Ascorbic acid enhances conception rates of Red Sokoto goats following progestin (FGA-30^®, FGA-45^® and CIDR^®) treatment during the rainy season

B O Omontese, P I Rekwot¹, I U Ate and J S Rwuaan

Department of Theriogenology and Production, Faculty of Veterinary Medicine, Ahmadu Bello University, Zaria, Nigeria
drobwealth@hotmail.com
¹Artificial Insemination Unit, National Animal Production Research Institute, Ahmadu Bello University, Zaria, Nigeria

Abstract

The effect of intramuscular administration of Ascorbic Acid (AA) on conception rates following oestrus synchronization using progestins was evaluated in Red Sokoto (RS) goats. At the start of the experiment, 60 RS does were equally allocated to three groups (20 per group) and treated with devices containing progesterone (CIDR group), or fluorogestone acetate sponges (FGA-30^® group and FGA-45^®) for 15 days. At withdrawal of intravaginal progestagens, does in oestrus were monitored and bred. Does in oestrus within the 72 hours in each group were further allocated equally (5 per group) into six different treatments; does treated intramuscularly with 50 mg AA (CIDRAA, FGA30AA, FGA40AA) and does not treated with AA (CIDRNN, FGA30NN, FGA40NN). Conception was determined using non-return rate of oestrus 21 – 24 days later. Progestin retention rates were 85 % (CIDR), 90 % (FGA-30) and 85 % (FGA-45).

There were no differences among treatments for does in oestrus (CIDR: 76.5 %, FGA-30: 77.8 %, FGA-45: 82.4 %). There were no significant differences (P<0.05) in the interval from withdrawal of progestagen to onset of oestrus (CIDR; 35.3±2.5, FGA-30; 36.1.4±2.1 and FGA-45; 35.8±2.2 h), duration of induced oestrus (CIDR; 30.3±1.5, FGA-30; 31.5±1.32 and FGA-45; 30.04±2.1) and mounts per oestrus period (CIDR; 7.3±1.1, FGA-30; 7.4±1.4 and FGA-45; 7.1±2.5). Conception rates were higher in the AA treated does (CIDRAA: 100 % versus CIDRNN: 80 %, FGA30AA: 100 % versus 60 %, FGA45AA: 100 % versus 80 %). We concluded that AA improves conception rates in progestin treated Red Sokoto does.

Keywords: does, fertility, oestrus response, progestagens, vitamin C

Introduction

Small ruminants such as goats play key roles in the economy, nutrition and livelihood of women and youth in Nigeria (Egwu et al 1995; Ajala, 2004). In Nigeria, goats are kept for economic reasons and serve as source of animal protein to support the national program on meat self-sufficiency. Red Sokoto (RS) goat accounts for over 65 % of the Nigerian goat population (FAOSTAT 1999). They are a good meat breed and are known for its suitability for fine leather (Adeyinka and Mohammed 2006). The application of assisted reproductive biotechnologies such as oestrus synchronization, superovulation and embryo transfer improves fertility rates of goats (Rahman et al., 2008; Riaz et al 2012; Omontese et al 2013a,b). Exogenous hormones for oestrus synchronization or induction is effective in increasing the number of females pregnant within a short predetermined interval (Husein et al 2005; Abecia et al 2012).

The use of prostaglandins or intravaginal progestagens followed by administration of gonadotrophins and male effect to synchronize oestrus or improve ovulation rate has been reported in sheep and goats (Oyedipe et al 1989; Husein et al 2005; Sousa et al 2011; Fonseca et al 2012;Omontese et al 2012; Omontese et al 2013b). Progesterone and its analogues (potent progestins) have been used to stimulate and control ovarian activity in goats with an aim of increasing fertility rates (Abecia et al 2012; Omontese et al 2013a,b). Intravaginal progestins maintained in situ for 14 days with equine gonadotrophin administration has been used to synchronize oestrus in Red Sokoto does (Omontese et al 2012; Omontese et al 2013a,b). The efficiency of an oestrus synchronization programme may be affected by several factors such as types of hormone used, breed, parity, nutrition, season, dose of hormone, duration of hormonal treatment, handling and heat stress (Oyedipe et al 1989; Mani et al 1992; Romano 1996, 2002; Dobson and Smith 2000; Ayo et al 2006; Minka et al 2009; Ungerfeld, 2011; Dobson et al 2012). Heat stress may be alleviated with the use of antioxidants (Ayo et al 2006; Minka et al 2009). Vitamin C, also known as ascorbic acid (ascorbic acid), has been associated with fertility and is reported to have evolutionary significance in man and animals (Millar 1992). In addition, it has been shown to be important for reproduction in several other mammalian species (Luck 1995). Studies have reported the beneficial effect of administration of ascorbic acid in both male and female reproductive processes (Phillips 1941; Ralston et al 1988; Heidari 2002; Sonmez and Demirci 2003). As an antioxidant, vitamin C helps maintain DNA, proteins, lipids, enzymes and other antioxidants in their normal form. It does this by scavenging oxygen and nitrogen radicals and reducing metal ions. Vitamin C protects the cells from the damage caused by reactive oxygen species and acts as an antioxidant by interrupting free-radical chain reactions in the body (Powers and Jackson 2008; Yarube et al 2009) and, thus, significantly decreases the levels of reactive oxygen species in the body (Droge 2002; Whitehead and Keller 2003).

The use of hormones for oestrus synchronization in small ruminants in Nigeria is still predominantly under investigation and the effect of ascorbic acid (vitamin C) on conception rates of RS goats following oestrus synchronization using progestins has not been reported. Therefore, an experiment was conducted to investigate the effect of intramuscular injection of ascorbic acid on conception rates of RS goats.

Materials and methods

Study location

This study was carried out during the rainy season at the Small Ruminant Research Programme (SRRP), National Animal Production Research Institute (NAPRI), Shika, Ahmadu Bello University, Zaria, Nigeria. Zaria 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. Zaria is characterized by a tropical climate with three distinct seasons; the cold dry (November - February), hot dry (March - April), rainy (May – October). Daily temperatures range from 13 ⁰C to 30 ⁰C with a relative humidity of 23 % during the dry seasons. The hamattern period which is the initial part of the dry season lasts from November to February and is usually characterized by cold weather and dry dusty winds. The average monthly rainfall for the rainy season is 153.2 mm with a range of 32.4 to 300.8 mm, while the dry season is characterized by a total lack of rainfall.

Experimental design 

Sixty (n=60) healthy Red Sokoto does, weighing 19 – 25 kg with body condition scores 3.0 – 3.5 (1 being thin and 5 being obese), aged between 2.5 - 3 years were used in 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 and concentrate supplement (0.5 kg/day). Water was provided ad libitum. Initially, the does were divided into three groups (20 per group); the CIDR treated group received EAZI-BREED^® CIDR^® (0.3 g of progesterone, InterAg, Hamilton, New Zealand) while the fluorogestone acetate groups received FGA-30^® (30 mg, Chronogest, Intervet, Netherlands) and FGA-45^® (45 mg, Chronogest, Intervet, Netherlands) for 14 days. Does that lost the intravaginal progestins before the end of the 14 day treatment were excluded from the study.

Oestrus detection and mating

Does were placed with experienced fertile Red Sokoto bucks (ratio 1 buck to 10 does) and observed visually for behavioral oestrus manifestation twice (0700-1000 and 1500-1800 hours) daily for 5 days after progestin withdrawal. Standing to be mounted was the cardinal sign used to determine oestrus response. Time interval to onset of oestrus and duration of oestrus was recorded. Conception was determined by measurement of non-return rate of oestrus 21-24 days after mating. 

Ascorbic Acid administration

Does in oestrus within 72 hours were further allocated into 6 groups (n=5 does each). They include does treated with 100 mg Ascorbic acid (AA) (ECNU-C Injection^®, Yanzhou Xierkangtai Pharmaceutical, China) during the oestrus period; CIDRAA, F30AA, F45AA and does without ascorbic acid treatment; CIDRNN, F30NN and F45NN.

Data and Statistical analyses

Progestin retention, oestrus response and conception rates were expressed in percentage. Data on time to initiation of oestrus and oestrus duration were expressed as mean ± standard error of mean (SEM). GraphPad^® Software Incorporated (San Diego, California, USA) was used for all analyses. Statistical level of significance was set at p < 0.05.

Results

There were no differences in progestin retention rates (CIDR^®: 85 %, FGA-30^®: 90 %, FGA-45^®: 90 %). The frequency of does in estrus, interval from device withdrawal to oestrus onset, duration of oestrus and mounts per oestrus period is presented in Table 1. Oestrus response rates did not differ between groups (CIDR; 76.5 % [13/17]), FGA-30 (77.8 % [14/18]) and FGA-45 (82.4 % [14/17]). The mean interval from progestagen withdrawal to onset of estrus, duration of induced oestrus period and the mounts per oestrus period did not differ significantly (p>0.05) between groups (Table 1). Conception rates were higher in the CIDRAA (100%) and F30AA (100%) does compared to the CIDRNN (60%) and F30NN (80 %) does. On the other hand, similar conception rates of 100 % were observed in the F45AA and F45NN does.

Discussion

Retention rates of intravaginal progestins were comparable in this study and are higher than previous reports for the Red Sokoto goat (Omontese et al 2013a,b). However, overall retention rates in this study is less than the 100 % reported by Romano (1996) in dairy goats. The frequency of does in oestrus was comparable in all groups and it ranged from 76 – 82 %. This is less than the oestrus response observed for does treated with progestins by Ungerfeld et al (2011) and Husein et al (2005) in Corriedale ewes and Mountain Black goats, respectively. It is also lower than the 100 % obtained by Dogan et al (2004) in Saanen does treated with MAP and FGA during the transition period. Differences in oestrus response may be due to type of hormone used, co-treatment with gonadotrophins, breed, location, management, season and nutritional status of the does (Mani et al 2002; Ungerfeld et al 2003; Dogan et al 2004; Husein et al 2005; Omontese et al 2013a,b).

The mean time to onset of oestrus reported in this study (30 h) falls within the range of 6 – 120 h reported by various researchers following progestagen withdrawal (Greyling and van der Nest 2000; Romano 2002; Ungerfeld and Rubianes 2002; Whitley and Jackson 2004; Omontese et al 2010, 2012). Ola and Egbunike (2005) reported a range of 40 – 72 h for West African Dwarf goats while Romano (1996) reported a mean time to onset of oestrus of 60.5 h in Nubian does. These differences may also be attributed to type of hormone used, co-treatment with gonadotrophins, breed, location, management, season and nutritional status of the does (Mani et al 1992; Dogan et al 2004; Evans et al 2004; Ungerfeld et al 2003; Omontese et al 2012, 2013b).

This study revealed that conception rates were higher in the ascorbic acid treated does except in the F45NN where conception was 100 % as in the F45AA group. The higher conception rate observed in this study may not be unconnected with the antioxidant activity of vitamin C in reducing the deleterious effect of reactive oxygen species on general reproductive processes in the does since vitamin C helps maintain DNA, proteins, lipids, enzymes and other antioxidants required for optimum reproductive interactions (Heidari, 2002; Sonmez and Demirci 2003; Ayo et al 2006; Minka et al 2009). This effect may also be due to the ability of ascorbic acid in scavenging oxygen and nitrogen radicals and, thus, increase fertility in animals (Ralston et al 1988; Sonmez and Demirci 2003; Minka et al 2009). Although sample size was a limitation in this study, all does treated with ascorbic acid conceived.

Conclusion

• From the results of this study, we conclude that administration of ascorbic acid during the oestrus period may enhance conception rates in Red Sokoto goats during the rainy season.

Acknowledgements

The authors acknowledge the assistance of the herdsmen, Professor J.O. Ayo for his contributions and the Director, NAPRI for permission to publish this work.

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Received 6 May 2014; Accepted 19 June 2014; Published 1 July 2014

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