIDR and FGA groups, respectively. The frequency of does in estrus, the interval from device withdrawal to estrus onset, the duration of estrus, number of mounts per estrus periods and pregnancy rates are presented in Table 1. Estrus response rates were 47 %, 100 %, 57 % and 74 % for the CIDR, CIDReCG, FGA and FGAeCG groups, respectively, with estrus response rates higher in the groups treated with progestagen and eCG than in those treated with progestagen alone. Time to onset of estrus was shorter (p<0.05) in the does treated with both progestagen and eCG than in does treated with progestagen alone (Table 1). The highest mounts per estrus period were observed in the FGAeCG group (Table 1).  Pregnancy rates ranged from 62 % to 100 % (Table 1). A summary of the distribution of animal showing estrus is shown is set out in Table 2.

Discussion

Results of this study showed that progestagen retention rate was lower in the CIDR (66 %) than FGA (76 %) treated Sahel does. This is similar to the report of Omontese et al (2010) who recorded a higher FGA (100 %) retention than CIDR (88.89 %) in Red Sokoto does. Retention rates observed in this study were less than the 83 % reported by Omontese et al (2012b) in Sahel does treated with FGA-30^® intravaginal sponge. Variation in progestagen retention rates may be due to differences in management system of does, size of vaginal of individual doe and experience of the operator. Sahel does treated with progestagen and eCG recorded higher estrus response rates than does treated with progestagen alone although in all cases, higher responses were observed with the FGA sponges than with the CIDR devices. The higher estrus response rates observed for does treated with progestagens and equine chorionic gonadotrophin (eCG) is similar but lower than the reports of Ungerfield and Rubaines (2002) in Polwarth ewes treated with progestagens and 380 IU PMSG. It is also lower than the 100 % obtained by Dogan et al (2004) in Saanen does treated with MAP and FGA with 750 IU PMSG. However, it is higher than the 73.5 % reported by Greyling and Van der Nest (2000) using intravaginal MAP progestagen sponges.  Observed differences may be explained by variation in breed, nutrition, season, use of gonadotrophin, presence of females in proestrus/estrus and presence of males after sponge removal (Romano 1998; Ahmed et al 1998 and Romano 2002).

Researchers have reported the onset of estrus to occur within 6 – 120 h following progestagen withdrawal (Greyling and Van der Nest 2000; Ungerfield and Rubaines 2002; Akusu 2003; Whitley and Jackson 2004; Kauser et al 2009; Omontese et al 2012a; 2012b). This is in agreement with observation in this study. The shorter time to onset of estrus observed in does treated with progestagens and eCG may be attributed to the FSH and LH-like activity of eCG administered at progestagen withdrawal (Leboeuf et al 1998). Duration of estrus observed in this study corroborates the findings of other researchers in other breeds of goats (Greyling and Van der Nest 2000; Ungerfield and Rubaines 2002; Akusu 2003). Mounts per estrus periods was higher in the progestagen plus eCG treated does. This corroborates the findings of Oyedipe et al (1989) in Yankasa ewes who reported higher mounts per oestrus periods in ewe treated with 750 IU equine chorionic gonadotrophin following progestagen treatment. This may be attributed to the stimulatory activity of gonadotrophins on the ovaries (Abecia et al 2012). Pregnancy rate was higher in the CIDR (93.5 %) group than the FGA (84.5 %) group. This is higher than the 52.6 % and 50 .0 % recorded by Dogan et al (2004) in Saanen does treated with MAP and FGA respectively.  It is also higher than the 33.33 % and 11.11 % for conception and pregnancy rate reported by Bello (2011) in does treated with FGA-30^® alone for 12 days. It is reported that progestagen plus eCG treatment permits a wide degree of variation in conception rate among flocks and in some cases, high incidence of complete embryo loss and infertility (Haresign 1992). In conclusion, both progestagens (CIDR and FGA) were equally effective for estrous induction in Sahel does, and the administration of equine chorionic gonadotrophin enhanced estrus response irrespective of the progestagen type used.  

Acknowledgements

The authors acknowledge the assistance of the herdsmen for caring for the animals and the Director, NAPRI for permission to publish the work.  

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Received 22 February 2013; Accepted 13 March 2013; Published 2 April 2013

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