Concentrations of Gonadotropins Estradiol And

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.Animal Reproduction Science 54 1998 3143

Concentrations of gonadotropins, estradiol andprogesterone in sows selected on an index of

ovulation rate and embryo survival

D.V. Mariscala,1

, E.G.M. Bergfelda,2

, A.S. Cuppa,3

,F.N. Kojima 4, K.E. Fike a, T. Sanchez a,5, M.E. Wehrman a,6,

R.K. Johnson a, R.J. Kittok a, J.J. Ford b, J.E. Kinder a,)

aDepartment of Animal Science, 224J, Institute of Agricultural and Natural Res., PO Box 830908, Uniersity

of Nebraska, Lincoln, NE 68583-0908, USAb

Roman L. Hruska Meat Animal Research Center, USDA, ARS, Clay Center, NE 68933-0166, USA

Accepted 17 August 1998

Abstract

The objective of this study was to determine concentrations of follicle stimulating hormone . . . .FSH , luteinizing hormone LH , progesterone P and 17b-estradiol E in sows from a line

4 2

.selected on an index which emphasized ovulation rate Select and from a control line. A further

classification of the sows in each line was made according to the estimated number of ovulations . .during an estrous cycle. Sows in the Select line were ranked into a high HI or low group LI

when their estimated number of ovulations were 25 or more and 14 to 15, respectively. Sows of . .the control line were classified into groups as high HC or low LC when the estimated values

for ovulation rate were 1415 and 89 ovulations, respectively. Blood samples were collectedevery 12 h during a complete estrous cycle and samples were analyzed for concentrations of FSH

and LH. Samples collected every 24 h were assayed for P and E . Mean concentrations of FSH,4 2

.LH, P and E did not differ P)0.10 between lines or between HI and LI or HC and LC4 2

)

Corresponding author. Tel.: q1-402-472-6438; Fax: q1-402-472-6362; Email: [email protected]

Present address: Departamento de Zootecnia, Universidad Autonoma Chapingo, Mexico.2

Present address: American Society of Animal Science, 111 N. Dunlap Ave., Savoy, IL 61874, USA.3

Present address: Center for Reproductive Biology, Department of Genetics and Cell Biology, Washington

State University, Pullman, WA 99164-4234, USA.4Also corresponding author. Present address: Department of Animal Science, University of Missouri,

Columbia, MO 65211, USA.5

Present address: Colegio de Posgraduados, Montecillos, Edo. Mexico.6

Present address: Trans Ova Genetics, Chillicothe, MO 64601, USA.

0378-4320r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. .P I I : S 0 3 7 8 - 4 3 2 0 9 8 0 0 1 4 1 - 9


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( )D.V. Mariscal et al.r Animal Reproduction Science 54 1998 3143 33

.The sample of sows used in this experiment 12 Index and 12 Control were selected

samples from all sows available. Ovulation rates of these sows and all relatives back to .generation 0 were used to calculate estimated breeding values EBV for each sow. The

six sows with the highest and lowest EBV in each line were used. Ovulation rates for .Index sows with a high EBV HI were 25 or more, and rates for sows with the low

. . .EBV LI were 15 or less. High HC and low LC Control sows had 15 or more and 9or less, respectively. These selections were conducted to estimate the effects of long

.term selection on endocrine profiles, and whether sows from the Index I and Control . .C lines with similar ovulation rates LI and HC have different endocrine profiles.

Stage of the estrous cycle of sows was synchronized with a synthetic progestin .Regumate, 15 mg daily per sow for 18 days approximately 14 days after the first

estrus, postweaning. Sows were subsequently cannulated as described by Ford and .Maurer 1978 , approximately 7 days before the first estimated period of estrus

following the synchronized estrus. The animals were individually housed and fed

.according to recommendations of the NRC 1988 . Detection of behavioral estrus wasaccomplished by use of a mature boar twice daily at 0600 and 1800 h. The first day of

.estrus standing reflex was considered as day 0 of the estrous cycle. Blood samples

were collected from each sow every 12 h during a complete estrous cycle, starting 5 .days before the anticipated period of behavioral estrus. The blood samples 10 ml were

collected in tubes with 7.0 mg of EDTA and centrifuged at 3000=g for 20 min. Plasma

fractions from each sample were collected and stored at y208C. Concentrations of FSH . .and LH were determined in all samples and 17-estradiol E and progesterone P were2 4

assayed in samples collected every 24 h.

Sows were slaughtered during the luteal phase of the estrous cycle subsequent to theestrous cycle when blood samples were collected. Reproductive tracts were collected at

the time of slaughter and the number of corpora lutea were determined by visual

observation.

2.2. Hormones assays

.For the FSH RIA, USDA-398-04P anti-pFSH was used as the first antibody and

USDA-pFSH-I-1 were used was used as radio labeled ligand and standard hormone

.Mariscal et al., 1996 . These products were kindly furnished by Dr. D.J. Bolt .Reproduction Laboratory, BARC-East, Beltsville, MD . The intra- and inter-assay

coefficients of variation were 4.1 and 14.3%, respectively. Assay sensitivity was 44.3

pgrml.

Concentrations of LH in plasma were determined by using purified porcine LH . LER-786-3 provided by Dr. L.E. Reichert Jr. Dept. of Biochemistry, Albany Medical

. College, Albany, NY as radio labeled ligand and standards Niswender et al., 1970;. Wolfe et al., 1989 . Dr. G.D. Niswender Dept. of Physiology, Colorado State Univ.,

. .Fort Collins, CO provided the rabbit anti-porcine LH a566 . The intra- and interassay

coefficients of variation were 2.8 and 9.2%, respectively. Assay sensitivity was 153pgrml.

Concentrations of E in the samples were determined by RIA using antisera to E2 2 .Lilly, lot a 022367, Lilly Research Laboratories, Indianapolis, IN and radioactive


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( )D.V. Mariscal et al.r Animal Reproduction Science 54 1998 314334

125 .tracer I-E , Amersham, Arlington Heights, IL were used. Concentrations of proges-2 .terone in plasma extracted were assayed by using the antisera at a dilution of

1:1 600 000. Samples were subjected to assays in which both unknowns and standard

curves were subjected to the extraction process. The assay was validated comparing

standards that were unextracted, extracted and extracted with the addition of charcoal

extracted barrow plasma. Parallelism of the standard curves and samples containing highand low amounts of E at 400, 200, 100, 50, 25 and 12.5 ml were evaluated by Allfit2

.and found to be parallel DeLean et al., 1978 . Charcoal-extracted barrow plasma was

added to standards because this negated the need to evaluate amount of recovery of

samples. Intra- and interassay coefficients of variation were 7.2 and 8.6%, respectively.

Assay sensitivity was 0.6 pgrml.

Plasma P was measured by RIA. Progesterone-11-hemisuccinate-TME kindly pro-4 .vided by Dr. A. Belanger Le Centre Hospitalier de IUniversite Laval, Quebec, Canada

Table 1

Mean concentrationsa of FSH and LH in different periods of the estrous cycle in sows from generation 10 of a .b .cline selected on an index of ovulation rate and embryonal survival and ranked into a high HI or low LI

.d .eestimated ovulation rate group and from an unselected control line and ranked into a high HC or low LC

estimated ovulation rate group

Periods of the estrous cycle

f g h i j1 2 3 4 5 X"SEM

( )FSH ngrml

HI 1.1 1.8 1.3 1.2 0.6 1.20".14LI 0.9 1.7 1.4 1.1 0.2 1.05".13

HC 1.0 1.5 1.2 1.0 0.3 0.97".15

LC 1.4 2.3 1.4 1.2 0.4 1.33".14k C A B C DMean 1.1 1.8 1.3 1.1 0.4

( ) LH ngrml

HI 2.7 1.0 1.0 0.9 1.0 1.32".12

LI 2.4 1.4 1.3 1.1 1.1 1.45".12

HC 3.0 1.2 1.3 1.0 0.9 1.49".14

LC 3.3 1.1 0.9 1.0 1.0 1.44".13k A B B B B

Mean 2.8 1.2 1.1 1.0 1.0a

Least square means.b

25 or more ovulations.c

14 to 15 ovulations.d

14 to 15 ovulations.e8 to 9 ovulations.

fPeriod of blood collection during days 0 to 1 of estrous cycle; day 0sfirst day of estrus.

gPeriod of blood collection during days 2 to 4 of estrous cycle.

hPeriod of blood collection during the first half of luteal phase of estrous cycle, considering luteal phase from

.day 5 to the day when P reached baseline Xs7 days .4i .Period of blood collection during second half of luteal phase of estrous cycle Xs7 days .jPeriod of blood collection from day when P reached baseline after luteolysis to the day prior to estrus4

.Xs2.1 days .k

Mean per period of blood sampling.A,B,C .Numbers with different superscripts within rows differ P-0.05 .


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.was used as radio labeled ligand and P Sigma Chemical, St. Louis, MO as standards.4This conjugate was labeled with

125I. A monoclonal antibody against progesterone-11-

.BSA Lot a 02-9b4-94; BiosPacific, Emeryville, CA was used as first antibody. Sheep .anti-mouse gamma globulin Lot a 20711; Pelfreeze, Rogers, AR was used as second

antibody. Assay determinations of P in 0.004, 0.008, 0.02, 0.03 and 0.3 ml of plasma4 .from each of three independent samples were highly correlated rs99 . Recovery of

.added mass 3.9, 7.8 and 15.5 pg P from 1 ml plasma averaged 90P14%. Intra- and4interassay coefficients of variation averaged 6.9 and 9.5%, respectively. Assay sensitiv-

ity was 96 pgrml.

2.3. Statistical analyses

All hormone data were analyzed with mixed model procedures using Proc Mixed of .SAS 1992 . The fitted model included the fixed effects of line, ovulation rate, and

Table 2a . .Mean concentrations of progesterone P and 17b-estradiol E in different periods of the estrous cycle in4 2

sows from generation 10 of a line selected on an index of ovulation rate and embryonal survival and ranked .b .cinto a high HI or low LI estimated ovulation rate group and from an unselected control line and ranked .d .einto a high HC or low LC estimated ovulation rate group

Periods of the estrous cycle

f g h i j1 2 3 4 5 X"SEM

( )P ngrml4

HI 2.1 41.8 106.1 92.0 9.3 50.2"12LI 0.6 14.1 45.3 46.0 4.2 22.0"12

HC 0.8 15.8 56.7 54.5 6.8 29.9"14

LC 1.2 15.2 42.6 42.0 3.4 20.9"13k D B A A CMean 1.2 21.7 62.7 58.6 5.9

( ) E pgrml2HI 32.7 3.6 5.8 8.4 108.4 31.8"8

LI 15.8 5.5 5.6 6.8 39.8 14.7"8

HC 30.3 3.9 4.5 7.6 46.4 18.6"10

LC 29.5 3.8 9.8 8.8 31.6 16.7"9k A B B B A

Mean 27.1 4.2 6.4 7.9 56.5a

Least square means.b

25 or more ovulations.c

14 to 15 ovulations.d

14 to 15 ovulations.e8 to 9 ovulations.

fPeriod of blood collection during days 0 to 1 of estrous cycle; day 0sfirst day of estrus.

gPeriod of blood collection during days 2 to 4 of estrous cycle.

hPeriod of blood collection during the first half of luteal phase of estrous cycle, considering luteal phase from

.day 5 to the day when P reached baseline Xs7 days .4i .Period of blood collection during second half of luteal phase of estrous cycle Xs7 days .jPeriod of blood collection from the day when P reached baseline after luteolysis to the day prior to estrus4

.Xs2.1 days .k

Mean per period of blood sampling.A,B,C,D .Numbers with differing superscripts within rows differ P-0.05 .


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period of estrous cycle. To account for the covariance between observations from the

same sow at different periods, different options of covariance structures for residuals

available in the repeated statement of Proc Mixed were considered and the model with

the best fit was chosen to analyze the data. Means were compared using the predicted .differences tables provided by the Proc Mixed procedure of SAS 1992 .

Hormone data were compared at five different periods over the estrous cycleconsidering the profile of P in circulation. The periods were established as follows:4

.Period 1s time of behavioral estrus days 0 to 1 ; Period 2sdays 2 to 4; Period3s first half of luteal phase considering luteal phase from days 5 to the day when

.concentration of P returned to basal concentrations at the time of luteal regression ;4Period 4s the second half of luteal phase; and Period 5s from the day when concentra-

Fig. 1. Concentrations of progesterone, 17b-estradiol, LH and FSH during an entire estrous cycle in a

representative sow selected on an index of ovulation rate and embryo survival and ranked into a high estimated .ovulation rate group HI .


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tions of P reached basal concentrations at the time of luteal regression through the day4before estrus.

3. Results

3.1. Oulation rate

One sow from the LC group failed to exhibit behavioral estrus during the experimen-

tal period and was excluded from the experiment. Data from one sow were excluded

Fig. 2. Concentrations of progesterone, 17b-estradiol, LH and FSH during an entire estrous cycle in a

representative sow selected on an index of ovulation rate and embryo survival and ranked into a low estimated .ovulation rate group LI .


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from the analyses because she had large variations in secretion of hormones and had an .abnormally long estrous cycle 35 days . With this exclusion, length of the estrous cycle

was not significantly different among sows of the various groups. Mean ovulation rate ."SEM , determined by counting number of corpora lutea present during the estrous

cycle after the blood samples were collected, were 51"20.82, 17"2.24, 22"7.16 and

12"0.22, respectively, for sows of the HI, LI, HC and LC groups.

3.2. Hormone concentrations

.Concentrations of FSH were similar P)0.10 among sows of the four groups. .However, a tendency for a line by ovulation rate interaction P-0.09 was detected.

Fig. 3. Concentrations of progesterone, 17b-estradiol, LH and FSH during an entire estrous cycle in a .representative sow from an unselected line and ranked into a high estimated ovulation rate group HC .


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Greater concentrations of FSH were detected in sows of the LC group than in sows of

the HC, HI and LI groups. Overall mean concentrations of FSH were not significantly .different and concentrations of LH, P , and E were not different P)0.10 among4 2

.sows of the I and C lines or groups H and L when compared at the various periods of .the estrous cycle. Concentration of gonadotropins and steroid hormones varied P-0.05

across the five periods of the estrous cycle. Data for mean concentrations of the . .gonadotropins FSH and LH and gonadal hormones P and E at the different periods4 2

of the estrous cycle are included in Tables 1 and 2, respectively. .Concentrations of FSH were greater P-0.05 during Period 2 than Period 1,

decreased and remained fairly constant during Periods 3 and 4 and decreased further .during Period 5. Concentrations of LH in plasma were greatest P-0.05 during Period

Fig. 4. Concentrations of progesterone, 17b-estradiol, LH and FSH during an entire estrous cycle in a .representative sow from an unselected line and ranked into a low estimated ovulation rate group LC .


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1, decreased and remained relatively constant during the remainder of the estrous cycle. .Concentrations of P were lower P-0.05 during behavioral estrus and after luteolysis.4

During days 2 to 4, concentrations of P began to increase and were greatest during the4luteal phase.

.Concentrations of E in plasma were greatest P-0.05 after luteolysis and before2behavioral estrus. At onset of behavioral estrus, concentrations of E decreased and a2further decrease occurred during the luteal phase of the estrous cycle. One sow from the

.HI group had much greater concentrations of P during Periods 3 351 ngrml and 44 . .269 ngrml and also E during Period 5 456 pgrml when compared with mean2concentrations of P and E during respective periods for the other sows of the HI4 2group. Without data from this sow, corresponding concentrations of P and E were 574 2ngrml, and 39 pgrml, respectively. However, patterns of P and E during the estrous4 2cycle from this sow were similar to those of other sows from the HI group. The

inference of the statistical analyses of the P and E data did not change with or without4 2

data from this sow included. Therefore, values from this sow were included in thestatistical analyses. Patterns of secretion of P , E , FSH and LH for a representative sow4 2of each group are shown in Figs. 14.

4. Discussion

Concentrations of FSH during the estrous cycle in sows from the index selected line

did not differ from sows in the control line. These results are consistent with those

.reported previously Hunter et al., 1993, 1996 in which prolific Meishan gilts and sowshad concentrations of FSH similar to Large White females. No differences in FSH were

observed during the periovulatory period in ewes from breeds with low and high . .ovulation rates Scaramuzzi et al., 1993 . In contrast, Kelly et al. 1988 and Knox

.1992 observed that sows selected for high ovulation rate had greater concentrations of

FSH than those of a control line. Inconsistency between results of studies may indicate

that when different systems of selection were used different physiological control

mechanisms may have affected ovulation rate. Collectively, the data from the various

studies suggest that differences in rate of ovulation may be affected by variation in

. .circulating concentrations of FSH Kelly et al., 1988 and or follicular sensitivity to .gonadotropins, variation in the biopotency of gonadotropins Adams et al., 1988 or

.altered autocrine and paracrine factors in the ovary Driancourt et al., 1990 .

Concentrations of FSH were greater during the secondary increases as expected

because it has been shown that the secondary increase of FSH release may be greaterand more prolonged than the primary preovulatory surge of FSH in pigs Van de Wiel et

.al., 1981; Kelly et al., 1988 . The physiological significance of this increase is not well

understood but it has been implicated in recruitment of ovarian follicles from the resting . .pool of follicles in the ovary Kelly et al., 1988 . In contrast, Knox et al. 1991 failed to

identify a difference in the rate of ovulation when the secondary surge of FSH waspartially suppressed using charcoal extracted follicular fluid. The amount of FSH in

circulation during the secondary increase has been associated with differences in .ovulation rates of ewes Cahill et al., 1981; Lahlou-Kassi et al., 1984 .


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The pattern of LH secretion during the estrous cycle was similar between lines in the

present study and the preovulatory surge of LH occurred during Period 1 correspondingto the time of behavioral estrus Van de Wiel et al., 1981; Kelly et al., 1988; Knox et al.,

.1991 . Likewise, no differences in LH were observed between Meishan and Large White .females Hunter et al., 1993, 1996 .

Concentrations of P in the two lines followed the pattern reported in several studies4 .Henricks et al., 1972; Parvizi et al., 1976; Van de Wiel et al., 1981; Kelly et al., 1988 .

Although line differences were detected in plasma P concentrations, samples were4collected too infrequently to determine possible differences in the immediate increase in

P that occurs after ovulation and appears to be associated with greater embryonic4 .survival Jindal et al., 1997 .

Plasma concentrations of E did not differ between the two lines of sows, a finding2which agrees with those of the previous studies using females with high and low

.ovulation rates Guthrie et al., 1974; Kelly et al., 1988; Hunter et al., 1993 . Hunter et

.al. 1993 reported similar concentrations of E in Meishan and Large White gilts that2had similar ovulation rates. In a second study where ovulation was greater in Meishan

than in Large White sows, there was an association between ovulation rates and .concentrations of E Hunter et al., 1996 . Thus, in Meishan females more ovulatory2

follicles produce greater circulating concentrations of E ; yet, Meishan females appear2 .to metabolize E more rapidly than Large White females Tilton et al., 1994 . In the2

current study, the peak concentrations of E occurred before the surge of LH when2lowest concentrations of FSH were observed. The relative contributions of E and2inhibin to negative feedback regulation of FSH secretion have not been defined in detail

in pigs. Both are produced by developing follicles during the follicular phase of theestrous cycle, and inhibin has been implicated to have a greater influence on FSH

.secretion during this time than E Hasegawa et al., 1988; Trout et al., 1992 .2Collectively, all the studies evaluating reproductive hormones during the periovulatory

period have indicated that genetic lines with differing ovulation rates may or may not

have different hormone concentrations.

5. Conclusions

Selection based on an index which emphasized increased ovulation rate did not affect

the concentrations and pattern of secretion of FSH, LH, P and E in sows. Sows with4 2similar ovulation rates from the select and control line also had similar concentrations of

FSH, LH, P and E and concentrations of these hormones in the blood were not related4 2to ovulation rate. Other factors such as interovarian components may be implicated in

regulation of ovulation rate in this line.

Acknowledgements

We thank Dr. D.J. Bolt for providing porcine antisera and FSH, and Bruce Melson

and Felipe Rodriguez for the assistance in laboratory and statistical analyses, respec-


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tively. This paper is published as paper no. 11913, Nebraska Agricultural Research

Division. Mention of a trade name, proprietary product or specific equipment does not

constitute a guarantee or warranty by the USDA and does not imply approval to the

exclusion of other products that may be suitable.

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