LH surge in Nelore cows (Bos indicus), after induced estrus or after ovarian superestimulation

Considering that there is limited information about the preovulatory LH surge in Zebu cattle (Bos indicus), the purpose of the present work was to assess the LH surge in Nelore cows during the estrous cycle and after ovarian superestimulation of ovarian follicular development with FSH. This information is particularly important to improve superovulatory protocols associated with fixed-time artificial insemination. Nelore cows (n=12) had their estrus synchronized with an intravaginal device containing progesterone (CIDR-B) associated with estradiol benzoate administration (EB, 2.5 mg, i.m., Day 0). Eight days later all animals were treated with PGF2alpha (Day 8) in the morning (8:00 h) and at night, when CIDR devices were removed (20:00 h). Starting 38h after the first PGF2alpha injection, blood sampling and ovarian ultrasonography took place every 4h, during 37 consecutive hours. Frequent handling may have resulted in a stress-induced suppression of LH secretion resulting in only 3 of 12 cows having ovulations at 46.7+/-4.9 and 72.3+/-3.8 h, respectively, after removal of CIDR-B. Thirty days later, the same animals received the described hormonal treatment associated with FSH (Folltropin), total dose=200 mg) administered twice a day, during 4 consecutive days, starting on Day 5. Thirty-six hours after the first injection of PGF2alpha, to minimize stress, only seven blood samples were collected at 4h interval each, and ultrasonography was performed every 12 h until ovulation. In 11 of 12 cows (92%) the LH surge and ovulation were observed 34.6+/-1.6 and 59.5+/-1.9 h, respectively, after removal of progesterone source. The maximum values for LH in those animals were 19.0+/-2.6 ng/ml (mean+/-S.E.M.). It is concluded that, in Nelore cows submitted to a ovarian superstimulation protocol, the LH surge occurs approximately 35 h after removal of intravaginal device containing progesterone, and approximately 12h before the LH surge observed after an induced estrus without ovarian superstimulation.     

Ovarian follicular dynamics in Nelore breed (Bos indicus) cattle

The most common beef cattle raised in Brazil is the Nelore breed (Bos indicus). Information obtained by ultrasonography on follicular growth in Bos taurus cattle has been accumulating rapidly. However, there are few publications to date on follicular development in Bos indicus breeds. The follicular dynamics in Nelore heifers and cows during natural or prostaglandin (PG)-induced estrous cycle were studied. From the detection of estrus onward, all animals were examined daily by ultrasonography for one (n = 35) or two (n = 10) consecutive estrous cycles. The follicular dynamic in Nelore cattle was characterized by the predominance of 2 follicular waves in the cows (83.3%, n = 18, P < 0.05) and 3 waves in the heifers (64.7%, n = 16, P < 0.05). Most of the cattle observed over 2 consecutive estrous cycles presented the same pattern of follicular waves in the first and second cycle, and only 30% showed variation in the number of waves from one cycle to the other. Most of the follicular parameters analyzed were not affected by PG treatment or age but were altered by follicular waves. Consequently, data on cows and heifers were combined according to the number of follicular waves. The ovulatory follicle was larger than the other dominant follicles (P < 0.05), and the ovulatory wave was shorter than the preceding waves (P < 0.05). The interovulatory interval was longer in animals showing 3 waves than those exhibiting 2 waves (P < 0.05). Maximum diameter of the dominant follicle (around 11 mm) and of the corpus luteum (CL, approximately 17 mm) were smaller than those reported for European breeds. In conclusion, the results demonstrate that although the dominant follicle and corpus luteum are smaller than in European breeds, the follicular dynamics in Nelore cattle were similar to those observed in European breeds and were characterized by 2 or 3 follicular waves for cows and heifers, respectively, during the natural or prostaglandin-induced estrous cycle.     

Synchronization of estrus in beef heifers with a norgestomet implant and prostaglandin F2alpha

In a 5-year study (1973-1977), 281 cycling beef heifers were treated with a 7-day norgestomet (SC21009) ear implant and an intramuscular injection of prostaglandin F(2alpha) (PGF(2alpha)) at the time of implant removal or 24 hr before implant removal. Percentages of heifers in estrus by 36, 48, 60, 72, and 120 hr after implant removal were 32.4, 52.7, 71.6, 80.1, and 93.2, respectively. Onset of estrus occurred an average of 49.8 +/- 4.7 hr after treatment. Percentages of heifers in estrus 36 hr after treatment were 5.7 and 51.7 for those with a corpus luteum and those without a corpus luteum (or determined regressing by palpation) at implant removal, respectively. When PGF(2alpha) was injected 24 hr before implant removal, 55% of the heifers were in estrus by 36 hr after implant removal compared to 30% when PGF(2alpha) was injected at the time of implant removal; however, by 60 hr after implant removal the difference was 76% vs. 71%. First-service conception rates for synchronized and nonsynchronized heifers were 62.2% and 59.6%, respectively. During 1976 and 1977 heifers were checked for estrus every 4 hr and inseminated 2, 6, 10, 14, 18, 22, 26, or 30 hr after first detected to be in standing estrus. Conception rate was not significantly affected by time of insemination but tended to be higher for heifers bred 26 and 30 hr after first being detected in standing estrus (78.9% and 70.0% vs. average 59.2%). Treatment with a 7-day norgestomet implant plus a single injection of PGF(2alpha) 24 hr before or at implant removal appears to be a practical technique for synchronizing estrus in cycling heifers without affecting conception.     

Synchronization of estrus in beef cows and heifers with prostaglandin F(2alpha) and estradiol benzoate

An experiment was conducted to study an estrous synchronization regimen that involved the use of prostaglandin F(2alpha) (PGF(2alpha)) alone or in combination with estradiol benzoate (EB) and appointment breeding. Fifty-three registered Angus yearling heifers and 167 registered Angus cows (3 to 9 yr of age) were given two injections of PGF(2alpha) 11 d apart. Forty-eight hours after the second injection of PGF(2alpha') a random sample consisting of 117 cows and heifers was injected with EB in sesame seed oil. All females in the herd were artificially inseminated 80 h after the second injection of PGF(2alpha). Nearly equal percentages (25.1 vs 25.6%; P = 0.93) of treated (EB) and control (no EB) females conceived at the appointment breeding. Use of EB tended to reduce (P = 0.06) natural service conception rate (83.4 vs 93.1% for EB and control groups, respectively). Estrous synchronization treatment did not affect interval from Day 1 of the breeding season to calving.     

Conception rates in repeat-breeders and dairy cattle with unobserved estrus after prostaglandin F(2) alpha and gonadotropin-releasing hormone

In Experiment 1, cows with a history of at least two previous unsuccessful inseminations were allocated to four groups. At the repeated estrus (third or greater service), some of the cows were inseminated according to the a.m.-p.m. rule (Controls, n = 83), or received i.m. 100 mug gonadotropin-releasing hormone (GnRH, n = 32) within 30 sec after insemination. Ovaries of the remaining cows to be treated were palpated during the anticipated ensuing luteal phase to determine the presence of a corpus luteum. Cows found to have luteal tissue received i.m. 25 mg prostaglandin F(2)-alpha (PGF(2)-alpha) and were inseminated after detected estrus or at 72 and 96 h after PGF(2)-alpha in the absence of estrus. Cows given PGF(2)-alpha either received no further treatment (PGF(2)-alpha, n = 40) or were given i.m. 100 mug GnRH (PGF(2)-alpha + GnRH, n = 29) after insemination or at 72 h after PGF(2)-alpha in the absence of estrus. Conception rate of control cows (39%) was similar to that of cows given PGF(2)-alpha (40%) or PGF(2)-alpha + GnRH (43%), but it tended to be lower (P = 0.13) than that of cows given only GnRH at insemination (54%). In Experiment 2, cows with unobserved estrus and diagnosed not pregnant (palpation) were palpated to detect a corpus luteum. Cows with luteal tissue received i.m. PGF(2)-alpha (n = 52) or PGF(2)-alpha + GnRH (n = 45) and were inseminated as described above. Conception rates were similar (39% vs 33%, respectively). In Experiment 3, cows in a large commercial dairy with (n = 93) or without (n = 420) previous reproductive problems were given i.m. 100 mug GnRH after insemination (n = 169) or were left untreated (n = 344) at repeat services (third and fourth services). Treatment with GnRH improved (P < 0.05) conception in normal (47% vs 36%) and abnormal (25% vs 12%) repeat-breeding cows. Treatment with PGF(2)-alpha alone or in conjunction with GnRH failed to further improve conception rates and only delayed intervals to rebreeding when administered during the luteal phase after the repeated estrus. The use of GnRH failed to reduce intervals from treatment to insemination or improve conception in cows with unobserved estrus compared to treatment with PGF(2)-alpha alone.     

Induction of estrus in cattle by intraovarian injection of prostaglandin F2alpha

An effective, reduced dosage (1 10 to 1 20 the systemic dose) method for administering prostaglandin F(2alpha) in heifers to induce estrus is presented in this study. The PGF(2alpha) was injected intraovarially in five heifers at a dose of 2 mg and in another five heifers at a dose of 1 mg. Five additional heifers were injected intraovarially with 0.5 ml of distilled water and served as the controls. Regression of the corpus luteum (CL) occurred in all PGF(2alpha)-treated heifers resulting in marked decline of the peripheral levels of progesterone 24 h after treatment. Estrus was expressed 1 to 3 d later. Regression of the CL, estrus, and decline in the peripheral levels of progesterone were not observed in the control heifers. Conception rates in the heifers given either 2 mg and 1 mg PGF(2alpha) were 60 and 100%, respectively. Seven calves were born at the end of the normal gestation period while one calf was aborted.     

Association between MUC1 gene polymorphism and expected progeny differences in Nelore cattle (Bos primigenius indicus)

MUC1 is a heavily glycosylated mammalian transmembrane protein expressed by mucosal secretory tissues for both protection against microbial infection and lubrication. An important characteristic of MUC1 is its variable number of tandem repeats (VNTR) containing several sites for O-glycosylation. VNTR length has been associated with many human diseases and with certain economically important traits in domestic ruminants. The aim of the present study was to correlate the length of MUC1 gene VNTR with expected progeny differences (EPDs) obtained for growth, fertility and carcass traits. Five alleles were identified, with alleles containing short VNTRs being more frequent than those with long, thereby demonstrating that Brazilian Nelore cattle are characterized by high frequencies in short MUC1 VNTRs. Statistical analyses revealed there to be no significant association between VNTR length and EPDs for weight at 120 days (W(120) ), scrotal circumference at 365 (SC (365) ) and 450 (SC (450) ) days, age at first calving (AFC), and rib eye area (REA).     

Plasma concentration of progesterone during normal estrous cycles and following prostaglandin F(2alpha) treatment of Bos indicus and tropic-adapted Bos taurus heifers

The introduction of the use of prostaglandin F(2alpha) (PGF(2alpha)) to synchronize estrus in cattle adapted to the tropics suggests a need to investigate the endocrine response to this treatment. Progesterone (P) concentrations in blood plasma of Bos indicus and tropic-adapted Bos taurus heifers during normal estrous cycles and following estrus synchronization were compared. After PGF(2alpha) administration, the heifers were divided into two groups on the basis of response to treatment. Mean P levels in heifers showing estrus after the first injection ranged from 1.0-3.0 ng/ml, decreasing to 0.2-0.4 ng/ml 24 to 48 hr after treatment. The second group exhibited estrus only after the second PGF(2alpha) injection and had low P (0.2-0.9 ng/ml) in plasma before the first injection. Mean peak P levels in both groups 8 to 12 d after the first injection in the periestrous period were not different from values in the same heifers at similar periods of the preceding control estrous cycle. Neither the tropical location nor breed affected the luteolytic effect of PGF(2alpha).     

Fertility trial in Zebu cattle after a natural or controlled estrus with prostaglandin F2 Alpha, comparing natural mating with artificial insemination

With the object of comparing reproductive efficiency obtained by natural mating and by artificial insemination (AI), not only following a natural estrus but also after an induced estrus with PGF2Alpha in Zebu cattle in the tropics, 244 adult cows were divided into 4 groups. Group I (N = 69) and Group III (n = 62) were injected with 25 mg of PGF2Alpha when a functional CL was found on rectal examination. Group I was inseminated and group III was served by natural mating, both groups within five days after injection. Groups II (n = 57) and IV (n = 56) were left untreated, group II being AI and group IV ran with a fertile bull for 22 days. Estrus detection was carried out only in the injected groups (I and III) for 15 minutes every three hours between 0600 and 1800. All information was analyzed by linear trigonometric models. The onset of estrus occurred on average 68.7 h after injection in group I and 59.5 h in group III. However only 46.3% and 54.8% of animals were detected in estrus in group I and III respectively, the difference being significant (P < 0.10). Conception rates were 18.6%, 29.8%, 19.3% and 33.9% for groups I, II, III, and IV respectively. A significant difference (P < 0.10) existed between the injected groups and the untreated ones.     

Heterologous expression and characterization of Indian Sahiwal cattle (Bos indicus) alpha inhibin

Inhibin is a non-steroidal glycoprotein hormone of gonadal origin with major action as negative feedback control of the production of FSH by the anterior pituitary gland. The physiological role of inhibin has led to the development of inhibin immunogens for fertility enhancement in farm animals. It is envisaged that a reduction of endogenous inhibin secretion would increase FSH concentrations and thus offers a potential for increasing the number of ovulatory follicles in the ovary. The present work was carried out to produce recombinant bovine (Indian Sahiwal Cattle; Bos indicus) alpha inhibin (bINH-α) in E. coli by optimizing its expression and purification in biologically active form and to study its immunological characterization. A bacterial protein expression vector system based on the phage T(5) promoter was used. The bINH-α encoding gene was successfully cloned and expressed in E. coli and the purified recombinant bINH-α was characterized. Recombinant bINH-α (25?μg?mL(-1)) immunized guinea pigs had a significant increase in litter size compared to the control group. These results indicate a role for recombinant bINH-α as a fecundity vaccine to enhance the ovulation rate and litter size in animals.     

Morphological characterization of follicle deviation in Nelore (Bos indicus) heifers and cows

Follicle diameter deviation is defined as the beginning of the differential change in growth rates between the largest and next largest follicles subsequent to wave emergence and is considered a key component of follicle selection. Follicle selection has been extensively studied in European breeds of cattle (Bos taurus) but has not been critically studied in Zebu breeds (Bos indicus). The objectives of the present study were to determine and compare the morphological characteristics of deviation associated with the first post-ovulatory wave (Wave 1) of the estrous cycle in Nelore heifers (n=8) and nonlactating cows (n=11). Beginning on the day of ovulation (day 0), the three largest follicles (F1-F3, respectively) were individually tracked every 12 h for 6d using transrectal ultrasonography. In individual animals, deviation was determined graphically using visual inspection of the diameter profiles of F1, F2 and sometimes F3 (observed deviation) and mathematically using segmented regression analysis of the diameter differences between F1 and F2 or sometimes F3 (calculated deviation). Mean day of emergence of Wave 1 when F1 reached >3 mm (approximately 1 d after ovulation) and growth rate of F1 during deviation (approximately 1.4 mm/d) were not significantly different between heifers and cows. The results of determining the beginning of deviation within heifers and cows using the observed and calculated methods were not significantly different. Averaged over both methods, diameter deviation occurred 2.8 d after ovulation when F1 reached 5.7 mm in heifers, and 2.4 d after ovulation when F1 reached 6.1 mm in cows. In conclusion, the emergence of Wave 1 and growth rates and diameters of the future dominant follicles at the beginning of deviation were similar in Nelore heifers and nonlactating cows, regardless of the methods used to determine deviation. Relative to Holstein cattle, emergence of Wave 1 appeared to occur about 1 d later and diameter of the future dominant follicle at the beginning of deviation was about 2 mm smaller in Nelore.     

Synchronization of ovulation in beef cows (Bos indicus) using GnRH, PGF2alpha and estradiol benzoate

The objective of this study was to evaluate protocols for synchronizing ovulation in beef cattle. In Experiment 1, Nelore cows (Bos indicus) at random stages of the estrous cycle were assigned to 1 of the following treatments: Group GP controls (nonlactating, n=7) received GnRH agonist (Day 0) and PGF2alpha (Day 7); while Groups GPG (nonlactating, n=8) and GPG-L (lactating, n=9) cows were given GnRH (Day 0), PGF2alpha (Day 7) and GnRH again (Day 8, 30 h after PGF2alpha). A new follicular wave was observed 1.79+/-0.34 d after GnRH in 19/24 cows. After PGF2alpha, ovulation occurred in 19/24 cows (6/7 GP, 6/8 GPG, 7/9 GPG-L). Most cows (83.3%) exhibited a dominant follicle just before PGF2alpha, and 17/19 ovulatory follicles were from a new follicular wave. There was a more precise synchrony of ovulation (within 12 h) in cows that received a second dose of GnRH (GPG and GPG-L) than controls (GP, ovulation within 48 h; P<0.01). In Experiment 2, lactating Nelore cows with a visible corpus luteum (CL) by ultrasonography were allocated to 2 treatments: Group GPE (n=10) received GnRH agonist (Day 0), PGF2alpha (Day 7) and estradiol benzoate (EB; Day 8, 24 h after PGF2alpha); while Group EPE (n=11), received EB (Day 0), PGF2alpha (Day 9) and EB (Day 10, 24 h after PGF2alpha). Emergence of a new follicular wave was observed 1.6+/-0.31 d after GnRH (Group GPE). After EB injection (Day 8) ovulation was observed at 45.38+/-2.03 h in 7/10 cows within 12 h. In Group EPE the emergence of a new follicular wave was observed later (4.36+/-0.31 d) than in Group GEP (1.6+/-0.31 d; P<0.001). After the second EB injection (Day 10) ovulation was observed at 44.16+/-2.21 h within 12 (7/11 cows) or 18 h (8/11 cows). All 3 treatments were effective in synchronizing ovulation in beef cows. However, GPE and, particularly, EPE treatments offer a promising alternative to the GPG protocol in timed artificial insemination of beef cattle, due to the low cost of EB compared with GnRH agonists.     

Synchronization of estrus in yearling beef heifers with melengestrol acetate and prostaglandin F(2alpha)

This study was designed to test the efficacy of melengestrol acetate (MGA) in combination with prostaglandin F(2alpha) (PGF(2alpha)) in synchronizing estrus in cyclic and noncyclic heifers. One hundred thirty-one cyclic and prepubertal crossbred heifers were randomly assigned to three treatment groups: Controls (n = 43); MGA (0.5 mg/d for 7 d) and PGF(2alpha) (25 mg i.m. on Day 7; n = 44); and PGF(2alpha) (25 mg i.m. on Day 7; n = 44). Observations for estrus were made at 6-n intervals throughout the 7-d treatment period followed by a 34-d artificial insemination breeding season. A greater percentage (P < 0.05) of MGA-PGF(2alpha) noncyclic heifers showed behavioral estrus (91%) than did Control (67%) or PGF(2alpha) heifers (61%) during the 34-d artificial insemination period. There was no difference (P > 0.05) between synchronization rates of the MGA-PGF(2alpha) heifers and PGF(2alpha) heifers 7 d after PGF(2alpha) administration. The percentage of control animals in estrus during the first 25 d of the breeding season did non differ from the synchronized rates of MGA-PGF(2alpha) and PGF(2alpha) heifers (P > 0.05). Conception rates (heifers pregnant/heifers inseminated) did not differ (P > 0.05) for cyclic or prepubertal heifers among Control, MGA-PGF(2alpha) or PGF(2alpha) heifers. Though conception rates did not differ, there was a trend toward lowered conception rates in MGA-PGF(2alpha) heifers.     

Synchronization of estrus in early diestral dairy heifers with Prostaglandin F(2)alpha and estradiol benzoate

Following observation of estrus, 134 Holstein heifers were given injections of Prostaglandin F(2)alpha (PGF(2)alpha) between Days 5 and 10 of their cycle (estrus = Day 0). They were then randomly assigned to either a group receiving 400 mug of estradiol benzoate (E(2)B) 40 h or maintained as controls. Heifers observed in estrus within 120 h of PGF(2)alpha administration were inseminated (approximately 12 h after initial observation of estrus). Blood samples for progesterone determination were drawn from the coccygeal vein on Days 15 and 21 after insemination. Pregnancy was confirmed by palpation per rectum between Days 5.0 and 60 post insemination. When control and treated heifers were compared it was found that a higher percentage of heifers treated with E(2)B exhibited estrus after PGF(2)alpha, but there had been no effect on subsequent progesterone concentrations or pregnancy rates.     

Doses of prostaglandin F(2)alpha effective for induction of estrus in goats

A total of 11 cycling does weighing between 24 and 50 kg were injected with varying dosages of prostaglandin F(2)alpha (PGF(2)alpha) between 7 and 10 days into each estrous cycle. Five injections each of 1.25, 2.5, 5.0, or 7.5 mg PGF(2)alpha were alternated with five injections of 1.0 ml saline. Saline treated does served as controls. All does were teased twice daily with a buck and observed for signs of estrus for 5 days post-injection. Daily systemic concentrations of progesterone (P(4)) were determined by radioimmunoassay. The mean (+/- S.E.) hours from injection to estrus was 47 +/- 3.3, 42 +/- 4.3, 44 +/- 8.5, and 43 +/- 5.5 for does receiving 1.25, 2.5, 5.0, and 7.5 mg PGF(2)alpha, respectively. None of the does receiving saline exhibited estrus in the 5-day post-injection observation period. Mean (+/- S.E.) concentrations of systemic P(4) in all does on the day of injection was 4.22 +/- 0.45 ng/ml. Concentrations 24 hours post-injection were 0.21 +/- 0.02, 0.15 +/- 0.05, 0.17 +/- 0.04, 0.16 +/- 0.04, and 4.5 +/- 1.36 ng/ml for does receiving 1.25, 2.5, 5.0, and 7.5 mg PGF(2)alpha, and 1.0 ml saline, respectively. The results suggested that 1.25 mg PGF(2)alpha was effective for induction of estrus in the cycling goat.     

The effect of prostaglandin F2 alpha treatments in superovulated cattle on estrus response and embryo production

Approximately 10% of cows in a commercial embryo transfer center that were superovulated for embryo production did not show estrus at the right time and therefore did not produce embryos. This problem was investigated by studying the effects of prostaglandin F2 alpha (PGF) treatment regime and dose rate on the superovulatory process. The cows in estrus following superovulation (96% vs. 86.6%), the % cleaved (62% vs. 51%) and the transferable embryo production (5.4 vs. 3.8) was increased when 50 mg. PGF was administered in three divided doses rather than in two doses. In a second experiment doses of 15 mg., 30 mg. and 45 mg. (each administered as three divided doses 6 hours apart) all produced the same estrus response (95.6, 97.9 and 95%) and production of transferable embryos (4.9, 3.6 and 4.6). Three-times-a-day PGF reduced the time interval from treatment to the onset of estrus, but the time from PGF to estrus was not correlated with embryo production.     

Estrous response and pregnancy rates following calf removal in beef cows treated with prostaglandin F(2)alpha

Five hundred fifty-four suckled beef cows in three herds were allotted within postpartum interval to one of four treatments. All cows received two injections of prostaglandin F(2)alpha (PGF(2)alpha) 11 days apart. Treatment I served as a control. Calves were removed for 48 hr following the first injection of PGF(2)alpha in treatment II. Calves were removed similarly after the second injection of PGF(2)alpha in treatment III and after both injections of PGF(2)alpha in treatment IV. Pregnancy rates at the synchronized service, by 24 days and by 45 days of breeding were not (P>0.05) affected by treatment. Similarly, the treatments had no significant (P>0.05) effect on percentage of animals exhibiting estrus following the first and second injections of PGF(2)alpha.     

Induction of parturition in swine with prostaglandin F(2)alpha, estradiol benzoate and oxytocin

Pregnant sows and gilts were administered either 0, 2.5, 5, 10 or 20 mg prostaglandin F(2)alpha (PGF(2)alpha) intramuscularly on Day 112 or 113 of gestation at 0800 h in an effort to induce parturition. The average interval from PGF(2)alpha injection to farrowing was 55.1 +/- 5.7, 29.4 +/- 3.1, 32.1 +/- 4.6, 27.8 +/- 1.8 and 26.9 +/- 1.1 h for 0, 2.5, 5, 10 and 20 mg, respectively. All PGF(2)alpha treatments increased (P < 0.01) over controls the number of sows farrowing 23 to 33 h after injection. The average gestation length was significantly shorter in treated gilts; however, no detrimental effect on pig performance or pig survivability was observed. A second trial evaluated the effect of a 10-mg dose of PGF(2)alpha on the induction of parturition in sows in order to obtain a majority of sows farrowing within normal working hours (0700 to 1700 h). The interval from injection to farrowing was decreased (P < 0.05) by PGF(2)alpha treatment (66.2 +/- 5.3 vs 28.1 +/- 2.2 h). Fifty-seven percent (P < 0.05) of PGF(2)alpha-treated sows farrowed between 0700 and 1700 h as compared to 13.6% for control sows. A third trial was conducted to examine a sequential treatment of PGF(2)alpha and oxytocin to control the time of parturition more precisely. Sows receiving only 10 mg of PGF(2)alpha farrowed on an average 31.1 +/- 1.4 h after injection. The injection of 40 IU oxytocin 24 to 28 h after PGF(2)alpha decreased (P < 0.05) the interval from PGF(2)alpha to farrowing (28.1 +/- 0.9 h). The addition of oxytocin increased (P < 0.05) the number of sows farrowing within 3 h of injection (33 vs 86% for PGF(2)alpha and PGF(2)alpha + oxytocin treatments, respectively). A fourth trial was designed to determine if the addition of exogenous estradiol benzoate (EB) to a sequential treatment of PGF(2)alpha and oxytocin would improve the predictability and synchronization of the induced parturition. Sows were assigned to receive either saline, 10 mg PGF(2)alpha + 40 IU oxytocin or 10 mg PGF(2)alpha + 5 mg EB + 40 IU oxytocin. The addition of EB reduced (P < 0.01) the variance in the interval from oxytocin to farrowing and added precision to the predicted time of induced parturition.     

Identical marker alleles in Podolic cattle (Bos taurus) and Indian zebu (Bos indicus)

In the context of biochemical marker research and in order to add new information on native breeds, the present work focuses on a local Southern Italy cattle, namely Italian Podolic. We provide the complete structural characterisation of alpha-lactalbumins and beta-globin chains isolated from Podolic cattle (Bos taurus). Given the unavailability of the complete sequence for alpha-lactalbumin A of taurine cattle in the literature, we intended to check its structure in order to ascertain the absence of any possible silent mutation. Screening the Podolic cattle, we found a new beta-globin variant not detectable by conventional methods. The presence of such a new variant might be helpful in the study of the Podolic population genetic structure and for a better knowledge of the gene pool per se, and in comparison with the other breeds. Structural analyses showed that the new beta-globin Podolic variant exhibited the same sequence as beta-globin Azebu. The alpha-lactalbumin A was the same as that isolated from zebu cattle (Bos indicus). The results are discussed in relation to the possible involvement of the two markers in the debate on the origin of the Podolic breed.     

Control of estrus in bos indicus and bos taurus heifers with prostaglandin F2 alpha

Lutalyse^*, a commercial preparation of prostaglandin F_2a was injected intramuscularly into nulliparous heifers of the German Brown, Holstein—Friesian and White Fulani cattle. Two injections, 25mg/animal each time, were given at intervals of 12 days. All the heifers were inseminated 80h after the second injection. Heifers that were cycling responded well to the treatment and had a higher conception rate than the controls.