Endocrine, estrous and pregnancy response to varying dosages of Luprostiol in beef cows

THERIOGENOLOGY

EN~CRI~,

N.I. Plata,l

ESTROUS AND PREGNANCY ~SPONSE TO VARYING DOSAGES OF LUPROSTIOL IN BEEF COWS

J.C. Sp.itser,1~3D.M. Henricks,l C.E. Thompson,1 B.B. Plylerl and T.J. Newby*

lDepartment of Animal Science Clemson University, Clemson, SC 29634 *Norden Laboratories, Inc, Lincoln, NE 68501 Received for publication: Accepted:

May 10, 1988 January 25, 2989

ABSTRACT Multiparous lactating beef cows were observed for estrus and randomly assigned to one of four Luprostiol (13, thia-PG-F2a analog) treatment groups receiving 3.8 (LI), 7.5 (LII), 15 (LIII) or 30 (LIV) mg Luprostiol, respectively, or to an untreated control group (C), or to a positive control group (E) receiving 500 mcg Estrumate. Cows received their respective treatments in a single dosage on Day 7, 8 or 9 of the estrous cycle (estrus = Day 0) and were artificially inseminated 12 h following the subsequent estrus. Blood samples were collected from all groups immediately prior to treatment and at 12-h intervals to 48 h post treatment and analyzed for progesterone (P4). Blood samples were collected at 3-h intervals from 24 to 72 h post treatment for animals in Group LIII and for 48 h (or observed estrus) starting on Day 19 of the estrous cycle for animals in Group C. These samples were analyzed for estradiol-17S(E2), follicle stimulating hormone (FSH) and luteinizing hormone (LH). Treatment with Luprostiol at doses 17.5 mg resulted in a synchronous estrous response during the first 5 d post treatment in 75 to 95% of cows treated. Luteal function, as evaluated by systemic P4 concentration, paralleled results observed for estrous response. Treatment with a 15 or 30 mg dose of Luprostiol resulted in greater overall pregnancy rate at synchronized estrus, No biologically significant differences were found in blood levels of E2, FSH or LH around the time of estrus between cows in Groups C and LIII. Results from these studies indicate treatment with Luprostiol at doses 2 7.5 mg resulted in a synchronous estrus during the first 5 d after treatment. Pregnancy rates and endocrine changes were similar to those observed in control and Estrumate-treated cows. Key

words:

cattle, luprostiol, synchronization, fertility

Acknowledgements Technical Contribution No. 2800 of the South Carolina Agricultural Experiment Station. The authors acknowledge Dr. H. S. Hill for assistance with analysis of data. 3Reprint requests: Dr. John C. Spitser. Animal Science Department, Clemson University, Clemson, SC 29634.

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THERIOGENOLOGY

INTRODUCTION Synchronization of estrus in beef cattle is of economic importance because it facilitates artificial insemination by decreasing the labor costs associated with detection of estrus (l), and by reducing the length of the breeding and calving seasons, resulting in more uniform, heavier calves at weaning and a more uniform group of replacement heifers (2-6). Synchronization of estrus increased the proportion of cows and heifers in estrus and pregnant in the first 5 d of the breeding season (6-9). Prostaglandin F2o (PGF2u) and its analogs are luteolytic in the cow (10-13). Fertility following prostaglandin-induced estrus was comparable to that of untreated control animals (14-16), indicating that prostaglandin compounds can be used successfully to synchronize estrus in the bovine. The objectives of this study were to evaluate the luteolytic effect of Luprostiol, a PGF2a analog, administered to beef cows to determine the most effective dosage for the control of estrus and to determine pregnancy response and endocrine patterns following the administration of Luprostiol. MATERIALS AND METHODS One hundred and nineteen multiparous lactating Angus crossbred cows were observed for estrus and randomly assigned to one of four Luprostiol-treatment groups: LI, LII, LX11 and LIV receiving 3.8, 7.5, 15 or 30 mg of Luprostiol (Norden Laboratories, Lincoln, NE), respectively, or to an untreated control group (C) receiving 2 ml of placebo (propylene glycol) or to a positive control group (E) receiving 500 mcg of Estrumate (Bayvet Division, Miles Laboratories, Inc., Shawnee, KS). All animals were more than 40 d postpartum and had a body condition score (BCS) (17,18) greater than 4 at the time of treatment. Cows received their respective treatments in a single dosage during midcycle (Day 7, 8, or 9; estrus = Day 0). Following treatment, cows were observed for estrus at dawn and dusk and were artificially inseminated (AI) approximately 12 h after standing estrus with semen from one of eight bulls randomly allotted. One technician performed all first service inseminations, while several technicians were used for subsequent inseminations. cows failing to conceive were bred again during the 40-d AI breeding season or the subsequent 20-d natural service breeding season. All animals were palpated per rectum 40 d after the last AI breeding date and again 40 d after the end of the breeding season to detect pregnancy. Blood samples were collected immediately prior to treatment and at 12-h intervals, to 48 h following treatment, from the first 10 animals assigned to each of the six groups. Blood was collected via jugular venipuncture and allowed to clot on ice.

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Serum was harvested within 8 h of collection. Serum was frozen at -2OOC until assayed for P4 concentration. Additional blood samples were collected from the first 10 animals assigned to Groups C and LIII, and these cows were observed for estrus every 3 h according to the following schedule: Animals in Group C were sampled every 3 h beginning on Day 19 of the cycle and continuing Animals in Group LIII were for 48 h or to observed estrus. sampled at 3-h intervals from 24 to 72 h post treatment. All blood was collected via jugular venipuncture and allowed to clot on ice. Serum was harvested within 8 h of collection. Serum was frozen at -2OOC until assayed for LH, E2 and FSH concentrations. Concentration of P4 was measured with the direct radioimmunoassay (RIA) system described by Breuel et al. (19), using a This RIA had a crossreactivity specific P4 antiserum (GDN 337). of less than 5% to So pregnane-3, 20-dione, corticosterone and 17o -hydroxy progesterone and less than 2% to 14 other steroids (20). Intraassay coefficient of variation (CV) was 11.3% and interassay CV was 12.7% for six pools across four assays. Serum LH concentrations were determined by the double antibody RIA described by Barnes et al. (Zl), with a specific LH-antiserum (GDN-225) used at 1:60,000 dilution. This dilution bound 35 to 40% of the lz51-labeled LH in the absence of unlabeled LH. Immunochemical grade bovine LH (USDA-bLH-I-1) was used for iodlnation as described by Bolt (22). Radio-labeled LH was tested for its quality (monomeric state and low specific binding) by use of the talc-resin-trichloroacetic acid test as described by Tower et al. Four serum pools across four assays had intraassay and (23). interassay CVs of 4.7 and 12.3X, respectively. Serum E2 concentration was measured using the specific RIA described by Breuel The antisera to E2 had a crossreactivity of less et al. (19). than 8% with El and less than 2% with 18 other steroids, including estriol, P4, cortisol, testosterone and cholesterol (24). Intraassay CV was 7.3% and interassay CV was 20.6% for six pools across six assays. A homologous double antibody RIA was used to determine serum FSH following the protocol described by Barnes et al. (25). The antiserum crossreacted slightly with NIH-TSH-B6 and NIH-LH-B9(<2%) and less than 1% with other pituitary hormones tested (25). A dilution of 1:15,000 of antiserum was used and bound 29% of the radiolabelled FSH when no unlabelled FSH was Purified FSH was used for both the standard curve and added. iodination as described by Hamrick and Gimenes (26). Six pools were measured across four assays and intra- and inter-assay CVs of 7.4 and 11.6%, respectively, were obtained. Estrous and pregnancy responses were analyzed in an analysis of covariance (27) using the General Linear Model (GLM) procedure (28) with treatment group as main effect, and BCS and days postpartum at treatment as covariates. Covariates had no significant effect on response to treatment, so they were deleted from the final model. Hormonal data were examined in an analysis

APRIL 1989 VOL. 31 NO. 4

THERIOGENOLOGY

of variance for repeated measures using the GLM procedure (28). After a stgniEtcant difference was noted in the analysis of variance, group differences were determined using repeated t-tests (29). RESULTS AND DISCUSSION Doses of Luprostiol > 7.5 mg resulted in synchronous estrous responses during the first 5 d following treatment. Estrous response was 0, 45, 75, 80, 95 and 90% for cows in C, LI, LII, LIII, LIV and E groups, respectively (C < LI < LII, LIV and E, P
Table 1.

Estrous response following treatment with varying dosages of Luprostiol in beef cows

Treatment group

No. of cows

5d

Cumulative % in estrus 10 d 21 d 60 d

C (placebo)

20

oa

10a

90

100

LI (3.8 mg)

20

45b

55b

90

100

LII (7.5 mg)

20

75c

8Oc

90

100

LIII (15.0 mg)

20

80c

85c

90

95

LIV (30.0 mg)

19

95c

95c

95

95

E (500 mcg estrumate)

20

9oc

9oc

95

100

asb*cPigures within the same column with diEferent superscripts differ significantly (P
804

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THERIOGENOLOGY First-service pregnancy rate based on the number of cows actually inseminated during the 5-d synchronized period in treated cows and during the first 21 d of breeding in control cows was 50, 89, 60, 94, 67 and 61% for cows in Groups C, LI, LII, LIII, LIV and E, respectively (LIII > C, LII and E, P
Table

Pregnancy rate varying dosages

2.

after breeding of Luprostiol

No. of cows

Treatment group

Firstservicea pregnancy

following in beef

Cumulative 5d

C (placebo)

20

sob

LI

20

89bc

40=

20

60b

20

LII

(3.8 (7.5

LIII LIV

mg) mg)

(15.0 (30.0

E (500

mg) mg)

mcg estrumate)

treatment cows

Ob

10d gb

with

% pregnant 21d

60d

50b

80

4oc

70bc

80

45c

45c

55bc

75

94c

75d

75d

80c

90

19

67bc

63cd

63cd

68bC

95

20

61b

55=d

55=d

60bc

75

aFirst service pregnancy rate is based on the number of cows actually inseminated during the first 5 d following treatment for the treated groups, and during the first 21 d of breeding for the controls. bsc)dFigures within the same column with different superscripts differ signiffcantly (P
Pregnancy rates within the first 5 d after treatment were 0, LIII and E, 40, 45, 75, 63 and 55% for cows in Groups C, LI, LII, respectively (P
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THERIOGENOLOGY

Prior to administration of Luprostiol, mean concentrations of P4 were 4.6, 4.5, 3.9, 4.1, 5.0 and 4.4 ng/ml for all cows in Groups C, LI, LII, LIII, LIV and E, respectively. These values are similar to those reported previously for cows at Days 7 to 9 of the estrus cycle (30,31). Mean levels of P4 (regardless of estrous response) following treatment indicate a more complete luteolytic response for cows treated with doses of Luprostiol > 7.5 mg (Figure 1). Control injections had no effect on corpusluteum function since serum progesterone increased continuously as expected in untreated cattle at this stage of the cycle. Progesterone levels in cows treated with Luprostiol or Estrumate and exhibiting estrus within 5 d after treatment dropped to 1 to 1.4 ng/ml by 48 h, indicating luteolysis (Table 3). Progesterone levels following treatment with Luprostiol and Estrumate were similar to those reported previously for cows treated wtth PGF2" (32,33) and with normal luteolysis (34).

Table 3.

Concentrations of progesterone following treatment with varying dosages of Luprostiol in cows that exhibited

Treatment group LI (3.8 mg)

No. of cows 10

No. of cows in estrus 2

Progesterone (ng/ml) hours after treatment 0 24 36 48 12 3.4ao 1.7 1.6 1.63 1.0

LII (7.5 mg)

10

7

3.6a

1.9

1.7

1.4

1.2

LIII (15.0 mg)

10

8

4.1ab 2.2

1.9

1.4

1.1

9

9

5.0b

2.2

1.8

1.4

1.3

E (500 mcg estrumate) 10

8

4.5ab 2.6

1.9

1.4

LIV (30.0 mg)

apbFigures within the same column with different superscripts differ significantly (P
Mean concentrations of estradiol-176 ranged from 5.9 to 10.4 and 6.4 to 10.8 pg/ml for cows in Groups C and LIII, respectively, during sampling intervals of 3 h, starting 45 h prior (-45) to estrus until 3 h following (+3) estrus. Estradiol-17S values followed the same pattern for both groups (Figure 2). Although two divergent values (at -21 and -12 h) were found, there would appear to be no biological significance of these two observed differences. These levels are similar to those reported previously in the bovine for prostaglandtn-induced cycles and for naturally occurring cycles (34,35). Mean concentrations of FSH ranged from 1.6 to 5.5 and 1.6 to 3.8 ng/ml for cows in Groups C and LIII, respectively, during sampling intervals of 3 h, starting 45 h prior (-45) to estrus

806

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THERIOGENOLOGY

6

-C --C-L1 -LII -Llll(l5.0 -LIV -E

(placebo) (3.8 mg) (7.5 mg) mg) (30.0 mg) (500 mcg)

2

1 12

0

36

24

48

Time after treatment (hours) Figure 1. Mean levels of progesterone following treatment in control (C), Estrumate (E) and Luprostiol-treated (LI, LII. LII I and LIV) COWS.

u ---t-Llll

-42

-36

-30

-24

-18

-12

-6

C

(placebo) (15.0 mg)

Est

Hours to estrus Figure 2. Mean levels of estradiol-176 preceding estrus in control (C) and Luprostiol-treated (LIII) cows.

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007

THERIOGENOLOGY

UC --+-Llll

7

I

I

I

I

(placebo) (15.0 mg)

I

39 -33 -27 -21 15 -9 1-3 -42 -36 -30 -24 -18 -12 -6 Est Hours to estrus Figure 3. Mean levels of follicle-stimulating hormone preceding estrus in control (C) and Luprostiol-treated (LIII) cows.

150’

0

VLIII

-42

-36

-30

-24

-18

-12

-6

C

(placebo) (15.0 mg)

Est

Hours to estrus Figure 4. Mean levels of luteinizing hormone preceding estrus in control (C) and Luprostiil-treated (LIII) cows.

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THERIOGENOLOGY until 3 h following (+3) estrus (Figure 3). No significant differences in FSH values were found between the two groups FSH values were lower than those during the sampling period. reported earlier in the bovine (36,37) due to the usage of both highly-specific bovine antiserum and a more purified FSH, which was used for both the standard curve and for iodination during our assay procedures (26).

a

Mean concentrations of LH ranged from 3.1 to 5.3 and 3.0 to 17.4 ng/ml for cows in Groups C and LIII, respectively, during sampling intervals of 3 h, starting 45 h prior (-45) to estrus to 3 h prior (-3) to estrus (Figure 4). LH began to increase shortly after estrus to values of 123.5 and 33.1 ng/ml at +3 h for cows in Groups C and LIII, respectively. LH followed the same pattern in the two groups and are similar to values reported previously for cows treated with prostaglandins and for control Even though the concentrations of LH at 3 h folcows (38-40). lowing estrus differed significantly between the two groups, there would appear to be no biological signiEicance due to the infrequency of blood collection (every 3 h) during the sampling period. More frequent samples are necessary to accurately describe LH patterns during the estrous cycle, and specifically at estrus, in the bovine (41). Results from our study indicate that doses of Luprostiol of 7.5 mg or greater result in a synchronous estrous response during The 15 and 30 mg doses of the first 5 d after treatment. Luprostiol resulted in the best overall synchrontzation and Luteal function as evaluated by systemic P4 pregnancy rates. concentrations paralleled results observed for the estrous response. REFERENCES

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