OVARIAN ACTIVITY IN ULTRASOUND IMAGE AND MILK PROGESTERONE CONCENTRATION IN POSTPARTUM DAIRY COWS

Dolezel, R., K. Karl berg, E. Ropstad: Ovarian Activity in Ultrasound Image and Milk Progesterone Concentration in Postpartum Dairy Cows. Acta vet. Bmo, 62, 1993: 173-178. Eighteen pluriparous dairy cows were ultrasonographically observed twice a week from day 9-10 post partum to the 2nd ovulation. Milk samples were taken three times a week and progesterone was assayed by RIA. Before the 1st postpartum ovulation and during the 1st sexual cycle, 1.09 ± 1.09 and 1.8 ± 1.11, respectively, subordinate follicles and 1.5 ± 0.52 and 2.4 ± 0.72, respectively, follicular waves were found. The 1st ovulation occurred 17.9 ± 5.04 days after parturition, the length of the 1st sexual cycle was 19.4 ± 4.66 days and clinical involution of the uterus was completed 22.6 ± 4.34 days after parturition. The period from parturition to the time of the 1st postpartum ovulation and the length of the 1st sexual cycle were positively correlated with the number of follicular waves during the periods. About 81 % of the first postpartum follicular waves and 88 % of the 1st ovulations occurred in the ovary contralateral to the previous pregnant uterine hom. The differences disappeared after the 1st postpartum ovulation. Average values of milk progesterone were discovered during the 1st and 2nd sexual cycles at day 5-7 (5.9 ± 4.78 and 6.3 ± 5.16ng/ml) and at day 10-12 (5.6 ± 5.83 and 11.4 ± 7.74 ng/ml). Follicular wave, ovulation, luteal structure, laterality A large variety of postpartum ovarian activity in cows was discovered using rectal palpation and morphological investigation after slaughter. Simultaneous occurrence of growth, maturation, luteinization and regression in follicular population is described by Morrow et al. (1966), Wagner and Hansel (1969), Schirar and Martinet (1982), Dufour and Roy (1985). Various quality and lifespan of the first postpartum luteal structures are cited by Lauderdaleet a1. (1968), Duby et al. (1985), Rutter and Randel (1985). Development of follicles influence the quality and lifespan of following luteal structures (Smith, 1986, Inskeep et al., 1988). For this reason continual observation of follicular population is important for the understanding of a resumption of sexual cycle in postpartum cows. Ultrasound imaging makes it possible to observe the dynamics of follicular development. Pier .. son and Ginther (1987a), Rojamahendran and Walton (1988) state sequential patterns of development and regression (follicular waves) during sexual cycle. in cattle. Likewise dominant follicles and follicular waves are described before the first postpartum ovulation and during the following sexual cycle in dairy (Rojamahendran and Taylor 1990, Savio et al. 1990) and beef (Braden et al., 1986; Murphy et al. 1990) cows. The objectives of our study were to characterize ovarian activity in cows using ultrasound scanning and milk progesterone assay from day 9-10 postpartum to the second postpartum ovulation.

The period from parturition to the time of the 1st postpartum ovulation and the length of the 1st sexual cycle were positively correlated with the number of follicular waves during the periods.About 81 % of the first postpartum follicular waves and 88 % of the 1st ovulations occurred in the ovary contralateral to the previous pregnant uterine hom.The differences disappeared after the 1st postpartum ovulation.Average values of milk progesterone were discovered during the 1st and 2nd sexual cycles at day 5-7 (5.9 ± 4.78 and 6.3 ± 5.16ng/ml) and at day 10-12 (5.6 ± 5.83 and 11.4 ± 7.74 ng/ml).

Follicular wave, ovulation, luteal structure, laterality
A large variety of postpartum ovarian activity in cows was discovered using rectal palpation and morphological investigation after slaughter.Simultaneous occurrence of growth, maturation, luteinization and regression in follicular population is described by Morrow et al. (1966), Wagner and Hansel (1969), Schirar and Martinet (1982), Dufour and Roy (1985).Various quality and lifespan of the first postpartum luteal structures are cited by Lauderdaleet a1.(1968), Duby et al. (1985), Rutter and Randel (1985).Development of follicles influence the quality and lifespan of following luteal structures (Smith, 1986, Inskeep et al., 1988).For this reason continual observation of follicular population is important for the understanding of a resumption of sexual cycle in postpartum cows.
Ultrasound imaging makes it possible to observe the dynamics of follicular development.Pier .. son and Ginther (1987a), Rojamahendran and Walton (1988) state sequential patterns of development and regression (follicular waves) during sexual cycle. in cattle.Likewise dominant follicles and follicular waves are described before the first postpartum ovulation and during the following sexual cycle in dairy (Rojamahendran andTaylor 1990, Savio et al. 1990) and beef (Braden et al., 1986;Murphy et al. 1990) cows.
The objectives of our study were to characterize ovarian activity in cows using ultrasound scanning and milk progesterone assay from day 9-10 postpartum to the second postpartum ovulation.

Materials and Methods •
Eighteen pluriparous dairy cows (Norwegian cattle) calving between August 26 and October 25 were included in the experiment.Two cows with pathological conditions (ovarian cysts, retentio secundinarum and endometritis) were excluded by the end of the experiment.Grass silage and concentrates formed principal part of diet.Calves were removed immediately after parturition.Cows were milked and were observed for estrus twice daily.
The cows were regularly investigated by rectal palpation and transrectal ultrasonography (Scanner 400 or 403, PIE Medical, The Netherlands) twice a week, ovarian structures and uterine horns were printed in different planes by video copy processor (Model P6IE, Mitsubishi, Japan) and follicles > 3 mm in diameter, corpora lutea and width of uterine horns (approximately in a third of its length) were evaluated.Ovarian structures were individualy identified by reference to their position and diameter in sequential images.Gradual growth of a dominant follicle (follicle in diameter at least 2mm more than other follicles) was considered a follicular wave.Day after estrus was determined as the time of ovulation.If estrus was not observed, day 2 after investigation of the largest dominant follicle, followed by disappearance of the follicle and formation of a CL, was determined as the time of ovulation.The largest follicle at day 9 -10 after calving was considered as the 1st postpartal dominant follicle.The time from which the width of uterine horns did not decrease gradually and distinctly was determined as the time of clinical involution of uterus.
The samples of whole milk were taken three times a week from day 9-10 after calving to the end of the 2nd postpartal sexual cycle and they were stored at -20° C until they were assayed • for progesterone by RIA .Student t-test was used for statistical evaluation.

Results
The number of follicular waves before and after the 1st postpartal ovulation, total number of follicles, time of the 1st ovulation, length of the 1st postpartal sexual cycle and time of clinical involution of uterus are included in Table 1.One follicular wave before the 1st ovulation occurred in 9 of 10 cows which ovulated before day 20 post partum.Two follicular waves were discovered in 1 cow which ovulated before day 20 and in all cows which ovulated later.Two follicular waves during the 1st sexual cycle were discovered in 8 of 9 cows with the 1st sexual cycles shorter than 20 days.One follicular wave occurred during one short sexual cycle.Three follicular waves were discovered in 5 of 7 cows with longer 1st sexual cycles, two and four follicular waves occurred in the remaining 2 cows.The mean length of the 1st postpartum sexual cycle in.cows which ovu-00 ipsilaterality 0 contralaterality

• • •
The first contralateral postpartal follicular wave and the 1st contralateral postpartal ovulation in relation to the previously pregnant uterine horn was discovered in 13 of 16 (81 %) and in 14 of 16 (88%) cows.Differences in laterality -of follicular waves and ovulations decreased after the 1st postpartal ovulation (Fig. 1).
The mean concentrations of milk progesterone at day 5-7 and 10-12 of the 1st and 2nd sexual cycles are included in table 2. Significantly (p < 0.05) higher concentration was discovered at day 10-12 of the 2nd postpartum sexual cycle (11.4± 7.74 ngjml) in comparison with concentration in the same period of the previous sexual cycle (5.6± 5.83 ng/ml).Term of the 1st postpartum ovulation 17.9 (11-28) days is shorter than it is usually discovered in crossbreds of Bohemian Pied and Holstein-Friesian cows (e.g.average value 27.74 days is stated by Kudhic and Vlcek (1970) but the term is comparable with the results of other authors (Morrow et al. 1969;Garcia and Larson 1982;Duby et al. 1985;Savio et al. 1990).We discovered a shorter length of the 1st postpartum seXual cycle in cows which ovulated before day 20 post partum than in cows which ovulated later.Some of the 1st postpartum luteal structures in cows having a short sexual cycle represented in ultrasound image corpus hemorhagicum (diameter < 20 mm, low echogenity of luteal tissue, sometimes cavity) throughout its lifespan.Shorter 1st postpartum sexual cycles, the relation of the length of the 1st sexual cycle to the term of the 1st postpartum ovulation, and different quality of the 1st postpartum corpus luteum are described by Morrow et al. (1966), Lauderdale et al. (1968), Garcia and Larsson (1982), Duby et al. (1985), Rutter and Randel (1985), Schallenberger (1985).Slightly higher levels of serum progesterone (0.6-• 1.0 ng/mI) are often accompanied by small atypical luteal structures in ovaries at day 20-25 post partum (Doleiel et al. 1991).Practically the same average levels of milk progesterone (5.94 and 6.25 ng/ml) at day 5-7 and different levels at day 10-12 post partum (5.56 and 11.38 ng/mI) in the 1st and the 2nd postpartum sexual cycle support clinical findings in our experiment.Perry et al. (1991) state similar concentrations of serum progesterone during the first 4 days in the 1st and 2nd postpartum sexual cycles but they describe higher concentration from day 5 to 8 of the 2nd sexual cycle.
We registered 81 % of the 1st postpartum follicular waves and 88% of the 1st ovulation occurring in contralateral ovary in relation to the previously pregnant uterine horn and the differences disappeared after the 1st postpartum ovulation.Inhibitory influence of corpus luteum graviditatis or pregnant uterine hom to early postpartum activity of ipsilateral ovary are shown by Morrow et al. (1968), Schirar and Martinet (1982), Bellin et al. (1984), Pierson and Ginther (1987b, c).Likewise, Kotik (1990) reports higher percentage of cows with first ovulation on the contralateral ovary in relation to the previous pregnant uterine hom.The differences are more distinct in primiparous cows with left-side previous pregnancy.Our results suggest more distinct inhibitory effect of previously pregnant uterine hom to early postpartum follicular development in compari-• son with effect of cyclical corpus luteum.On the other hand Rajamahendran and Taylor (1990) did not discover any relation of pregnancy to laterality of the 1st postpartum ovulation.

Table 1
Number of folUcular waves from calviDa to the 1st ovulation (A) and durin8 the 1st sexual cycle (B), number of subordlnate folUcles from calviDa to the 1st ovulation (C) and during the 1st sexual cycle (D), Interval (day pp) from calviDa to the 1st ovulation (E) and to the complete uterine Involution (F), and lenath(dllYS) Concentration of mOlt progesterone at day 5-7 and 10-12 of the 1st and 2st postpartum sexual cycle.cycle in 18 of 21 cows.Periods among investigation (3 and 4• days) prevented to evaluate the length of follicular waves in our experiemnt.