Effect of prostaglandin and equine chorionic gonadotrophin on estrus behaviour of Sahel goats during the harmattan season

The study was designed to evaluate the effect of administration of equine chorionic gonadotrophin on prostaglandin treated does and to determine whether estrus synchrony was improved in Sahel goats during the harmattan season in Nigeria. This study was conducted using thirty-six multiparous Sahel does during the harmattan season breeding to compare different protocols with prostaglandin (PGF2α) and equine chorionic gonadotrophin (eCG) to synchronize estrus. Does were treated with PGF2α (SHPG; n=12), PGF2α plus eCG (SHPGeCG; n=12) and eCG (SHeCG; n=12). Does were grouped with sexually active bucks for 5 days.

Estrus response rates were 41.6 %, 91.6 % and 66.7 % for the SHPG, SHPGeCG and SHeCG groups, respectively. Onset of estrus and estrus duration did not differ (p>0.05) between treatments. Although treatments had significant effect on estrus response rates, the use of PGF2α plus eCG resulted in more compact estrus synchronization in Sahel goats during the harmattan season.

Introduction

Estrus synchronization is a valuable management tool for increasing optimum production in does (Lymberopoulos et al 2002). Over the past few decades, hormonal treatments have been employed to manipulate reproduction in goats. Several techniques have been developed to synchronize estrus in goats thereby allowing farmers to raise and provide kids year round (Abecia et al 2012). Estrus synchronization involves the use of intravaginal devices containing different types of progestagens maintained in situ during 12–14 days or the use of prostaglandins administered intramuscularly (Moradi Kor et al 2011; Kawu 2011; Omontese et al 2012). Prostaglandins control the estrus cycle by shortening the luteal phase due to its effect on the corpus luteum (Abecia et al 2011; Abecia et al 2012).

The use of progestagens and eCG administered at the time of sponge withdrawal has being evaluated in Sahel goats (Omontese et al 2012). There are many factors influencing the effect of including eCG in estrus synchronization protocols including the dose, time of administration, co-treatment hormone and season of breeding (Oyedipe et al 1989; Timurkan and Yildiz 2005; Kawu 2011). The Sahel goat is the third most numerous goat in Nigeria but this breed have been neglected in research regarding endocrine control of reproduction. The Sahel breed of goat presents a good carcass conformation and stands out as being very fertile besides being adapted to the semi-arid zone of Nigeria (Maina et al 2006; Igbokwe et al 2009). There is a dearth of information on the use of prostaglandins alone or in combination with eCG on the nature and efficiency of synchronized estrus in Sahel breed of goats indigenous to Nigeria during the harmattan season. The harmattan season is one of the three (harmattan, hot-dry and rainy) seasons in the zone, occurring between November and February (Ayo et al 2011). It is characterized by cold-dry winds laden with dust and scarcity of pasture. Therefore the main objective of this experiment was to evaluate the effect of three different estrus synchronization treatments on the estrus behaviour of Sahel goats during the harmattan season.

Materials and Methods

Location, Housing and Management

This 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 %. The harmattan season lasts from November to February with mean daily temperatures ranging from 15 – 36 ⁰C and mean relative humidity of between 20 – 37 %. Does were housed in a pen and allowed to graze within large paddocks, fed Digitaria smutsii (wooly finger grass) hay; concentrate supplement (0.5 kg/day), and water provided ad libitum.

Animals and hormonal treatment

Sahel does (n=36) weighing between 15 to 18 kg with body condition scores (BCS, range 1 - 5) 2.5 – 3.5 (Spahr 2005) and aged between 2 – 3 year were used for this study. Does were divided into three treatments of 12 does each. The SHPG group received 10 mg prostaglandin (Lutalyse^® Phizer, USA) intramuscular, the SHPGeCG group received 10 mg prostaglandin (Lutalyse^® Phizer, USA) plus 200 IU equine chorionic gonadotrophin (PMSG-Intervet, Ireland) intramuscular while the SHeCG group received 200 IU eCG (PMSG-Intervet, Ireland) only intramuscular.

Estrus detection and natural mating

Does were placed with sexually experienced Sahel bucks in the ratio of 1 buck to 10 does (Abecia et al 2012). Does were observed visually for behavioral estrus manifestation twice (0700-1000 and 1500-1800 hours) daily for 5 days following treatments. Standing to be mounted was used to determine estrus response. Estrus activity occurring within 120 hours post administrations of treatments were classified as synchronized. Estrus response, time interval to initiation of estrus and duration of estrus were evaluated. Estrus response was calculated as the number of does that showed standing estrus and subsequently mated, over the total number of does in each treatment group, expressed as percentage. Time to initiation of estrus was evaluated as the time (hours) interval from when the treatments were administered to the time when the doe first expressed standing estrus (heat) after being exposed to the buck expressed as mean ± standard error of mean (s.e.m); while duration of estrus was measured as the time (hours) between the first and last standing estrus expressed as the mean ± standard error of mean (s.e.m).

Statistical analyses

All data was analyzed using one way analysis of variance to compare means between treatment groups. ANOVA was used to evaluate the effect of treatment on estrus parameters. The test was performed using the SPSS 17.0 package (Chicago, IL. USA, 2007). Values of p< 0.05 were considered significant.

Results

Estrus response was higher in the SHPGeCG group than in SHPG and the SHeCG groups (Table 1). Time to onset of estrus and duration of induced estrus period did not differ between groups (Table 1). More Sahel does were in estrus within 3 days following hormone treatments in the SHPGeCG group (83.3 %) than in the SHPG (33.3 %) and SHeCG (50 %) groups (Figure 1).

Table 1: Estrus parameter of Sahel does synchronized using prostaglandin and equine chorionic gonadotrophin
Estrus properties	SHPG (n=12)	SHPGeCG (n=12)	SHeCG (n=12)
Estrus response rate (%)	8/12 (66.7)^a	11/12 (91.6)^b	5/12 (41.6)^c
Time to onset of estrus (hours)	37.9 ± 4.6^a	37.4 ± 7.3^a	39.1 ± 4.5^a
Duration of estrus (hours)	43.2 ± 3.4^a	42.5 ± 5.8^a	42.3 ± 3.2^a
PG = Prostaglandin; eCG= equine chorionic gonadotrophin; n= Number of does per group ^abcMean values along the same row with different superscripts are statistically different (p<0.05).

Discussion

Results from this study showed an increased number of does expressing estrus in the group treated with prostaglandin and equine chorionic gonadotrophin compared to does in groups treated with either hormone alone. The percentage of does exhibiting estrus in this study (66.63 %) is comparable to values reported for Red Sokoto goats (Omontese et al 2010), Boer goat (Greyling and van Neikerk 1990), dairy goats (Fonseca et al 2005), Sahel goats (Omontese et al 2012) and West African dwarf goats (Oyeyemi et al 2011). Higher estrus response rates than those obtained in this study have been reported following estrus synchronization in Raieni goat (Moradi and Ziael 2012), multiparous cross bred goats (Nava-Trujillo et al., 2007) and primiparous Saanen does (Kulaksiz and Daskin, 2012) following treatment with prostaglandin and equine chorionic gonadotrophin. Ungerfeld 2011 reported lower estrus response rate in Corriedae x merino ewes treated with prostaglandin and the male effect. Observed differences may be due to differences in the breed of goats, species, season, hormonal treatment, presence of males during treatment and nutrition of does (Mani et al 1992; Fonseca et al 2005; Ataman et al 2006; Omontese et al 2010; Ungerfeld 2011; Omontese et al 2012 Moradi and Ziaei 2012). The estrus response rate obtained in the SHPGeCG group in this study is higher than the 73.8 % reported by Omontese et al (2012) for the same breed of goats treated with fluorogestone acetate sponges and eCG. This response may be attributed to differences in hormone treatment and stage of the estrus cycle (Abecia et al 2012).

The mean time to onset of estrus was lower in the SHPGeCG group than in the SHPG and SHeCG groups although these differences were not statistically significant. The mean onset of estrus observed in this study is less than the 47 ± 3.3 reported by Bretzlaff et al (1981) in does receiving 1.25 mg PGF_2a. However our result is similar to the 38.4 ± 9.6 h reported by Omontese et al (2012) but less than the 42 ± 4.3 h reported by Bretzlaff et al (1981) for does receiving 2.5 mg PGF_2a. These differences may be attributed to the higher dose of PGF_2aadministered in this study.

Although the duration of induced estrus period was longer in the SHPGeCG groups than in the SHPG and SHeCG groups, these differences were also not statistically significant. The mean duration of estrus recorded in this study is longer than the reports of Omontese et al (2012) in the same breed of goats but similar to other researchers in other breeds of goats (Ungerfeld 2011; Kawu 2011; Awak 2011). This study revealed a tighter synchrony of estrus in the does treated with prostaglandins and equine chorionic gonadotrophin. This is similar to the reports of Omontese et al (2012) in Sahel does treated with a progestagen and equine chorionic gonadotrophin.

Conclusion

Acknowledgement

The authors would like to thank the herdsmen for assisting with caring for the does and the Director, NAPRI for permission to publish this work.

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Received 24 November 2012; Accepted 18 December 2012; Published 5 February 2013