Seasonal LH profile in ovariectomized cattle

Critser, John K.; Miller, Kathleen B.; Gunsett, F. C.; Ginther, O.J.

doi:10.1016/0093-691x(83)90004-3

Cited by 30 publications

(12 citation statements)

References 25 publications

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“…The seasonal effect on follicular development observed in this study is in agreement with the data of Bulman & Lamming (1978) who found an earlier resumption of cyclicity, based on progesterone analysis, in autumn-calving cows compared to spring calvers. These results and those of Hansen et al (1983), Critser et al (1983, 1987), McNatty et al (1984 and Stanisiewski et al (1988) strongly support the hypothesis of occurrence of seasonality in cattle, which although less marked than in sheep, can modulate some reproductive patterns. In agreement with the hypothesis of seasonality and with previous reports of higher incidence of cystic ovaries during winter months (Roberts, 1955), all the cysts observed in the early post-partum period in the present study were found in the ovaries of cows calved during autumn.…”

Section: Discussionsupporting

confidence: 83%

Resumption of follicular activity in the early post-partum period of dairy cows

Savio

Boland²,

Hynes³

et al. 1990

Reproduction

206

119

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Summary. Lactating Friesian dairy cows (2nd\p=n-\4thparity) which calved in spring (N = 7) or autumn (N = 15) were used. Their ovaries were examined by ultrasound scanning and blood samples were obtained daily for progesterone and oestradiol concentrations from the 5th day after calving until the first post-partum ovulation occurred. Five autumn-calving cows selected at random were bled every 15 min over a 6-h period on 1 day each week for 4 weeks after calving to assess the patterns of LH secretion. Follicular development during the post-partum anoestrous period was characterized by the growth and regression of small ( \ m=l e\ 4 mm) and medium-sized (5\ p=n-\ 9 mm) follicles, until a dominant follicle (> 10 mm) was detected. The first detected dominant follicle ovulated in 14 cows, became cystic in 4 cows (all in autumn), and failed to ovulate in 1 cow. It was not possible to detect a dominant follicle in 3 cows due to scanning difficulties. The post-partum interval to detection of the first dominant follicle (mean \ m=+-\ s.d.) was shorter (P < 0\m=.\05) in autumn (6\m=.\8\ m=+-\ 1\m=.\8days) than in spring (20 \m=+-\10\m=.\1days). However, there was no significant difference between the respective intervals to first ovulation (autumn 27\m=.\4\ m=+-\25\m=.\9and spring 27\m=.\3\ m=+-\18\m=.\9 days). Autumncalved cows which had cysts had longer (P < 0\m=.\001) intervals to first ovulation (58\m=.\2\ m=+-\ 23\m=.\5days) than did normal cows (12\m=.\0\ m=+-\2\m=.\5 days). All cows with cysts had twin ovulations at their first post-partum ovulation. A pulsatile pattern of LH secretion was detected in the first week post-partum and LH pulse frequency was 2\p=n-\3 per 6-h period in Weeks 1 and 2 post partum and increased to 5\p=n-\7 pulses per 6-h period in the presence of a dominant or cystic follicle. Concentrations of progesterone in plasma during post-partum anoestrus were usually low (< 0\m=.\2 ng/ml); oestradiol concentrations were also low (<5pg/ml), but higher values (5\p=n-\110 pg/ml) were observed in cows that had a dominant or a cystic follicle.

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Section: Discussionsupporting

confidence: 83%

Resumption of follicular activity in the early post-partum period of dairy cows

Savio

Boland²,

Hynes³

et al. 1990

Reproduction

206

119

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“…In ovariectomized postpartum cows chronically treated with estradiol implants (Acosta et al, 1983;Garcia-Winder et al, 1986), peripheral concentrations of luteinizing hormone (LH) were increased above those in ovariectomized control cows. Similar results have been reported for beef heifers ovariectomized and treated with estradiol prepubertally or postpubertally (Critser et al, 1983;Kinder et al, 1983). An injection of estradiol decreased the postpartum interval to first estrus or ovulation and improved concep- 27, 1986.…”

Section: Introductionsupporting

confidence: 83%

Ovulation in Postpartum Beef Cows Treated with Estradiol

Garcia-Winder

Lewis

Inskeep

1988

Journal of Animal Science

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The effect of implants of estradiol on initiation of ovarian cycles postpartum was studied in 201 anestrous beef cows. Cows from four farms were used over a 2-yr period in a 2 x 3 factorial arrangement of treatments with estradiol implants and stage postpartum as main effects. Cows were assigned at random within date of calving within farm to receive an ear implant containing estradiol-17 beta (24 mg) for 21 d or to serve as controls. Stages postpartum at implantation were divided into less than or equal to 25, 26 to 39, and greater than or equal to 40 d, three stages that should reflect potential changes in hypothalmic-hypophysial sensitivity to estradiol. Blood samples for determination of progesterone were obtained and rectal examinations of the ovaries performed at implant insertion, 14 d after insertion, at implant removal (d 21), and 14 d after removal (d 35) to assess ovulatory response to treatment. Circulating concentrations of estradiol on d 14 of treatment averaged 3.2 +/- 1.0 and 23.1 +/- 4.7 pg/ml for control and estradiol-treated cows, respectively. Compared with control cows, treatment with estradiol initiated after d 26 postpartum increased the proportion of cows that ovulated during the experimental period. No differences were seen in the average days postpartum when cows were first determined to have ovulated.

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“…Pubertal ovariectomized heifers with or without replacement oestradiol treatment have low concentrations of LH in summer and high concentrations of LH in winter (Critser et al, 1983). In addition, pubertal ovariectomized heifers with replacement oestradiol have lower concentrations of gonadotrophins when exposed to long photoperiod and higher concentrations of gonadotrophins when exposed to short photoperiod (Critser et al, 1987).…”

Section: Resultsmentioning

confidence: 99%