| Title |
Investigators | Department | Objectives | Approach Keywords | Progress Reports | Impact Statements | Publications | |
Project * COL00670 | |
| Title | Enhancing Efficiency in Cow-Calf Production |
| Investigator(s) | Archibeque, S; |
| Department | Animal Science |
| Objectives | 1) To elucidate the intracellular signaling mechanisms that lead to an increase in cyclooxygenase-2 gene expression and prostaglandin F2a synthesis in bovine endometrial and luteal tissues. 2) Examine how the n-3 fatty acids (eicosapentaenoic and docosahexaenoic acids)attenuate prostaglandin F2a metabolism in these tissues and potentially enhance fertility. 3) To determine incorporation and retention rates of n-3 fatty acids into reproductive tissues. |
| Approach | Luteal and endometrial tissue will be obtained from a local abattoir to study mechanisms controlling cyclooxygenase-2 gene expression and prostaglandin F2a synthesis in vitro. Stage of the estrous cycle will be estimated by gross ovarian morphology (i.e. size and color of the corpus luteum; size and number of follicles present on the ovary). Luteal tissue will be collected from animals that are estimated to be days 10 to 12 of the estrous cycle and endometrial tissue from animals that are estimated to be days 2 to 4 of the estrous cycle. Tissues will be transported to the laboratory and prepared for in vitro incubation. Corpora lutea will be dissected from ovarian stroma and cells isolated using collagenase. The intracellular signaling pathway that leads to prostaglandin synthesis has been studied in a number of tissues. Based on information from these reports, luteal cells will then be incubated using known activators and inhibitors of prostaglandin synthesis. Western and Northern analysis will be used to identify key intracellular signaling proteins and gene expression of these proteins that mediate prostaglandin synthesis in this tissue. Once key signaling proteins have been identified, we will examine how n-3 fatty acids effect gene expression and activity of these proteins. Carunucular endometrium will be dissected from uteri. Cells will be isolated using collagenase and seeded into six well culture dishes. We have identified several key proteins that mediate cyclooxygenase-2 gene expression and prostaglandin F2a synthesis in bovine and ovine endometrial cells. Western and Northern analysis will be used to determine how n-3 fatty acids effect gene expression and activity of these proteins. In vivo studies will also be conducted to determine incorporation and retention rates of n-3 fatty acids into bovine endometrial and luteal tissues. To determine incorporation of n-3 fatty acids into endometrial and luteal tissues, estrous cycles will be synchronized in twenty cows. On day 15 to 16 after estrus, a uterine and luteal biopsy will be collected. Tissue will be snap frozen in liquid nitrogen and stored at -80C until determination of fatty acid composition via gas liquid chromatography. Cows will then receive fish meal, a supplement high in eicosapentaenoic and docosahexaenoic acids, or control supplement for six consecutive estrous cycles. Uterine and luteal biopsies will be conducted on day 15 of the each cycle. To examine retention rate of n-3 fatty acids, twenty cows will be supplemented with fish meal until uterine and luteal tissues become saturated with eicosapentaenoic and docosahexaenoic acids as determined from the incorporation experiment. Supplementation will cease and estrous cycles will be synchronized in all cows. Uterine and luteal biopsies will be conducted on day 15 to 16 after estrus for six consecutive estrous cycles. Tissues will be harvested and stored as described above. Fatty acid composition will be determined using gas liquid chromatography. |
| Keywords | Cow, Fertility, Prostaglandin, Uterus, Corpus Luteum, n 3 Fatty Acids, Embryo, Metabolism, Gene Expression, Cyclooxygenase 2, Signal Transduction |
| Progress Reports | |
| 1998 | Less than 6% of beef cows in the United States are artificially inseminated each year. One of the biggest reasons that so few beef cattle are artificially inseminated each year is due to problems associated with detection of estrus. The goal of this research was to develop estrous and ovulation synchronization protocols that would induce estrous cycles, be easy to administer, be relatively cheap, be administered in a short period of time, and synchronize follicular development to allow timed insemination in beef cattle. Beef cows (n = 1,939) from 7 locations were used to evaluate variations of the Ovsynch protocol for synchronization of estrus and (or) ovulation. Treatment groups varied by location, but included direct comparisons of the Ovsynch protocol (n = 220) verses Syncro-Mate B (n = 216), Ovsynch protocol (n = 627) verses the CO-Synch protocol (n = 594), and Select Synch protocol (n = 116) verses 2x prostaglandin (PGF; n = 109). The Ovsynch, CO-Synch, and Select Synch protocols include the following injection schedules: GnRH--7 d--PGF--2 d--GnRH--1 d--AI, GnRH--7 d--PGF--2 d--GnRH+AI, and GnRH--7 d--PGF + 5d AI 12 hr after detection of estrus, respectively. Calf removal (48-hr) initiated at the time of the PGF injection was evaluated in a subset of cows that received the Ovsynch (n = 235) or CO-Synch (n = 234) protocol. Daily ultrasound and electronic estrous detection were used to evaluate estrous and ovarian response to the Select Synch protocol (n = 57). Progesterone analyses of two blood samples collected 10-d apart prior to treatment indicated that each of the GnRH/PGF2a protocols were capable of inducing ovulation/estrus in previously anestrous cows. Pregnancy rates were greater (P < .025) for cows that received the Ovsynch protocol (54%) than cows that received Syncro-Mate B (42%). Pregnancy rates were not different (P > .1) among cows that received the Ovsynch (58%) or CO-Synch protocol (54%). However, 48-hr calf removal improved (P < .05) pregnancy rates by 8% across both treatments. Synchronization, conception and pregnancy rates were not different among cows that received the Select Synch (77%, 61%, and 47%,) or 2x PGF protocol (81%, 60%, and 49%, respectively). Ovarian response of cows that were between d 15-17 of their estrous cycle at the time of the 1st GnRH injection was poor and these cows exhibited estrus earlier (approximately 11 hr prior to the PGF injection) than expected. Insemination of cows that exhibit estrus early results in high pregnancy rates. The GnRH/PGF protocols can result in high pregnancy rates to timed insemination or breeding by estrus in beef cows. These protocols provide beef producers with estrous/ovulation synchronization protocols that are easy to administer, induce estrous cycles in anestrous cows, and result in high pregnancy rates. It is important that producers using the GARH/PGF protocols begin observing cows about 1 day before the PGF injection, as approximately 8% of cows may show estrus at this time. We have recently been working on methods to decrease the cost (currently $5 - $9 per cow) of this type of synchronization, without harming pregnancy rates. |
| 1999 | In non-pregnant ruminants, prostaglandin (PG) F2a is released from the uterus in a pulsatile manner to cause the regression of the corpus luteum and initiation of a new estrous cycle. Oxytocin appears to be the endogenous stimulus that generates these pulses late in the estrous cycle. The detailed cellular and molecular mechanisms by which oxytocin stimulates uterine PGF2a are still largely unknown. We have recently reported that one of the mitogen-activated protein kinases, extracelluar signal regulated protein kinase (ERK), plays a critical role in mediating oxytocin-induced PGF2a release. In intact non-pregnant ewes, oxytocin induced a rapid increase in serum PGF2a. Associated with this increase in serum PGF2a was an increase in endometrial concentrations of phosphorylated ERK. An inhibitor of ERK activation blocks the ability of oxytocin to induce uterine PGF2a release in vitro. We are currently investigating the cellular mechanisms that leads to the activation of ERK activity in sheep endometrium. The ewe is an ideal model for studying the cellular and molecular mechanisms by which oxytocin induces uterine PGF2a synthesis in domestic ruminants. Results from these experiments can be then be applied to cattle. |
| 2000 | In non-pregnant ruminants, prostaglandin (PG) F2a is released from the uterus in a series of high amplitude pulses late in the estrous cycle to cause the regression of the corpus luteum and initiation of a new estrous cycle. Oxytocin appears to be the endogenous stimulus that generates these pulses. Oxytocin binds to a cell surface membrane receptor that activates a complex signaling cascade that leads to the activation of phospholipase A2 and mobilization of membrane bound arachidonic acid, the precursor to all PGs. After being mobilized, arachidonic acid is rapidly converted to PGH2 by the enzyme cyclooxygenase-2 (Cox-2) and then to PGF2a by the enzyme prostaglandin F synthase. Our laboratory is investigating the cellular and molecular mechanisms by which oxytocin mediates PGF2a synthesis in bovine and ovine endometrium. We have shown that oxytocin increases phosphorylation of extracellular regulated signal protein kinase (ERK) in vivo and in vitro. PD98059, an inhibitor of ERK activation, blocked oxytocin-induced PGF2a release, indicating that ERK plays a critical role in mediating PGF2a synthesis in this tissue. Preliminary studies indicate that ERK may mediate oxytocin-induced PGF2a synthesis by increasing Cox-2 mRNA. We are also investigating the possibility of using fishmeal as a lipid supplement to increase fertility in first-calf beef cows. In order for pregnancy to be established, the conceptus (embryo and associated membranes) must block uterine PGF2a synthesis so that the corpus luteum is maintained. Fishmeal contains a high percentage of the omega-3 fatty acids eicosapentaneoate (EPA) and docosahexaenoate (DHA). In a number of cells and tissues, both EPA and DHA have been shown to inhibit Cox-2 gene expression and activity, resulting in decreased PG synthesis. We have shown that fishmeal supplementation increases plasma and endometrial concentrations of EPA and DHA. Preliminary studies from our laboratory indicate that fishmeal supplementation increases fertility by 15% in postpartum first-calf beef cows. We hypothesize that the omega-3 fatty acids found in fishmeal become incorporated in uterine endometrium and attenuate PGF2a synthesis during maternal recognition of pregnancy resulting in enhanced fertility. |
| 2001 | Early embryonic mortality continues to be a major problem in animal agriculture. One possible cause of embryonic mortality is failure in maternal recognition of pregnancy. The conceptus (embryo and associated membranes) must inhibit uterine prostaglandin (PG) F2a synthesis between 14 and 18 days post-breeding so that the corpus luteum continues to secrete progesterone and pregnancy can be established. It has been proposed that in some situations the conceptus fails to effectively control uterine PGF2a resulting in regression of the corpus luteum and embryonic death. Cyclooxgenase-2 (Cox-2) is a critical enzyme that controls uterine PGF2a synthesis in bovine endometrial tissue. Our laboratory is currently investigating the cellular and molecular mechanisms that regulate Cox-2 gene expression. Using immortalized bovine endometrial cells as a model, we have shown that phorbol ester, an activator of PG synthesis, increases Cox-2 mRNA. Actinomycin D, an inhibitor of gene transcription, totally abolished the phorbol-induced increase in Cox-2 mRNA, suggesting that the increase in mRNA is due to an increase in gene transcription rather than stabilization of existing message. It is also evident that the increase in message is mediated through the activation of both p44/42 and p38 MAP kinases. At this time, we have partially cloned the 5' flanking region of the Cox-2 promotor and experimentation is ongoing to determine what transcription factors are involved in inducing Cox-2 gene expression. In addition, we are also investigating the possibility of using fishmeal as a lipid supplement to increase fertility in first-calf beef cows. Fishmeal contains a high percentage of the omega-3 fatty acids eicosapentaenoate (EPA) and docosahexaenoate (DHA). Both of these omega-3 fatty acids have been shown to inhibit Cox-2 gene expression and activity in a number of cells and tissues, resulting in decreased PG synthesis. We have just completed a two-year study that shows fishmeal supplementation increases plasma EPA and DHA in lactating first-calf beef cows fed a corn silage diet when compared to cows supplemented with corn gluten meal. Furthermore, first service conception rates were higher in cows receiving fishmeal supplement. Current studies are underway to determine if fishmeal supplementation increases fertility in cows grazing pasture. |
| 2002 | In cows, prostaglandin (PG) F2a is released from the uterus between days 17 and 18 of the estrous cycle to cause regression of the corpus luteum. In the pregnant female, the embryo must inhibit the release of PGF2a during this period so that the corpus luteum continues to secrete progesterone and the pregnancy can be established. However, often the embryo fails to adequately inhibit the release of uterine PGF2a resulting in the regression of the corpus luteum and termination of the pregnancy. Therefore, gaining insight as to how the uterus synthesizes PGF2a and developing novel methods to reduce secretion of PGF2a after mating is of critical importance. Recent studies have shown that n-3 fatty acids have the ability to reduce PG synthesis in bovine endometrial tissue in vitro. Fish meal is a rich source of eicosapentaenoic (EPA) and docosahexaenoic (DHA) n-3 fatty acids. We have recently reported that fish meal supplementation increases plasma EPA and DHA, which then become incorporated into uterine tissues. Furthermore, we have shown that fish meal supplementation increases fertility in lactating first calf beef cows housed in a dry lot. The objective of the present study was to determine if fish meal supplementation increases fertility in young lactating cows (2 to 3 yrs of age) grazing native range. Cows grazed native range with or without fish meal supplementation (5 percent dry matter intake). Supplementation began 25 days before the start of the breeding season and continued until the end of the 70 day breeding season. Estrous cycles were synchronized using a modified Select Synch program. Cows detected in estrus during the first 3 days of the breeding season were artificially inseminated 12 h after being detected in estrus. Cows not detected in estrus by day 3 were mass mated. Cows were exposed to bulls beginning 14 days after the mass mating until the end of the breeding season. Cows supplemented with fish meal had greater concentrations of plasma EPA when compared to cows receiving no supplement (P less than 0.05). However, fish meal supplementation had no effect on 72 h estrus response, first service conception rates, AI pregnancy rates, or final pregnancy rates (P greater than 0.10). Cows grazing range alone had greater plasma linolenic acid (an n-3 fatty acid found in plants and shown to inhibit PG synthesis) at the start of the breeding season compared to cows supplemented with fish meal (P less than 0.05). We conclude that diets limited in linolenic acid might require supplemental n-3 fatty acids in order to optimize fertility. |
| 2003 | The objective of this study was to determine if n-3 fatty acids in fish meal inhibit oxytocin-induced uterine prostaglandin (PG) F2a release in heifers with low luteal phase progesterone (P4). Animals were individually fed a corn silage-based diet supplemented with fish meal (5 percent dry matter intake; n equals 12) or corn gluten meal (6 percent dry matter intake; n equals 13). Heifers were given 25 mg of PGF2a (i.m.) on d 25 of supplementation to induce estrus. Random heifers from each supplement group (n equals 6 fish meal and n equals 7 corn gluten meal) were given 3 additional injections of PGF2a (25 mg; i.m.) at 12 h intervals beginning on d 3 after estrus to induce formation of corpora lutea that secrete lower concentrations of P4. Jugular blood samples were collected daily on d 1 through d 16 of the estrous cycle to determine serum P4 concentrations. Heifers were administered oxytocin (100 IU ; i.v.) on d 16 after estrus to stimulate uterine PGF2a synthesis. Before statistical analysis , heifers were sorted to either high or low luteal phase P4 as determined by serum P4 on d 9 of the estrous cycle. After sorting, treatment groups consisted of 1) high luteal P4 plus fish meal (n equals 6), 2) low luteal P4 plus fish meal (n equals 6), 3) high luteal P4 plus corn gluten meal (n equals 6), and 4) low luteal progesterone plus corn gluten meal (n equals 7). Serum concentrations of the PGF2a metabolite following oxytocin stimulation were greater (P less than 0.01) in heifers having low luteal phase P4 compared to heifers having high luteal phase P4. Fish meal supplementation attenuated this response in heifers having low luteal phase P4 (P less than 0.05), but had no effect (P greater than 0.10) on heifers having high luteal phase P4. In conclusion, the n-3 fatty acids in fish meal appear to decrease uterine PGF2a synthesis in heifers having low luteal phase concentrations of P4. |
| 2004 | Copper (Cu), zinc (Zn), and manganese (Mn) are essential for normal reproduction in mammalian species (Underwood and Suttle, 1999). Therefore, supplementation of trace minerals to beef cattle is a common practice. However, problems associated with supplementation strategies to beef cattle do occur and most likely are related to the extreme variability in forage quality and trace mineral content across the U.S. (Corah and Arthington, 1993). Furthermore, the specific effects of trace minerals on reproductive efficiency, growth, and immune function have not been well defined (Corah and Arthington, 1993). Moreover, limited research has been conducted to investigate the effects of long term trace mineral supplementation and source on reproductive efficiency in cow herds. Therefore, the objective of this study was to determine the effect of the supplementation and source of Cu, Zn, and Mn at levels recommended by NRC (1996) on reproductive efficiency, mineral status, and performance in grazing beef cattle over a 2 year period. Crossbred, multiparous (n equal to 178 in Year 1; n equal to 148 in Year 2) grazing beef cattle in eastern Colorado were utilized in this experiment. Cows were stratified by expected calving date, age, BW, BCS, and liver mineral status and assigned to the following treatments: 1) control (no supplemental Cu, Zn, or Mn); 2) organic (ORG; 50 percent organic and 50% inorganic Cu, Zn, and Mn); and 3) inorganic (ING; 100 percent inorganic Cu, Zn, and Mn) trace minerals. Free-choice mineral feeders were used to provide current NRC-recommended concentrations of Cu, Zn, and Mn from 82 d (Year 1) and 81 d (Year 2) before the average calving date of the herd through 110 d (Year 1) and 135 d (Year 2) after calving. At the end of Year 1, supplemented cows had greater liver Cu (P less than 0.01), Zn (P less than 0.05), and Mn (P less than 0.01) concentrations than controls, whereas liver Cu concentration was greater (P less than 0.01) in ORG vs. ING cows. At the end of Year 2, supplemented cows had greater (P less than 0.01) liver Cu concentrations relative to controls, whereas control cows had greater (P less than 0.02) liver Mn concentration than supplemented cows. In Year 1, pregnancy rate to AI in control cows did not differ (P equal to 0.47) from supplemented cows, but there was a trend (P less than 0.08) for pregnancy rate to be higher for ORG than ING cows . In Year 2, supplemented cows had a higher (P less than 0.02) pregnancy rate to AI than controls. In both years, when cows were inseminated after an observed estrus, supplemented cows had a higher (P less than 0.04) pregnancy rate than controls. Also, for both years, overall 60-d pregnancy rate tended (P equal to 0.10) to be higher for supplemented cows than for controls. Results indicate that supplementation and source of trace minerals affected mineral status and supplementation also improved pregnancy rate to AI compared with cows not supplemented with Cu, Zn, or Mn for more than 1 yr. Furthermore, mineral source may influence pregnancy rate to AI. |
| 2005 | Copper (Cu) is essential for normal reproduction in mammalian species (Underwood and Suttle, 1999); however, the mechanisms of action have not been clearly identified. Early studies have shown that Cu administration induced ovulation in rabbits (Fevold et al., 1936; Suzuki and Bialy, 1964). More recently, GnRH increased LH and FSH release from rat pituitaries when Cu was present in the portal blood (Kochman et al., 1992), possibly by influencing GnRH receptor binding (Kochman et al., 1997) and(or) intracellular calcium activity (Hazum, 1983; Schvartz and Hazum, 1986) in anterior pituitary cells. In Cu-deficient dairy heifers, Phillippo et al. (1987) reported that supplemental molybdenum (Mo; used to induce a Cu deficiency) caused a lower pre-ovulatory LH surge compared to a Cu deficiency induced by iron supplementation, leading to the conclusion that Mo supplementation, and not Cu deficiency, directly affected the hypothalamic-pituitary axis. Based on the importance of Cu in reproduction, the effect of Cu on the hypothalamic-pituitary axis in laboratory animals, and reported differences in Cu availability by source (Nockels et al., 1993), we hypothesized that pituitary sensitivity to GnRH (as determined by LH released in response to exogenous GnRH administration) would vary with Cu status, supplementation, and source. Therefore, the effect of Cu on pituitary responsiveness to exogenous GnRH was evaluated using 9 multiparous, non-pregnant, non-suckling, ovariectomized Angus cows. Cows were considered Cu deficient based on liver Cu concentrations (greater than 30 mg Cu/kg DM) after receiving a low Cu forage-based ration supplemented with Mo and sulfur for 216 d. Copper-deficient cows were stratified based on age , BW, BCS, and liver Cu concentration and randomly assigned to repletion phase treatments. Treatments included: 1) control (no supplemental Cu), 2) organic Cu, and 3) inorganic Cu. During the 159-d repletion phase, Cu status was monitored and all cows received exogenous progesterone. A controlled intravaginal releasing device was used to maintain luteal phase progesterone as a means to provide negative feedback on the hypothalamic-pituitary axis. By d 77 of the repletion phase, all supplemented cows were considered adequate in Cu, and liver Cu concentrations were greater in supplemented vs. non-supplemented control cows. Beginning on d 99, exogenous GnRH was administered to all cows at low (0, 3, and 9 ug; Experiment 1) and high doses (0, 27, and 81 ug; Experiment 2) at six different times. Repeated blood samples were collected pre- and post- GnRH administration and analyzed for LH concentration. In Experiment 1, Cu status and supplementation did not affect basal or peak LH concentrations, but total LH released tended to be greater in Cu supplemented vs. control cows when 3 ug GnRH was administered. In Experiment 2 there was no effect of Cu supplementation or source on basal, peak, or total LH released, regardless of GnRH dose. Pituitary LH concentrations were not different across treatments. In conclusion, Cu status, supplementation, and source did not affect pituitary sensitivity to GnRH or pituitary stores of LH in beef cows. |
| 2006 | Source (organic vs. inorganic) of trace minerals such as copper (Cu), zinc (Zn), and manganese (Mn), has been shown to affect the performance of grazing beef cattle. Improved pregnancy rate to AI (Stanton et al., 2000), reduced postpartum interval to breeding, and enhanced repair of uterine tissue following parturition have been associated with organic trace mineral supplementation. When organic trace minerals were supplemented to dams, suckling calves had enhanced performance and immune response compared to calves whose dams received inorganic trace minerals. Other experiments showed no effect of trace mineral source on reproductive performance or calf performance. Due to reports of enhanced cattle performance and increased bioavailability associated with organic trace minerals, some cow/calf producers have begun to include organic trace minerals into grazing cow and calf mineral supplements. Comparisons of inorganic and organic trace mineral supplements on grazing cattle performance at NRC (1996) recommended concentrations for more than one year are limited, particularly in young cows. Therefore, the objectives of this study were to determine the effects of Cu, Zn and Mn source (at current NRC recommendations) on mineral status, reproductive performance, immune response, and calf performance over a two-year period. Crossbred beef females (n equals 43 nulliparous heifers, Year 1; n equals 37 primiparous cows, Year 2) were utilized in this experiment. Pregnant nulliparous heifers were stratified by expected calving date, BW, BCS, and liver mineral status and assigned to treatments, 1) organic (ORG; 50 percent organic and 50% inorganic Cu, Zn, and Mn); and 2) inorganic (ING; 100 percent inorganic CuSO4, ZnSO4, and MnSO4) trace minerals. Treatments were formulated to provide current NRC recommended concentrations via free-choice mineral feeders from 54 (Year 1) and 81 d (Year 2) prior to the average calving date through 119 (Year 1) and 135 d (Year 2) post-calving. There were no treatment (times) yr interactions (P greater than 0.10) for any of the responses evaluated. Final liver Cu concentrations were greater (P less than 0.05) and final liver Mn concentrations tended to be greater (P less than 0.06) in ORG vs. ING females. Estrous cyclicity tended (P less than 0.08) to be greater in ORG vs. ING females and there was a tendency (P less than 0.07) for higher pregnancy rate in ING vs. ORG females after a 60-d breeding season. Primary humoral immune response was measured in Year 1 only by injecting (i.m.) a 20 percent porcine red blood cell (PRBC) solution into pregnant heifers and collecting blood samples immediately pre-injection (d 0) and on d 7, 14, and 21 post-injection. Concentrations of immunoglobulin (Ig) G antibody titers specific for PRBC were greater (P less than 0.03) in ORG than ING heifers on d 14, and total Ig titers specific for PRBC were greater (P less than 0.05) in ORG than ING heifers on d 21. Kilograms of calf weaned per female exposed were not affected (P greater than 0.10) by trace mineral source. |
| Impact | |
| 1999 | Early embryonic mortality continues to be a major problem in animal agriculture. Approximately 30% of all viable cow embryos are lost during the first 30 days of pregnancy. A significant number of these losses are due to the failure of the embryo to block uterine PGF2a synthesis and release. It is anticipated that these studies will provide basic knowledge in the regulation of prostaglandin synthesis and may allow for the development of new techniques to manipulate endogenous PGF2a secretion as to more effectively reduce embryonic mortality in beef cattle and sheep. |
| 2000 | Approximately 30% of all cow embryos are lost during the first 30 days of pregnancy, costing the US beef industry millions of dollars annually. It is anticipated that these studies will provide basic knowledge in the regulation of PG synthesis. This may allow for the development of new techniques to manipulate endogenous PGF2a secretion and reduce embryonic mortality in beef cattle. |
| 2001 | Results from the current studies provide basic knowledge in the cellular and molecular mechanisms regulating endometrial PG synthesis in ruminants. It is anticipated that this knowledge may allow for the development of new techniques to manipulate endogenous PGF2a secretion and reduce embryonic mortality in beef cattle. Additionally, fishmeal supplementation may be a practical way to alter uterine PGF2a synthesis during maternal recognition of pregnancy and thus enhance fertility in beef cattle. |
| 2002 | It has been estimated that 20 to 30% of all pregnancies terminate within the first 30 days of gestation. Half of the losses are due to the inability of the embryo to control uterine PGF2a release between days 17 and 18 post mating. Fish meal supplementation may attenuate PGF2a during this period and improve fertility, especially if n-3 fatty acids are limited in the diet. |
| 2003 | Mated cows that undergo luteolysis and fail to become pregnant often have low luteal phase progesterone. Often the uterus secretes greater amounts of PGF2a in response to oxytocin in mated cows having low luteal phase progesterone. We anticipate that fish meal supplementation may improve pregnancy rates in cattle that have low luteal phase progesterone by reducing PGF2a release following mating. |
| 2004 | Both supplementation (at concentrations recommended by the NRC) and source of copper, zinc, and manganese affected the concentration of these minerals in the liver of multiparous beef cows, although the effect of these differing body mineral concentrations on reproduction or calf performance is unclear. After 1 yr without supplemental copper, zinc, and manganese, pregnancy rate to a synchronized artificial insemination may be decreased, and season-long reproductive performance also may be affected. Additionally, trace mineral source may affect pregnancy rate to a synchronized artificial insemination. |
| 2005 | Results of the current experiment imply that the mechanism(s) of action by which copper affects reproduction do not appear to be at the level of the hypothalamic-pituitary axis. Further research is needed in areas where copper may impact reproductive performance in beef cows, including hypothalamic sensitivity to ovarian hormones, ovarian response to circulating gonadotropins, ovarian activity including follicular and luteal function, uterine repair, and(or) biological activity of circulating hormones. |
| 2006 | Results of the current experiment indicate a potential difference in the availability and(or) metabolism of trace mineral sources. Pregnancy rate to a synchronized AI was not affected by trace mineral source; however, estrous cyclicity tended to be higher in organic supplemented females, and season-long reproductive performance tended to be greater in females receiving inorganic trace minerals. The reproductive data were not very informative since data were categorical, and low numbers of cattle were evaluated. Primary humoral immune response to a foreign antigen was higher in young grazing females receiving organic versus inorganic trace minerals. Although morbidity was extremely low in this experiment, an enhanced ability to respond to a foreign antigen may be beneficial if animals encounter a stressor or are exposed to disease. |
| Publications | |
| 1998 |
DOHERTY, D.R., WHITTIER, J.C., LEFEVER, D.G., MORTIMER, R.G. and GEARY, T.W. 1998. Modifications of the Select Synch Estrous Synchronization Protocol to Include Mass Mating at 72 or 84 Hours. Colorado State University 1998 Beef Program Report, pp. 193-198 DOHERTY, D.R., WHITTIER, J.C., LEFEVER, D.G., MORTIMER, R.G. and GEARY,T.W. 1998. Increasing the Use of Artificial Insemination: An Undergraduate Internship Program Using Variations of the Select Synch Estrous Synchronization Protocol. J. Anim. Sci. 76(Suppl. 1):368 DOHERTY, D.R., WHITTIER, J.C., LEFEVER, D.G., MORTIMER, R.G. and GEARY, T.W. 1998. Increasing the use of artificial insemination: An Undergraduate Internship Program Using Variations of the Select Synch Estrous Synchronization Protocol. Proc. Wes. Sec. Am. Soc. An. Sci., Vol. 49:254-256 DOWNING, E.R., BRUEMMER, J.E., SCHUTZ, D., COUCH, D., WHITTIER, J.C. and GEARY, T.W. 1998. Ovarian Response to the Select Sync Protocol by Day of Estrous Cycle. Colorado State University 1998 Beef Program Report, pp. 181-186 DOWNING, E.R., SCHUTZ, D., COUCH, D. LEFEVER, D.G., WHITTIER, J.C. and GEARY, T.W. 1998. Methods of Estrous Detection to Increase Pregnancies Using the Select Synch Protocol. Colorado State University 1998 Beef Program Report, pp. 175-180 DOWNING, E.R., SCHUTZ, D., COUCH, D., LEFEVER, D.G., WHITTIER, J.C. and GEARY, T.W. 1998. Estrous and Ovarian Response to the Select Synch Protocol. J. Anim. Sci. 76(Suppl. 1):373 DOWNING, E.R., SCHUTZ, D., COUCH, D.G., LEFEVER, J.C., WHITTIER, J.C. and GEARY, T.W. 1998. Estrous and Ovarian Response to the Select Synch Protocol. Proc. West. Sec. Am. Soc. Anim. Sci . Vol. 49:17-19 GEARY, T.W. 1998. Estrous Synchronization Programs. Proceedings 59th Annual Conference for Veterinarians. pp. 34-39 GEARY, T.W. 1998. Use of GnRH in Synchronizing Ovulation for Timed Insemination in Beef Cows. Proceedings of NCBA: IRM Produer Education Seminars, pp. 59-61 GEARY, T.W., WHITTIER, J.C., DOWNING, E.R., LEFEVER, D.G., HOLLAND, M.D., NETT, T.M. and NISWENDER, G.D. 1998. Pregnancy Rates of Postpartum Beef Cows That Were Synchronized With the Syncro-Mate B or Ovsynch Protocol. J. Anim. Sci. 76:1523 GEARY, T.W., WHITTIER, J.C., LEFEVER, D.G. and HALLFORD, D.M. 1998. Effect of Calf Removal on Pregnancy Rates of Cows Synchronized with the Ovsynch or CO-Synch protocol. Proc. West. Sec. Am. Soc. Anim. Sci., Vol. 49:205-207 GEARY, T.W., WHITTIER, J.C., LEFEVER, D.G. and HALLFORD, D.M. 1998. Effect of Calf Removal on Pregnancy Rates of Cows Synchronized with the Ovsynch or Co-Synch Protol. J. Anim. Sci .76(Suppl. 1):278 GEARY, T.W., WHITTIER, J.C., LEFEVER, D.G., MATHIEWS, G.L. and PATTERSON, H.H. 1998. Effect of Calf Removal on Pregnancy Rates of Cows Synchronized with the Ovsynch or CO-Synch Protocol. Colorado State University 1998 Beef Program Report, pp. 187-192 LEFEVER, D.G., SCHAFER, D.W., MATHIEWS, G.L., WHITTIER, J.C. and GEARY, T.W. 1998. A Method to Increase the Number of Cyclic Yearling Heifers at the Beginning of the Breeding Season. J. Anim. Sci. 76(Suppl. 1):281 STENQUIST, N.J. and GEARY, T.W. 1998. Synchronizing Estrus in Beef Cattle. Cooperative Extension Bulletin CL405. In: Cow-Calf Management Guide and Cattle Producer's Library. Cooperative Extension System |
| 2000 |
Bonnette T.R., Abbey, D.B., Whittier, J.C., and Burns, P.D. 2000. Effects of fishmeal supplementation on first service pregnancy rates in primiparous lactating beef cows. Proc. West. Sec. Am. Soc. Anim. Sci. 51:351-355. Burns P.D. 2000. Enhancing first service conception by feeding fishmeal to beef cows. Proceeding Colorado Nutrition Roundtable: Supplementing Fats and Oils to Livestock. Burns P.D., Abbey, D.B., Bonnette, T.R., Harris, M.A., and Whittier, J.C. 2000. Effects of fishmeal supplementation on bovine endometrial concentrations of omega-3 fatty acids. Proc. West. Sec. Am. Soc. Anim. Sci. 51:360-362. Burns P.D., Graf, G.A., Hayes, S.H., and Silvia, W.J. 2000. Effect of oxytocin on expression of cytosolic phospholipase A2 mRNA and protein in ovine endometrial tissue in vivo. Domest Anim Endocrinol 19:237. Mendes J.O.B., Jr., Burns, P.D., Bonnette, T.R., Yemm, R.S., Nelson, S.E., and Clay, C.M. 2000 . Cellular mechanisms by which oxytocin mediates uterine prostaglandin F2a synthesis: does Gi proteins and extracellular regulated signal protein kinase play a role? Proc. West. Sec. Am. Soc. Anim. Sci. 51:363-366. |
| 2001 |
Bonnette T.R., J.C. Whittier, T.E. Engle, and P.D. Burns. 2001. Effect of fishmeal supplementation on fertility in primiparous, lactating beef cows. Western Section American Society of Animal Science 52:74-78. Bonnette T.R., J.C. Whittier, T.E. Engle, and P.D. Burns. 2001. Effect of fishmeal supplementation on fertility in primiparous, lactating beef cows. Journal of Animal Science 79(suppl. 2):124. Bonnette T.R., M.N. Piazza, T.E. Engle, J.C. Whittier, D.B. Abbey, and P.D. Burns. 2001. Effect of fishmeal supplementation on fertility in first-calf beef cows. In: Animal Sciences Research Report, Ed: TL Stanton. pp 27-30. Burns P.D., J.O.B. Mendes Jr., R.S. Yemm, C.M. Clay, S.E. Nelson, S.H. Hayes, and W.J. Silvia. 2001. Cellular mechanisms by which oxytocin mediates ovine endometrial prostaglandin F2a synthesis: Role of Gi proteins and mitogen-activated protein kinases. Biology of Reproduction 65:1150-1155. Burns P.D., S.E. Nelson, J.E. Bruemmer, J.M. Escudero, and C.M. Clay. 2001. Regulation of cyclooxygenase-2 gene expression in bovine endometrial cells. Biology of Reproduction 64(suppl . 1):256. Burns P.D., T.R. Bonnette, J.C. Whittier, T. Farner, and T.E. Engle. 2001. Effects of fishmeal supplementation on plasma and endometrial concentrations of omega-3 fatty acids in beef cows. In: Animal Sciences Research Report, Ed: TL Stanton. pp 31-34. |
| 2002 |
Burns, P.D., Bonnette, T.R., Engle, T.E. and Whittier, J.C. 2002. Case study - effects of fish meal supplementation on fertility and plasma omega-3 fatty acid profiles in primiparous, lactating beef cows. Prof. Anim. Sci 18, 373-379. Burns, P.D., Downing, E.R., Engle, T.E., Whittier, J.C. and Enns, R.M. 2002. Effect of fish meal suppmentation on fertility in young beef cows grazing pasture. Proceedings Western Section, American Society of Animal Science, 53, 392-396. Burns, P.D., Downing, E.R., Engle, T.E., Whittier, J.C. and Enns, R.M. 2002. Effect of fishmeal supplementation on fertility in young beef cows grazing pasture. J. Anim. Sci. 80 (suppl. 2), 127. |
| 2003 |
Ahola J.K., Engle, T.E., Baker, D.S., Sharpe, L.R., Whittier, J.C., Burns, P.D., Enns, R.M., and Mortimer, R.G. 2003. Impact of trace mineral supplementation and source on grazing beef cattle over a two-year period. Proceedings, Western Section American Society of Animal Science 54:9-11. Ahola J.K., Engle, T.E., Baker, D.S., Sharpe, L.R., Burns, P.D., Enns, R.M., and Mortimer, R.G . 2003. Impact of trace mineral supplementation and source on grazing beef cattle over a two-year period. Journal of Animal Science 81(suppl. 1):36. Baker D.S., Ahola, J.K., Burns, P.D., and Engle. T.E. 2003. Trace mineral metabolism in ruminants: impact on production, reproduction and the environment. In: Beyond the Tornado: The Calm after the Storm. Nutritional Biotechnology in the Feed and Food Industries. Eds: TP Lyons and KA Jacques. Nottingham University Press, Nottingham, UK. pp 275-287. Burns P.D., Engle, T.E., Harris, M.A., Enns, R.M., and Whittier, J.C. 2003. Effect of fish meal supplementation on plasma and endometrial fatty acid composition in non-lactating beef cows. Journal of Animal Science 81:2840-2846. Mendes, J.O.B. Jr., Burns, P.D., De La Torre-Sanchez, J.F., and Seidel, G.E., Jr. 2003. Effect of heparin on cleavage rates and embryo production with four bovine sperm preparation protocols. Theriogenology 60:331-340. Merrill M.L., Ansotegui, R.P., Wamsley, N.E., Burns, P.D., and Geary, T.W. 2003. Effects of flunixin meglumine on embryonic loss in stressed beef cows. Proceedings, Western Section American Society of Animal Science 54:53-55. Merrill M.L., Ansotegui, R.P., Wamsley, N.E., Burns, P.D., and Geary, T.G. 2003. Effects of fluxin meglumine on embryonic loss in stressed beef cows. Journal of Animal Science 81(suppl. 1):35. Walker R.S., Burns, P.D., Sides, G.E., and Zalesky, D.D. 2003. Evaluation of time to AI with a modified CO-synch protocol and calf removal in postpartum beef cows. Proceedings, Western Section American Society of Animal Science 54:87-89. Walker R.S., Burns, P.D., Sides, G.E., and Zalesky, D.D. 2003. Effects of feeding supplemental safflower seed with human chorionic gonadotropin following AI on pregnancy rates in heifers. Journal of Animal Science 81(suppl. 1):186. Walker R.S., Burns, P.D., Sides, G.E., and Zalesky , D.D. 2003. Evaluation of time to AI with a modified Co-synch protocol and calf removal in postpartum beef cows. Journal of Animal Science 81(suppl. 1):12. Walker R.S., Burns, P.D., Sides, G.E., and Zalesky, D.D. 2003. Effects of feeding supplemental safflower seed with human chorionic gonadotropin following AI on pregnancy rates in heifers. Proceedings, Western Section American Society of Animal Science 54:298-301. Wamsley N.E., Burns, P.D., Engle, T.E., and Enns, R.M. 2003. Effect of fish meal supplementation on endometrial sensitivity to oxytocin in beef heifers having low luteal phase progesterone. Proceedings, Western Section American Society of Animal Science 54:302-305. Wamsley N.E., Burns, P.D., Engle, T.E., and Enns, R.M. 2003. Effect of fish meal supplementation on endometrial sensitivity to oxytocin in beef heifers having low luteal phase progesterone. Journal of Animal Science 81(suppl. 1):102. |
| 2004 |
Ahola, J. K. D. S. Baker, P. D. Burns, R. G. Mortimer, R. M. Enns, J. C. Whittier, T. W. Geary , and T. E. Engle. 2004. Effect of copper, zinc, and manganese supplementation and source on reproduction, mineral status, and performance in grazing beef cattle over a two-year period. J . Anim. Sci. 82:2375-2383. Bryant, T. C., J. J. Wagner, T. E. Engle, K. L. Dorton, P. D. Burns, and M. L. Galyean. 2004. Effects of feeding supplemental vitamin A concentration on growth, intake, and marbling of yearling feedlot steers. J. Anim. Sci (Suppl. 1):270. Creech, B. L., J. W. Spears, W. L. Flowers, G. M. Hill, K. E. Lloyd, T. A. Armstrong, and T. E . Engle. 2004. Effects of trace mineral concentration and source (inorganic vs. chelated) on performance, mineral status, and fecal mineral excretion in pigs for weaning through finishing . J. Anim. Sci. 82:2140-2147. Engle, T. E. and J. W. Spears. 2004. Effects of finishing system (feedlot or pasture), high oil maize, and copper on conjugated linoleic acid and other fatty acids in muscle of finishing steers. Anim. Sci.78:261-269. Whitman, K. J., T. E. Engle, P. D. Burns, K. L. Dorton, J. K. Ahola, K. J. LaVelle, N. E. Wamsley, C. R. Johnson, and T. L. Stanton. 2004. Effects of copper and zinc source on performance and carcass characteristics in finishing steers. 2004. Animal Sciences Research Report. Pp. 1-4. |
| 2005 |
Ahola, J. K., Baker, D.S., Burns, P.D., Whittier, J.C., and Engle, T.E. 2005. Effect of copper , zinc, and manganese source on mineral status, reproduction, immunity, and calf performance in young beef females over a two-year period. Prof. Anim. Sci. 21:397-304. Ahola, J. K., Engle, T.E., and Burns, P.D. 2005. Effect of copper status, supplementation, and source on pituitary responsiveness to exogenous gonadotropin-releasing hormone in ovariectomized beef cows. J. Anim. Sci. 83:1812-1823. Aznarez, V. A., Whittier, J.C., Engle, T.E., Sampio, P.A.G.A., and Mackay, W.S. 2005. Characterization of protein degradability and diet nutritive value of beef cows grazing native ranger in eastern Colorado. J. Anim. Sci 81 (Suppl. 1):205. Walker, R. S., Burns, P.D., Engle, T.E., Sides, G.E., and Zalesky. D.D. 2005. Effects of human chorionic gonadotrophin administration on artificial insemination pregnancy rates in beef heifers. Prof. Anim. Sci. 21:361-364. Wamsley, N. E., Burns, P.D., Engle, T.E., and Enns, R.M. 2005. Fish meal supplementation alters uterine prostaglandin F2-alpha synthesis in beef heifers with low luteal-phase progesterone. J. Anim. Sci. 83:1832-1838. |
| 2006 |
Archibeque, S. L., Miller, D.N., Freetly, H.C., and Ferrell, C.L. 2006. Feeding high-moisture corn instead of dry-rolled corn reduces odorous compound production in manure of finishing beef cattle without decreasing performance. J. Anim. Sci. 84:1767-1777. Baszczak, J. A., Grandin, T., Gruber, S.L., Engle, T.E., Platter, W.J., Laudert, S.B., Schroeder, A.L., and Tatum J.D. 2006. Effects of ractopamine supplementation on behavior of British, Continental, and Brahman crossbred steers during routine handling. J. Anim. Sci. 84:3410-3414. Berry, E. D., Wells, J.E., Archibeque, S.L., Ferrell, C.L., Freetly, H.C., and Miller, D.N. 2006. Influence of genotype and diet on steer performance, manure odor, and carriage of pathogenic and other fecal bacteria. II. Pathogenic and other fecal bacteria. J. Anim. Sci. 84:2523-2532. Dorton, K. L., Engle, T.E., and Enns, R.M. 2006. Effects of trace mineral supplementation and source, 30 days post-weaning and 28 days post receiving, on performance and health of feeder cattle. Asian-Aust. Anim. Sci. 19:1450-1454. Legleiter, L. R., Ahola, J.K., Engle, T.E., and Spears, J.W. 2006. Decreased brain copper due to copper deficiency has no effect on bovine prion proteins. Biochem. Biophy. Res. Comm. 352:884-888. Miller, D. N., Berry, E.D., Wells, J.E., Ferrell, C.L., Archibeque, S.L., and Freetly, H.C. 2006. Influence of genotype and diet on steer performance, manure odor, and carriage of pathogenic and other fecal bacteria. III. Odorous compound production. J. Anim. Sci. 84:2533-2545. Murrieta, C. M., Hess, B.W., Scholljegerdes, E.J., Engle, T.E., Hossner, K.L., Moss, G.E., and Rule, D.C. 2006. Evaluation of milk somatic cells as a source of mRNA for study of lipogenesis in the mammary gland of lactating beef cows supplemented with dietary high-linoleate safflower seeds. J. Anim. Sci. 84:2399-2405. Richardson, S. M., Siciliano, P.D., Engle, T.E., Larson, C.K., and Ward, T.L., 2006. Effect of selenium supplementation and source on the selenium status of horses. J. Anim. Sci. 84:1742-1748. |