R.P. Del Vecchio

Effect of pregnancy-specific protein B on prostaglandin F2α and prostaglandin E2 release by day 16-perifused bovine endometrial tissue

Five normal estrous cycling multiparous non-lactating Brahman cows were utilized to determine if pregnancy-specific protein B (PSPB) would alter prostaglandin F2 alpha (PGF) and prostaglandin E2 (PGE) synthesis/release by endometrial tissue. The uterine horn ipsilateral to the corpus luteum was excised on Day 16 of the estrous cycle. Endometrial tissue (200 mg wet wt) was cultured in Nutrient Mixture F-10 medium in a perifusion system. The tissue and medium were aerated with 95% O2: 5% CO2 and temperature was maintained at 39 degrees C. The medium flow rate was 100 microliters/min and fractions were collected at 20 min intervals. After a 120 min settling period, tissue culture continued with: 1) control (medium only); 2) 2 micrograms [Asu1,6]-oxytocin/ml medium for 1 h; 3) 4 or 8 micrograms PSPB/ml medium for 2 h; or 4) 4 or 8 micrograms PSPB/ml medium for 2 h plus 2 micrograms oxytocin/ml medium during the second h. Differences in PGF and PGE secretion rate were not found between 4 and 8 micrograms PSPB. Therefore, groups were combined and data were analyzed according to tissue not receiving PSPB (control); receiving PSPB and receiving PSPB plus oxytocin. A nonsignificant rise (p greater than 0.10) in PGF secretion was observed in response to PSPB and PSPB plus oxytocin above the control by the end of the perifusion period (263.7 +/- 41.7, 220.0 +/- 41.7 and 166.1 +/- 41.7 pg/(100 mg tissue/min), respectively). Treatment with PSPB alone elevated (p less than 0.05) PGE secretion rate above control by 100 and 160 min post-removal of PSPB treatment. Treatment with PSPB plus oxytocin elevated (p less than 0.05) PGE release above control by 20 min after starting oxytocin treatment and continued throughout the duration of the perifusion. Pregnancy-specific protein B plus oxytocin-induced PGE release was greater (p less than 0.05) than PSPB alone after initiating the oxytocin treatment until 20 min after removal of the treatments. However, no further differences between PSPB alone and PSPB plus oxytocin treatments were detected throughout the remainder of the perifusion period. It appears that PSPB tends to elevate PGF release and significantly elevates PGE release from Day 16 endometrial tissue.

Effect of alfaprostol on postpartum reproductive efficiency in brahman cows and heifers

Brahman cows (n=54) and heifers (n=18) were randomly allotted by calving date, sex of calf and age to one of four treatment groups. Group 1 received no treatment (control), Group 2 received 5 mg alfaprostol (AP) i.m. on Day 21 postpartum, Group 3 received 5 mg AP i.m. on Day 32 postpartum and Group 4 received 5 mg AP i.m. on both Days 21 and 32 postpartum. Blood samples were collected via tail vessel puncture at 30 min-intervals for 8 h from half the animals in each group on Days 21 and 32 postpartum, with AP injection administered 2 h after sampling had begun. All cows were bled at weekly intervals. Samples were processed to yield serum and stored at -20 degrees C until assayed for luteinizing hormone (LH) or progesterone (P4). All cattle were maintained with epididymectomized marker bulls and were artificially inseminated (A.I.) at first estrus. Serum P4 was below 1 ng/ml prior to AP treatment in all animals and did not differ (P>0.10) between treatments. Alfaprostol treatment affected mean postpartum interval (from parturition to return to standing estrus and subsequent corpus luteum formation with serum progesterone concentrations>1 ng/ml; P<0.08). The control group (84.8+/-7.9 d) did not differ from Group 2 (86.3+/-11.1 d) or Group 3 (66.7+/-5.5 d) but did differ (P<0.09) from Group 4 (65.1+/-6.4 d). Cattle injected on Day 32 had a shorter (P<0.01) postpartum interval than those not receiving treatment on that day (65.9+/-4.2 vs 85.7+/-6.8 d). Pregnancy rate was affected (P<0.05) by AP treatment. The control group (72.2%) did not differ (P>0.10) from any group but, Group 2 (50.0%) was lower (P<0.04) than Group 3 (83.3%) and (P<0.02) Group 4 (88.9%). Cattle treated on Day 32 (Groups 3 and 4) had a higher (P<0.02) pregnancy rate (86.1%) than those not treated on Day 32 (Groups 1 and 2; 61.1%). Serum LH was affected by day (P<0.0003) and treatment by day (P<0.07) but not by time (P>0.10). Treatment Group 3 (P<0.08) and Group 4 (P<0.0003) mean LH concentrations differed between Days 21 and 32 postpartum. Cattle receiving AP treatment on Day 32 postpartum had a higher (P<0.04) cumulative frequency of return to estrus by 100 days postpartum than nontreated cattle.

Effect of alfaprostol, lasalocid, and once-daily suckling on postpartum interval in Brahman and Brahman crossbred cattle

Brahman cows (n = 49) and primiparous heifers (n = 11), Brahman x Hereford primiparous F1 heifers (n = 86) and Simmental x Brahman primiparous F1 heifers (n = 13) were randomly allotted by breed, age and date of calving to one of eight treatment groups: 1) control; 2) once-daily suckling; 3) lasalocid (200 mg/hd/d); 4) alfaprostol (5 mg intermuscular injections on Days 21 and 32 post partum); 5) lasalocid + once-daily suckling; 6) alfaprostol + once daily suckling; 7) alfaprostol + lasalocid; 8) alfaprostol + lasalocid + once daily suckling. All animals received 2.3 kg/hd/d of a concentrate (6 corn : 1 cottonseed meal) and lasalocid was mixed and fed in the concentrate. Body weights and condition scores were taken on Day 1 post partum and every 28 d thereafter. All animals were maintained with sterile marker bulls with Brahman and Simmental x Brahman cattle artificially inseminated at first estrus. Blood samples were collected at weekly intervals starting on Day 21 post partum until estrus and at nine to twelve days post estrus when the ovaries were palpated for corpora lutea. After the first postpartum estrus with a corpora lutea, cows were placed with fertile bulls. Mean serum progesterone concentrations were below 0.5 ng/ml prior to treatment. Calf weight gains to 90 d were not affected by age (P > 0.10) but were lower in the once-daily suckling group (P < 0.05). Treatment did not affect cow weight or condition score (P > 0.10). Cows had a shorter postpartum interval (P < 0.0001) than heifers. Once-daily suckling shortened postpartum interval (P < 0.0001) and positively influenced the cumulative frequency of return to estrus by 40 d post partum (P < 0.02). Alfaprostol did not affect postpartum interval (P > 0.10) but did increase the cumulative frequency of return to estrus by 90 d post partum (P < 0.03). Lasalocid did not affect postpartum interval or cumulative frequency of return to estrus (P > 0.10). Both once-daily suckling and alfaprostol were effective in increasing the numbers of animals inseminated by 90 d post partum. The once-daily suckling + alfaprostol treatment resulted in the shortest postpartum interval.

Oxytocin-induced prostaglandin release from perifused bovine caruncular and intercaruncular endometrial tissue on days 20, 30 and at first estrus postpartum.

Twenty-two multiparous Brahman x Hereford F1 cows were utilized to determine the effect of oxytocin (OT) on prostaglandin F2 alpha (PGF) release from caruncular and intercaruncular endometrial tissues and prostaglandin E2 (PGE) release from intercaruncular tissue. The previously gravid uterine horn was removed on d 20 postpartum (n = 7), on d 30 postpartum (n = 7) or the uterine horn ipsilateral to the dominant follicle was removed 12-18 h after onset of first behavioral estrus postpartum (ES; n = 8). Tissues (200 mg wet wt) were cultured in Nutrient Mixture F-10 medium in a perifusion system. The medium and tissues were aerated with 95% O2: 5% CO2 and temperatures were maintained at 39 degrees C. The flow rate was 100 microliters/min and fractions were collected at 20 min intervals for 400 min. After a 2 h settling phase, the tissues were challenged with 1, 2 or 4 micrograms [Asu1,6]-OT/ml of media for 1 h. Basal release of PGE and PGF on d 20 was greater than on d 30 and at ES (P less than .02) which were similar. All doses of OT increased PGE and PGF with both remaining elevated throughout the duration of the perifusion (P less than .008). However, there were no differences among doses. Release of PGE in response to OT on d 20 and 30, was higher than at ES (P less than .008). More PGF was released in response to OT from intercaruncular than caruncular tissue on d 20 (P less than .0001) and at ES (P less than .003). Release of PGF in response to OT on d 20 was higher (P less than .0001) than on d 30 and d 30 was higher than at ES (P less than .007). Basal and OT-induced release of PGE and PGF declined as day postpartum increased. We conclude that intercaruncular tissue released more PGF than caruncular tissue and both intercaruncular and caruncular tissue responded to OT with a sustained release of prostaglandins in a non-dose-dependent manner on d 20, 30 and at ES postpartum.

Concentrations of 13, 14-dihydro-15-keto-prostaglandin F2α, estradiol-17β and progesterone during the peripubertal period in heifers

Twenty prepubertal Holstein heifers were utilized to assess plasma 13, 14-dihydro-15-keto-prostaglandin F2α (PGFM), serum progesterone (P4) and estradiol-17β (E2) concentrations as well as the E2:P4 ratio during the onset of puberty in cattle. All animals were maintained as a group along with a sterile marker bull to assist in the detection of estrus. Upon detection of the first estrus (Day=O), daily blood samples were collected from a jugular vein until the heifers had completed 3 estrous cycles. The average body weight and age at first estrus were 247.6±4.8 kg and 304.0±7.5 days, respectively. Frequency of abnormal length estrous cycles was greater (P<0.02) during the first (40%) and second (35%) cycles than during the third estrous cycle (0%). All heifers had normal cycle lengths (18 to 24 days) by the third estrous cycle. Serum P4 was greater during the third cycle (P<0.05) from Day 10 to Day 4 before the next estrus compared with the same period of the first estrous cycle. Serum E2 did not peak until the day of estrus in the first cycle, whereas E2 reached a maximal level 2 days before estrus in the third estrous cycle. Serum E2 was higher (P<0.0001) 2 days before estrus in the third cycle than in the first estrous cycle. Plasma PGFM reached maximum concentrations 3 days before estrus in the third cycle compared with 1 day before estrus at the end of first estrous cycle. As estrus approached during the third cycle, PGFM rose 1 day before E2 rose and P4 declined, while the rise in PGFM and E2 occurred simultaneously, with P4 declining at the end of the first estrous cycle. During diestrus, the E2:P4 ratio was lower (P<0.07) in the third cycle than in the first, but it was higher (P<0.04) at estrus and 1 day before in the third estrous cycle. These data reveal a high incidence of abnormal length estrous cycles during the first two estrous cycles of the peripubertal period, and demonstrate anomalies in uterine and ovarian endocrine activity during the peripubertal period in cattle.

Plasma 13,14-dihydro-15-keto-prostaglandin F2α concentrations in prepubertal dairy heifers challenged with oxytocin

Twenty-nine prepubertal Holstein heifers were assigned by age to one of three age groups to determine if the prepubertal bovine uterus could respond to an oxytocin stimulus. Group 1 heifers were 6 to 7 months of age (AGE1; n = 11), group 2 heifers were 8 to 9 months of age (AGE2; n = 11) and group 3 heifers were 10 to 11 months of age (AGE3; n = 7). Blood samples were collected via an indwelling jugular catheter. Four samples were collected at 15-min intervals prior to oxytocin administration to determine basal 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) concentrations. Each heifer received 100 IU of oxytocin i.v., blood sampling continued at 5 min intervals for the next 30 min and for an additional 90 min at 15-min intervals. Heifers were considered responders to oxytocin if mean PGFM concentrations increased at least 1.5 times the SD of their basal PGFM concentration. Age of the heifer (P less than .0001) and responder status (P less than .05) affected plasma PGFM. Plasma PGFM was higher in AGE1 and AGE3 heifers than AGE2 (P less than .0001). The number of responders was greatest at AGE3 (P less than .03) with AGE1 and AGE2 being similar. Mean basal PGFM was lower (P less than .04) at AGE2 than AGE1 with AGE3 being intermediate. In addition, basal PGFM at AGE1 tended to be lower (P less than .08) in the responders than in the non-responders, while AGE2 basal PGFM did not differ between responders and non-responders (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)