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Time of the preovulatory LH surge in the gilt and sow relative to the onset of behavioral estrus
THERIOGENOLOGY
TIME OF THE PREOVULATORY LH SURGE IN THE GILT AND SOW RELATIVE TO THE ONSET OF BEHAVIORAL ESTRUSl J.E. Tiltona, G.R.bFoxcroftb, A.J. Zieacikayc, S.L. Coombs and G.L. Williams aAnimal Science Department North Dakota State University Fargo, ND 58105 b
Dept. of Physiology and Environment University of Nottingham School of Agriculture Sutton Bonington Received for Publication: Accepted:
May 11, 1982 June 22, 1982
ABSTRACT Two experiments were conducted to study the time of occurrence of the preovulatory LH surge in pigs. Sampling every ten minutes in six cycling gilts before and after onset of standing estrus revealed the preovulatory surge began from 8 hr before to 12 hr after the lordosis reflex was elicited. Three of six gilts initiated the preovulatory LH release coincident with the onset of estrus. Data from 28 postpartum sows, with samples drawn every six hours commencing with the onset of estrus, indicated maximum LH levels were present at the first observance of estrus. Six of the 28 sows had an LH peak 18-24 hr after the onset of estrus.
lPublished with approval of Director, North Dakota Experiment Station. 'Present address: Institute of Animal Physiology & Biochemistry, University of Agriculture & Technology, lo-718 Olsztyn, Poland. Reprint Requests to Dr. J.E. Tilton
AUGUST
1982
VOL.
18 NO. 2
227
Se~~eral auti13;5 describe smiler patterns of 1.2 secretion at the time sf tfie prto\:ularory LB Surge in rhe cyclic gilt or sow. Considerable variability Is reported in the relat ianship between the time cf the ie srrrge and the cnSec of beharioral est-ras. Some of this variability relates to differint eqerimenral prctocols, particularly the frequency of estrus detection, and of LEi decermications, Iioueve-r i assuming thar eSKriis resting ~a.5 standardized te once per day at 0800 h, eke onset. of esrryJs appears to eirher precede the time of maximai LH ievels b?~ a variable -period (-14 to -24 h, (1); -7 h (2); -1 ’n (3)) -’ CT e!.se these ev~fits are reported TC 15e coir,ciden: !1,5). Tlisrf appears to be csnsiderab>e among-animal varilabilizy iri the relationship between escrus onSet and maximal I.11 lerzis (3, 5) ir, sr.iidiesin uhic.h individual data Even greater divergencies in haTTe been reported, the timisg of these phecomena have been reported, blit i;ere possibly unreliable estlmares due to methsdclogical limiraticns (6). The n-&eel- 3f narurz1 Ser‘!i::es3r arr;ficial _J ir,se,ninat.ians -ased to ~&;a72 sor,zeptirn in model-n hasbandry pracrise are generalljr rimed to tzhe onset of behavioral eStrz:s~ If the ttme of the ~rtovulatcry LH surge (and, hence, ovuiation) does not show a consistent relaticoship to the onset of behavLora1 escrlls, 1esS thar. optimal fertility may or insemim.zions at an result fr om S27CiCES lnapprupriate time. Experience, ir. some herds, thar: addirianal ser!rices or Lnseminatlons increase overall conception rates and fertility sends tc scpFort this suggestion, A better understanding of the extent of vzriah:llry in the relationship betveen z're onset zf escrus and ~i;e time of the LH surge too;rldtherefore clearly be of importance and the pressn; stcdies :a'ereGlidertaken for this pUrpoSCZ.
THERIBGENOL
MATERIALS AND METHODS Experiment 1 Six cycling gilts of mixed breeding were cannulated via the cephalic vein approximately 6 days prior to the onset of estrus. All animals were individually penned and fed daily approximately 2 kg per head of a 14% gestation ration throughout the experiment. Estrus detection was conducted in one area specifically designated for that purpose, and gilts were exposed to two boars twice daily until vulva1 swelling or increased physical activity indicated pending estrus. Thereafter, the frequency of exposure to boars was increased to once every two Blood samples were hours until mating was observed. drawn four times daily (0800, 1200, 1600 and 2000 h) before the expected onset of estrus and then every 10 min until 24 h after the detegtion of standing estrus. Sample volume was 3 ml of whole blood during the four times daily sampling period and 1 ml when the blood was removed at lo-min intervals. The samples were centrifuged at 30,000 rpm (4" C) for 10 min following collection. T'ne plasma was removed and stored at -20" C until analyzed. LH concentrations were estimated by a homologous double-antibody radioimmunoassay using porcine LH-GPZ-1 (potency 0.63 X NIH-LH-Sl) as a standard and for iodination (7). Anti-LH serum (8) was used at a 1:200,000 final dilution. The sensitivity of the assay was 0.10 ng LH/ml with a between assay variation of 11.3 and a within assay coefficient of variation of 4.6 %. Experiment 2 Landrace x (Landrace x Large White) sows (N=37) were weaned at 4 weeks postpartum and group-housed in open strawed yards with both auditory and olfactory contact with boars. All sows were individually fed 1.81 kg of a standard ration once daily. The sows were tested with mature stock boars twice daily (0800 and 2000 h) for estrous behaviour from the third or fourth day after weaning until
AUGUST
1982 VOL. 18 NO. 2
229
THERIOGENOLOGY
mating was observed. First acceptance of mounting by a boar was designated as the onset of estrus. Where possible, ear vein samples were taken every 6 hours (0300, 0900, 1500 and 2100) for a minimum of 24 hours from the observed onset of estrus without restraining the sows. Heparinized samples were immediately centrifuged with the plasma stored at -20" C before being assayed for LH. Plasma LH determinations (9) were carried out using a standard porcine LH preparation (IVO; 0.6 x NIH-LH-Sl). All samples were measured in a single assay with a sensitivity of 0.2 ng/ml using 200 ~1 plasma with an intra-assay coefficient of variance of 7%.
RESULTS In both experiments, the time of the preovulatory LH surge varied in relation to the onset of standing estrus. Intensive sampling in the cyclic gilts in Experiment 1 revealed that the preovulatory surge began from 8 h before to 12 h after the onset of standing estrus under conditions in which the onset of a positive lordosis reflex was very accurately determined (Fig. 1). Peak levels of LH in the same gilts occurred from 2 h before to 22 h after the onset of estrus. The majority of the 28 postpartum sows, for which adequate LH data were available, exhibited maximum LH levels at or before the first observation of standing heat (Fig. 2); however, in a significant proportion of these sows (6/28), the LH peak occurred 18-24 h after onset of estrus. Figure 3 illustrates the variable time of occurrence of the preovulatory surges in these animals.
DISCUSSION The experimental protocol that we used to study the cyclic gilts permitted a very accurate assessment of the relationship between onset of estrous behavior and either the initiation of the preovulatory LH surge or the attainment of peak LH
230
AUGUST
1982 VOL. 18 NO. 2
THERIOGENQLBGY
(-lWKIN) Hl
AUGUST
1982 VOL. 18 NO. 2
231
THERJOGENOLOGY
levels. The results demonstrate considerable variability in these relationships, even within this limited group of animals. The time span relationship between estrus onset and peak LH levels of -2 to +22 h are consistent with the variability apparent in other data (3,5). Although the intensity of LH sampling and testing for estrus was relatively infrequent in the weaned sows of Experiment 2, a similar variable pattern was observed between the onset of estrus and the time of the LH surge. Furthermore, with larger numbers of animals studied in Experiment 2, some indication emerged as to the proportional distribution of animals within the range of variability observed. The time of peak LH levels immediately preceded or was coincident with the onset of behavioral estrus in a majority of sows (approximately 60% - 70%). This is in agreement with the data reported for a majority of gilts or sows by other workers (4,5,3). However, in approximately 20% of the sows studied in the present experiment, the LH surge was delayed for 18 to 24 h with respect to the onset of estrus. The extent to which the LH surge might precede the onset of estrus could not be precisely determined, as samples were only drawn once when a standing reflex was present. However, as LH levels were seen to be falling, but not basal, in a number of sows when sampling was initiated (see Fig. 3), it can be reliably inferred that peak LH levels would have been present no more than 12 h previously since the LH surge is typically about 20 h long (see Fig. 1). The variability demonstrated in the timing of the LH surge and the onset of behavioral estrus would therefore provide a physiological basis for explaining both non-pathological conception and fertilization failures. Delayed preovulatory LH surges associated with service or insemination early in estrus could result in ovulation up to 25 h after semen deposition in the uterus and the availability of poor quality semen at the time of ovulation. In contrast, artificial or natural matings in females, in which the LH surge preceded the onset of estrus, would result in aged ova being present when
232
AUGUST 1982VOL. 18 NO. 2
THEWIOGENQLOGY
Tim?
/.
!
of
Sample
18
12
b
After
Onset
of
Es~rus
24
(Hours)
THERIOGENOLOGY
capacitated sperm arrived at the site of fertilization; this would potentially result in fertilization failure or early embryonic death. Such conclusions are consistent with other findings (lo), showing that an increased mating frequency boosted litter size and increased number of inseminations had a positive effect on fertility in sows (11). Three approaches could be taken to avoid potential infertility due to a lack of synchrony between the onset of estrus and the timing of the preovulatory LH surge: the frequency with which checks are made 1) for estrous behavior could be increased to at least twice daily, the number of services or inseminations 2) per heat period could be increased, or, attempts could be made to synchronize the 3) time of the LH surge and therefore ovulation. Recent data (12) suggest that.the latter approach may be practicable and would involve a reduction, rather than an increase, in the labor required for the adequate supervision of natural service or artificial insemination.
LITERATURE CITED
234
1.
Brinkley, H.J. Endocrine signaling and Biol. Reprod. female reproduction. 24:22-43 (1981).
2.
Henricks, D.M., Guthrie, H.D. and Handlin, D.L. Plasma oestrogen, progesterone and LH levels during the oestrus cycle in pigs. Biol. of Reprod. 6:210-218 (1972).
3.
Van de Wiel, D.F.M., Erkens, J., Kroops, W., Vos, E., and Van Landeghem, A.A.J. Periestrous and midluteal time courses of circulating LH, FSH, prolactin, estradiol-178 and progesterone in the
AUGUST 1982 VOL. 18 NO. 2
THERlOGENOLOGY
domestic pig. (1981).
Biol. Reprod. 24~223-233
4.
Niswender, G.D., Reichert, L.E. and Zimmerman, D.R. Radioimmunoassay of serum levels of luteinizing hormone throughout the estrous cycle in pigs. Endocrinology 87:576-580 (1970).
5.
Parvizi, N., Elsaesser, F., Smidt, D., and Ellendorff, F. Plasma luteinizing hormone in the adult female pig during the estrous cycle, late pregnancy and lactation and after ovariectomy and pentobarbitone treatment. 69:193:203 J. Endocrinology. (1976).
6.
Vandalem, J.L., Bodart, Ch. Pirens, G., Glosset, J., and Hennen, G. Development and application of homologous radioimmunoassays for porcine Endocrinology 81:1-10 gonadotrophins. (1979).
7.
Ziecik, A., Goralska, M., Kryzmowski, T., and Pogorzelski, K. Isolation and purification of porcine LH for radioimmunoassay and radioreceptorassay. Bull. Acad. Sci. Polon. Sot. Sci. Biol. 26:139-744 (1978).
8.
Ziecik, A., Kryzmowska, H. and Sobczak, B. Production of antibodies against the porcine luteinizing hormone by two immunization methods. Endocrinologie 74:304 (1978).
9.
Foxcroft, G.R., Pomerantz, D.K. and Nalbandov, A.V. Effects of oestradiol-178 on LH-RH/FSH-RH-induced and spontaneous LH release in prepubertal female pigs. Endocrinology 96:551-557 (1975).
10.
Domanski, J. Effect of time of repeat mating in
AUGUST
1982 VOL. 18 NO. 2
235
THEIUQGENOLOGY
a double mating system on the fertility of the sow. Zess. Probl. Postys. Hauk. p. 27 (An. Br. Abstr. 35:2760) (1966). 11.
Reed, H.C.B. Artificial insemination; In The Control of Pig Reproduction. D.J.A. Cole and G.R. Foxcroft (Ed.) Butterworths, London - in press (198i).
12.
Edwards, S. and Foxcroft, G.R. The response of sows to oestradiol benzoate treatment after weaning at two stages of lactation. .I. Reprod. Fert. - in press (1982).
236
AUGUST
1982 VOL. 18 NO. 2
TIME OF THE PREOVULATORY LH SURGE IN THE GILT AND SOW RELATIVE TO THE ONSET OF BEHAVIORAL ESTRUSl J.E. Tiltona, G.R.bFoxcroftb, A.J. Zieacikayc, S.L. Coombs and G.L. Williams aAnimal Science Department North Dakota State University Fargo, ND 58105 b
Dept. of Physiology and Environment University of Nottingham School of Agriculture Sutton Bonington Received for Publication: Accepted:
May 11, 1982 June 22, 1982
ABSTRACT Two experiments were conducted to study the time of occurrence of the preovulatory LH surge in pigs. Sampling every ten minutes in six cycling gilts before and after onset of standing estrus revealed the preovulatory surge began from 8 hr before to 12 hr after the lordosis reflex was elicited. Three of six gilts initiated the preovulatory LH release coincident with the onset of estrus. Data from 28 postpartum sows, with samples drawn every six hours commencing with the onset of estrus, indicated maximum LH levels were present at the first observance of estrus. Six of the 28 sows had an LH peak 18-24 hr after the onset of estrus.
lPublished with approval of Director, North Dakota Experiment Station. 'Present address: Institute of Animal Physiology & Biochemistry, University of Agriculture & Technology, lo-718 Olsztyn, Poland. Reprint Requests to Dr. J.E. Tilton
AUGUST
1982
VOL.
18 NO. 2
227
Se~~eral auti13;5 describe smiler patterns of 1.2 secretion at the time sf tfie prto\:ularory LB Surge in rhe cyclic gilt or sow. Considerable variability Is reported in the relat ianship between the time cf the ie srrrge and the cnSec of beharioral est-ras. Some of this variability relates to differint eqerimenral prctocols, particularly the frequency of estrus detection, and of LEi decermications, Iioueve-r i assuming thar eSKriis resting ~a.5 standardized te once per day at 0800 h, eke onset. of esrryJs appears to eirher precede the time of maximai LH ievels b?~ a variable -period (-14 to -24 h, (1); -7 h (2); -1 ’n (3)) -’ CT e!.se these ev~fits are reported TC 15e coir,ciden: !1,5). Tlisrf appears to be csnsiderab>e among-animal varilabilizy iri the relationship between escrus onSet and maximal I.11 lerzis (3, 5) ir, sr.iidiesin uhic.h individual data Even greater divergencies in haTTe been reported, the timisg of these phecomena have been reported, blit i;ere possibly unreliable estlmares due to methsdclogical limiraticns (6). The n-&eel- 3f narurz1 Ser‘!i::es3r arr;ficial _J ir,se,ninat.ians -ased to ~&;a72 sor,zeptirn in model-n hasbandry pracrise are generalljr rimed to tzhe onset of behavioral eStrz:s~ If the ttme of the ~rtovulatcry LH surge (and, hence, ovuiation) does not show a consistent relaticoship to the onset of behavLora1 escrlls, 1esS thar. optimal fertility may or insemim.zions at an result fr om S27CiCES lnapprupriate time. Experience, ir. some herds, thar: addirianal ser!rices or Lnseminatlons increase overall conception rates and fertility sends tc scpFort this suggestion, A better understanding of the extent of vzriah:llry in the relationship betveen z're onset zf escrus and ~i;e time of the LH surge too;rldtherefore clearly be of importance and the pressn; stcdies :a'ereGlidertaken for this pUrpoSCZ.
THERIBGENOL
MATERIALS AND METHODS Experiment 1 Six cycling gilts of mixed breeding were cannulated via the cephalic vein approximately 6 days prior to the onset of estrus. All animals were individually penned and fed daily approximately 2 kg per head of a 14% gestation ration throughout the experiment. Estrus detection was conducted in one area specifically designated for that purpose, and gilts were exposed to two boars twice daily until vulva1 swelling or increased physical activity indicated pending estrus. Thereafter, the frequency of exposure to boars was increased to once every two Blood samples were hours until mating was observed. drawn four times daily (0800, 1200, 1600 and 2000 h) before the expected onset of estrus and then every 10 min until 24 h after the detegtion of standing estrus. Sample volume was 3 ml of whole blood during the four times daily sampling period and 1 ml when the blood was removed at lo-min intervals. The samples were centrifuged at 30,000 rpm (4" C) for 10 min following collection. T'ne plasma was removed and stored at -20" C until analyzed. LH concentrations were estimated by a homologous double-antibody radioimmunoassay using porcine LH-GPZ-1 (potency 0.63 X NIH-LH-Sl) as a standard and for iodination (7). Anti-LH serum (8) was used at a 1:200,000 final dilution. The sensitivity of the assay was 0.10 ng LH/ml with a between assay variation of 11.3 and a within assay coefficient of variation of 4.6 %. Experiment 2 Landrace x (Landrace x Large White) sows (N=37) were weaned at 4 weeks postpartum and group-housed in open strawed yards with both auditory and olfactory contact with boars. All sows were individually fed 1.81 kg of a standard ration once daily. The sows were tested with mature stock boars twice daily (0800 and 2000 h) for estrous behaviour from the third or fourth day after weaning until
AUGUST
1982 VOL. 18 NO. 2
229
THERIOGENOLOGY
mating was observed. First acceptance of mounting by a boar was designated as the onset of estrus. Where possible, ear vein samples were taken every 6 hours (0300, 0900, 1500 and 2100) for a minimum of 24 hours from the observed onset of estrus without restraining the sows. Heparinized samples were immediately centrifuged with the plasma stored at -20" C before being assayed for LH. Plasma LH determinations (9) were carried out using a standard porcine LH preparation (IVO; 0.6 x NIH-LH-Sl). All samples were measured in a single assay with a sensitivity of 0.2 ng/ml using 200 ~1 plasma with an intra-assay coefficient of variance of 7%.
RESULTS In both experiments, the time of the preovulatory LH surge varied in relation to the onset of standing estrus. Intensive sampling in the cyclic gilts in Experiment 1 revealed that the preovulatory surge began from 8 h before to 12 h after the onset of standing estrus under conditions in which the onset of a positive lordosis reflex was very accurately determined (Fig. 1). Peak levels of LH in the same gilts occurred from 2 h before to 22 h after the onset of estrus. The majority of the 28 postpartum sows, for which adequate LH data were available, exhibited maximum LH levels at or before the first observation of standing heat (Fig. 2); however, in a significant proportion of these sows (6/28), the LH peak occurred 18-24 h after onset of estrus. Figure 3 illustrates the variable time of occurrence of the preovulatory surges in these animals.
DISCUSSION The experimental protocol that we used to study the cyclic gilts permitted a very accurate assessment of the relationship between onset of estrous behavior and either the initiation of the preovulatory LH surge or the attainment of peak LH
230
AUGUST
1982 VOL. 18 NO. 2
THERIOGENQLBGY
(-lWKIN) Hl
AUGUST
1982 VOL. 18 NO. 2
231
THERJOGENOLOGY
levels. The results demonstrate considerable variability in these relationships, even within this limited group of animals. The time span relationship between estrus onset and peak LH levels of -2 to +22 h are consistent with the variability apparent in other data (3,5). Although the intensity of LH sampling and testing for estrus was relatively infrequent in the weaned sows of Experiment 2, a similar variable pattern was observed between the onset of estrus and the time of the LH surge. Furthermore, with larger numbers of animals studied in Experiment 2, some indication emerged as to the proportional distribution of animals within the range of variability observed. The time of peak LH levels immediately preceded or was coincident with the onset of behavioral estrus in a majority of sows (approximately 60% - 70%). This is in agreement with the data reported for a majority of gilts or sows by other workers (4,5,3). However, in approximately 20% of the sows studied in the present experiment, the LH surge was delayed for 18 to 24 h with respect to the onset of estrus. The extent to which the LH surge might precede the onset of estrus could not be precisely determined, as samples were only drawn once when a standing reflex was present. However, as LH levels were seen to be falling, but not basal, in a number of sows when sampling was initiated (see Fig. 3), it can be reliably inferred that peak LH levels would have been present no more than 12 h previously since the LH surge is typically about 20 h long (see Fig. 1). The variability demonstrated in the timing of the LH surge and the onset of behavioral estrus would therefore provide a physiological basis for explaining both non-pathological conception and fertilization failures. Delayed preovulatory LH surges associated with service or insemination early in estrus could result in ovulation up to 25 h after semen deposition in the uterus and the availability of poor quality semen at the time of ovulation. In contrast, artificial or natural matings in females, in which the LH surge preceded the onset of estrus, would result in aged ova being present when
232
AUGUST 1982VOL. 18 NO. 2
THEWIOGENQLOGY
Tim?
/.
!
of
Sample
18
12
b
After
Onset
of
Es~rus
24
(Hours)
THERIOGENOLOGY
capacitated sperm arrived at the site of fertilization; this would potentially result in fertilization failure or early embryonic death. Such conclusions are consistent with other findings (lo), showing that an increased mating frequency boosted litter size and increased number of inseminations had a positive effect on fertility in sows (11). Three approaches could be taken to avoid potential infertility due to a lack of synchrony between the onset of estrus and the timing of the preovulatory LH surge: the frequency with which checks are made 1) for estrous behavior could be increased to at least twice daily, the number of services or inseminations 2) per heat period could be increased, or, attempts could be made to synchronize the 3) time of the LH surge and therefore ovulation. Recent data (12) suggest that.the latter approach may be practicable and would involve a reduction, rather than an increase, in the labor required for the adequate supervision of natural service or artificial insemination.
LITERATURE CITED
234
1.
Brinkley, H.J. Endocrine signaling and Biol. Reprod. female reproduction. 24:22-43 (1981).
2.
Henricks, D.M., Guthrie, H.D. and Handlin, D.L. Plasma oestrogen, progesterone and LH levels during the oestrus cycle in pigs. Biol. of Reprod. 6:210-218 (1972).
3.
Van de Wiel, D.F.M., Erkens, J., Kroops, W., Vos, E., and Van Landeghem, A.A.J. Periestrous and midluteal time courses of circulating LH, FSH, prolactin, estradiol-178 and progesterone in the
AUGUST 1982 VOL. 18 NO. 2
THERlOGENOLOGY
domestic pig. (1981).
Biol. Reprod. 24~223-233
4.
Niswender, G.D., Reichert, L.E. and Zimmerman, D.R. Radioimmunoassay of serum levels of luteinizing hormone throughout the estrous cycle in pigs. Endocrinology 87:576-580 (1970).
5.
Parvizi, N., Elsaesser, F., Smidt, D., and Ellendorff, F. Plasma luteinizing hormone in the adult female pig during the estrous cycle, late pregnancy and lactation and after ovariectomy and pentobarbitone treatment. 69:193:203 J. Endocrinology. (1976).
6.
Vandalem, J.L., Bodart, Ch. Pirens, G., Glosset, J., and Hennen, G. Development and application of homologous radioimmunoassays for porcine Endocrinology 81:1-10 gonadotrophins. (1979).
7.
Ziecik, A., Goralska, M., Kryzmowski, T., and Pogorzelski, K. Isolation and purification of porcine LH for radioimmunoassay and radioreceptorassay. Bull. Acad. Sci. Polon. Sot. Sci. Biol. 26:139-744 (1978).
8.
Ziecik, A., Kryzmowska, H. and Sobczak, B. Production of antibodies against the porcine luteinizing hormone by two immunization methods. Endocrinologie 74:304 (1978).
9.
Foxcroft, G.R., Pomerantz, D.K. and Nalbandov, A.V. Effects of oestradiol-178 on LH-RH/FSH-RH-induced and spontaneous LH release in prepubertal female pigs. Endocrinology 96:551-557 (1975).
10.
Domanski, J. Effect of time of repeat mating in
AUGUST
1982 VOL. 18 NO. 2
235
THEIUQGENOLOGY
a double mating system on the fertility of the sow. Zess. Probl. Postys. Hauk. p. 27 (An. Br. Abstr. 35:2760) (1966). 11.
Reed, H.C.B. Artificial insemination; In The Control of Pig Reproduction. D.J.A. Cole and G.R. Foxcroft (Ed.) Butterworths, London - in press (198i).
12.
Edwards, S. and Foxcroft, G.R. The response of sows to oestradiol benzoate treatment after weaning at two stages of lactation. .I. Reprod. Fert. - in press (1982).
236
AUGUST
1982 VOL. 18 NO. 2