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Increasing lambing perfcrmance of ewes by active immunization with polyandroalbumin
THERIOGENOLOGY
R.K.Daroliya,S.K.Verma and R.K.Chandolia Department of Gynaecolcgyand Obstetrics College of VeterinarySciences Haryana AgriculturalMiversity Hisar-125004, India Received for publication:May 23, 1988 Accepted:March 7, 1990
This study was conducted on U-0 cross-bredHisardale x Nali ewes. The ewes were divided into two groups: one group was treated with 2 ml of polyandroalbuminsubcutaneously(s.c.) twice at an interval of 28 d, with breeding rams introduced 28 d after the second injectionof the drug. The second group served as the untreatedcontrols. M the 55 ewes in each group, 52 were mated during the 40d breeding period. The occurance of estrus and estrous cycle length were the same in the two groups. Fortysix ewes in the treated group and 47 ewes.in the control group lambed, producing55 and 47 lambs, respectively. In the treated group, the lambing rate, fecundityand fertilitywere 100, 96.36 and 88.46%,whilethese values for the control group were tj5.45,83.64 and 90.38%b; Prolificityrates were 1.15 and 0.98 for the treated dnd control group, respectively. Key words: polyandroalbumin,immunization,ewes* lambing fertility,fecundity,estrus
An increase in the wuldtion rate of ewes would also ;;l=pkincredse the no.of lambs hdrvested using the available . bong the several techniquesthat are availableto increasethe wuldtion rate, the hormone inqunoneutralitation technique has been employed in ewes. This techniqueworks on the principle of delayingthe negative feed back of ovarian steroids on pitutary,intern causing high levels of gonadotropichornones and increasedwulation. Immunizationdgdinst androstenedioneshows an increase in the ovulationrate in ewes(l,Z)and ovulationfrequency with only small estrus abnormalities(3). &I the other hand, Ackncwledgements The authors thank M/s Glaxo Animal Health Division New Zealand for the free supply of Fecundin.
MAY
1990VOL. 33 NO. 5
1143
THERIOGENOLOGY
active immunization M ewes against androstenedione has no significant effect on the frequency of estrus(3,4) or estrous cycle length in ewes(5). Treatment with polyandroalbumin(an ismunochemical composed of 4 - androstene-3-17 dione 7 alpha carboxy ethylth ether) conjugated with human serum albunin which is marketed ds fecundin, immunizes ewes against androstenedione and increases the lamb crop (6,7). Hence in our study, poly androalbumin was used to study its effect on the estrus cycle, fertility, lambing percentage, lambing rate, fecundity and prolificacy.
Our study was conducted on 110 nonpregnant, cyclic cross bred Hisardale x Nali ewes maintained at the Governneti Sheep Breeding Farm in Hisar from April 1986 to February 1987. The ewes were selected based on their records and on abdominal palpation, and they were then randomly divided into two equal groups of 55 ewes edch. Ewes-in the tredted group received 2 ml. of polyandroalbumin S.C. in the anterior neck region and were kept isolated from the males. Four weeks later, a booster dose of 2 ml. S.C. Wds administered to each ewe. Then 20 d later, both the treated and control groups of ewes were weighed and mixed together, and teaser rams were presented for detection of estrus during the morning and evening hours for 8 d. Breeding rdfnswere introduced into the flock at the rate of 1~15 4 wk after the injection. The breeding of each ewe was recorded during the subsequent 40d period and the ewes were monitored during gestation and lambing. Fertility, lambing percentage lambing rate, fecundity and prolificacy of these groups were recorded. The stdtistical analysis of data was done by applying t-test (22). BEsuLTs The mean body weight of ewes was 34.14 and 32.53 Kg.in treated and control groups, respectively. The length of the estrous cycle was nonsignificant between treated(17.6 2 0.31 d) and control(17.3 40.15) group ewes. The number of ewes returnin to estrus and the ferti exhibiting estrus, mati lity rate at first cycle "9iirst 20 dB and the second cycle (next 20 d) are presented in Table 1. During first cycle, a higher number of ewes exhibited estrus and were mated(63.64) in the treated group than in the control group(56.36%), but the increase was nonsignificant. The fertilit rdte was nonsignificdntly lmver in the treated group(74.28%r than in the control group(80.64). During the second cycle, the same number(25) of ewes were mated in both the groups, but the fertility rate was nonsignificantly lower
1144
MAY 19W VOL. 33 NO. 5
ol
55
55
treated
y--w
--
(6X;%)
(56.$%) 26
25 74.28
80.64 (2288%)
25
20
22
3m-
E13
88
kcurrence of estrus dnd fertility at first and secand cycle in control and treated groups ~_c~--~--_---~_ No.of First cycle Fertility-TturnsdEwes Sec~ktility Ewe s Ewes Ewes lambed to heat mated lambed mated % %
Control
Group
Table 1.
THERIOGENOLOGY
in the treated group(8i)sthan in the control group(88%). Eight ewes(22.8%)in the treated group and four(12.9%)in the control group returnedto estrus after the first cycle. The mating percentagefor both the groups was the same (94.55%)with 52 of 55 ewes in each group exhibitingestrus and mating. The remainin three ewes in each group did not exhibit estrus at a&l wit;I* in the 40d breeding period. Fifty-two ewes were mated in each group; of these 46 ewes in the treated group and 47 ewes in the control group lambed, result-g in the fertilityrate of 88.46 and 90.38, respectively as presented in Table 2. However, the decrease in the fertility rate of the treated group was nonsignificant. Qf the 55 ewes in each group, a total of 46 and 47 ewes lambed, resulting in a lambing rate of 83.64 and 85.45% in
the treated and control groups, respectively. A significantly (PLO.01) higher lambing rate(100 vs 85.45%) was observed
in the treated group(55 lambs) than the control group(47 lambs). This incredse in lambing rdte was mostly attributed to twinning. The twinning percentage was 16.4% in the treat ed group; No twin births were recorded in the control group. Fecundity and prolificity in the treated group was 96.36% and 1.15, while these values were 83.64% and 0.98 for the control group. The fecundity and prolificity were significantly(Pf.01) higher in the treated than in the control group.
The nonsignificantvariations in estrus occurrenceand iength of the strous cycle in our study were in agreement with earlier reports(5,8). A higher return to estrus in treated ewes may be attributedto greater wastage of embryos in this group (9). A decrease in the fertility rate with polyandroalbunin treatment has been reported previously. The decline may possibl have been due to a high embryo loss in immunized
r to a high rate of embryo failureto implant, or to ~~~h$i& during early pregnancy (10 11) However, in our study, fertilitydid not decrease sigkfidantly; a possible reason may be that the breed used was not highly proliferative, thus the,chance of reproduction wastage was also minimal. In highly proliferative breeds reproductive wastage increases linearly(l1). A similar lambing percentage for both roups in our study was also reported in an earlier study9 11). Since poly androalbum is not a tredtment for anestrus, its use cdnnot
1145
MAY
1990VOL. 33 NO. 5
55
47 90.38 86.45 eb.45
Total no. of lambs born
Fertility rate(No.ofewes lambedxmoj mofes mated
Lambing percentage(No.ofewes lambed No.of ewes availableXIM))
Lambing rate(No. of lambs born No. of ewes available
ccntrol group values(PjG).
--
0.98
Prolificacy(No. of tii?:WJ
*SignificantlygreGGan
03.64
Fecundity (No. of lambs born alive ~=)I No. ewes available far &%.hg
-BP-
46
47
No.of ewes lambed
XJW
52
52
Tutal no.of ewes mated
1.15*
96.361,
loo.oo*
83.M
88.46
55
55
_-
Tutal no.of ewes
Variables
Treated group --
Fertility rate, lambing percentage,lambing rate, fecundityand proficity in control and treated groups of ewes Control group
Table 2.
increase the lambing percentage. In our study, the singi fxant incredse in the lambing rate of the treated group was due to 16.4%twin births in the treated group. similar results have been reported by elsewhere (16). however, as even higher twinning rate has been observed (17, 18). The significant increase in fecundity and prolificity in the treated group in our study is similar to results of other researcherS(1,17-19). The increase in lambing performance in our study was due to twinning, and is in accordance with results of other researchers(l8,20). This increasing lambing performance, (due to twinning) may indicate that immunized ewes ovulate only two follicles. Since it had also been reported that none of the New Zealand Romney ewes immunized a ainst andro stenedione ovulated more than two follicles (133 . However. an increase in the lambing rate was due to t&pie and quad&u ple births in imnunized group (21), the result of an increcls ed ovulation rate(12-15) in various sheep breeds.
1.
nlifakiotis, T. Increasing wuldtion rdte and lambing rate by active immunization against androstenedione in dairy sheep breeds Theriogenology 25:681-688 (1986).
2.
Cox,
R.I., Yiilson,P.A. and Xong, M.S.E. Changes in wulation r&e with time in ewes immunized a ainst andro Conf. Aust. ?!cc. Reprod. stenedione. In Proc. 16th AM. Biol., Melbourne(l984). Also cited in(Anim. Breed. tibstr. 1985. =:2l68).
3.
I*nart.in, G.B., Scaramuzzi, R,J ., Cox, R.I. and Gheradi, P.B. Effect of active imnunization against androstene dione or oestrcne on oestrus ovulation and lambing in Merino ewes. Aust. J. Exp; Agric. tinin.Husb. 19:673678 (1979).
4.
Tflartin, GIB., Scaramuzzi, R.J. and Lindsay, R.D. Induction of wulation in.seasonally anwular ewes by the introduction of rams: effect of progesterone and active innunization agdinst androstenedione. JZust.J. Biol. SC i. 3 :569-575 ( 1981) .
5.
Scaramuzzi, R.J., Davidson, >h.G. and Look P.F.A., Van. Increasing ovulation rate in sheep by active immuniza tion against an ovarian steroid androstenedione. Nature. 269:817-818 (1977;.
6.
Look, p.Fn., Van, Clarke, I.J., Davidson, V,G. and Scaraauzzi, K.J. Qlulation and lambing rates kmiewes activDly immunized against androstenedione. J. Reprod. Fertil. 53:329-l= (1978). -
1148
MAY 1880VOL. 33 NO. 5
THERIOGENOLOGY 7.
Hdndrahdn, J.P., Kilpatrich, M. and Box, %*” kffect J*F** of immunization against androstenedione on c&&&ion rate and littre size in sheep. In 34th Ann. Mtg. European Assoc. Anim. Pred. Madrid, Spain(l981). Also cited in(Anim. Breed. nbstr. 1984. 5_2: 1833).
8.
Martensz, W.D. and jcaramuzzi, R.J. Plasma concentra tion of LH, FSH and progesterone during breeding season in ewes immunized against androstenedione or testostero ne. J. Endrocrinol. 81~249-259 (1979).
9.
Boland, &?.P.,Murray, .J.D,,Scarmuzzi, H.J. Nancarro+v, CD., Hoskinson, R,M., Sutton, R. and Hazelton, I. Embryonic mortality in steroid immunized sheep. Anim. Breed. Abstr. 54:5231 (1986).
Xl.
Keeling, B.J., King, M.F. and Gunn, G.J. &tive immuni zation against androstenedione in a synchronized early lambing flock. Br. 5. Anim. Prod. Animal Breed. Abstr. 52x3831 (1986). Smith, J.F., Cox, R-I., ,McGufl~an, L.T., klilson,P.X. dnd Koskinson, R.M. Increasing the wuldtion rate in e_rJes by immunization. Proc. N.Z. jot. Anim. Prod. Anin. Breed. Abstr. %:3199 (1982).
12.
Haresign, iI.and Ldn.mingG.E. Fhysiologiciilbasis for vdriation in ovulatisn rate dnd littre size. Prx. 35th Ann. l&-t. European Assoc. Thericgenology 2_5:681-688 (1984).
13.
Gibb, M. Hudson, N. Killboom, L. and #onatty, K.P. Longten active immunization of Romney ewes with an androstenedione protein conjugate, dffects on oestrus, ovulation and lambing. N. Z. J. Exp. Agri. 1_0:125-128 (1982).
14 .
Scaramuzzi, R.J., Baird, D.T., Clarke, IJ., '.ldrtensz, N.D. and Look P.F.A., Van. Dvdridn norphology and the concentr&ion of steroids during the cestrus cycle of sheep actively ianunized dgdinst androstenedione. J. Reprod. Fertil. 52~25-27 (19a).
15 .
Ihurray,D.J., Boltind,>1.P,,rhorah,C., NArcbrrow, D.S., sc;;rd-nuzzi, i;.J.,Sutton, E., Hoskinson, M.R. dnd Hdzelton, 1.2. E:nbryonic,chraaosonal abnormalities and reproductive wastage in fecundin tredted and control abstr. (i-935). &rino ewes. Theriogenology 23:211 -
16 .
;&tind,B.11.Breeding ewes, dn ev;lluationof the Llseof Facundin under field conditions. Br. Sot. Anin. Prod. 1986. Sited in Anin. Breed, Abstr. 5_4:44 (19%).
17.
Hdrding, R.B., Hardy, P.F,.D.and Joby, R. Increasing lambing rdte viith wandrotone-albumin. 'Jeti:ec. 115:601 &str.(1984). -
MAY 1990VOL. 33 NO. 5
1148
18.
Celdard, H., Dav, J., jcdrdmuzti, R.J., Hoskinson, il.& CUNS, R.I. and Breeds, 2.X. Iimmunization'3fewes with Polydndroalbumin to improve fecundity. dust. Vet. J. 6_1:130-131(1984b).
19.
Hanrahan, J.P. and auirke, J.F. Evaluation of immuni ration with Fecundin as d trectnent for increasing prolificacy in sheep in Ireland, 35th Ann. Cons. European Assoc. Anin. Prod. The Hague cited in Anim. Breed. nbstr. 53~1400 (1985).
20.
Land, R.B., Morris, B.A., Baxyer, G., Bordyce, M. and Forster, J. Improvewnt of sheep fecundity by treat ment with antisera to gonaddl steroids. J. Reprod. Fertil. 66:625-634(1982). -
21.
Vipond, J.E.,Kee-ling,8. and Hunter, E.A. Lambing response in lc~ land ewes cn commercial fdrms to active immUniZati3n against androstenedione. Br. 5~. Anim. Prad. dinter i&etina 1986. Cited in Anim. Breed. Xbstr. 52:3856 (19&j.
22.
Snedecor, G. and Cxhran, iJ.G. Statistical Sthc,ds. d+lliedpacific Ltd., Bombay, 1967.
1160
MAY 1900 VOL. 33 NO. 5
R.K.Daroliya,S.K.Verma and R.K.Chandolia Department of Gynaecolcgyand Obstetrics College of VeterinarySciences Haryana AgriculturalMiversity Hisar-125004, India Received for publication:May 23, 1988 Accepted:March 7, 1990
This study was conducted on U-0 cross-bredHisardale x Nali ewes. The ewes were divided into two groups: one group was treated with 2 ml of polyandroalbuminsubcutaneously(s.c.) twice at an interval of 28 d, with breeding rams introduced 28 d after the second injectionof the drug. The second group served as the untreatedcontrols. M the 55 ewes in each group, 52 were mated during the 40d breeding period. The occurance of estrus and estrous cycle length were the same in the two groups. Fortysix ewes in the treated group and 47 ewes.in the control group lambed, producing55 and 47 lambs, respectively. In the treated group, the lambing rate, fecundityand fertilitywere 100, 96.36 and 88.46%,whilethese values for the control group were tj5.45,83.64 and 90.38%b; Prolificityrates were 1.15 and 0.98 for the treated dnd control group, respectively. Key words: polyandroalbumin,immunization,ewes* lambing fertility,fecundity,estrus
An increase in the wuldtion rate of ewes would also ;;l=pkincredse the no.of lambs hdrvested using the available . bong the several techniquesthat are availableto increasethe wuldtion rate, the hormone inqunoneutralitation technique has been employed in ewes. This techniqueworks on the principle of delayingthe negative feed back of ovarian steroids on pitutary,intern causing high levels of gonadotropichornones and increasedwulation. Immunizationdgdinst androstenedioneshows an increase in the ovulationrate in ewes(l,Z)and ovulationfrequency with only small estrus abnormalities(3). &I the other hand, Ackncwledgements The authors thank M/s Glaxo Animal Health Division New Zealand for the free supply of Fecundin.
MAY
1990VOL. 33 NO. 5
1143
THERIOGENOLOGY
active immunization M ewes against androstenedione has no significant effect on the frequency of estrus(3,4) or estrous cycle length in ewes(5). Treatment with polyandroalbumin(an ismunochemical composed of 4 - androstene-3-17 dione 7 alpha carboxy ethylth ether) conjugated with human serum albunin which is marketed ds fecundin, immunizes ewes against androstenedione and increases the lamb crop (6,7). Hence in our study, poly androalbumin was used to study its effect on the estrus cycle, fertility, lambing percentage, lambing rate, fecundity and prolificacy.
Our study was conducted on 110 nonpregnant, cyclic cross bred Hisardale x Nali ewes maintained at the Governneti Sheep Breeding Farm in Hisar from April 1986 to February 1987. The ewes were selected based on their records and on abdominal palpation, and they were then randomly divided into two equal groups of 55 ewes edch. Ewes-in the tredted group received 2 ml. of polyandroalbumin S.C. in the anterior neck region and were kept isolated from the males. Four weeks later, a booster dose of 2 ml. S.C. Wds administered to each ewe. Then 20 d later, both the treated and control groups of ewes were weighed and mixed together, and teaser rams were presented for detection of estrus during the morning and evening hours for 8 d. Breeding rdfnswere introduced into the flock at the rate of 1~15 4 wk after the injection. The breeding of each ewe was recorded during the subsequent 40d period and the ewes were monitored during gestation and lambing. Fertility, lambing percentage lambing rate, fecundity and prolificacy of these groups were recorded. The stdtistical analysis of data was done by applying t-test (22). BEsuLTs The mean body weight of ewes was 34.14 and 32.53 Kg.in treated and control groups, respectively. The length of the estrous cycle was nonsignificant between treated(17.6 2 0.31 d) and control(17.3 40.15) group ewes. The number of ewes returnin to estrus and the ferti exhibiting estrus, mati lity rate at first cycle "9iirst 20 dB and the second cycle (next 20 d) are presented in Table 1. During first cycle, a higher number of ewes exhibited estrus and were mated(63.64) in the treated group than in the control group(56.36%), but the increase was nonsignificant. The fertilit rdte was nonsignificdntly lmver in the treated group(74.28%r than in the control group(80.64). During the second cycle, the same number(25) of ewes were mated in both the groups, but the fertility rate was nonsignificantly lower
1144
MAY 19W VOL. 33 NO. 5
ol
55
55
treated
y--w
--
(6X;%)
(56.$%) 26
25 74.28
80.64 (2288%)
25
20
22
3m-
E13
88
kcurrence of estrus dnd fertility at first and secand cycle in control and treated groups ~_c~--~--_---~_ No.of First cycle Fertility-TturnsdEwes Sec~ktility Ewe s Ewes Ewes lambed to heat mated lambed mated % %
Control
Group
Table 1.
THERIOGENOLOGY
in the treated group(8i)sthan in the control group(88%). Eight ewes(22.8%)in the treated group and four(12.9%)in the control group returnedto estrus after the first cycle. The mating percentagefor both the groups was the same (94.55%)with 52 of 55 ewes in each group exhibitingestrus and mating. The remainin three ewes in each group did not exhibit estrus at a&l wit;I* in the 40d breeding period. Fifty-two ewes were mated in each group; of these 46 ewes in the treated group and 47 ewes in the control group lambed, result-g in the fertilityrate of 88.46 and 90.38, respectively as presented in Table 2. However, the decrease in the fertility rate of the treated group was nonsignificant. Qf the 55 ewes in each group, a total of 46 and 47 ewes lambed, resulting in a lambing rate of 83.64 and 85.45% in
the treated and control groups, respectively. A significantly (PLO.01) higher lambing rate(100 vs 85.45%) was observed
in the treated group(55 lambs) than the control group(47 lambs). This incredse in lambing rdte was mostly attributed to twinning. The twinning percentage was 16.4% in the treat ed group; No twin births were recorded in the control group. Fecundity and prolificity in the treated group was 96.36% and 1.15, while these values were 83.64% and 0.98 for the control group. The fecundity and prolificity were significantly(Pf.01) higher in the treated than in the control group.
The nonsignificantvariations in estrus occurrenceand iength of the strous cycle in our study were in agreement with earlier reports(5,8). A higher return to estrus in treated ewes may be attributedto greater wastage of embryos in this group (9). A decrease in the fertility rate with polyandroalbunin treatment has been reported previously. The decline may possibl have been due to a high embryo loss in immunized
r to a high rate of embryo failureto implant, or to ~~~h$i& during early pregnancy (10 11) However, in our study, fertilitydid not decrease sigkfidantly; a possible reason may be that the breed used was not highly proliferative, thus the,chance of reproduction wastage was also minimal. In highly proliferative breeds reproductive wastage increases linearly(l1). A similar lambing percentage for both roups in our study was also reported in an earlier study9 11). Since poly androalbum is not a tredtment for anestrus, its use cdnnot
1145
MAY
1990VOL. 33 NO. 5
55
47 90.38 86.45 eb.45
Total no. of lambs born
Fertility rate(No.ofewes lambedxmoj mofes mated
Lambing percentage(No.ofewes lambed No.of ewes availableXIM))
Lambing rate(No. of lambs born No. of ewes available
ccntrol group values(PjG).
--
0.98
Prolificacy(No. of tii?:WJ
*SignificantlygreGGan
03.64
Fecundity (No. of lambs born alive ~=)I No. ewes available far &%.hg
-BP-
46
47
No.of ewes lambed
XJW
52
52
Tutal no.of ewes mated
1.15*
96.361,
loo.oo*
83.M
88.46
55
55
_-
Tutal no.of ewes
Variables
Treated group --
Fertility rate, lambing percentage,lambing rate, fecundityand proficity in control and treated groups of ewes Control group
Table 2.
increase the lambing percentage. In our study, the singi fxant incredse in the lambing rate of the treated group was due to 16.4%twin births in the treated group. similar results have been reported by elsewhere (16). however, as even higher twinning rate has been observed (17, 18). The significant increase in fecundity and prolificity in the treated group in our study is similar to results of other researcherS(1,17-19). The increase in lambing performance in our study was due to twinning, and is in accordance with results of other researchers(l8,20). This increasing lambing performance, (due to twinning) may indicate that immunized ewes ovulate only two follicles. Since it had also been reported that none of the New Zealand Romney ewes immunized a ainst andro stenedione ovulated more than two follicles (133 . However. an increase in the lambing rate was due to t&pie and quad&u ple births in imnunized group (21), the result of an increcls ed ovulation rate(12-15) in various sheep breeds.
1.
nlifakiotis, T. Increasing wuldtion rdte and lambing rate by active immunization against androstenedione in dairy sheep breeds Theriogenology 25:681-688 (1986).
2.
Cox,
R.I., Yiilson,P.A. and Xong, M.S.E. Changes in wulation r&e with time in ewes immunized a ainst andro Conf. Aust. ?!cc. Reprod. stenedione. In Proc. 16th AM. Biol., Melbourne(l984). Also cited in(Anim. Breed. tibstr. 1985. =:2l68).
3.
I*nart.in, G.B., Scaramuzzi, R,J ., Cox, R.I. and Gheradi, P.B. Effect of active imnunization against androstene dione or oestrcne on oestrus ovulation and lambing in Merino ewes. Aust. J. Exp; Agric. tinin.Husb. 19:673678 (1979).
4.
Tflartin, GIB., Scaramuzzi, R.J. and Lindsay, R.D. Induction of wulation in.seasonally anwular ewes by the introduction of rams: effect of progesterone and active innunization agdinst androstenedione. JZust.J. Biol. SC i. 3 :569-575 ( 1981) .
5.
Scaramuzzi, R.J., Davidson, >h.G. and Look P.F.A., Van. Increasing ovulation rate in sheep by active immuniza tion against an ovarian steroid androstenedione. Nature. 269:817-818 (1977;.
6.
Look, p.Fn., Van, Clarke, I.J., Davidson, V,G. and Scaraauzzi, K.J. Qlulation and lambing rates kmiewes activDly immunized against androstenedione. J. Reprod. Fertil. 53:329-l= (1978). -
1148
MAY 1880VOL. 33 NO. 5
THERIOGENOLOGY 7.
Hdndrahdn, J.P., Kilpatrich, M. and Box, %*” kffect J*F** of immunization against androstenedione on c&&&ion rate and littre size in sheep. In 34th Ann. Mtg. European Assoc. Anim. Pred. Madrid, Spain(l981). Also cited in(Anim. Breed. nbstr. 1984. 5_2: 1833).
8.
Martensz, W.D. and jcaramuzzi, R.J. Plasma concentra tion of LH, FSH and progesterone during breeding season in ewes immunized against androstenedione or testostero ne. J. Endrocrinol. 81~249-259 (1979).
9.
Boland, &?.P.,Murray, .J.D,,Scarmuzzi, H.J. Nancarro+v, CD., Hoskinson, R,M., Sutton, R. and Hazelton, I. Embryonic mortality in steroid immunized sheep. Anim. Breed. Abstr. 54:5231 (1986).
Xl.
Keeling, B.J., King, M.F. and Gunn, G.J. &tive immuni zation against androstenedione in a synchronized early lambing flock. Br. 5. Anim. Prod. Animal Breed. Abstr. 52x3831 (1986). Smith, J.F., Cox, R-I., ,McGufl~an, L.T., klilson,P.X. dnd Koskinson, R.M. Increasing the wuldtion rate in e_rJes by immunization. Proc. N.Z. jot. Anim. Prod. Anin. Breed. Abstr. %:3199 (1982).
12.
Haresign, iI.and Ldn.mingG.E. Fhysiologiciilbasis for vdriation in ovulatisn rate dnd littre size. Prx. 35th Ann. l&-t. European Assoc. Thericgenology 2_5:681-688 (1984).
13.
Gibb, M. Hudson, N. Killboom, L. and #onatty, K.P. Longten active immunization of Romney ewes with an androstenedione protein conjugate, dffects on oestrus, ovulation and lambing. N. Z. J. Exp. Agri. 1_0:125-128 (1982).
14 .
Scaramuzzi, R.J., Baird, D.T., Clarke, IJ., '.ldrtensz, N.D. and Look P.F.A., Van. Dvdridn norphology and the concentr&ion of steroids during the cestrus cycle of sheep actively ianunized dgdinst androstenedione. J. Reprod. Fertil. 52~25-27 (19a).
15 .
Ihurray,D.J., Boltind,>1.P,,rhorah,C., NArcbrrow, D.S., sc;;rd-nuzzi, i;.J.,Sutton, E., Hoskinson, M.R. dnd Hdzelton, 1.2. E:nbryonic,chraaosonal abnormalities and reproductive wastage in fecundin tredted and control abstr. (i-935). &rino ewes. Theriogenology 23:211 -
16 .
;&tind,B.11.Breeding ewes, dn ev;lluationof the Llseof Facundin under field conditions. Br. Sot. Anin. Prod. 1986. Sited in Anin. Breed, Abstr. 5_4:44 (19%).
17.
Hdrding, R.B., Hardy, P.F,.D.and Joby, R. Increasing lambing rdte viith wandrotone-albumin. 'Jeti:ec. 115:601 &str.(1984). -
MAY 1990VOL. 33 NO. 5
1148
18.
Celdard, H., Dav, J., jcdrdmuzti, R.J., Hoskinson, il.& CUNS, R.I. and Breeds, 2.X. Iimmunization'3fewes with Polydndroalbumin to improve fecundity. dust. Vet. J. 6_1:130-131(1984b).
19.
Hanrahan, J.P. and auirke, J.F. Evaluation of immuni ration with Fecundin as d trectnent for increasing prolificacy in sheep in Ireland, 35th Ann. Cons. European Assoc. Anin. Prod. The Hague cited in Anim. Breed. nbstr. 53~1400 (1985).
20.
Land, R.B., Morris, B.A., Baxyer, G., Bordyce, M. and Forster, J. Improvewnt of sheep fecundity by treat ment with antisera to gonaddl steroids. J. Reprod. Fertil. 66:625-634(1982). -
21.
Vipond, J.E.,Kee-ling,8. and Hunter, E.A. Lambing response in lc~ land ewes cn commercial fdrms to active immUniZati3n against androstenedione. Br. 5~. Anim. Prad. dinter i&etina 1986. Cited in Anim. Breed. Xbstr. 52:3856 (19&j.
22.
Snedecor, G. and Cxhran, iJ.G. Statistical Sthc,ds. d+lliedpacific Ltd., Bombay, 1967.
1160
MAY 1900 VOL. 33 NO. 5