Characterization and proteolytic activity of a cathepsin L-like polypeptide in endometrium and uterine flushings of cycling, pregnant and steroid-treated ovariectomized gilts.

Cathepsin L has been proposed to be involved with the endothelial-chorial type of placentation in the cat. Little information concerning the presence and secretion of cathepsin L is available for a species with noninvasive epitheliochorial placentation such as the pig. Cathepsin L activity in uterine flushings and endometrium from gilts during different days of the oestrous cycle and early pregnancy was analysed through specific substrate metabolism and Western blot analyses with antiserum against cat endometrial cathepsin L. This antiserum was utilized to determine the cellular localization of the enzyme within porcine endometrium. Cathepsin L activity within uterine flushings was elevated on Day 15 of the oestrous cycle and early pregnancy, with activity declining on Day 18. Cat cathepsin L antiserum cross-reacted with a group of 46, 40 and 38 kDa uterine proteins and detected a product within the surface and glandular epithelium of the endometrium. The appearance of the 40 kDa protein was first detected on Day 10 of the oestrous cycle with the 38 kDa proteins appearing on Day 15 and 18 of pregnancy. The 40 and 38 kDa uterine proteins appear to be steroid regulated as 12 days of progesterone administration is necessary to detect the proteins and cathepsin L activity.

Uterine cellular changes in 2',5'-oligoadenylate synthetase during the bovine estrous cycle and early pregnancy.

The signal for maternal recognition of pregnancy in cattle is bovine trophoblast protein-1 (bTP-1), a Type I trophoblast interferon. One of the many functions of interferons is the induction of the 2',5'-oligoadenylate (2-5[A]) system, which is involved in cell division and selective degradation of mRNA. The present study focused on the cellular changes of 2-5(A) synthetase in bovine endometrium during the estrous cycle and early pregnancy. Ability of recombinant bTP-1 to stimulate activity of the enzyme in uterine cells throughout the estrous cycle was also evaluated in vitro. Surface epithelium, glandular epithelium, and stroma were enzymatically separated in cows on Day 5, 10, 15, or 18 postestrus and on Day 15 or 18 of pregnancy. Cell samples were lysed and frozen for determination of the endogenous cellular content of 2-5(A) synthetase. Additional cells obtained during the estrous cycle were cultured and treated with increasing doses of recombinant bovine interferon alpha (rbIFN-alpha) or recombinant bTP-1 (rbTP-1). During the estrous cycle, 2-5(A) synthetase was greatest on Day 5 and declined approximately 10-fold by Day 15 (p < 0.01). Cellular content of 2-5(A) synthetase was similar among all three endometrial cell types. In the gravid horn of pregnant animals, presence of a conceptus significantly increased (p < 0.01) 2-5(A) synthetase in all endometrial cell types compared to levels on Days 15 and 18 of the estrous cycle. On Day 18, levels of 2-5(A) synthetase were 30-fold greater (p < 0.01) in epithelium (surface and glandular) from pregnant cows compared to that from cyclic cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between ovulation rate and concentrations of insulin-like growth factor-1 in plasma during the oestrous cycle in various genotypes of sheep.

To determine whether concentrations of insulin-like growth factor-1 (IGF-1) in blood of ewes change during the oestrous cycle, oestrus was synchronized for 45 ewe lambs from four genotypes (Finn ewes selected for low ovulation rate (LF), Finn ewes selected for high ovulation rate (HF), unselected control Finn ewes (CF) and Cambridge ewes (CAM)) using progestin sponges and blood samples were taken every day from day 0 (day 0 = day of progestin sponge removal) to day 5, and then every second or third day until 3 days after the next oestrus. Ovulation rates (determined via laparoscopy) following the first oestrus were 1.3, 3.3, 2.0 and 2.1 for LF, HF, CF and CAM groups, respectively. In a second experiment, jugular and utero-ovarian venous blood samples were collected simultaneously from seven Rambouillet crossbred ewes during the mid-luteal phase of an oestrous cycle to determine whether the ovary is a major source of blood IGF-1. In the first experiment, plasma IGF-1 concentrations increased (P < 0.05) between days 0 and 3, and then decreased (P < 0.05) between days 4 and 8 in all groups. IGF-1 concentrations increased again at the subsequent oestrus. There was no significant difference in plasma IGF-1 between HF and LF ewe lambs. Overall, plasma IGF-1 was lowest (P < 0.05) in CAM and highest in CF ewe lambs at all stages. Plasma IGF-1-binding protein activity did not vary with stage of cycle or differ (P > 0.10) among genotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of initial restraint, weaning, and transport stress on baseline and ACTH-stimulated cortisol responses in beef calves of different genotypes.

The productivity and well-being of animals can be substantially affected by stress. This is particularly true in the case of beef calves that are subjected to a multitude of stressors over a short period during the first year of life. Perhaps the most often studied stress-responsive variable has been blood corticosteroid concentrations. Factors such as age, gender, genetics, and degree of prior experience, can influence how an animal perceives and responds to a given stressor. Few studies have tried to control these variables, and accordingly, many conflicting results have been published regarding the impact of various stressors on cortisol response. We measured baseline plasma cortisol concentration over a 44-day study in Bos indicus and Bos taurus calves. Plasma cortisol values in Bos indicus calves were higher (32.60 +/- 0.66 ng/ml) than values in calves of Bos taurus (25.81 +/- 0.76) breeding. A precipitous decrease in cortisol concentration was observed 7 days after transport stress in all calves. Baseline cortisol concentration did not provide any indication of the intensity of the various stressors. However, significant differences were readily observed after ACTH administration. On the basis of cortisol secretion, stresses of transport and weaning were similar and were the most stressful to calves, regardless of genotype.

Endocrine events associated with endometrial function and conceptus development in cattle.

Regulation and timing of luteolysis during the bovine oestrous cycle is controlled by the initiation and length of progesterone stimulation. Results have demonstrated that early administration of progesterone shortens the interoestrous interval in the ewe and cow, and removal of progesterone stimulation through a progesterone receptor antagonist delays luteolysis in sheep. Current data suggest that down-regulation of progesterone receptors in the uterine epithelium may initiate events involved in the synthesis and release of prostaglandin F2 alpha (PGF2 alpha) for luteolysis. Progesterone is also involved in the stimulation of the uterine secretions that regulate conceptus growth and the release of the bovine trophoblast protein-1 (bTP-1) necessary for inhibiting endometrial PGF2 alpha release. Conceptus secretion of bTP-1, a Type I trophoblast interferon, increases the concentration of the cellular enzyme 2',5'-oligoadenylate synthetase within the endometrium. The biological role of 2',5'-oligoadenylate synthetase in the establishment of pregnancy is discussed.

Expression of messenger RNAs encoding insulin-like growth factor-I, -II, and insulin-like growth factor binding protein-2 in bovine endometrium during the estrous cycle and early pregnancy.

The present study characterized the changes in concentrations of insulin-like growth factors-I and -II (IGF-I and IGF-II) in uterine luminal flushings, and the endometrial mRNA levels of IGF-I, IGF-II, and IGF binding protein-2 (IGFBP-2) obtained from Days 0 through 18 of the bovine estrous cycle and early pregnancy. Concentrations of IGF-I and IGF-II in uterine flushings were greater on Days 0 and 5 than on other days of the estrous cycle or pregnancy. Northern blot analysis of endometrial poly(A)+ RNA revealed two major transcripts of 7.5 and 1.0 Kb for IGF-I, one major transcript of 4.0 Kb for IGF-II, and one major transcript of 1.3 Kb for IGFBP-2. RNA dot-blot analyses indicated that endometrial expression of IGF-I mRNA was unaffected by day of the estrous cycle or status (cyclic vs. pregnancy). However, endometrial expression of IGF-II mRNA was greater in pregnant than in cyclic endometrium on Days 15 and 18. Levels of endometrial IGFBP-2 mRNA increased (p less than 0.05) between Days 10 and 18 of the estrous cycle and early pregnancy. Results suggest that the presence of the bovine conceptus has a stimulatory effect on endometrial expression levels of IGF-II, whereas progesterone appears to be involved with enhancement of IGFBP-2.

Effect of asynchronous transfer and oestrogen administration on survival and development of porcine embryos.

Results indicate that recovery of embryos on Days 11 and 13 of pregnancy was reduced for Day 5 embryos transferred to recipients on Day 6 of their oestrous cycle and was greatly reduced when embryos were transferred to recipients on Day 7 of the cycle (P less than 0.01). Administration of oestradiol-17 beta on Day 11 of the recipient's cycle did not appear to affect embryo development on Day 13. Day 6 embryos transferred to recipients on Day 8 of the oestrous cycle deteriorated rapidly within 24 h of transfer; there was no recovery of embryos from the uterus after 36 h. Treatment of pregnant gilts with 1 mg oestradiol-17 beta (i.v.) on Day 10.5 resulted in total embryonic loss by Day 23, but pregnancy rates of gilts treated with oestradiol-17 beta on Day 12 were similar to those of vehicle-treated gilts (60.6 vs. 71.4%).

Effect of histamine-H2 receptor antagonists on serum gastrin levels in swine.

We evaluated the serum gastrin response to feeding and increasing age in swine. In addition, metiamide (SKF 92058) and the more potent H2 receptor antagonist, SKF 93479, were administered in the feed after which, serum was evaluated for changes in gastrin. We also measured metiamide clearance from the blood after an intravenous bolus infusion of the drug. Gastrin levels measured 15 minutes after feeding decreased as a consequence of increasing animal age (P less than 0.0001). Postprandial serum gastrin levels increased to maximal levels by approximately 60 minutes postfeeding and declined slowly during the subsequent 60 minutes. There were no differences in the postprandial gastrin responses during the morning or evening feeding, although evening levels tended to be higher (P greater than 0.10). Metiamide fed at 50 or 500 mg/kg of feed caused a significant increase (P less than 0.02) in gastrin 15 minutes postfeeding (31.0 and 39.7%, respectively). Metiamide in serum decreased to undetectable levels by 120 minutes after an intravenous infusion of 10 mg/kg in two pigs. Metiamide fed at 162 mg/kg and SKF 93479 fed at 54 mg/kg of ration resulted in similar elevations in gastrin, indicating that SKF 93479 was as potent as metiamide in eliciting a gastrin response by using only one-third of the concentration in the feed. These results provide evidence for similarities between swine and humans in serum gastrin responses.

Survival of bovine embryos transferred to progesterone-treated asynchronous recipients.

Treatment of recipient cows with 100 mg of progesterone daily from Days 1 to 5 of the oestrous cycle increased plasma progesterone compared with vehicle-treated recipients. Embryo transfer to progesterone-treated recipients which showed oestrus 72 h after the donor cows resulted in pregnancy rates at Day 35 similar to those of synchronous (+/- 12 h) recipients (42 vs. 50%). Only 1 of 22 (4.8%) asynchronous (-72 h) vehicle-treated recipients established pregnancy. Similar treatments of cyclic cows with progesterone shortened (P less than 0.01) the interoestrous interval by 3.2 days. When assessed on Day 7 of pregnancy, administration of progesterone to superovulated donor cows on Days 1-4 of pregnancy did not affect early embryo development compared with superovulated cows treated with vehicle alone. Plasma progesterone increased rapidly in superovulated cows compared with cows during the oestrous cycle. The results indicate that administration of progesterone early in the oestrous cycle of the recipient can effectively advance uterine receptivity for the transfer of older asynchronous embryos.

Endometrial surface and secretory alterations associated with embryonic mortality in gilts administered estradiol valerate on days 9 and 10 of gestation.

Administration of estrogen to gilts on Days 9 and 10 of pregnancy results in total embryonic loss by Day 18. The present study examined changes in the uterine endometrial surface and secretion during conceptus attachment in control and estrogen-treated (Days 9 and 10) pregnant gilts. Gilts were unilaterally hysterectomized on either Days 12 and 14 or Days 16 and 18 of gestation. Uterine horns were flushed with saline and conceptuses were evaluated. Intact conceptuses were recovered from all control gilts, whereas estrogen-treated gilts contained normal intact conceptuses only on Day 12 of gestation. Antiviral activity, which reflects conceptus viability, was reduced (p less than 0.01) in uterine flushings after Day 14 in estrogen-treated gilts. Culture of endometrial explants with [3H]glucosamine revealed several glycoproteins that are synthesized during the period of conceptus attachment; however, no difference in glycoprotein synthesis between treatment groups was detected by analysis with two-dimensional PAGE and fluorography. Analyses of the uterine epithelium by scanning and transmission electron microscopy demonstrated that estrogen administration caused an alteration in the uterine surface, a thinning of the uterine epithelial glycocalyx, and a reduction of cationic ferritin binding to the microvilli of the uterine epithelium. Results indicate that conceptus mortality after early administration of estrogen is associated with alterations in the uterine endometrial surface during the period of conceptus attachment in the pig.

Expression of antiviral activity and induction of 2',5'-oligoadenylate synthetase by conceptus secretory proteins enriched in bovine trophoblast protein-1.

Establishment of pregnancy in cattle has been proposed to depend on production of a conceptus protein, bovine trophoblast protein-1 (bTP-1), which has a high degree of sequence homology with bovine interferon-alpha (bIFN-alpha), especially the alpha II subfamily. A preparation of bovine conceptus secretory proteins enriched for bTP-1 has antiviral and physico-chemical properties similar to other bIFN-alpha. Antiviral activity is initially detectable in uterine flushings on Day 14 of pregnancy, when the conceptus measures 4-5 mm in length, and increases as the conceptus elongates through Day 18. Day 17 conceptuses produce more than 10(6) U antiviral activity during 24 h of culture. All IFNs induce the enzyme 2',5'-oligoadenylate synthetase, which catalyzes production of 2',5'-oligo(A), which in turn is involved in antiviral and growth inhibitory effects of IFNs. This enzyme activity is induced in Madin-Darby bovine kidney cells by the partially purified bTP-1 preparation similarly to IFN-alpha, -beta, and -gamma. Likewise, the partially purified bTP-1 and bIFN-alpha 1 induce 2',5'-oligo(A) synthetase activity in monolayers of endometrial epithelial and stromal cells. Compared to epithelial cells, stromal cells have higher baseline activity of 2'-5'-oligo(A) synthetase activity (p less than 0.01) and show a greater degree of induction in the presence of either the partially purified bTP-1 or bIFN-alpha 1 (p less than 0.01). Also, 2',5'-oligo(A) synthetase of endometrial stromal cells is induced to a greater degree by our enriched bTP-1 preparation than by bIFN-alpha 1 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of estrogen inhibitors on conceptus estrogen synthesis and development in the gilt.

Two estrogen antagonists (keoxifene and clomiphene) and two aromatase inhibitors (LY56110 and 4-hydroxyandrostenedione, 4-OHA) were utilized to determine the role of conceptus estrogen in trophoblastic elongation and maintenance of pregnancy in the pig. Pregnant gilts were unilaterally hysterectomized on day 10.5, and infused via a uterine arterial catheter with 200 mg of keoxifene or vehicle. The remaining uterine horn was removed based on time estimated for conceptus elongation. In a second study, pregnant gilts were injected daily with 200 mg (i.m.) of clomiphene or vehicle during pregnancy (days 10-16) and hysterectomized on day 30. A third study assessed in vitro aromatase inhibition by 4-OHA and LY56110 using trophoblastic microsomes incubated with [1 beta, 2 beta-3H]-androstenedione for 6 hr. In a fourth study, in vivo inhibition of aromatase activity was determined. For this study pregnant gilts, unilaterally hysterectomized on day 10.5, received either 4-OHA, LY56110, or vehicle. Conceptus development and uterine estrogens were quantified. None of the estrogen antagonists and aromatase inhibitors interferred with conceptus elongation. Uterine protein, calcium and acid phosphatase were similar (P greater than .10) between keoxifene- and vehicle-treated gilts. Embryonic survival of clomiphene- and vehicle-treated gilts was similar (91.5 vs 87.4%). In vitro, 4-OHA and LY56110 had 50% inhibitory concentrations of 0.1 microM and 13 nM. Treatment of gilts with 4-OHA reduced total estrogens in uterine flushings by 57% (P less than .02), whereas treatment with LY56110 did not significantly lower total estrogen content in uterine flushings. Estrogen antagonists were not effective in blocking conceptus elongation and maintenance of pregnancy. Although estrogen synthesis can be inhibited in vitro, dosages of aromatase inhibitors used were not totally effective in vivo.

Embryonic steroids and the establishment of pregnancy in pigs.

In the pig, establishment of pregnancy begins about 11-12 days after the start of oestrus. The ability of pig conceptuses to synthesize and release oestrogens during this period, as well as the ability of exogenous oestrogens to induce pseudo-pregnancy when administered from Day 11-15 of the oestrous cycle, provide evidence for an involvement of oestrogen in the maternal recognition of pregnancy in the sow. Oestrogen derived from the conceptus or from administration to cyclic gilts stimulates uterine secretion of calcium and specific polypeptides on Day 11-12. The specific roles for the uterine secretory response to oestrogen in the maintenance of pregnancy are unknown. However, it has been proposed that oestrogen prevents luteolysis in the sow through reorientation of endometrial prostaglandin release, i.e. into the uterine lumen rather than into the uterine vasculature. Oestrogen may interact with prolactin and/or conceptus secretory proteins to shift the direction of prostaglandin movement. Although conceptus oestrogen synthesis triggers a number of uterine secretory events on Day 11, a second sustained phase of oestrogen stimulation from Day 14 to 18 appears to be necessary for luteal maintenance beyond Day 25. Pig conceptuses synthesize and release large amounts of oestrogens between Days 14 and 18 of pregnancy. Conceptus oestrogens are clearly involved with the establishment of pregnancy. However, the conceptus also secretes a number of biologically active substances such as catechol oestrogens, prostaglandins and polypeptides which could interact with oestrogen to prevent luteolysis. The roles of these factors in control of vascular permeability, blood flow, placental attachment and immunological protection certainly indicate that, in addition to oestrogens, other factors are involved in the establishment of pregnancy in pigs.

Insulin, growth hormone, glucose, and fatty acids in gilts selected for rapid vs. slow growth rate.

Twelve-hour plasma profiles of growth hormone (GH), insulin, glucose, and nonesterified free fatty acids (NEFA), as well as GH, insulin, and glucose responses to saline, glucose, arginine, and human pancreatic growth hormone-releasing factor (GRF) infusion were examined in 15 crossbred gilts, selected for rapid vs. slow growth. For experiment 1 GH and insulin patterns differed (P less than 0.05) between the rapid growth line (RGL) and slow growth line (SGL). Mean GH concentrations in SGL and RGL gilts were 4.1 and 3.2 ng/ml, respectively (P less than 0.05). Plasma GH profile area was greater (P less than 0.08) for SGL than RGL gilts. Glucose level, glucose area, and insulin level were higher (P less than 0.05) for RGL than SGL gilts. Plasma NEFA levels and area were greater (P less than 0.05) for SGL gilts. In experiment 2 responses of GH, insulin, and glucose to saline, glucose, arginine, and GRF infusions varied (P less than 0.05) between and within lines relative to control values. These results indicate that selection for growth rate results in concomitant changes in endocrine and metabolic status.

Uterine secretory alterations coincident with embryonic mortality in the gilt after exogenous estrogen administration.

Sixteen crossbred gilts were assigned randomly to receive either an i.m. injection of sesame oil (control) or estrogen (E), 5 mg of estradiol valerate, on d 9 and 10 of pregnancy. Gilts were unilaterally hysterectomized on either d 12 and 14 or 16 and 18. Uterine horns were flushed with 20 ml of .9% sterile NaCl solution to recover conceptus tissue. Conceptuses and endometrial explants were cultured for 24 h with 100 microCi [3H] leucine in 15 ml of minimum essential media. After dialysis, culture media were submitted to 2D-polyacrylamide gel electrophoresis and incorporated proteins were analyzed by fluorography. Normal, intact conceptus tissue was recovered from control gilts. Estrogen-treated gilts flushed on d 12 and 14 contained intact conceptuses; however, uteri from two gilts on d 16 and three on d 18 contained degenerating conceptus tissue. Comparison of endometrial polypeptides synthesized in vitro indicated an alteration in E-treated gilts on d 12 through 18. Although similar polypeptides were present, a band of polypeptides with a Mr of approximately 30,000 and pI from 7.9 to 8.9 and a larger, acidic polypeptide (Mr = 100,000, pI 3.5 to 5.0) were faint or absent in E-treated gilts. Conceptuses elongated normally in the altered uterine environment, but failed to survive past d 14 in E-treated gilts. Although loss of specific polypeptides in E-treated gilts coincides with conceptus death, their function in conceptus development or attachment is unknown.

Gizzard ulceration in chicks fed cysteamine alone or in combination with a histamine H2-receptor antagonist.

A study was carried out to evaluate the effect of cysteamine-HCl administration on gizzard ulceration and growth performance in broiler chicks. The effectiveness of the histamine H2-receptor antagonist, SKF 93479, in preventing gizzard ulcerations when given in combination with cysteamine-HCl was also examined. In the initial experiment cysteamine-HCl at the level of 2400 mg/kg of the diet caused severe gizzard ulceration and mortality and decreased feed intake and growth in chicks. The effect was not seen when cysteamine-HCl was administered at 600 or 1200 mg/kg of the diet. In Experiment 2 broiler chicks administered cysteamine-HCl at 1800 mg/kg of the diet had an increased incidence of gizzard ulceration and decreased growth performance. The severity of gizzard lesions and the depression of growth performance were not as great as in the group in Experiment 1 which received the 2400 mg/kg level of cysteamine-HCl. Addition of the H2 antagonist SKF 93479 at 54 mg/kg of the diet had no effect on improving gizzard ulcer score or growth performance in chicks which received cysteamine-HCl at the 1800 mg/kg of the diet level. From these data it appears that the administration of ulcerogenic levels of cysteamine-HCl in the chicken may involve a more complex pathogenesis in which factors other than acid hypersecretion are involved.

Evidence for maternal regulation of early conceptus growth and development in beef cattle.

Fifty-one cyclic beef cows were mated with fertile bulls. At 36 h after the start of oestrus, cows were assigned to receive sesame oil (controls) or progesterone (100 mg) on Days 1, 2, 3 and 4 of pregnancy. Peripheral plasma concentration of progesterone was measured until slaughter on Days 5 or 14. Cows were randomly assigned to be slaughtered on Days 5 or 14 or remain intact and palpated per rectum on Day 40 to verify pregnancy. Uteri on Days 5 and 14 were flushed for recovery of luminal protein and conceptus tissue. Conceptus and endometrial tissues were cultured with [3H]leucine and submitted to two-dimensional-PAGE and fluorography. Administration of progesterone increased peripheral plasma progesterone concentration on Day 2-5. Conceptuses recovered from progesterone-treated cows on Day 14 were advanced in development compared to conceptuses from control cows. Conceptuses recovered from progesterone-treated cows were viable as polypeptides associated with maintenance of pregnancy in cattle were synthesized and released at an earlier time and pregnancy was maintained beyond Day 40. Early progesterone stimulation altered the synthesis and release of polypeptides from endometrial explant cultures on Day 5. Results indicate a role of progesterone in the maternal regulation of conceptus growth and development in early pregnancy of cattle.

Estrogen-induced pseudopregnancy in gilts: Its use in estrus synchronization and subsequent influence on litter response.

The effectiveness of using estrogen-induced pseudopregnancy followed by PGF(2alpha) (Lutalyse) treatment to synchronize estrus in gilts and the subsequent effect of pseudopregnancy on litter parameters was examined in two experiments. Experiment 1 consisted of a control (n = 49) group and a pseudopregnant (n = 49) group. Pseudopregnant gilts received PGF(2alpha) between Days 25 and 38 and were bred at the ensuing estrus. Ninety-two percent of the gilts responded to PGF(2alpha) and exhibited estrus in 4.9 +/- 0.2 (Least Square Mean +/- SEM) days. Duration of estrus was longer in pseudopregnant compared to control gilts (2.8 vs 1.7 d, P<0.001). Experiment 2 consisted of a control (n = 24) group and a pseudopregnant (n = 24) group. All pseudopregnant gilts received PGF(2alpha) on Day 38 and 79% responded with a mean onset of estrus at 5.2 +/- 0.2 d. As in Experiment 1, duration of estrus was longer in gilts from the pseudopregnant group (2.2 vs 1.7 d, P<0.005). The percentage of farrowing was similar for both groups in both experiments, and no differences existed in the number of pigs born and those alive at 21 d post partum. Litters from gilts in the pseudopregnant groups were heavier at birth than those in the control group (Experiment 1, 17.21 vs 15.25 kg, P<0.01; Experiment 2, 15.31 vs 13.55 kg, P<0.02) and at 21 d (Experiment 1, 60.81 vs 56.79 kg, P<0.01; Experiment 2, 51.89 vs 46.96 kg, P<0.02). Survival rate at 21 d was higher in offspring from pseudopregnant gilts in both experiments (Experiment 1, 85.3% vs 78.2%, Experiment 2, 91.4% vs 81.2%).

Effect of exogenous progesterone on prostaglandin F2 alpha release and the interestrous interval in the bovine.

The present study was developed to determine if administration of progesterone, early in the estrous cycle of the cow, stimulated an advanced pulsatile release of PGF2 alpha from the uterine endometrium resulting in a decreased interestrous interval. Twenty-three cyclic beef cows were randomly assigned to receive either sesame oil or progesterone (100 mg) on Day 1, 2, 3 and 4 of the estrous cycle. Peripheral plasma concentrations of progesterone and the metabolite of prostaglandin F2 alpha, 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) were measured by radioimmunoassay. Administration of exogenous progesterone increased peripheral plasma concentration of progesterone in treated (3.67 ng/ml) compared to control (1.28 ng/ml) cows from Day 2 through 5 of the estrous cycle. Progesterone administration shortened the interestrous interval (16.7 d) compared to controls (21.6 d). The shortened interestrous intervals in treated cows resulted from an earlier decline in peripheral plasma progesterone. Decline of peripheral plasma progesterone concentrations is coincident with an increased pulsatile release of PGFM in both progesterone treated and control cows. Results indicate that administration of exogenous progesterone stimulates an earlier maturation of endometrial development, causing an advanced release of PGF2 alpha which shortens the interestrous interval of the cow.

Effect of cysteamine administration on growth and efficiency of food utilisation in chicks.

1. Cysteamine hydrochloride, which is a potent inhibitor of somatostatin secretion, was fed to male broiler chicks at dietary inclusion rates of 0, 25, 125, 250, 600, 1200, 1800 and 2400 mg/kg during three separate experiments. 2. Weight gain, food intake and efficiency of food utilisation were measured weekly over a two (experiment 1 and 2) or three-week period (experiment 3) during which chicks were 3 to 10 d old (week 1) to 17 to 24 d old (week 3). 3. Cysteamine hydrochloride included in the food at 1200 and 1800 mg/kg resulted in a significant increase in efficiency of food utilisation, attributable to a significant decrease in food intake. 4. There was no difference in weight gains between chicks in the control group and those receiving 1200 mg/kg. However a significant decrease in weight gain was observed in chicks receiving 1800 mg/kg.