Oestrous synchronisation and pregnancy rate following artificial insemination (AI) in South African indigenous goats

Abstract

The study evaluated the effect of duration of progestagen treatment and breed on response to oestrous synchronisation and pregnancy rate following AI in 47 Boer and 27 unimproved indigenous goats. Each breed was subdivided into two groups, based on the duration of progestagen treatment. In the long-term progestagen treatment, controlled internal drug release dispensers (CIDRs) were inserted for 16 days, while in the short-term progestagen treatment, CIDRs were inserted for 9 days. Oestrous detection was performed for a period of 72 h, starting at CIDRs withdrawal. AI was performed 48 h following CIDRs removal with raw or frozen/thawed semen. Pregnancy diagnosis was performed at day 35 following AI. Boer goat exhibited a significantly (p <0.05) higher oestrous response (100%) than unimproved indigenous goats (88.9%). Breed had no effect on the onset of oestrus. Boer goat does recorded a longer duration of the induced oestrous period, compared to the unimproved indigenous goats. No significant difference was observed between short or long-term progestagen, with respect to the oestrous response, onset and duration of the induced oestrous period. The pregnancy rate was not affected by breed and semen cryopreservation. However, long-term progestagen treatment drastically reduced pregnancy rate. In conclusion, breed had an effect on oestrous response and the duration of induced oestrous period. The interaction of breed and duration of progestagen treatment had no effect on response to oestrus and onset of oestrus. The pregnancy rates of the current study were generally low and were affected by the duration of progestagen treatment.

Keywords:

• goats
• oestrous synchronisation
• progestagen treatment
• frozen semen

Introduction

South Africa has a fairly wide variety of unimproved indigenous goats, such as the Nguni and locally improved breeds such as the Boer goat (Ramsay and Donkin 2000; Lehloenya et al. 2005). Unimproved indigenous goats are essential animals in many countries due to the fact that they can survive under harsh conditions and their maintenance costs are low when compared with exotic breeds (Chemineau et al. 1997). The average litter size of unimproved indigenous goats is 1.7 kids per doe and kidding rates of 96% can be obtained (Webb and Mamabolo 2004). On the other side, the average litter size of the Boer goat is 1.93 kids per doe (Lehloenya et al. 2005). Reproduction in goats under commercial management conditions depends largely on oestrous synchronisation (modification of the ovarian cycle) and ovulation, with AI being performed at a fixed-time (Chemineau et al. 1997; Leboeuf et al. 2000).

Modifying the ovarian cycle of mammals has been based on the hypothesis that high fertility potential depends on a balanced endocrine response. Manipulative actions that are aimed at controlling the time of oestrus and ovulation must maintain this balance if satisfactory fertility is to be attained (Greyling and Van der Nest 2000; Amarantidis et al. 2004; Rahman et al. 2008b). The induction and synchronisation of oestrus in small stock thus has theoretical and practical potential for researchers and farmers. Generally, the main reason for oestrous synchronisation is to increase the kidding rate and prolificacy during either the oestrous and anoestrous seasons (Bogdan et al. 2008). The synchronisation technique offers the opportunity to increase the efficiency of an animal to produce, as it allows mating or AI at a predetermined time. This reduces the time needed for the detection of oestrus. Synchronisation also helps to reduce mortality rates at birth by avoiding breeding during detrimental climatic periods (Lopez-Sebastian et al. 2007; Rahman et al. 2008a; Imasuen and Ikhimioya 2009).

Short-term (6–11 days) and long-term (12–19 days) progestagen protocols can be used for oestrous synchronisation in goats (Lehloenya et al. 2005; Chao et al. 2008; Rahman et al. 2008a; Tibary 2009). Generally, the most commercially used intravaginal devices for oestrous synchronisation in goats are medroxyprogesterone (MAP), flurogestone acetate (FGA) and controlled internal drug release dispensers (CIDRs) (Motlomelo et al. 2002). However, it is said to be advisable to use CIDRs for oestrous synchronisation in does, as the devices do not absorb the vaginal fluids and initiate bacteria contamination. Furthermore, the CIDRs induce oestrus earlier and lead to a more compact oestrous response, when compared to other intravaginal progestagen sponges (MAP and FGA). This occurrence can be ascribed to higher serum progesterone concentrations in day 16 of CIDR treatment (Motlomelo et al. 2002). Oestrous synchronisation in goats, using intravaginal progestagen combined with equine chorionic gonadotrophin (eCG) administration at progestagen removal, has been extensively applied generally achieving acceptable oestrous response. The eCG injections are implemented additionally to the progesterone treatment in an effort to improve the ovulation rate during synchronisation (Lopez-Sebastian et al. 2007; Chao et al. 2008; Tibary 2009).

In South Africa, the long-term progestagen protocol has been mostly used for oestrous synchronisation in goats. Pregnancy rate following oestrous synchronisation using this long-term protocol has generally been low (52%) in South African indigenous goats (Motlomelo et al. 2002). Although, short-term progestagen treatments have been reported to be effective in synchronising oestrous in other goat breeds (Karaca et al. 2010) it is not usually used in South Africa. Whether a similar response in the South African indigenous goats could be obtained, is uncertain. The current study was thus conducted to determine the effect of the duration of progestagen treatment and breed following AI in South African indigenous goats.

Materials and methods

The experiments were evaluated and approved by the Agricultural Research Council ethics committee under the cryo-gene bank programme and also the Tshwane University of Technology ethics committee. The trial was conducted at the Agricultural Research Council, Irene in Pretoria (25° 55′ S; 28° 12′E), South Africa. The research centre is situated at an altitude of 1525 m above sea level. The weather condition ranging from hot days and cool nights in summer to moderate winter days with very cold nights (Webb et al. 2004).

In this trial, 6 bucks (3 unimproved indigenous and 3 Boer goat bucks) and 74 does (27 unimproved indigenous and 47 Boer goat does) were used. The bucks and does were kept separately in roofed pens. All the experimental goats grazed on natural pasture during the day and were supplemented with Lucerne in winter as the pasture was poor, while water was provided ad libitum. The electro-ejaculation technique was used to collect semen. Immediately after semen collection, semen samples were evaluated for semen volume, pH, sperm cell motility and concentration. An egg yolk Tris based extender was used to dilute semen, before freezing into liquid nitrogen (−196°C).

Each breed was subdivided into two groups, based on the duration of the progestagen synchronisation treatment (short-term or long-term). The oestrous cycles of the does in the long-term progestagen group were synchronised with CIDRs (0.3 g progesterone) [(Pfizer™. New Zealand) (Ltd)], inserted for 16 days. In the short-term progestagen group, CIDRs were inserted for 9 days. At the time of progestagen withdrawal, all the experimental does were injected intramuscularly with 300 IU of eCG (Intervet Schering-Plough Animal Health, South Africa). After progestagen withdrawal all the does were observed for signs of oestrus for 30 minutes using vasectomised bucks, at 8 hourly intervals (6 h, 14 h and 22 h) for a period of 4 days (96 h). All does were laparoscopically inseminated at 48 h for the raw semen and at 52 h following CIDR removal for the frozen/thawed semen groups. All the does were fasted for 24 h before being subjected to laparoscopic insemination. For anaesthesia, the does were injected intravenously with Ketamine chloride (0.2 mL/10 kg live weight) [(TYpharma, China) (Ltd)] 10 minutes before AI. For AI, only raw semen with sperm cell motility of approximately 80% for both goat breeds, were used. For the frozen/thawed semen, the sperm cell motility recorded approximately 40% for both goat breeds. Pregnancy rates were determined by using an Ultrasound scanner [(Aloka^®, SSD, Tokyo, Japan) (Ltd)] 35 days post-insemination.

The data regarding the oestrous onset and duration were analysed using general liner model, while the oestrous response and pregnancy rate were analysed with the aid of the Chi-square test (SAS 2003).

Results and discussion

The oestrous response, interval to onset of oestrus and oestrous duration results of the Boer and unimproved indigenous goats following oestrous synchronisation with short-term or long-term progestagen are set out in Table 1. The interaction of breed and duration of progestagen treatment had no effect on response to oestrus and onset of oestrus. However, the duration of induced oestrus for unimproved indigenous goats treated with long-term progestagen was shorter compared to the other groups. This may have an effect on fixed-timed AI, as these animals will be inseminated late (Greyling et al. 1997; Lopez-Sebastian et al. 2007). The ovarian activity of Boer goats was not affected by the progestagen treatment. These findings are in agreement with Vinoles et al. (2001), who reported no difference with respect to oestrous response and onset of oestrus in sheep following oestrus synchronisation with short-term or long-term progestagens.

Table 1. Effect of breed and duration of progestagen treatment on oestrous synchronisation of Boer and unimproved indigenous goats.

	n	Oestrous response%	Onset of oestrous (Mean±SE) (h)	Oestrous duration (Mean±SE) (h)
Boer goat + short-term	25	(25)100^a	35.5±0.1^a	40.6±0.2^a
Boer goat + long-term	22	(22)100^a	34.5±0.1^a	40.4±0.2^a
Unimproved + short-term	14	(12) 85.7^a	33.1±0.2^a	33.1±0.2^a,b
Unimproved + long-term	13	(12) 92.3^a	31.4±0.1^a	26.5±0.2^b
Boer	47	(47)100^a	35.1±0.1^a	40.5±0.2^a
Unimproved indigenous	27	(24) 88.9^b	32.3±0.2^a	29.9±0.2^b
Short-term progestagen	39	(37) 94.9^a	34.7±0.2^a	37.9±0.2^a
Long-term progestagen	35	(34) 97.1^a	33.4±0.1^a	35.2±0.2^a
^a,bValues with different superscripts within same cell differ significantly (p <0.05).

In this study, breed affected the oestrous response (100% versus 88.9% for Boer goats and unimproved indigenous goats, respectively). These results are in agreement with Greyling et al. (1997) and Vinoles et al. (2001) who indicated the oestrous response vary significantly, depending on goat breed. Short-term and long-term progestagen synchronisation protocols were equally effective in controlling oestrus in Boer goats. However, in unimproved indigenous goats long-term progestagen treatment is effective in inducing oestrous. The time from CIDR removal to the onset of oestrus was not significantly different between the two breeds. However, these results are contradicting with Amarantidis et al. (2004) findings who documented that the onset of oestrus is also influenced by breed. In this trial, does exhibited oestrous within 24–64 h after synchronisation treatment termination, suggesting that some of the does reacted later Other researchers have reported that the onset of oestrus occurs within 21–50.7 h following progestagen withdrawal, using different goat breeds (Zarkawi et al. 1999; Greyling and Van der Nest 2000; Greyling et al. 2002). Boer goat does resulted in significantly (p <0.05) higher duration of oestrous compared to unimproved indigenous goat does. This agrees with Amarantidis et al. (2004) who indicated that there is breed effect with respect to duration of oestrous. However, the duration of the induced oestrous period of 29.9 h and 40.5 h for the unimproved indigenous goats and Boer goats, respectively, were acceptable. According to Rahman et al. (2008b) the oestrous period for goats lasts between 24 h and 48 h following oestrus synchronisation.

The pregnancy rates of unimproved indigenous and Boer goats following progestagen treatment and insemination with raw or frozen/thawed semen are set out in Table 2. The overall pregnancy rate following laparoscopic AI for all does in this trial was 39.4%, which is lower than the 52% reported by Motlomelo et al. (2002) and 74% reported by Greyling and van der Nest (2000). These differences may be due to the different intravaginal progestagen devices used (Amarantidis et al. 2004), as they contain different concentration of progesterone (Motlomelo et al. 2002). The low pregnancy rate in this study might also be attributed to semen cryopreservation, as the sperm cell motility used for AI was < 40% post-thaw. Pregnancy rate of 34.3% for the long-term progestagen treated does was also lower compared to the pregnancy rate of 46.7% reported by Motlomelo et al. (2002), using the similar protocol and goat breeds. Furthermore, other factors such as nutrition, stress, body condition, physiological status of the female, delayed ovulation and changes in the hormonal environment could result in an asynchrony between oestrus and ovulation (Vinoles et al. 2001; Greyling et al. 2002; Ustuner et al. 2007; Tibary 2009).

Table 2. Pregnancy rate of Boer and unimproved indigenous goats following oestrus synchronisation and artificial insemination.

Breed	n	Progestagen treatment	Semen	Pregnancy rate%
Boer goat	12	Short-term	Raw	(6) 50
	13		Frozen/thawed	(4) 30.8
	11	Long-term	Raw	(5) 36.4
	11		Frozen/thawed	(4) 36.4
Unimproved indigenous goat	8	Short-term	Raw	(4) 50
	6		Frozen/thawed	(3) 50
	7	Long-term	Raw	(2) 28.6
	6		Frozen/thawed	(2) 33.3
Note: No significant differences.

Three does in this trial did not show any signs of oestrus following treatment (two unimproved indigenous goats and one Boer goat). In these three does which did not respond to the treatment, one unimproved indigenous doe from the short-term progestagen group fell pregnant after laparoscopic AI. It was assumed that this doe experienced a silent heat. The pregnancy rate of the goats treated with short-term progestagen (43.6%) was significantly (p < 0.05) higher compared to goats treated with long-term progestagen (34.3%). Similar tendencies have been reported (Vinoles et al. 2001; Tibary 2009; Karaca et al. 2010). The lower pregnancy rate in long-term progestagen treated does might be due to poor sperm cell transportation in the reproductive tract. Poor sperm cell transportation is associated with increase amount of cervical mucus usually observed when this protocol is used (Tibary 2009). Though, the pregnancy rate of the goats treated with short-term progestagen was higher in this study, it was still lower compared the pregnancy rate of 72% reported by Karaca et al. (2010) during short-term progestagen treatment when FGA sponges were used.

Conclusions

Breed had an effect on the oestrous response and duration of the induced oestrus period. The short-term and long-term progestagen synchronisation protocols are equally effective in controlling oestrus in Boer goats. However, in unimproved indigenous goats long-term progestagen treatment reduced the duration of the induced oestrous period and this observation might have implications on timing of AI. Pregnancy rate of the goats treated with short-term progestagen was higher. In general, the pregnancy rate of the current study was low and was not affected by breed and semen cryopreservation. More research is necessary with larger numbers of does regarding pregnancy rate of the South African indigenous goat breeds following oestrous synchronisation.

Acknowledgements

Thanks to the UFS and ARC for providing necessary facilities and financial support. Further to the DAFF, NRF and TUT for providing financial support, the TUT and ARC Statistical Support Units (K. Patrick, L. Maupi and N. Thiebaut) are also acknowledged for data analysis and T. Netshirovha for his technical assistance.