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Estrous response to synchronization of estrus using different progesterone treatments outside the natural breeding season in ewes
Small Ruminant Research 65 (2006) 279–283
Technical note
Estrous response to synchronization of estrus using different progesterone treatments outside the natural breeding season in ewes M. Hashemi a,∗ , M. Safdarian a , M. Kafi b a
Department of Animal Science, Research Center for Agriculture and Natural Resource of Fars Province, 71555-617 Shiraz, Iran b Department of Animal Reproduction, Veterinary Faculty, Shiraz University, 71345 Shiraz, Iran Received 4 March 2004; received in revised form 21 July 2005; accepted 21 July 2005 Available online 22 September 2005
Abstract A trial was conducted to investigate the efficiency of synchronization using different progesterone treatments outside the natural breeding season. Ninety multiparous Karakul ewes were randomly assigned to one of three treatment groups (n = 30/group). In the progesterone treated group, ewes were injected intramuscularly (i.m.) with 20 mg progesterone acetate in oil every second day for 12 days, plus an i.m. injection of 500 IU eCG on day 12. The CIDR treated group, the animals were treated with the intravaginal devices impregnated with 0.3 g of progesterone for 12 days and injected i.m. with 500 IU eCG at withdrawal while in the third group, the ewes were treated with MAP sponges impregnated with 60 mg medroxyprogesterone acetate (MAP) for 12 days and injected i.m. with 500 IU eCG at sponge withdrawal. The interval from the cessation of treatment to the onset of estrus was significantly (p < 0.05) longer in the progesterone in oil group, compared to CIDR and MAP sponge groups (51.4 ± 10, 30.1 ± 7.6 and 29.6 ± 5.6 h, respectively). The estrous response for the sponge and device groups was higher, compared to the group injected with progesterone (93.3% for CIDR, 100% for MAP sponge and 80% for the oil treated group). The duration of the induced estrous period did not differ significantly between the treatment groups. The results of the present study show that estrous synchronization with CIDR and MAP sponge followed by an i.m. administration of eCG is superior under local conditions for fixed time AI in Karakul ewes outside the natural breeding season. © 2005 Elsevier B.V. All rights reserved. Keywords: Karakul ewe; Estrous synchronization; Progesterone; Estrous characteristics
1. Introduction
∗ Corresponding author. Tel.: +98 711 7204959; fax: +98 711 7205107. E-mail address: [email protected] (M. Hashemi).
0921-4488/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2005.07.051
Estrous synchronization is a valuable management tool that has been successfully employed to enhance reproductive efficiency, particularly in ruminants (Kusina et al., 2000). In small ruminants, estrous synchronization is achieved either by reducing the
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length of the luteal phase of the estrous cycle with prostaglandin F2␣ or by extending the cycle artificially with exogenous progesterone or more potent progestagens (Evans and Maxwell, 1986; Kusina et al., 2000; Jainudeen et al., 2000). As prostaglandin treatment is limited to the breeding season, different protocols of estrous synchronization using progestins have been introduced (Anisworth and Wolynetz, 1982; Hamra et al., 1989; Wheaton et al., 1993; Godfrey et al., 1997; Rosado et al., 1998; Boscos et al., 2002). More information regarding the estrous response following different treatments is necessary to pinpoint the time of ovulation. One of the main problems associated with artificial breeding is the estimation of the time of estrus and duration of the synchronized estrous period. These are important factors to ensure that mating or AI takes place at a time when maximum fertility can be obtained, especially in fixed time AI programmes (Romano, 1996). The Persian Karakul is a fat-tailed sheep of medium size and the characteristics of the breed have been described by Farid and Makarechian (1976). The mean duration of the natural estrous cycle, duration of the estrous period and ovulation rate in Persian Karakul sheep have been reported as being 17.6 days, 35.2 h and 1.07, respectively (Sefidbakht et al., 1978). Despite the extensive distribution of the Karakul (an important sheep breed for pelt in the south of Iran), little information is available regarding the efficiency following different hormonal treatments of inducing and synchronizing estrus in this breed. The trial was undertaken to determine estrous response in Karakul ewes synchronized with different protocols of progesterone outside the natural breeding season.
groups were synchronized with one of the following treatments. Treatment1: intramuscular (i.m.) injection of 20 mg progesterone acetate in oil (progesterone, Aboureihan, Iran). Ewes were treated every second day for a 12 day period and were administrated an i.m. injection of 500 IU equine choronic gonadotropin (eCG) (Folligon, Intervet, Holland) on day 12. Treatment2: treatment with intravaginal CIDR devices containing 0.3 g progesterone (CIDR, inter Ag, New Zealand) for 12 days, followed by an i.m. injection of 500 IU eCG at CIDR removal. Treatment 3: treatment with intravaginal sponges containing 60 mg medroxyprogesterone acetate (MAP)(Veramix, Pharmacia & Upjohn, Greece) for 12 days and an i.m. injection of 500 IU eCG at sponge withdrawal. Animals were housed in pens (10 ewes/pen) and allowed free access to water and feed (hay and dried wheat chaff). Following termination of treatment three fertile rams were introduced to each pen and ewes were tested for estrus at 8 h intervals. The occurrence of estrus was monitored up to the end of the induced estrous period, or for a total observation period of 120 h following the cessation of treatment. The end of estrus was taken as the time, when the ewe did not accept the ram following two consecutive teasing sessions. The interval between the onset of estrus and the end of estrus was determined as the duration of estrus. Data regarding the onset, end and duration of estrus were analyzed using General Linear Models (GLM) procedure of SAS (1991). A chi-square test was used to analyse the estrous response. The mean time interval from the end of treatment to the onset of estrus, the time interval from the end of treatment to the end of estrus and the duration of the estrous periods were compared using the Duncan test (SAS, 1991).
2. Material and methods 3. Results A total of 90 Karakul ewes, 3–5 years of age and a body weight of between 40 and 45 kg were used in the trial. The experiment was conducted during spring at the research farm of Jihad-Agriculture Ministry in Fasa City (latitude 28◦ 54 , longitude 52◦ 43 , altitude 1288 m) located 130 km from Shiraz in Iran. Ewes were randomly allocated to three treatments groups, based on BW and age (30 ewes/group). The protocol was performed in three replicates for each group. The estrous cycles of ewes in each of the
The response to synchronization and mean (±S.D.) time interval from the end of treatment to the onset of estrus and the time interval from the end of treatment to the end of estrus and the duration of estrous period is summarized in Table 1. No ewes lost intravaginal sponges or CIDRs. A mucosal discharge with an odour was observed only when sponges were withdrawn. The distribution of the onset of estrus following treatment with progesterone in oil, CIDR and the MAP
M. Hashemi et al. / Small Ruminant Research 65 (2006) 279–283
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Table 1 Mean (±S.D.) estrous responses following estrous synchronization with the aid of different progesterone protocols in ewes Treatment
n
Estrous response (%)
Interval from end of treatment to onset of estrus (h)
Interval from end of treatment to end of estrus (h)
Duration of estrus (h)
Progesterone + eCG CIDR + eCG MAP sponge + eCG
30 30 30
24 (80)a 28 (93.3)b 30 (100)b
51.4 ± 10a 30.1 ± 7.6b 29.6 ± 5.6b
87.9 ± 4.9a 61.9 ± 12.5b 51.7 ± 7.2b
27.56 ± 13.5 31.87 ± 11 22.11 ± 3.4
Different superscripts (a and b) in each column differ significantly (p < 0.05).
Fig. 1. Distribution of the onset of estrus after treatment of Persian Karakul ewes with progesterone in oil, CIDR and MAP sponges.
sponge is illustrated in Fig. 1. Only 24 out of the 30 (80%) ewes injected with progesterone, exhibited estrus within the 48–64 h period after the last injection. Estrus was detected in 28 (93.3%) of the ewes 32–48 h after CIDR removal (overall 93.3%). Twentyseven (90%) and 3 (10%) ewes exhibited estrus 32 and 48 h after sponge removal (overall 100%), respectively. The estrous response was significantly (p < 0.05) lower following progesterone in oil treatment, compared to other treatments. The time interval from the end of treatment to the onset of estrus and the time interval from the end of treatment to the end of estrus were significantly (p < 0.05) longer in the progesterone in oil group, compared to CIDR and MAP sponge groups. There was no significant difference in the duration of induced estrous period between all treatments.
4. Discussion The estrous response observed in this comparative study showed that estrus in Karakul ewes can be
efficiently synchronized using the different protocols tested but the CIDR and MAP sponge treatments were more effective. The results from this study indicate that 80% of the ewes showed estrus 48–64 h following the last i.m. injection of progesterone. This was lower than that reported by Dutt (1953) who quoted a 88.8% estrous response within 10 days when 30 mg progesterone in oil was injected every third day for 15 days with 500 IU eCG 3 days after the last injection of progesterone. No significant difference in estrous response between CIDR and MAP sponge treatment was observed in this study, but Knight and Hall (1988) cited the estrous response following CIDR removal to be significantly lower than following sponge treatment (87% versus 94%). This was, however, related to higher loss of CIDRs, compared to sponges (6.3% versus 0.8%). The estrous response in this study was 100% following MAP sponge treatment which is higher than what obtained by Tritschler et al. (1991), who reported a 94% estrous response when using MAP sponges and 500 IU eCG. Simonetti et al. (2000) recorded a 79.3%, 77.4% and 80.9% incidence of estrus with intravaginal sponges impregnated with 40, 50 and 60 mg MAP, respectively. In a study by Mutiga and Mukasa-Mugerwa (1992) estrus synchronized using MAP sponge and 200 IU eCG following sponge withdrawal showed an estrous response similar to the present study. In the current study estrous response using CIDR was 93.3%, which is in agreement with Wheaton et al. (1993). Contrary to the findings in the present study Godfrey et al. (1999) reported an estrous response of 100% and 94.4% in ewes treated by CIDR or progesterone sponge without eCG. The estrous response obtained in this trial with CIDR and MAP sponge was higher than the 81% and 88% reported by Cardwell et al. (1998) who administrated norgestomet alone or norgestomet with eCG.
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The interval from the end of treatment to the onset of estrus and the interval from the end of treatment to the end of estrus are important parameters to determine the duration of the induced estrous period and estimate the time of ovulation. These two periods in the progesterone in oil treatment were significantly (p < 0.05) longer than the CIDR and MAP sponge treatments. A possible explanation may be due to the difference in plasma progesterone levels at the time of CIDR removal and the time of the last injection of progesterone in oil (Anisworth and Downey, 1986). No significant difference was recorded between the CIDR and MAP sponge treatments regarding the duration from the end of treatment to the onset of estrus in this trial. Contrary, the onset of estrus from CIDR removal was found to be earlier compared to following MAP sponge withdrawal (more than 8 h) (Shackell, 1991; Smith et al., 1991). Fukui et al. (1993) reported the onset of estrus to be significantly earlier in anestrous ewes treated with CIDR than MAP sponges (24.9 h versus 30 h). Estrus occurred 29.6 ± 5.6 h after MAP sponge and 30.1 ± 7.6 h after CIDR withdrawal which is sooner than the period reported by Fuentes et al. (2001), (35 ± 3 h after sponge withdrawal). Simonetti et al. (2000) recorded estrus to occur 55.94, 56.74 and 57.7 h after 40, 50 and 60 mg progesterone sponge treatment respectively. These differences may be explained by acceleration of the onset of estrus using eCG either concomitant with or before progesterone removal (Mutiga and Mukasa-Mugerwa, 1992; Gordon, 1997; Cardwell et al., 1998; Hoseini-pajooh et al., 1998). The duration of estrus showed no significant difference between progesterone treatments. The mean duration of the induced estrous period obtained in this study (27.2 h) was lower than that recorded for natural estrous in Karakul ewes (35.2 h) (Sefidbakht et al., 1978). The mean duration of the estrous period using MAP sponges in this trial (22.1 ± 3.4 h) was lower than the 27 ± 2.5 h reported by Fuentes et al. (2001). This difference may be due to differences in breed, age and geographical location which are known to influence this period (Evans and Maxwell, 1986; Gordon, 1997). In conclusion, it can be said that estrous synchronization with CIDR and MAP sponge because of inducing a more compact estrous response is more acceptable as a reproductive management tool for fixed time AI in Persian Karakul ewes.
References Anisworth, L., Downey, B.R., 1986. A controlled internal drugrelease dispenser containing progesterone for control of the estrous cycle of ewes. Theriogenology 26, 847–856. Anisworth, L., Wolynetz, M.S., 1982. Synchronization estrus and reproductive performance of ewes treated with synthetic progestogens administered by subcutaneous ear implant or by intravaginal sponge pessary. J. Anim. Sci. 54, 1120–1127. Boscos, C.M., Samartzi, F.C., Dellis, S., Rogge, A., Stefanakis, A., Krambovitis, E., 2002. Use of progestagen-gonadotropin treatments in estrus synchronization of sheep. Theriogenology 58, 1261–1272. Cardwell, B.E., Fitch, G.Q., Geisert, R.D., 1998. Ultrasonic evaluation for the time of ovulation in ewes treated with norgestomet and norgestomet followed by pregnant mare’s serum gonadotropin. J. Anim. Sci. 76, 2235–2238. Dutt, R.H., 1953. Induction of estrus and ovulation in anestrous ewes by use of progesterone and pregnant mare serum. J. Anim. Sci. 12, 515–523. Evans, G., Maxwell, W.M.C., 1986. Salamon’s Artificial Insemination of Sheep and Goats. Butterworths, Sydney, 194 pp. Farid, A., Makarechian, M., 1976. Some sources of variation in the body weights of Karakul, Mehraban, Naeini and Bakhtiari breeds of sheep. Iran. J. Agric. Res. 4, 7–16. Fuentes, V.O., Sanchez, V., Rosiles, R., Fuentes, P.I., 2001. The effect of low doses of naloxone on the preovulatory surge of LH and on the onset and duration of estrus in the ewe with induced oestrus during the non-breeding season. Anim. Reprod. Sci. 65, 225– 230. Fukui, Y., Hirai, H., Honda, K., Hayashi, K., 1993. Lambing rates by fixed-timed intrauterine insemination with frozen semen in seasonally anoestrous ewes treated with a progestogen-impregnated sponge or CIDR device. J. Rep. Dev. 39, 1–5. Godfrey, R.W., Gray, M.L., Collins, J.R., 1997. A comparison of two methods of oestrous synchronisation of hair sheep in the tropics. Anim. Reprod. Sci. 47, 99–106. Godfrey, R.W., Collins, J.R., Hensley, E.L., Wheaton, J.E., 1999. Estrus synchronization and artificial insemination of hair sheep ewes in the tropics. Theriogenology 51, 985–997. Gordon, I., 1997. Controlled reproduction in Sheep and Goats. Cab International, Wallingford, 450 pp. Hamra, A.H., McNally, J.W., Marcek, J.M., Carlson, K.M., Wheaton, J.E., 1989. Comparison of progesterone sponges, Cronolone sponges and controlled internal drug release dispensers on fertility in anestrous ewes. Anim. Reprod. Sci. 18, 219–226. Hoseini-pajooh, K., Gharagozloo, F., Jafari, Y., Tajik, P., 1998. Synchronization and superovulation for embryo transfer in Moghani sheep in spring and autumn. Pajouhesh-va-Sazandegi 37, 102–104 (in Persian with English abstract). Jainudeen, M.R., Wahid, H., Hafez, E.S.E., 2000. Ovulation induction, embryo production and transfer. In: Hafz, B., Hafez, E.S.E. (Eds.), Reproduction in Farm Animals, seventh ed. Lippincott Williams & Wilkins, Philadelphia, pp. 405–409. Knight, T.W., Hall, D.R.H., 1988. Effect of immunisation with polyandroalbumin (Fecundin); pasture allowance, post-mating shearing and method of synchronisation on reproductive perfor-
M. Hashemi et al. / Small Ruminant Research 65 (2006) 279–283 mance of Romney and Marshall Romney ewes. N. Z. J. Agric. Res. 31, 243–247. Kusina, N.T., Tarwirei, F., Hamudikuwanda, H., Agumba, G., Mukwena, J., 2000. A comparison of the effects of progesterone sponges and ear implants, PGF2alpha, and their combination on efficacy of estrus synchronization and fertility of Mashona goat does. Theriogenology 53, 1567–1580. Mutiga, E.R., Mukasa-Mugerwa, E., 1992. Effect of the method of estrus synchronization and PMSG dosage on estrus and twinning in Ethiopian Menze sheep. Theriogenology 38, 727–734. Romano, J.E., 1996. Comparison of fluoregestone and medroxyprogesterone intravaginal pessaries for estrus synchronization in dairy goats. Small Rumin. Res. 22, 219–223. Rosado, J., Silva, E., Galina, M.A., 1998. Reproductive management of hair sheep with progesterone and gonadotropins in the tropics. Small Rumin. Res. 27, 237–242. SAS, 1991. SAS for P.C. 6.04. SAS Institute, Inc., Cary, NC, USA. Sefidbakht, N., Mostafavi, M.S., Farid, A., 1978. Annual reproductive rhythm and ovulation rate in four fat-tailed sheep breeds. Anim. Prod. 26, 177–184.
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Shackell, G.H., 1991. The timing of oestrus, LH surge and ovulation in ewes following synchronisation with MAP sponges, FGA sponges or CIDRs. Proc. N. Z. Soc. Anim. Prod. 51, 73– 78. Simonetti, L., Blanco, M.R., Gardon, J.C., 2000. Estrus synchronization in ewes treated with sponge impregnated with different doses of medroxyprogesterone acetate. Small Rumin. Res. 38, 243–247. Smith, J.F., Konlechner, J.A., Parr, J., 1991. Factors influencing the time to onset of oestrus after synchronisation treatment in ewes. Proc. N. Z. Soc. Anim. Prod. 51, 117–121. Tritschler, J.P., Duby, R.T., Parsons, E.M., Parsons, M.J., Giordano, D.J., 1991. Comparison of two progestagens during out-ofseason breeding in a commercial ewe flock. Theriogenology 35, 943–952. Wheaton, J.E., Carlson, K.M., Windels, H.F., Johnston, L.J., 1993. CIDR: a new progesterone-releasing intravaginal device for induction of estrus and cycle control in sheep and goats. Anim. Reprod. Sci. 33, 127–141.
Technical note
Estrous response to synchronization of estrus using different progesterone treatments outside the natural breeding season in ewes M. Hashemi a,∗ , M. Safdarian a , M. Kafi b a
Department of Animal Science, Research Center for Agriculture and Natural Resource of Fars Province, 71555-617 Shiraz, Iran b Department of Animal Reproduction, Veterinary Faculty, Shiraz University, 71345 Shiraz, Iran Received 4 March 2004; received in revised form 21 July 2005; accepted 21 July 2005 Available online 22 September 2005
Abstract A trial was conducted to investigate the efficiency of synchronization using different progesterone treatments outside the natural breeding season. Ninety multiparous Karakul ewes were randomly assigned to one of three treatment groups (n = 30/group). In the progesterone treated group, ewes were injected intramuscularly (i.m.) with 20 mg progesterone acetate in oil every second day for 12 days, plus an i.m. injection of 500 IU eCG on day 12. The CIDR treated group, the animals were treated with the intravaginal devices impregnated with 0.3 g of progesterone for 12 days and injected i.m. with 500 IU eCG at withdrawal while in the third group, the ewes were treated with MAP sponges impregnated with 60 mg medroxyprogesterone acetate (MAP) for 12 days and injected i.m. with 500 IU eCG at sponge withdrawal. The interval from the cessation of treatment to the onset of estrus was significantly (p < 0.05) longer in the progesterone in oil group, compared to CIDR and MAP sponge groups (51.4 ± 10, 30.1 ± 7.6 and 29.6 ± 5.6 h, respectively). The estrous response for the sponge and device groups was higher, compared to the group injected with progesterone (93.3% for CIDR, 100% for MAP sponge and 80% for the oil treated group). The duration of the induced estrous period did not differ significantly between the treatment groups. The results of the present study show that estrous synchronization with CIDR and MAP sponge followed by an i.m. administration of eCG is superior under local conditions for fixed time AI in Karakul ewes outside the natural breeding season. © 2005 Elsevier B.V. All rights reserved. Keywords: Karakul ewe; Estrous synchronization; Progesterone; Estrous characteristics
1. Introduction
∗ Corresponding author. Tel.: +98 711 7204959; fax: +98 711 7205107. E-mail address: [email protected] (M. Hashemi).
0921-4488/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.smallrumres.2005.07.051
Estrous synchronization is a valuable management tool that has been successfully employed to enhance reproductive efficiency, particularly in ruminants (Kusina et al., 2000). In small ruminants, estrous synchronization is achieved either by reducing the
280
M. Hashemi et al. / Small Ruminant Research 65 (2006) 279–283
length of the luteal phase of the estrous cycle with prostaglandin F2␣ or by extending the cycle artificially with exogenous progesterone or more potent progestagens (Evans and Maxwell, 1986; Kusina et al., 2000; Jainudeen et al., 2000). As prostaglandin treatment is limited to the breeding season, different protocols of estrous synchronization using progestins have been introduced (Anisworth and Wolynetz, 1982; Hamra et al., 1989; Wheaton et al., 1993; Godfrey et al., 1997; Rosado et al., 1998; Boscos et al., 2002). More information regarding the estrous response following different treatments is necessary to pinpoint the time of ovulation. One of the main problems associated with artificial breeding is the estimation of the time of estrus and duration of the synchronized estrous period. These are important factors to ensure that mating or AI takes place at a time when maximum fertility can be obtained, especially in fixed time AI programmes (Romano, 1996). The Persian Karakul is a fat-tailed sheep of medium size and the characteristics of the breed have been described by Farid and Makarechian (1976). The mean duration of the natural estrous cycle, duration of the estrous period and ovulation rate in Persian Karakul sheep have been reported as being 17.6 days, 35.2 h and 1.07, respectively (Sefidbakht et al., 1978). Despite the extensive distribution of the Karakul (an important sheep breed for pelt in the south of Iran), little information is available regarding the efficiency following different hormonal treatments of inducing and synchronizing estrus in this breed. The trial was undertaken to determine estrous response in Karakul ewes synchronized with different protocols of progesterone outside the natural breeding season.
groups were synchronized with one of the following treatments. Treatment1: intramuscular (i.m.) injection of 20 mg progesterone acetate in oil (progesterone, Aboureihan, Iran). Ewes were treated every second day for a 12 day period and were administrated an i.m. injection of 500 IU equine choronic gonadotropin (eCG) (Folligon, Intervet, Holland) on day 12. Treatment2: treatment with intravaginal CIDR devices containing 0.3 g progesterone (CIDR, inter Ag, New Zealand) for 12 days, followed by an i.m. injection of 500 IU eCG at CIDR removal. Treatment 3: treatment with intravaginal sponges containing 60 mg medroxyprogesterone acetate (MAP)(Veramix, Pharmacia & Upjohn, Greece) for 12 days and an i.m. injection of 500 IU eCG at sponge withdrawal. Animals were housed in pens (10 ewes/pen) and allowed free access to water and feed (hay and dried wheat chaff). Following termination of treatment three fertile rams were introduced to each pen and ewes were tested for estrus at 8 h intervals. The occurrence of estrus was monitored up to the end of the induced estrous period, or for a total observation period of 120 h following the cessation of treatment. The end of estrus was taken as the time, when the ewe did not accept the ram following two consecutive teasing sessions. The interval between the onset of estrus and the end of estrus was determined as the duration of estrus. Data regarding the onset, end and duration of estrus were analyzed using General Linear Models (GLM) procedure of SAS (1991). A chi-square test was used to analyse the estrous response. The mean time interval from the end of treatment to the onset of estrus, the time interval from the end of treatment to the end of estrus and the duration of the estrous periods were compared using the Duncan test (SAS, 1991).
2. Material and methods 3. Results A total of 90 Karakul ewes, 3–5 years of age and a body weight of between 40 and 45 kg were used in the trial. The experiment was conducted during spring at the research farm of Jihad-Agriculture Ministry in Fasa City (latitude 28◦ 54 , longitude 52◦ 43 , altitude 1288 m) located 130 km from Shiraz in Iran. Ewes were randomly allocated to three treatments groups, based on BW and age (30 ewes/group). The protocol was performed in three replicates for each group. The estrous cycles of ewes in each of the
The response to synchronization and mean (±S.D.) time interval from the end of treatment to the onset of estrus and the time interval from the end of treatment to the end of estrus and the duration of estrous period is summarized in Table 1. No ewes lost intravaginal sponges or CIDRs. A mucosal discharge with an odour was observed only when sponges were withdrawn. The distribution of the onset of estrus following treatment with progesterone in oil, CIDR and the MAP
M. Hashemi et al. / Small Ruminant Research 65 (2006) 279–283
281
Table 1 Mean (±S.D.) estrous responses following estrous synchronization with the aid of different progesterone protocols in ewes Treatment
n
Estrous response (%)
Interval from end of treatment to onset of estrus (h)
Interval from end of treatment to end of estrus (h)
Duration of estrus (h)
Progesterone + eCG CIDR + eCG MAP sponge + eCG
30 30 30
24 (80)a 28 (93.3)b 30 (100)b
51.4 ± 10a 30.1 ± 7.6b 29.6 ± 5.6b
87.9 ± 4.9a 61.9 ± 12.5b 51.7 ± 7.2b
27.56 ± 13.5 31.87 ± 11 22.11 ± 3.4
Different superscripts (a and b) in each column differ significantly (p < 0.05).
Fig. 1. Distribution of the onset of estrus after treatment of Persian Karakul ewes with progesterone in oil, CIDR and MAP sponges.
sponge is illustrated in Fig. 1. Only 24 out of the 30 (80%) ewes injected with progesterone, exhibited estrus within the 48–64 h period after the last injection. Estrus was detected in 28 (93.3%) of the ewes 32–48 h after CIDR removal (overall 93.3%). Twentyseven (90%) and 3 (10%) ewes exhibited estrus 32 and 48 h after sponge removal (overall 100%), respectively. The estrous response was significantly (p < 0.05) lower following progesterone in oil treatment, compared to other treatments. The time interval from the end of treatment to the onset of estrus and the time interval from the end of treatment to the end of estrus were significantly (p < 0.05) longer in the progesterone in oil group, compared to CIDR and MAP sponge groups. There was no significant difference in the duration of induced estrous period between all treatments.
4. Discussion The estrous response observed in this comparative study showed that estrus in Karakul ewes can be
efficiently synchronized using the different protocols tested but the CIDR and MAP sponge treatments were more effective. The results from this study indicate that 80% of the ewes showed estrus 48–64 h following the last i.m. injection of progesterone. This was lower than that reported by Dutt (1953) who quoted a 88.8% estrous response within 10 days when 30 mg progesterone in oil was injected every third day for 15 days with 500 IU eCG 3 days after the last injection of progesterone. No significant difference in estrous response between CIDR and MAP sponge treatment was observed in this study, but Knight and Hall (1988) cited the estrous response following CIDR removal to be significantly lower than following sponge treatment (87% versus 94%). This was, however, related to higher loss of CIDRs, compared to sponges (6.3% versus 0.8%). The estrous response in this study was 100% following MAP sponge treatment which is higher than what obtained by Tritschler et al. (1991), who reported a 94% estrous response when using MAP sponges and 500 IU eCG. Simonetti et al. (2000) recorded a 79.3%, 77.4% and 80.9% incidence of estrus with intravaginal sponges impregnated with 40, 50 and 60 mg MAP, respectively. In a study by Mutiga and Mukasa-Mugerwa (1992) estrus synchronized using MAP sponge and 200 IU eCG following sponge withdrawal showed an estrous response similar to the present study. In the current study estrous response using CIDR was 93.3%, which is in agreement with Wheaton et al. (1993). Contrary to the findings in the present study Godfrey et al. (1999) reported an estrous response of 100% and 94.4% in ewes treated by CIDR or progesterone sponge without eCG. The estrous response obtained in this trial with CIDR and MAP sponge was higher than the 81% and 88% reported by Cardwell et al. (1998) who administrated norgestomet alone or norgestomet with eCG.
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The interval from the end of treatment to the onset of estrus and the interval from the end of treatment to the end of estrus are important parameters to determine the duration of the induced estrous period and estimate the time of ovulation. These two periods in the progesterone in oil treatment were significantly (p < 0.05) longer than the CIDR and MAP sponge treatments. A possible explanation may be due to the difference in plasma progesterone levels at the time of CIDR removal and the time of the last injection of progesterone in oil (Anisworth and Downey, 1986). No significant difference was recorded between the CIDR and MAP sponge treatments regarding the duration from the end of treatment to the onset of estrus in this trial. Contrary, the onset of estrus from CIDR removal was found to be earlier compared to following MAP sponge withdrawal (more than 8 h) (Shackell, 1991; Smith et al., 1991). Fukui et al. (1993) reported the onset of estrus to be significantly earlier in anestrous ewes treated with CIDR than MAP sponges (24.9 h versus 30 h). Estrus occurred 29.6 ± 5.6 h after MAP sponge and 30.1 ± 7.6 h after CIDR withdrawal which is sooner than the period reported by Fuentes et al. (2001), (35 ± 3 h after sponge withdrawal). Simonetti et al. (2000) recorded estrus to occur 55.94, 56.74 and 57.7 h after 40, 50 and 60 mg progesterone sponge treatment respectively. These differences may be explained by acceleration of the onset of estrus using eCG either concomitant with or before progesterone removal (Mutiga and Mukasa-Mugerwa, 1992; Gordon, 1997; Cardwell et al., 1998; Hoseini-pajooh et al., 1998). The duration of estrus showed no significant difference between progesterone treatments. The mean duration of the induced estrous period obtained in this study (27.2 h) was lower than that recorded for natural estrous in Karakul ewes (35.2 h) (Sefidbakht et al., 1978). The mean duration of the estrous period using MAP sponges in this trial (22.1 ± 3.4 h) was lower than the 27 ± 2.5 h reported by Fuentes et al. (2001). This difference may be due to differences in breed, age and geographical location which are known to influence this period (Evans and Maxwell, 1986; Gordon, 1997). In conclusion, it can be said that estrous synchronization with CIDR and MAP sponge because of inducing a more compact estrous response is more acceptable as a reproductive management tool for fixed time AI in Persian Karakul ewes.
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