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Cyclic reproductive activity and efficiency of reproduction in Serrana goats
ANIMAL REPRODUCTION SCIENCE Animal Reproduction Science 38 (1995) 223-229
ELSEVIER
Cyclic reproductive activity and efficiency of reproduction in Serrana goats R. Mascarenhas a'*, A. S i m 6 e s N u n e s b, J. R o b a l o Silva c aEstaf{w Zootbcnica Nacional, Vale de Santarbm, Santarbm, Portugal blnstituto de Estruturas Agrdrias e Desenvoh, imento Rural, Rua Elias Garcia 38, Amadora, Portugal ~Faculdade de Medicina Veterinaria, Rua Gomes Freire, Lisbon, Portugal
Accepted 25 October 1994
Abstract Reproductive efficiency was studied in mature Serrana goats in three commercial units with ovarian activity being assessed from plasma progesterone profiles between October and May. Over a 2 year period, the mean fertility was 76.2% and the prolificacy was 1.73. Parturitions were recorded between 1 October and 28 February, with 50% of them occurring before the end of October. Goats kidding in October had a significantly shorter (P< 0,01 ) postpartum anoestrous period in the first year (33.0 _+9.4 days; n = 20 ) than in the second year of this experiment (50.3 _+19.7 days; n = 20). Ovarian activity, assessed by plasma progesterone profiles, was low in October (postpartum anoestrus); increased until early January, then declined suddenly to less than 3% and remained low until the first week of May (seasonal anoestrus) when the breeding period commenced. The data suggest that Serrana goats have a period of anoestrus from January to May. Fertility in the beginning of the breeding period (May) could be improved by adequate management techniques so that most parturitions occur in October/November. Keywords: Goat; Seasonality; Anoestrus
1. Introduction Ovarian activity o f goats living at high or mid-latitudes varies throughout the year (Shelton, 1978; C h e m i n e a u et al., 1987; T h i m o n i e r and Chemineau, 1988) but there is little i n f o r m a t i o n on the seasonality o f sexual activity in Portuguese breeds o f goats. The mating period is c o m m o n l y from May to September, but is * Corresponding author. 0378-4320/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSD10378-4320 (94) 01370-5
224
R. Mascarenhas et al, / Animal Reproduction Science 38 (1995) 223-~229
mainly dependent on the price of the kids. This peaks at Christmas and Easter (Fonseca, 1988). The claim that Portuguese breeds of goats can be bred all year round (Sobral et al., 1987 ) has not been supported by studies on ovarian activity assessed by progesterone profiles during specific periods of the year. This showed that Serrana goats were anoestrous from February to July and then started to cycle in August (Leitao et al., 1987 ). However, monitoring ovarian activity from January to June in goats of the same breed, which were isolated from males, Robalo Silva (personal communication, 1993) showed that cyclicity recommenced in early May, alter fertile bucks had been introduced into the flock. Ovulation occurred in every goat within 2 weeks following buck exposure, with differences being explained by the male effect once it had been demonstrated that the presence or absence of males markedly altered the seasonal pattern of ovarian activity (Restall, 1992 ). This study was undertaken to measure the reproductive performance and the resumption and the incidence of ovarian activity from parturition to the onset of the breeding period in Serrana goats bred from May to September.
2. Materials and methods
This study was conducted in 2 consecutive years, using animals in three commercial units located in the central region of Portugal (39 ° 28' latitude North). The number of goats observed each year is shown in Table 1. The animals of each unit were managed under range conditions as one group on natural pasture and bushes of spontaneous Mediterranean forest or under olive or fig trees. Milked goats were supplemented with a commercial concentrate (0.5 kg per animal per day). The goats were continuously exposed to bucks (one male to 20-30 females) and mating was prevented out of the breeding period by fitting aprons to the males from October to May. Changes in plasma progesterone concentrations in Table 1 Reproductive efficiency in Serrana goats Flock 1 Year: Total no. of goats Fertility (%)" Prolificacy b Fecundity (%)°
Flock 2
Flock 3
1
2
1
2
1
2
Total
62 79.0 1.90 150.0
68 72.1 1.76 126.5
76 78.9 1.82 143.4
77 80.5 1.76 141.6
90 74.4 1.66 123.3
102 73.5 1.59 116.7
475 76.2 1.73 132.0
aNumber of goats that k i d d e d / n u m b e r of goats joined to the bucks × 100. bNumber of kids b o r n / n u m b e r of goats that kidded. CNumber of kids b o r n / n u m b e r of goats joined to the bucks × 100.
R. Mascarenhas et al. / Animal Reptvduction Science 38 (1995) 223-229
225
blood samples taken at 7 day intervals were used to determine ovarian activity from October to May in 2 consecutive years in 20 females which had kidded in October. Normal ovarian function was assumed for goats which showed progesterone concentrations above 0.5 ng ml-~ in two consecutive samples, with concentrations at or near the baseline in the following sample. The recurrence of acyclicity was assumed when progesterone concentrations were below 0.5 ng m l - i in at least two or more consecutive samples. Progesterone concentrations of plasma were measured by solid phase radioimmunoassay using commercial kits (Diagnostic Products, Los Angeles, USA ). The inter- and intra-assay coefficients of variation were 9.6% and 8.9% respectively, at the level of 8.5 ng m l - 1 plasma. Analyses of data were performed by tests of independence (chi square) and analysis of variance using the Statgraphics U M C / U S A program.
3. Results
Fertility ranged from 72.1% to 80.5% with a overall mean of 76.2% (Table 1 ). Prolificacy ranged from 1.59 to 1.9 (overall mean, 1.73 ). There were no significant differences among flocks or between years. Parturitions started on 1 October and continued for 22 weeks to 28 February (Fig. 1 ). About 50% of the kiddings were concentrated in October. A second smaller peak of parturitions occurred 3-4 weeks after the first one, followed by a period of 1 month of few or no kiddings. The remaining kiddings were irregularly distributed throughout the final months of the kidding period. In Year 1, 75% of the goats resumed ovarian activity between Days 20 and 50 postpartum; in Year 2, the resumption of ovarian activity occurred between Days 30 and 45 for 60% of the goats and between Days 70 and 85 for 29% (Fig. 2). Kidding (%) 35 3o 25 20 15 10 5 0
oct/4
octJ25
Nov/15
Dec/6
Dec/27
Jan/17
Feb/7
Feb/28
Weeks o
Year 1
Year 2
Fig. 1. Weekly distribution of kiddings from 1 October to 2 8 February in 2 consecutive years.
226
R. Mascarenhas et al. / Animal Reproduction Science 38 (1995) 223-229 35 Cyclic Goats (%) 35 25 25 15 10 5 0
25
30
25
35
Ii0 4o
45 5o 5'~ 5o Days Postpartum
5'~
li,,
70
75
80
85
~ 1 1 Year 2
I~;:iii:i;:~:~lYear 1
Fig. 2. Resumptionof postpartumovarian activity in goats kiddingin October (n = 20). 1oo
Cyclic Goats (%)
80
I
IM II
Onset of matings
60
40
20
0¢ Oct/23
Nov/20
Dec/18
Ja~l"5
Feb'/12 - ~1~/11
-Ap'r/8
May/5
Date
Fig. 3. Incidence of cyclic ovarian activity from November to May in Serrana goats kidding in October.
Twenty-five percent of goats in Year 1 and 11% of goats in Year 2 had a prolonged lactational anoestrus which was extended by seasonal anoestrus until the beginning of next mating period. The mean intervals from kidding to resumption of postpartum ovarian activity were 33.0 _+9.4 (n= 20) and 50.3 +_ 19.7 ( n = 2 0 ) days in Years 1 and 2, respectively ( P < 0.0 1 ) but variation was also significantly higher in Year 2 (9.4 vs. 14.7 days). The occurrence of ovarian activity as determined using plasma progesterone concentrations from October to May is represented in Fig. 3. Ovarian activity increased in the postpartum period, to reach a maximum of 80% on the first week of January. Then it declined suddenly to 3%, remaining low until the second fortnight of April when it started to increase again. Sexual activity, determined after May by heat detection, increased from 10.7% in late April to 88.5% in June. Maximum sexual activity was reached during the first week of August.
R. Mascarenhas et aI, / Animal Reproduction Science 38 (1995) 223-229
227
4. Discussion The overall fertility rate observed in this study (76.2%) was based on the number of goats kidding at term. Failures due to embryo losses and abortions were not considered and this could explain differences in the fertility ranges of 8096% reported by others from enquires to the farmers, but without any experimental support (Sobral et al., 1987; Fonseca, 1988 ). Prolificacy rate was 1.73, involving 63% of twins and 6% triplets. Data from Fonseca (1988) indicate similar values, suggesting that these goats are quite prolific even in extensive breeding systems. The distribution of kiddings shows that about 50% of goats conceived in May. This is considered to be a period of anoestrus for other European breeds (Mateos et al., 1985; Falagan et al., 1989; Chemineau, 1992). The remaining does conceived throughout the period between June and September. A sudden occurrence ofoestrus in a large number of does was observed in early May, when aprons were removed from males and an increase of buck sexual activity and odour were observed. This could stimulate ovarian activity in anoestrous females at the beginning of the breeding period. Although the successful response of females to the male effect needs a previous period of isolation, continuous association with males also resulted in an extended period of ovulation (Restall, 1992). It is possible that the social interaction between females also exerts a stimulatory effect, especially since a direct effect of oestrous females on ovulation in anovulatory counterparts has been demonstrated in goats (Walkden-Brown et al., 1993). The observed kidding pattern suggests that there was a decline in fertilization rate during June-July. This could be due to a return of some does to an anoestrous condition, to the stress of high environmental temperatures and/or to low forage availability during these summer months. Walkden-Brown et al. (1993) observed a less synchronous response and a great tendency to lapse into an anovulatory state in does submitted to stimuli of low intensity when compared to does submitted to stronger stimuli. A significant correlation between conception rate and rainfall in the month preceding fertilization has also been demonstrated (Corteel, 1973 ). This suggests that forage availability was one of the factors limiting conception. Other environmental cues, like the natural spring flushing, may influence ovarian activity and conception rate in May-June (Chemineau, 1992 ). A period of low fertility in Spanish goats during summer was also observed by Gonzalez Valle et al. ( 1993 ), who suggested that it must be due to the high environmental temperatures. Females kidding in October had a variable period of lactational anoestrus of from 20 to more than 50 days. Resumption of postpartum ovarian activity differed significantly between years, probably due to variations in environmental conditions and nutritional factors. The spring and summer periods were drier and hotter in the second year (Instituto Nacional de Meteorologia e Geofisica, 1990, 1991 ). This may have influenced the availability of forage during late summer and early autumn and, consequently, the body condition of females at parturition.
228
R. Mascarenhas et al. / Animal Reproduction Science 38 (1995) 223-229
Females that do not resume postpartum ovarian activity during the normal sexual season will have a prolonged anoestrous condition from February to April. This will be under direct effects of environmental and management factors. In the ewe, Mauleon and Dauzier (1965) observed an interaction between lactational and seasonal anoestrus. This was more evident when lambings occurred towards the end of the sexual season when they found that the number of lambing ewes not resuming ovarian activity increased from September to November. Plasma progesterone concentrations evaluated from the early postpartum (October) to the onset of the next mating period (May) showed that the number of cyclic goats increased after kidding, reaching a maximum in December and declining suddenly around mid-January. A period of anovulation commenced and lasted 3-4 months. Horta et al. (1987) also showed that non-lactating goats are acyclic from January to April, suggesting that there is a true seasonal anoestrus during that period. The results presented here suggest an annual rhythm of ovarian activity for Serrana goats consisting of three periods: ( 1 ) a period of anoestrus between January and April; (2) a transitional period from anoestrus to sexual activity in late April-May, when the does respond positively to the male-effect; (3) a period of normal sexual activity from June to January. Accurate definition of the proposed periods and identification of the factors affecting their duration and intensity need further investigation.
Acknowledgements This study was financed by Junta Nacional de Investiga~o Cientifica e Tecnol6gica, Lisbon, Portugal (Contract No. PMCT/AGR/298/90).
References Chemineau, P., 1992. Seasonality and photoperiodic influence in the female goat reproduction. Vth International Conference on Goats, 2-8 March, New Delhi, India. Pre-Conference Proceedings/ Invited Papers, Vol. II, Part 2, pp. 355-368. Chemineau, P., Daveau, A., Maurice, F. and Thimonier, J., 1987. Seasonality and light control of reproduction in the goat. 38th Annual Meeting of the European Association for Animal Production, Lisbon, Portugal, 28 September to 1 October. Proceedings, Vol. II, Abstract 5.1.4, pp. 906907. Corteel, J.M., 1973. L'insemination artificielle caprine: bases physiologiques, 6tat actuel et perspectives d'avenir. World Rev. Anim. Prod., 9: 73-99. Falagan, A., Gonzalez, C. and Lopez, A., 1989. Anoestrous periods in the Murciano-GranadinaGoat in the Region of Murcia. Proceedings of the 3rd Meeting on Animal Production, Info. Tec. Econ. Agraria., 9: 298-300. Fonseca, P.D., 1988. Situation of the goat breeding in Portugal. II Jornadas Nacional de Caprinicultura, Sociedade Portugese de. Ovinotecnia e Caprinotecnia, Castelo Branco (Portugal), 7-9 April. Proceedings, pp. 87-117. Gonzalez Valle, F., Gracia Mollina, A., Batista Artiaga, M. and Lopez Fernandez, J.L., 1993. Repro-
R. Mascarenhas et al. / Animal Reproduction Science 38 (1995) 223-229
229
ductive performance of goats in the Iberico-Aragonez system. Adv. Alimentation Mejor Anim., 33: 11-16. Horta, A.E.M., Ribeiro, L., Santos, F.P. and Vasques, M.I., 1987. Study of the onset of puberty in Serrana goats by plasma progesterone profiles--first approach. Proceedings of the XXXVIII Annual Meeting of the EAAP, 28 September - 1 October, Lisbon. Vol. II, pp. 918-919. Horta, A.E.M., Vasques, M.1., Leitao, R.M. and Robalo Silva, J., 1990. Resumption of postpartum ovarian activity in the Alentejana cow. Influence of calving period and year. V InternationalMeeting on Animal Reproduction and A.I., Zaragoza (Spain), 14-17 June. Proceedings, Vol. III, pp. 229-236. Instituto Nacional de Meteorologia e Geofisica, 1990. National Institute of Meteorology and Geophysic. Advising Service for Agriculture, Ribatej o (Santardm). Instituto Nacional de Meteorologia e Geofisica, 1991. National Institute of Meteorology and Geophysic. Advising Service for Agriculture. Ribatejo (Santar6m). Leit~o, R.M., Mauricio, R. and Vasques, M.I., 1987. Etude de la variation de l'activit6 ovarienne et du comportement sexuel chez la ch~vre Serrana. 38~me R6union Annuelle de la Federation Europeanne de Zootechnie. Lisbonne (Portugal), 28 Set to 1 Oct. Proceedings, Vol. lI, Abstract S. 1.13, pp. 924-925. Mateos, E., Cuenca, R. and Serrano, A., 1985. Reproduction in the Verata goat: reproductive efficiency and control of reproduction. 1 Meeting on Animal Production, Informacion Tecnics Economics Agraria, Vol. 5, pp. 310-313. Mauleon, P. and Dauzier, L., 1965. Variations de dur6e de l'anoestrus de lactation chez les brebis de race Ile-de-France. Ann. Biol. Anim. Biochem. Biophys., 5:131-I 43. Restall, B.J., 1992. Seasonal variation in reproductive activity in Australian goats. Anim. Reprod. Sci., 27: 305-318. Sbelton, M., 1978. Reproduction and breeding of goats. J. Dairy Sci., 61: 994-1010. Sobral, M., Antero, C., Borrego, J.D. and Domingos, A.N., 1987. Genetical Resources. Local Breeds: Sheep and Goats. Dire9ao Geral da Pecufiria, Lisboa, pp. 195-205. Thimonier, J. and Chemineau, P., 1988. Seasonality of reproduction in female farm animals under a tropical environment. 1lth International Congress on Animal Reproduction and A.I., Dublin, Proceedings, Vol. 5, pp. 229-237. Walkden-Brown, S.W., Restall, B.J. and Henniawati, 1993. The male effect in the Australian cashmere goat. 3. Enhancement with buck nutrition and use of oestrous females. Anim. Reprod. Sci., 32, 69-84.
ELSEVIER
Cyclic reproductive activity and efficiency of reproduction in Serrana goats R. Mascarenhas a'*, A. S i m 6 e s N u n e s b, J. R o b a l o Silva c aEstaf{w Zootbcnica Nacional, Vale de Santarbm, Santarbm, Portugal blnstituto de Estruturas Agrdrias e Desenvoh, imento Rural, Rua Elias Garcia 38, Amadora, Portugal ~Faculdade de Medicina Veterinaria, Rua Gomes Freire, Lisbon, Portugal
Accepted 25 October 1994
Abstract Reproductive efficiency was studied in mature Serrana goats in three commercial units with ovarian activity being assessed from plasma progesterone profiles between October and May. Over a 2 year period, the mean fertility was 76.2% and the prolificacy was 1.73. Parturitions were recorded between 1 October and 28 February, with 50% of them occurring before the end of October. Goats kidding in October had a significantly shorter (P< 0,01 ) postpartum anoestrous period in the first year (33.0 _+9.4 days; n = 20 ) than in the second year of this experiment (50.3 _+19.7 days; n = 20). Ovarian activity, assessed by plasma progesterone profiles, was low in October (postpartum anoestrus); increased until early January, then declined suddenly to less than 3% and remained low until the first week of May (seasonal anoestrus) when the breeding period commenced. The data suggest that Serrana goats have a period of anoestrus from January to May. Fertility in the beginning of the breeding period (May) could be improved by adequate management techniques so that most parturitions occur in October/November. Keywords: Goat; Seasonality; Anoestrus
1. Introduction Ovarian activity o f goats living at high or mid-latitudes varies throughout the year (Shelton, 1978; C h e m i n e a u et al., 1987; T h i m o n i e r and Chemineau, 1988) but there is little i n f o r m a t i o n on the seasonality o f sexual activity in Portuguese breeds o f goats. The mating period is c o m m o n l y from May to September, but is * Corresponding author. 0378-4320/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSD10378-4320 (94) 01370-5
224
R. Mascarenhas et al, / Animal Reproduction Science 38 (1995) 223-~229
mainly dependent on the price of the kids. This peaks at Christmas and Easter (Fonseca, 1988). The claim that Portuguese breeds of goats can be bred all year round (Sobral et al., 1987 ) has not been supported by studies on ovarian activity assessed by progesterone profiles during specific periods of the year. This showed that Serrana goats were anoestrous from February to July and then started to cycle in August (Leitao et al., 1987 ). However, monitoring ovarian activity from January to June in goats of the same breed, which were isolated from males, Robalo Silva (personal communication, 1993) showed that cyclicity recommenced in early May, alter fertile bucks had been introduced into the flock. Ovulation occurred in every goat within 2 weeks following buck exposure, with differences being explained by the male effect once it had been demonstrated that the presence or absence of males markedly altered the seasonal pattern of ovarian activity (Restall, 1992 ). This study was undertaken to measure the reproductive performance and the resumption and the incidence of ovarian activity from parturition to the onset of the breeding period in Serrana goats bred from May to September.
2. Materials and methods
This study was conducted in 2 consecutive years, using animals in three commercial units located in the central region of Portugal (39 ° 28' latitude North). The number of goats observed each year is shown in Table 1. The animals of each unit were managed under range conditions as one group on natural pasture and bushes of spontaneous Mediterranean forest or under olive or fig trees. Milked goats were supplemented with a commercial concentrate (0.5 kg per animal per day). The goats were continuously exposed to bucks (one male to 20-30 females) and mating was prevented out of the breeding period by fitting aprons to the males from October to May. Changes in plasma progesterone concentrations in Table 1 Reproductive efficiency in Serrana goats Flock 1 Year: Total no. of goats Fertility (%)" Prolificacy b Fecundity (%)°
Flock 2
Flock 3
1
2
1
2
1
2
Total
62 79.0 1.90 150.0
68 72.1 1.76 126.5
76 78.9 1.82 143.4
77 80.5 1.76 141.6
90 74.4 1.66 123.3
102 73.5 1.59 116.7
475 76.2 1.73 132.0
aNumber of goats that k i d d e d / n u m b e r of goats joined to the bucks × 100. bNumber of kids b o r n / n u m b e r of goats that kidded. CNumber of kids b o r n / n u m b e r of goats joined to the bucks × 100.
R. Mascarenhas et al. / Animal Reptvduction Science 38 (1995) 223-229
225
blood samples taken at 7 day intervals were used to determine ovarian activity from October to May in 2 consecutive years in 20 females which had kidded in October. Normal ovarian function was assumed for goats which showed progesterone concentrations above 0.5 ng ml-~ in two consecutive samples, with concentrations at or near the baseline in the following sample. The recurrence of acyclicity was assumed when progesterone concentrations were below 0.5 ng m l - i in at least two or more consecutive samples. Progesterone concentrations of plasma were measured by solid phase radioimmunoassay using commercial kits (Diagnostic Products, Los Angeles, USA ). The inter- and intra-assay coefficients of variation were 9.6% and 8.9% respectively, at the level of 8.5 ng m l - 1 plasma. Analyses of data were performed by tests of independence (chi square) and analysis of variance using the Statgraphics U M C / U S A program.
3. Results
Fertility ranged from 72.1% to 80.5% with a overall mean of 76.2% (Table 1 ). Prolificacy ranged from 1.59 to 1.9 (overall mean, 1.73 ). There were no significant differences among flocks or between years. Parturitions started on 1 October and continued for 22 weeks to 28 February (Fig. 1 ). About 50% of the kiddings were concentrated in October. A second smaller peak of parturitions occurred 3-4 weeks after the first one, followed by a period of 1 month of few or no kiddings. The remaining kiddings were irregularly distributed throughout the final months of the kidding period. In Year 1, 75% of the goats resumed ovarian activity between Days 20 and 50 postpartum; in Year 2, the resumption of ovarian activity occurred between Days 30 and 45 for 60% of the goats and between Days 70 and 85 for 29% (Fig. 2). Kidding (%) 35 3o 25 20 15 10 5 0
oct/4
octJ25
Nov/15
Dec/6
Dec/27
Jan/17
Feb/7
Feb/28
Weeks o
Year 1
Year 2
Fig. 1. Weekly distribution of kiddings from 1 October to 2 8 February in 2 consecutive years.
226
R. Mascarenhas et al. / Animal Reproduction Science 38 (1995) 223-229 35 Cyclic Goats (%) 35 25 25 15 10 5 0
25
30
25
35
Ii0 4o
45 5o 5'~ 5o Days Postpartum
5'~
li,,
70
75
80
85
~ 1 1 Year 2
I~;:iii:i;:~:~lYear 1
Fig. 2. Resumptionof postpartumovarian activity in goats kiddingin October (n = 20). 1oo
Cyclic Goats (%)
80
I
IM II
Onset of matings
60
40
20
0¢ Oct/23
Nov/20
Dec/18
Ja~l"5
Feb'/12 - ~1~/11
-Ap'r/8
May/5
Date
Fig. 3. Incidence of cyclic ovarian activity from November to May in Serrana goats kidding in October.
Twenty-five percent of goats in Year 1 and 11% of goats in Year 2 had a prolonged lactational anoestrus which was extended by seasonal anoestrus until the beginning of next mating period. The mean intervals from kidding to resumption of postpartum ovarian activity were 33.0 _+9.4 (n= 20) and 50.3 +_ 19.7 ( n = 2 0 ) days in Years 1 and 2, respectively ( P < 0.0 1 ) but variation was also significantly higher in Year 2 (9.4 vs. 14.7 days). The occurrence of ovarian activity as determined using plasma progesterone concentrations from October to May is represented in Fig. 3. Ovarian activity increased in the postpartum period, to reach a maximum of 80% on the first week of January. Then it declined suddenly to 3%, remaining low until the second fortnight of April when it started to increase again. Sexual activity, determined after May by heat detection, increased from 10.7% in late April to 88.5% in June. Maximum sexual activity was reached during the first week of August.
R. Mascarenhas et aI, / Animal Reproduction Science 38 (1995) 223-229
227
4. Discussion The overall fertility rate observed in this study (76.2%) was based on the number of goats kidding at term. Failures due to embryo losses and abortions were not considered and this could explain differences in the fertility ranges of 8096% reported by others from enquires to the farmers, but without any experimental support (Sobral et al., 1987; Fonseca, 1988 ). Prolificacy rate was 1.73, involving 63% of twins and 6% triplets. Data from Fonseca (1988) indicate similar values, suggesting that these goats are quite prolific even in extensive breeding systems. The distribution of kiddings shows that about 50% of goats conceived in May. This is considered to be a period of anoestrus for other European breeds (Mateos et al., 1985; Falagan et al., 1989; Chemineau, 1992). The remaining does conceived throughout the period between June and September. A sudden occurrence ofoestrus in a large number of does was observed in early May, when aprons were removed from males and an increase of buck sexual activity and odour were observed. This could stimulate ovarian activity in anoestrous females at the beginning of the breeding period. Although the successful response of females to the male effect needs a previous period of isolation, continuous association with males also resulted in an extended period of ovulation (Restall, 1992). It is possible that the social interaction between females also exerts a stimulatory effect, especially since a direct effect of oestrous females on ovulation in anovulatory counterparts has been demonstrated in goats (Walkden-Brown et al., 1993). The observed kidding pattern suggests that there was a decline in fertilization rate during June-July. This could be due to a return of some does to an anoestrous condition, to the stress of high environmental temperatures and/or to low forage availability during these summer months. Walkden-Brown et al. (1993) observed a less synchronous response and a great tendency to lapse into an anovulatory state in does submitted to stimuli of low intensity when compared to does submitted to stronger stimuli. A significant correlation between conception rate and rainfall in the month preceding fertilization has also been demonstrated (Corteel, 1973 ). This suggests that forage availability was one of the factors limiting conception. Other environmental cues, like the natural spring flushing, may influence ovarian activity and conception rate in May-June (Chemineau, 1992 ). A period of low fertility in Spanish goats during summer was also observed by Gonzalez Valle et al. ( 1993 ), who suggested that it must be due to the high environmental temperatures. Females kidding in October had a variable period of lactational anoestrus of from 20 to more than 50 days. Resumption of postpartum ovarian activity differed significantly between years, probably due to variations in environmental conditions and nutritional factors. The spring and summer periods were drier and hotter in the second year (Instituto Nacional de Meteorologia e Geofisica, 1990, 1991 ). This may have influenced the availability of forage during late summer and early autumn and, consequently, the body condition of females at parturition.
228
R. Mascarenhas et al. / Animal Reproduction Science 38 (1995) 223-229
Females that do not resume postpartum ovarian activity during the normal sexual season will have a prolonged anoestrous condition from February to April. This will be under direct effects of environmental and management factors. In the ewe, Mauleon and Dauzier (1965) observed an interaction between lactational and seasonal anoestrus. This was more evident when lambings occurred towards the end of the sexual season when they found that the number of lambing ewes not resuming ovarian activity increased from September to November. Plasma progesterone concentrations evaluated from the early postpartum (October) to the onset of the next mating period (May) showed that the number of cyclic goats increased after kidding, reaching a maximum in December and declining suddenly around mid-January. A period of anovulation commenced and lasted 3-4 months. Horta et al. (1987) also showed that non-lactating goats are acyclic from January to April, suggesting that there is a true seasonal anoestrus during that period. The results presented here suggest an annual rhythm of ovarian activity for Serrana goats consisting of three periods: ( 1 ) a period of anoestrus between January and April; (2) a transitional period from anoestrus to sexual activity in late April-May, when the does respond positively to the male-effect; (3) a period of normal sexual activity from June to January. Accurate definition of the proposed periods and identification of the factors affecting their duration and intensity need further investigation.
Acknowledgements This study was financed by Junta Nacional de Investiga~o Cientifica e Tecnol6gica, Lisbon, Portugal (Contract No. PMCT/AGR/298/90).
References Chemineau, P., 1992. Seasonality and photoperiodic influence in the female goat reproduction. Vth International Conference on Goats, 2-8 March, New Delhi, India. Pre-Conference Proceedings/ Invited Papers, Vol. II, Part 2, pp. 355-368. Chemineau, P., Daveau, A., Maurice, F. and Thimonier, J., 1987. Seasonality and light control of reproduction in the goat. 38th Annual Meeting of the European Association for Animal Production, Lisbon, Portugal, 28 September to 1 October. Proceedings, Vol. II, Abstract 5.1.4, pp. 906907. Corteel, J.M., 1973. L'insemination artificielle caprine: bases physiologiques, 6tat actuel et perspectives d'avenir. World Rev. Anim. Prod., 9: 73-99. Falagan, A., Gonzalez, C. and Lopez, A., 1989. Anoestrous periods in the Murciano-GranadinaGoat in the Region of Murcia. Proceedings of the 3rd Meeting on Animal Production, Info. Tec. Econ. Agraria., 9: 298-300. Fonseca, P.D., 1988. Situation of the goat breeding in Portugal. II Jornadas Nacional de Caprinicultura, Sociedade Portugese de. Ovinotecnia e Caprinotecnia, Castelo Branco (Portugal), 7-9 April. Proceedings, pp. 87-117. Gonzalez Valle, F., Gracia Mollina, A., Batista Artiaga, M. and Lopez Fernandez, J.L., 1993. Repro-
R. Mascarenhas et al. / Animal Reproduction Science 38 (1995) 223-229
229
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