Predicting dry matter intake in beef cattle.

Technology that facilitates estimations of individual animal dry matter intake (DMI) rates in group-housed settings will improve production and management efficiencies. Estimating DMI in pasture settings or facilities where feed intake cannot be monitored may benefit from predictive algorithms that use other variables as proxies. This study examined the relationships between DMI, animal performance, and environmental variables. Here we determined whether a machine learning approach can predict DMI from measured water intake variables, age, sex, full body weight, and average daily gain (ADG). Two hundred and five animals were studied in a drylot setting (152 bulls for 88 d and 53 steers for 50 d). Collected data included daily DMI, water intake, daily predicted full body weights, and ADG using In-Pen-Weighing Positions and Feed Intake Nodes. After exclusion of 26 bulls of low-frequency breeds and one severe (>3 standard deviations) outlier, the final number of animals used for modeling was 178 (125 bulls, 53 steers). Climate data were recorded at 30-min intervals throughout the study period. Random Forest Regression (RFR) and Repeated Measures Random Forest (RMRF) were used as machine learning approaches to develop a predictive algorithm. Repeated Measures ANOVA (RMANOVA) was used as the traditional approach. Using the RMRF method, an algorithm was constructed that predicts an animal's DMI within 0.75 kg. Evaluation and refining of algorithms used to predict DMI in drylot by adding more representative data will allow for future extrapolation to controlled small plot grazing and, ultimately, more extensive group field settings.

In animal agriculture, passive monitoring technology has the potential to lead to needed innovations as we look for solutions to make global food production more resilient. Here, we use passive intake systems to measure daily weight, water intake, and climatic variables to accurately predict dry matter intake. Such an approach, if it can be successfully applied for grazing animals would dramatically improve the ability of animal agriculture to reduce the ecological footprints of food production. Two hundred and five animals were studied in a drylot setting (152 bulls for 88 d and 53 steers for 50 d). We used both traditional statistical and modern machine learning approaches to test the ability to predict dry matter intake. Although all approaches had success in predicting dry matter intake, the best prediction came from a machine learning approach which was able to predict the average daily dry matter intake during a test to within 0.75 kg/d. Evaluation and refining of algorithms used to predict dry matter intake in the drylot by adding more representative data will allow for future extrapolation to controlled small plot grazing and, ultimately, more extensive grazing animal intakes at a production scale.

Special Forces Medical Sergeant/Special Operations Independent Duty Corpsman Candidates: Large Animal Module.

BACKGROUND: Medical care provided by Special Operations Forces (SOF) combat medics is vital for establishing communication with local populations. In many of these communities, livestock hold a valuable position within the social, political, and cultural structure. The West Virginia University (WVU) Special Forces Medical Sergeant/Special Operations Independent Duty Corpsman (SFMS/SOIDC) Large Animal Module is designed to provide a foundational experience in livestock husbandry and veterinary procedures to SOF combat medic candidates. This study was conducted to determine the participants' base knowledge of food animal production and to evaluate if the program content was sufficient for increasing their knowledge of the subject matter. METHODS: A quasi-experimental design utilizing pre-test and post-test instruments was used. The validity of the testing instruments was established by a panel of subject matter experts and the instruments' reliability was determined by a split-half analysis using SPSS® statistical software. The difference between the pre-test and post-test examinations were compared for 66 candidates who were assigned to WVU Health Sciences Center for the applied medical experience program and 46 counterparts assigned to other institutions by a match pair analysis. RESULTS: Seventy-five percent of the subjects had no previous livestock exposure, and only 7% had previously participated in the 4-H program or Future Farmers of America (FFA). The average improvement in scores, pre-test versus post-test, was significantly greater for those that attended the module (18.5 versus 0.9). CONCLUSION: Few SFMS/SOIDC candidates have prior knowledge of livestock husbandry practices. The large animal module successfully provides education on livestock husbandry practice to participants. Knowledge of livestock production can assist SOF medics in establishing rapport with indigenous populations while on mission.

The Stockman's Scorecard: quantitative evaluation of beef cattle stockmanship.

An animal's action, or inaction, is the direct result of a stockman's action or inaction. The Stockman's Scorecard is a novel observation instrument that has been proven to be a valid and reliable tool to measure the quality of beef cattle stockmanship. Specific handler actions have been weighted based on their perceived negative relationship to cattle stress from handling. The purpose of this article is to 1) document the initial use of the scorecard in a beef cattle feedlot setting and 2) provide further support to its validity by establishing an association with other quantitative and qualitative means of evaluating stockmanship. The Scorecard was used at 39 beef feedlots in Texas between March 2018 and April 2019. Eighty-four stockman were observed, and the average score received was 84.5 (SD = 14.73, range = 20 to 100). The most frequent mistakes observed were as follows: fills crowd pen/tub over half full (n = 39), slow to remove pressure (n = 29), uses unnecessary noise (n = 25), stands in front and taps rear (n = 24), and fails to regulate animal flow through a pinch point (n = 22). A strong negative association (ρ = -0.51) was found between the points deducted from the Noise and Physical Contact theme of the Scorecard and the number of animals touched with an electric prod from the BQA Feedyard Assessment. Moderate negative associations were found between the Scorecard final score and the number of animals that vocalize in the chute prior to procedures (ρ = -0.31). Those stockmen that scored above average on the Scorecard were qualitatively observed to be calm and quiet while working with the cattle (Kappa = 0.44). The qualitative disposition of cattle had little effect on the final score of stockmen using the Scorecard (Kappa = 0.17). The use of the Scorecard in a feedlot setting has demonstrated that as stockman scores decrease, there is an increase in the number of negative actions toward cattle and a negative behavioral response of the cattle themselves. Establishment of an association between a stockman's score using the Stockman's Scorecard and the animal-based observations from the BQA Feedyard Assessment further strengthens the validity of the Stockman's Scorecard as a tool to measure the quality of beef cattle stockmanship. The Scorecard has application as a tool to identify specific stockmanship deficiencies in order to target stockmanship training.

The identification of differentially expressed genes between extremes of placental efficiency in maternal line gilts on day 95 of gestation.

BACKGROUND: Placental efficiency (PE) describes the relationship between placental and fetal weights (fetal wt/placental wt). Within litters, PE can vary drastically, resulting in similarly sized pigs associated with differently sized placentas, up to a 25% weight difference. However, the mechanisms enabling the smaller placenta to grow a comparable littermate are unknown. To elucidate potential mechanisms, morphological measurements and gene expression profiles in placental and associated endometrial tissues of high PE and low PE feto-placental units were compared. Tissue samples were obtained from eight maternal line gilts during gestational day 95 ovario-hysterectomies. RNA was extracted from tissues of feto-placental units with the highest and lowest PE in each litter and sequenced. RESULTS: Morphological measurements, except placental weight, were not different (P > 0.05) between high and low PE. No DEG were identified in the endometrium and 214 DEG were identified in the placenta (FDR < 0.1), of which 48% were upregulated and 52% were downregulated. Gene ontology (GO) analysis revealed that a large percentage of DEG were involved in catalytic activity, binding, transporter activity, metabolism, biological regulation, and localization. Four GO terms were enriched in the upregulated genes and no terms were enriched in the downregulated genes (FDR < 0.05). Eight statistically significant correlations (P < 0.05) were identified between the morphological measurements and DEG. CONCLUSION: Morphological measures between high and low PE verified comparisons were of similarly sized pigs grown on different sized placentas, and indicated that any negative effects of a reduced placental size on fetal growth were not evident by day 95. The identification of DEG in the placenta, but absence of DEG in the endometrium confirmed that the placenta responds to the fetus. The GO analyses provided evidence that extremes of PE are differentially regulated, affecting components of placental transport capacity like nutrient transport and blood flow. However, alternative GO terms were identified, indicating the complexity of the relationship between placental and fetal weights. These findings support the use of PE as a marker of placental function and provide novel insight into the genetic control of PE, but further research is required to make PE production applicable.

Factors contributing to the variation in placental efficiency on days 70, 90, and 110 of gestation in gilts.

Variations in placental efficiency (PE), a measure of grams of fetus produced per gram of placenta, were initially researched between swine breeds, where increased PE was associated with larger litters. Placental efficiency was also found to vary greatly within production herds and individual litters; however, the use of PE as a selection tool has been debated. Nonetheless, PE is an index of feto-placental adaptation and may help identify compensatory mechanisms that maintain fetal growth when placental size is reduced, potentially providing an opportunity to address production concerns like low birth weights and preweaning survival. Since the nutrient transport capacity of the placenta largely depends on vasculature and nutrient transporter abundance, the objectives of this experiment were to 1) determine the mRNA expression of genes encoding nutrient transporters in the placenta and adjacent endometrium, and 2) evaluate if a relationship existed between PE and vascular density and/or nutrient transporters. Gilts (n = 19) were ovario-hysterectomized on day 70, 90, or 110 of gestation to collect placental and adjacent endometrial samples. The mean litter size was 11.1. Placental efficiency increased (P < 0.0001) throughout the end of gestation, while the range of PE increased from day 70 to 90 and was reduced on day 110 (P < 0.0001). Placental efficiency and placental weight were negatively correlated throughout gestation (70 d, r = -0.83, P < 0.0001; 90 d, r = -0.81, P < 0.0001; 110 d, r = -0.44, P < 0.0007), but the negative correlation between PE and fetal weight was not maintained as gestation progressed (70 d, r = -0.58, P < 0.0001; 90 d, r = -0.36, P < 0.0005; 110 d, r = 0.09, P = 0.51). Based on conditional effects plots, variations in PE were associated with alterations in amino acid transporter expression in the placenta (SLC7A7, SLC3A1) and endometrium (SLC7A1) on day 70. On day 90, PE had a positive relationship with placental expression of a glucose transporter (SLC2A3), and on day 110 PE was positively related to placental vascular density. The results suggest utero-placental adaptations occur as a compensation for reduced placental size to meet the increasing nutrient demands of the growing fetus during late gestation in swine. Furthermore, nutrient requirements differ for individual feto-placental units on a given day; therefore, optimizing nutrient availability during late gestation may improve fetal growth and survival.

Effect of melatonin or maternal nutrient restriction on vascularity and cell proliferation in the ovine placenta.

Previously we reported increased umbilical artery blood flow in ewes supplemented with melatonin from mid- to late-pregnancy, while maternal nutrient restriction decreased uterine artery blood flow. To further unravel these responses, this study was designed to assess placental cell proliferation and vascularity following supplementation with melatonin or maternal nutrient restriction. For the first experiment, 31 primiparous ewes were supplemented with 5mg of melatonin per day (MEL) or no melatonin (CON) and allocated to receive 100% (adequate fed; ADQ) or 60% (restricted; RES) of their nutrient requirements from day 50 to 130 of gestation. To examine melatonin receptor dependent effects, a second experiment was designed utilizing 14 primiparous ewes infused with vehicle, melatonin, or luzindole (melatonin receptor 1 and 2 antagonist) from day 62 to 90 of gestation. For experiment 1, caruncle concentrations of RNA were increased in MEL-RES compared to CON-RES. Caruncle capillary area density and average capillary cross-sectional area were decreased in MEL-RES compared to CON-RES. Cotyledon vascularity was not different across dietary treatments. For experiment 2, placental cellular proliferation and vascularity were not affected by infusion treatment. In summary, melatonin interacted with nutrient restriction to alter caruncle vascularity and RNA concentrations during late pregnancy. Although melatonin receptor antagonism alters feto-placental blood flow, these receptor dependent responses were not observed in placental vascularity. Moreover, placental vascularity measures do not fully explain the alterations in uteroplacental blood flow.

Examination of adipocere formation in a cold water environment.

Adipocere is a late-stage postmortem decomposition product that forms from the lipids present in soft tissue. Its formation in aquatic environments is typically related to the presence of a moist, warm, anaerobic environment, and the effect of decomposer microorganisms. The ideal temperature range for adipocere formation is considered to be 21-45°C and is correlated to the optimal conditions for bacterial growth and enzymatic release. However, adipocere formation has been reported in cooler aquatic environments at considerable depths. This study aimed to investigate the chemical process of adipocere formation in a cold freshwater environment in Lake Ontario, Canada. Porcine tissue was used as a human tissue analogue and submerged at two depths (i.e., 10 and 30 feet) in the trophogenic zone of the lake. Samples were collected at monthly postmortem submersion intervals and analysed using diffuse reflectance infrared Fourier transform spectroscopy to provide a qualitative profile of the lipid degradation and adipocere formation process. Early stage adipocere formation occurred rapidly in the cold water environment and proceeded to intermediate stage adipocere formation by the second month of submersion. However, further adipocere formation was inhibited in the third month of the study when temperatures approached the freezing point. The depth of submergence did not influence the chemical conversion process as similar stages of adipocere formation occurred at both depths investigated. The study demonstrated that adipocere can form rapidly, even on small amounts of soft tissue, which may be representative of dismembered or disarticulated limbs discovered in an aquatic environment.

Protein-induced alterations in murine hepatic alpha-aminoadipate delta-semialdehyde synthase activity are mediated posttranslationally.

The molecular mechanisms responsible for alterations in lysine alpha-ketoglutarate reductase (LKR) activity are unknown. Therefore, the aim of these studies was to discern the mechanism(s) responsible for induction of hepatic LKR activity in rodents fed excess dietary protein. Four studies were conducted that used 84 mice. Mice were fed either a high-protein (50% casein) or adequate-protein (20% casein) diet in powder form in study 1 and a high-protein (46% casein) or adequate-protein (21% casein) diet in pellet form in the remaining studies. No significant differences in weight gain between the mice fed the different diets were detected. As expected, mice fed high-protein diets had a greater (P< .05) LKR activity in all 4 experiments. Mice fed high- and adequate-protein diets for 8 days showed no difference (P> .1) in alpha-aminoadipate delta-semialdehyde synthase (AASS) mRNA in experiment 1. However, after pooling the data from the remaining 3 experiments, mice receiving the high-protein diet had greater (P< .05) AASS mRNA compared to mice fed the adequate protein diet. In this investigation, no differences (P> .1) in AASS protein abundance were detected. The results are consistent with a mechanism in which posttranslational regulation is responsible for hepatic induction of LKR activity in mice fed high-protein diets.

Effect of feeding flax or linseed meal on progesterone clearance rate in ovariectomized ewes.

Ovariectomized ewes (n=22; 68.76+/-2.34 kg initial body weight; 2.9+/-0.1 initial body condition score) were individually fed one of three diets: (1) control (phytoestrogen-free; n=7), (2) flax containing diet (n=8), or (3) linseed meal (LSM) containing diet (n=7) to investigate the rate of progesterone (P4) clearance. On day 20 of feeding (day 0=initiation of treatment), a P4 releasing device (CIDR) was placed in the vagina and jugular blood samples were obtained prior to CIDR insertion and 15, 30, 60, and 120 min following CIDR insertion. Further, blood samples were obtained daily between days 21 and 24. On day 25, blood samples were retrieved prior to CIDR removal and 2, 5, 10, 15, 30, 60, 120, and 360 min following CIDR removal. There was no difference in initial or final body weight or body condition score and there were no time by diet interactions on P4 clearance. The fractional rate of P4 uptake measured prior to CIDR insertion through day 4 following insertion tended to be greater (P=0.07) in LSM fed ewes (508.75+/-71.37%/min) compared to flax (295.39+/-66.76%/min) and control fed (287.54+/-71.37%/min) ewes. Diet tended (P=0.10) to influence P4 clearance rate when measured from prior to CIDR removal through 120 min following CIDR removal with LSM fed ewes having a greater (1.26+/-0.2) fractional rate constant than flax (0.929+/-0.09) and control fed (0.922+/-0.09) ewes. Flax fed ewes also had more (P<0.01) omega-3 fatty acids and total fatty acids in plasma. Reports of increased pregnancy rates in dairy cows fed flax may relate to P4 metabolism.

Mechanisms of reduced luteal sensitivity to prostaglandin F2alpha during maternal recognition of pregnancy in ewes.

During maternal recognition of pregnancy, the conceptus stimulates endometrial secretion of PGF2alpha and PGE2. However, PGF2alpha is less effective in causing luteal regression in pregnant than in non-pregnant ewes. Experiments were conducted to elucidate mechanisms for reduced luteal sensitivity to PGF2alpha during maternal recognition of pregnancy. Corpora lutea (CL) were collected from pregnant and non-pregnant ewes 0, 4, or 12h following treatment with PGF2alpha on day 12 after estrus. Luteal PTGHS2 mRNA did not differ due to PGF2alpha or pregnancy status. Luteal PTGES mRNA was reduced in both pregnant and non-pregnant ewes after PGF2alpha treatment; while, luteal PTGFS mRNA was reduced 4h after PGF2alpha in pregnant, but not non-pregnant ewes. The result was a greater ratio of PTGES to PTGFS mRNA in pregnant ewes. Luteal mRNA for HPGD did not differ between pregnant and non-pregnant ewes on day 12. Luteal END1 mRNA was reduced in pregnant as compared to non-pregnant ewes prior to PGF2alpha challenge. Luteal END1 mRNA was increased after PGF2alpha in pregnant and non-pregnant ewes; however, ECE1 mRNA was reduced 4h after PGF2alpha in pregnant, but not non-pregnant ewes. The in vitro conversion of PGF2alpha to PGFM was greater in CL of pregnant than non-pregnant ewes at day 14. Luteal conversion of PGF2alpha to PGFM appears to be regulated post-transcriptionally. During maternal recognition of pregnancy, mechanisms of reduced luteal sensitivity to PGF2alpha may include a shift in prostaglandin production to the luteotropin PGE2, a reduction of ECE1 mRNA, and increased catabolism of PGF2alpha.

Circulating levels of nitric oxide and vascular endothelial growth factor throughout ovine pregnancy.

Nitric oxide (NO) production has been shown to increase uterine blood flow and be elevated in ewes carrying multiple fetuses during late gestation. Vascular endothelial growth factor (VEGF) has been reported to increase eNOS expression and NO production in endothelial cell cultures. As angiogenesis and vasodilatation of the uterine and placental vascular beds are important at all stages of pregnancy, it is important to understand how VEGF and NO change throughout gestation in circulation. Therefore the objectives of the current study were to evaluate the systemic levels of VEGF and NO metabolite (NOx) throughout ovine gestation and to determine if there was an effect of sheep carrying singletons versus multiple fetuses. NOx and VEGF concentrations were analysed in systemic blood from pregnant ewes starting on day 27 of pregnancy and at multiple intermittent intervals throughout pregnancy until term. Blood samples from non-pregnant and postpartum ewes were also analysed. NOx concentrations in maternal blood expressed a biphasic pattern with NOx concentrations increasing (P < 0.05) over non-pregnant values on days 40-69 of gestation, returning to non-pregnant concentrations from days 70-100, and again increasing (P < 0.05) until term. Postpartum NOx concentrations were similar to non-pregnant values. While ewes carrying multiple fetuses had increased (P < 0.05) concentrations of NOx on days 60-69, there were no differences in NOx concentrations in ewes carrying singletons or multiples from day 70-99 of gestation. Starting on day 100 and continuing throughout the duration of pregnancy, ewes carrying multiple fetuses had increased (P < 0.05) concentrations of NOx compared to ewes carrying singletons. Concentrations of VEGF showed a different pattern from NOx with VEGF decreasing (P < 0.05) from day 20-69 of pregnancy compared to non-pregnant ewes. Concentrations of VEGF returned to non-pregnant levels by day 70 and remained constant throughout the duration of pregnancy. On days 20-39, ewes carrying singleton fetuses had an increased VEGF concentration (P < 0.05), whereas ewes carrying multiple fetuses demonstrated elevated VEGF concentrations from day 90-109 of gestation. Concentrations from non-pregnant and postpartum ewes did not differ (P > 0.1). While there was no effect of fetal number on circulating VEGF concentrations, circulating levels of NOx were substantially increased (P < 0.05) in ewes carrying multiple fetuses, compared to ewes carrying singletons. The pattern of the rise in NOx in circulating plasma was not directly associated with changes in VEGF regardless of the number of fetuses present. However, circulating concentrations of NOx and VEGF appear to, respectively, follow patterns of uterine blood flow and angiogenesis of the uterus. An understanding of these circulatory patterns may have important implications for fetal size, birth weight and fetal/developmental origins of adult disease.

Lysine alpha-ketoglutarate reductase and lysine oxidation are distributed in the extrahepatic tissues of chickens.

In animals, lysine oxidation is thought to occur primarily via the activity of lysine alpha-ketoglutarate reductase (LKR). This activity was reported previously in chicken liver, but no work on the tissue distribution of the enzyme in chickens has been reported. Therefore, LKR activity was assayed in liver, kidney, pancreas, heart, brain, lung, spleen, muscle, and intestinal tissues in chickens as was the in vitro ability of tissue homogenates to oxidize lysine. Additionally, the expression of LKR mRNA was assessed by RT-PCR. We found LKR to be present in all tissues studied by both enzymatic analysis and mRNA abundance. Additionally, all tissues assayed oxidized lysine. The extent of lysine oxidation differed among the tissues, consistent with the different pathways of lysine oxidation in the different tissues. These studies demonstrate that LKR is widely distributed in chicken tissues and that tissues other than liver can contribute to whole-body lysine oxidation.

Prostaglandin F2alpha (PGF2alpha) independent and dependent regulation of the bovine luteal endothelin system.

We have examined the genes of the endothelin system that are targets for regulation by prostaglandin F2alpha (PGF2alpha). The effects of a luteolytic dose of PGF2alpha ) on the mRNA encoding endothelin converting enzyme-1 (ECE-1), pre-pro endothelin-1 (pp ET-1) and the ET receptors ETA, ETB, in bovine corpus luteum (CL) during the early (days 1 and 4), mid (day 10) or late (day 17) luteal phases were examined. The effect of the PGF(2alpha) treatment on ECE-1 protein, Big ET-1 and the biologically active mature ET-1 peptide were also examined. Most importantly, the direct ECE-1 activity was determined. Before day 10 of the cycle, in a PGF2alpha-independent manner, the amounts of mRNA encoding ET-1, ECE-1, ETA, and ETB were increased steadily from day 1. After day 10 of the cycle, expression of mRNA encoding pp ET-1 and ETA acquired responsiveness to exogenous PGF2alpha and both genes were up-regulated by the PGF2alpha treatment. This effect of PGF2alpha was also detected for the proteins corresponding to the mature ET-1. The enzymatic activity of ECE-1 remained unchanged throughout the lifespan of the CL in spite of the detected changes in mRNA and protein. The results suggest that the luteal endothelin system is regulated in a PGF2alpha-independent and -dependent manner. Importantly, an alteration in luteal ET-1 availability is most likely achieved by modulating the expression of mRNA encoding pp ET-1 and not by the amount or activity of ECE-1. This interpretation is supported by the observation that the activity of ECE-1 remained unchanged throughout the ovarian cycle. The combined effects of greater ET-1 availability and gene expression encoding the ETA receptor in the late luteal phase could render the CL, at this developmental stage, more sensitive or responsive to ET-1. If the luteal tissue is responsive to the available ET-1 during the early phase of the ovarian cycle, an additional role for ET-1 should be considered beyond mediating the luteolytic actions of PGF2alpha. Agents blocking the actions of ET-1 might be the best approach to interfere with the luteal ET system and test its physiological role(s) in vivo.

Experimental manipulation of steroid concentrations in circulation and in egg yolks of turtles.

Steroid hormones in egg yolks are increasingly recognized as an important component of maternal and offspring fitness in oviparous vertebrates. Yet, except for in birds, the mechanism by which females allocate these resources is poorly understood. We manipulated systemic levels of hormones in reproductively mature female red-eared slider turtles (Trachemys scripta elegans) with silastic implants to test the hypothesis that hormones are allocated to developing follicles as a quantitative function of circulating levels in the females. Turtles exhibited similar amounts (<1 ng/ml) of circulating steroids (dihydrotestosterone, estradiol-17 beta, or testosterone) in early September immediately prior to experimental manipulation. After treatment with silastic implants, circulating levels of steroids increased markedly. By the following April after hibernation, circulating levels of dihydrotestosterone had returned to preimplantation levels, but circulating levels of estradiol-17 beta and testosterone in estradiol-17 beta- and testosterone-treated turtles, respectively, remained substantially elevated through April. Focusing on testosterone, we detected nearly six-fold higher concentrations in yolk from mature follicles from testosterone-treated turtles than in yolk from mature follicles from control turtles. Our results provide support for the hypothesis that concentrations of steroids in egg yolks of turtles reflect circulating concentrations of steroids during follicular development rather than the hypothesis that females selectively allocate specific amounts of steroid hormones to each egg separately. Our findings also highlight an unambiguous physiological mechanism by which nongenetic maternal effects in oviparous species can directly influence the nutritional milieu experienced by developing embryos.

Differential expression of cyclooxygenase-2 around the time of elongation in the pig conceptus.

Alterations in uterine luminal fluid composition as a result of conceptus estradiol-17beta production are believed to play a significant role in the loss of 30-40% of potential pig conceptuses. Shortly after the initiation of conceptus estradiol-17beta synthesis and secretion, the conceptuses are transformed from 1cm spheres to 2-5cm tubular forms and finally to filamentous threads of variable length via a process known as elongation. We have attempted to characterize gene products whose expression is either initiated or terminated as the conceptus elongates. Using RNA fingerprinting, we determined that the inducible form of the rate-limiting enzyme in prostaglandin synthesis, cyclooxygenase-2, is expressed in the filamentous pig conceptus, but not in either the spherical or transitional morphologies. Furthermore, increased expression of cyclooxygenase-2 by the filamentous conceptus was associated with increases in the content of prostaglandins (particularly prostaglandin E(2)) found in uterine luminal fluid.