Progress 07/01/00 to 06/30/06
Outputs
Research continues to determine the impact of fescue toxicosis and heat stress on animal performance. Different animal models are used to test different treatments and procedures to alleviate the reduction in production associate with these stress conditions. We have been successful this year in determining specific markers for fescue toxicosis across several different animal species, and in creating a greater understanding of potential mechanisms of action associated with these toxins. In addition, we were successful in separating the effects of fescue toxicosis and heat stress on feed intake and control of body temperature. Future studies will concentrate on testing heat tolerant and intolerant breeds of Bos taurus cattle to determine specific differences in physiology and genomics to continue identifying markers of resistance to stress.
Impacts
This research will help to reduce the impact of heat stress and fescue toxicosis on animal production and performance. Ultimately, animal well-being will be improved. In addition, it will provide the producer with more powerful decision-making tools for reduction in overall stress to farm animals.
Publications
- No publications reported this period
|
Progress 01/01/05 to 12/31/05
Outputs
Research continues to determine the impact of fescue toxicosis and heat stress on animal performance. Different animal models are used to test different treatments and procedures to alleviate the reduction in production associate with these stress conditions. We have been successful this year in determining specific markers for fescue toxicosis across several different animal species, and in creating a greater understanding of potential mechanisms of action associated with these toxins. In addition, we were successful in separating the effects of fescue toxicosis and heat stress on feed intake and control of body temperature. Future studies will concentrate on testing heat tolerant and intolerant breeds of Bos taurus cattle to determine specific differences in physiology and genomics to continue identifying markers of resistance to stress.
Impacts
This research will help to reduce the impact of heat stress and fescue toxicosis on animal production and performance. Ultimately, animal well-being will be improved. In addition, it will provide the producer with more powerful decision-making tools for reduction in overall stress to farm animals.
Publications
- Bhusari, S., L.B. Hearne, D.E. Spiers, W.R. Lamberson, and E. Antoniou. 2006. Effect of fescue toxicosis on hepatic gene expression. J. Anim. Sci.
- Cammack, K.M., D.E. Spiers, P.A. Eichen, and W.R. Lamberson. 2005. Relationships between body temperature and performance traits in heat-stressed rats. J. Therm. Biol.
- Settivari, R.S., S. Bhusari, T. Evans, P.A. Eichen, L.B. Hearne, E. Antoniou, and D.E. Spiers. 2006. Genomic analysis of the impact of fescue toxicosis on hepatic function. J. Anim. Sci.
|
Progress 01/01/04 to 12/31/04
Outputs
Fescue toxicosis is a serious problem for any animal industry that utilizes fescue as a food source. A model of fescue toxicosis has been developed where rats consume a diet of endophyte-infected fescue seed (EIF) before and during exposure to heat stress. Although fescue toxicosis is known to impact female reproductive function, little is known about its effects on male reproduction. A preliminary study was performed to investigate the effects of heat stress (HS; 31C), combined with endophyte toxins and associated decreased feed intake on male reproductive function. Total sperm motility decreased with HS. Reduced feed intake, associated with fescue toxicosis tended to decrease total sperm motility. Many problems associated with fescue toxicosis may be linked to reduced caloric intake. A study was performed using pair-fed groups of rats to identify this condition. Results show that although intake of rats fed an endophyte-infected diet are similar to their pair-fed
counterparts under thermoneutral and heat stress conditions, the utilization of the food and corresponding thermoregulatory ability are very different. Our rat model was also used to evaluate the effects of endophyte toxins on Phase I and II hepatic detoxification systems at the cellular level. Fescue toxicosis reduced core temperature, feed intake, growth rate and activity level at thermoneutrality. Fescue toxins induced various CYP isoforms (Phase I), but lowered levels of antioxidants (Phase II) at the hepatic level. We have developed a bovine model for fescue toxicosis that can be used to evaluate potential treatments. However, it is essential that we identify a dose of ergovaline (EV; i.e., a primary ergopeptine alkaloid responsible for fescue toxicosis) that reliably produces symptoms associated with this condition. Two studies were conducted to determine a dose-response relationship for a diet containing endophyte-infected tall fescue and identify the time of administration
that produces the greatest response (i.e., EV treatment before or during heat stress. Administration of E+ during HS resulted in a greater separation of response compared to treatment prior to HS. A more distinct separation of dose effects was seen when seed was administered after the initiation of heat stress. In addition, feed intake appeared to be more responsive than core temperature to EV dose. Feed intake is an important determinant of the fescue toxicosis in that it determines, as the initial response, if the animal will consume sufficient toxin to produce the condition.
Impacts
Both basic and applied studies are in progress to determine the mechanisms of action of fescue toxicosis and appropriate treatments for this condition. Genomics studies show that the liver is extremely important in determining the impact of fescue toxicosis. Genetic expression of enzymes that break down these toxins is increased at the same time that antioxidant expression is reduced. These differences in gene expression might be used to identify sensitivity or resistance to fescue toxicosis. Future studies will examine ways to increase antioxidant level. Additional studies are separating the reduction in feed intake and hyperthermia associated with fescue toxicosis to improve our model and identify additional treatments.
Publications
- Nihsen, M., E.L. Piper, C.P. West, R.J. Crawford, T.M. Denard, Z.B. Johnson, C.A. Roberts, D.E. Spiers, and C.F. Rosenkrans. 2004. Growth rate and physiology of steers grazing tall fescue inoculated with novel endophytes. J. Anim. Sci. 82:878.
- Spiers, D.E., J.N. Spain, J.D. Sampson, and R.P. Rhoads. 2004. Use of physiological parameters to predict milk yield and feed intake in heat-stressed dairy cows. J. Therm. Biol. 29: 759.
- Spiers, D.E., P.A. Eichen, M.J. Leonard, L.E. Wax, G.E. Rottinghaus, J.E. Williams, and D.P. Colling. 2004. Benefit of dietary seaweed (Ascophyllum nodosum) extract in reducing heat strain and fescue toxicosis: a comparative evaluation. J. Therm. Biol. 29: 753.
- Brown-Brandl, T.M., R.A. Eigenberg, G.L. Hahn, J.A. Nienaber, T.L. Mader. D.E. Spiers, and A.M. Parkhurst. 2005. Analyses of thermoregulatory responses of feeder cattle exposed to simulated heat waves. Int. J. Biomet. (In press).
- Spiers, D.E., P.A. Eichen, and G.E. Rottinghaus. 2005. A model of fescue toxicosis: Responses of rats to intake of endophyte-infected tall fescue. J. Anim. Sci. 83:1423. Spiers, D.E., T.J. Evans, and G.E. Rottinghaus. Interaction between thermal stress and fescue toxicosis: Animal Models. In: Neotyphodium in Cool-Season Grasses. C.A. Roberts, C.P. West, and D.E. Spiers, Eds, Blackwell Publishing, Ames, IA. Neotyphodium in Cool-Season Grasses. C.A. Roberts, C.P. West, and D.E. Spiers, Eds.
|
Progress 01/01/03 to 12/31/03
Outputs
Studies were conducted to develop a dose-response curve for fescue toxicosis. Normal administration of endophyte-infected tall fescue (EIF) is conducted using whole fescue seed as a component of the daily diet. We are comparing responses to ground and whole EIF seed administered directly into the rumen via fistula. Ultimately, the ideal ergovaline dose, form of administration and time of administration will be determined. Cattle vary genetically in their response to fescue toxicosis. Knowing genes expressed or suppressed in response to endophyte toxins would identify genes involved in resistance or susceptibility to fescue toxicosis in rats and cattle. In 3 separate experiments, rats were fed different diets at thermoneutral (Study 1), early heat stress at 31C(Study 2), or chronic heat stress at 31C (Study 3). Measurements included determinations of body weight, feed intake, and core temperature. Liver samples were removed from euthanized rats on sample dates and are
currently being analyzed to analyze genetic expression. A dairy study (IFAFAS) is underway in collaboration with Michigan State University, University of Arizona, and other institutions to understand the genomics of heat stress. In the initial study, lactating dairy cows were exposed to continuous heat stress for up to 96 hours. Measurements during this period included determinations of skin and rectal temperatures, respiration rate, dry matter intake, and milk production. Tissue samples included blood, skin, liver, fat, ovary and mammary sites at 24, 48, and 96 hours. All samples are currently being analyzed. Previous studies indicate that adding seaweed extract (Tasco) to the diet results in decreased core body temperature in rats experiencing heat stress and fescue toxicosis. A rat model was used to test Tasco versus ethylenediamine dihydroiodide, at an iodide level equal to Tasco. These results indicate that dietary iodide is associated with some, but not all, responses to Tasco.
A 50-day study was conducted to determine if Tasco can reduce heat strain in cattle. In summary, it lowered core temperature when fed just prior to initial heat stress, but had no significant effect on skin temperature or respiration rate.
Impacts
Studies are underway to determine the amount of toxins in endophyte infected tall fescue that are needed to display symptoms associated with fescue toxicosis. There is reliable evidence that a dietary seaweed product will produce a temporary reduction in core body temperature during heat stress in both chamber and field environments. Studies are underway to determine those genes which are responsible for sensitivity to heat stress and fescue toxicosis.
Publications
- Roberts, C.A., Spiers, D.E., Karr, A.L., Benedict, H.R., Sleper, D.A., Eichen, P.A., West, C.P., Piper, E.L. and Rottinghaus, G.E. 2002. Use of a Rat Model to Evaluate Tall Fescue Seed Infected with Introduced Strains of Neotyphodium coenophialum. J. Agric. Food Chem. 50: 5742.
- Al-Tamimi, H., Rottinghaus, G.E., Spiers, D.E., Spain, J., Chatman, D., Eichen, P.A., Carson, T.L. and Hill, N.S. 2003. Thermoregulatory response of dairy cows fed ergotized barley during summer heat stress. J. Vet. Diag. Invest. 15: 355.
- Gadberry, M.S., Denard, T.M., Spiers, D.E. and Piper,E.L. 2003. Effects of feeding ergovaline on lamb performance in a heat stress environment. J. Anim. Sci. 81: 1538.
- Heat Stress and the Associated Effects on Thermal Balance of the Dairy Cow. Concordia Annual Dairy Day, MO, November 2002.
|
Progress 01/01/02 to 12/31/02
Outputs
Exposure to summer heat stress in the absence of shade can have significant impact on thermal status of cattle. Few studies have considered the direct impact of solar radiation on thermal status. Recent advances in telemetry technology provide continuous monitoring of core body temperature (Tb) in a field environment, allowing for assessment of relationships with ambient endpoints. A study was conducted during peak summer heat to record Tb via radiotelemetry and simultaneously monitor ambient conditions. Angus x Simmental steers were maintained in a feedlot environment without access to shade, and provided a typical finishing diet and water ad libitum. Core body temperature (Tb) was continuously recorded using a telemetric temperature transmitter in the peritoneal cavity. Best-fit relationships between Tb and all environmental variables, using all day values, were second-order polynomial regressions. Correlation (R) between air temperature (Ta) and Tb was 0.85, and
increased only to 0.86 with a 1 hour Tb delay behind Ta. These results indicate telemetric transmitters can be used to reliably predict changes in thermal status within the natural environment, and identifies that the best prediction is achieved with a 1-2 hour delay in core temperature behind changes in ambient thermal conditions. In a separate study, ambient conditions were monitored over a 61day period for Angus steers on tall fescue pastures at the University of Missouri. A telemetric temperature transmitter was surgically implanted into the peritoneal cavity of each animal prior to the study to measure Tb. Four animals in this group had an additional transmitter implanted in the rumen to monitor the temperature of this region (i.e., Tru). Use of average Tb and Ta values for the entire period showed a hysterersis loop, with no increase in Tb until Ta was above 20C and no reduction until Ta was below 25C. Maximum separation between the daily rise and fall in Tb was 0.6C. The entire
hysteresis loop for Tru was above that for Tb, with only the lower or ascending portion of the Tru loop intersecting the upper or descending portion of the Tb loop. General shapes of the loops were similar. Hysteresis loops were followed through 6 phases of the 61day period, and included the initial short, less intense heat period (HS1), followed by recovery and a second longer, more intense period (HS2). All phases showed distinctive hysterersis loops. The initial non-stress period was characterized by a large separation in Tb that equaled 0.7C. This separation decreased to 0.4C or less during HS1, indicating less Tb delay in response to Ta. Loops for the 2 recovery periods overlapped. Comparisons of heat stress periods showed that the initial phase of HS2 was similar to HS1, with the primary difference being an increased separation of the HS2 loop. These results show that hysteresis loops can be used to characterize core body temperature response of cattle to heat stress in the
field. It appears that cattle adapt to heat in this environment by delaying the change in core body temperature with the daily shift in air temperature.
Impacts
Air temperature can be used to predict core body temperature of cattle in feedlot and pasture situations with a 1 to 2 hour delay in the body temperature response. Cattle exhibit a delay in the rise in core temperature during the daily ascent in air temperature, and a similar delay in the fall in core temperature with the daily descent in air temperature. This pattern is a hysterersis loop.
Publications
- Mader, T.L., Holt, S.M., Hahn, G.L., Davis, M.S. and Spiers, D.E. 2002. Feeding strategies for managing heat load in feedlot cattle. J. Anim. Sci. 80: 2373
|
Progress 01/01/01 to 12/31/01
Outputs
Studies are continuing to develop a model of feedlot cattle response to heat stress using both controlled environmental chamber and field test conditions. A field study was conducted to refine a predictive model of core temperature. Angus x Simmental steers (Avg. BW 428 kg; n=24) were kept in unshaded feedlot pens, and provided with a typical finishing diet and water ad libitum. Implanted telemetric temperature transmitters (CowTemp, Model BV-010) were placed in the peritoneal cavity (Tcore) and rumen (Trm) to continuously monitor core temperature. Data loggers recorded ambient conditions, including percent relative humidity, air temperature (Ta), and black globe temperature (BG) to identify radiant heat load. Both temperature-humidity (THI) and black globe temperature-humidity (BGTHI) indices were calculated using these values. Initial comparisons showed that Trm was 0.6C higher than Tcore at non-heat stress Ta of 25C or less, with a gradual reduction to 0.3C at 35C.
Temperature of both sites reached lowest level at 0700 and highest within 1-2 h of daily maximum Ta. Highest correlation coefficients for prediction of Tcore were obtained with Ta x BG (r = .90; P < .001) and THI x BGTHI (r = .89; P < .001) values that preceded Tcore by 1 h. In contrast, highest correlation coefficients for prediction of Trm (2000) utilized THI x BGTHI (r = .84; P < .001) and Ta x BG (r = .81; P < .001) values at 3 h before Trm. A second-order polynomial expression best described these relationships with only a 1-2 h delay. However, comparable correlations at a 3 h delay required only a linear expression. An important component of cattle response to heat challenge is the ability to adapt. A second study was conducted to assess adaptation to repeated sinusoidal heat waves. Twelve Angus x Simmental steers (419+ 9.8 kg) were provided a typical finishing diet and water ad libitum, and first exposed to either 21 days thermoneutral (TN; 19+/-7C, 30-80% RH) or 7 days TN
followed by 14 days heat challenge (HS; 33+/-7C, 15-55% RH). After a 14-day recovery (TN), all cattle were exposed to 7 days TN followed by 14 days HS. Thermal conditions were recorded continuously, and temperature humidity index was calculated. The predicted point at which Tcore increased was best determined by using a Tcore lag of 3 hours relative to Ta. The breakpoints between prior heat-challenged animals and 1st exposure animals were similar (24.8-25.1C). Temperatures above these break points were used to plot the slope of Tcore to Ta relationships for beginning and ending periods of HS for both groups (days 11-13 and 19-21). The slope of the line did not change with seconded HS exposure, but the line shifted downward approximately 0.3C for both 1st exposure groups during the 14 day HS period. There was overlap of Tcore to Ta relationship at the start of HS for steers exposed for the first or second time to HS indicating little effect of previous exposure. However, steers exposed
a second time to HS experienced a 0.5C reduction in Tcore response to Ta with repeated exposure.
Impacts
Changes in thermal status of cattle in a feedlot environment can be predicted using the combination of air and black globe temperature inputs. Predictive success is improved with inclusion of time delays of 1-3 h. Separate predictive equations for internal temperature must be developed for different core regions. Adaptation to heat stress does occur with continuous heat challenge, but there is no clear indication that adaptation carries over following a 14-day recovery period at thermoneutrality.
Publications
- Leonard, M.J., D.E. Spiers, and G.L. Hahn. 2001. Adaptation of feedlot cattle to repeated sinusoidal heat challenge. Proc. 6th Int. Livestock Symposium.
|
Progress 01/02/00 to 12/31/00
Outputs
Fescue toxicosis is a serious problem for any animal industry that utilizes fescue as a food source. A model of fescue toxicosis has been developed where rats consume a diet of endophyte-infected fescue seed (EIF) for several days before and during exposure to heat stress. Two studies using the rat model were conducted. Study 1 determined the appropriate sequence for administration of EIF diet and heat stress. Telemetric transmitters were surgically implanted in rats to monitor core body temperature (Tcore). Rats were housed at thermoneutrality (TN; 21C) and fed endophyte-free diet (EFF). After equilibration, rats were randomly assigned to EIF or EFF diets, and simultaneously exposed to heat stress (HS; 31C) for 23 days. Diets containing EIF were formulated to deliver ergovaline (i.e., primary toxin in EIF) at 160 ug/kg BW/d. Rats receiving EIF showed decreased feed intake within one day of exposure to stressors, and decreased weight gains by day 3 of exposure.
Average daily Tcore was higher for EIF-fed rats by day 2 of exposure to dual stressors. These rats also had higher average daily maximum Tcore throughout, reaching a peak of 40C on day 3 of exposure. The major difference between EIF and EFF groups was in maximum daily Tcore. In a previous study, animals received EIF at TN, one week prior to HS. Reduction in feed intake occurred upon introduction of EIF, and equaled reduction in the present study during HS. Weight gains were also immediately decreased with EIF. Significant EIF-induced hyperthermia did not occur until day 3 of HS, with maximum Tcore on day 6 (39.9C). As in the present study, this remained in effect for the duration of HS. These results suggest that administration of endophyte-infected fescue seed before, or in conjunction with heat stress, has similar effects on performance and thermoregulatory ability. Study 2 examined the vasoconstrictor response that occurs with fescue toxicosis. Nitric oxide is a vasodilator that
might reduce effects of EIF. All animals were maintained at 21C for 4 days followed by 20 days exposure to 31C. Treatment diets began after 5 days at 31C. Nitric oxide donor rats received 120 mg molsidomine/ml drinking water (M), and EIF diets contained 160 ug ergovaline/kg BW/day. Ingesting EIF increased Tcore at night. In contrast, M-treated animals had lower Tcore at night compared to M-free animals. Moreover, animals treated with combination of EIF and M had lower Tcore during the night than animals ingesting EIF alone. Feed intake of all animals decreased at 31C. Ingesting EIF caused a reduction in daily feed intake, daily gain and feed efficiency. Even though molsidomine had no effect on these three variables, it reduced daily water intake compared to M-free treated animals. The EIF diet caused a reduction in serum cholesterol and amylase levels, as well as serum alkaline phosphatase, and phosphorus. Results from the current study confirm increased hyperthermia due to
EIF-ingestion, and suggest that nitric oxide has an alleviating-effect on heat stress.
Impacts
It is possible to use a rat model of fescue toxicosis to identify treatments. Administration of endophyte-infected fescue seed before, or in conjunction with heat stress, has similar effects on performance and thermoregulatory ability. Fescue toxicosis-induced hyperthermia can be reduced using nitric oxide to increase peripheral vasodilation and heat loss.
Publications
- Eichen, P.A., D.E. Spiers, G. Rottinghaus, and K. Fritsche. A chronic model of performance and thermoregulatory responses to ergot bodies. . J. Anim. Sci. 78 (Suppl. 2): 37, 2000
- Eichen, P.A., M.S. Eibs, D.E. Spiers, G. Rottinghaus, and K. Fritsche. A model of fescue toxicosis: Effect of exposure time to endophyte-infected diet.. J. Anim. Sci. 78 (Suppl. 1): 45, 2000
- Al-Tamimi, H., D.E. Spiers, and M. Ellersieck. Nitric oxide effects on rats fed an endophyte-infected seed diet. J. Anim. Sci. 78 (Suppl. 1): 46, 2000
|
Progress 01/01/99 to 12/31/99
Outputs
The Midwest experienced several heat waves during July and August 1999 that had a large impact on feedlot cattle. One heat episode in Nebraska resulted in death losses and lower production totaling $21 million dollars. Problems associated with environmental stress are significant, and they must be addressed in order to improve the agricultural system. The first phase of a collaborative study with the University of Nebraska and ARS (MARC and Texas Tech locations) began at the University of Missouri in the summer of 1999 to develop a model of the dynamic responses of cattle to heat stress. Twelve Angus/Simmental steers were implanted IP with 2 different telemetric transmitters (Innotek, Inc. vs. Mini-Mitter Co., Inc.) for comparison of performance. All animals were placed in the Brody Environmental Chambers and exposed to thermoneutral conditions of 12-26C for 7 days of equilibration. Animals were then exposed to either 26-40C or 12-26C for 2 weeks. Daily measurements
included determinations of respiration rate and skin temperature at 0600, 1000, 1800, and 2200 h, and measurement of feed and water intakes. Following the initial test, animals were provided 2 weeks of recovery in a thermoneutral environment. The study was then repeated with all animals exposed to the heat stress condition of 26-40C to determine the effect of short-term heat acclimation on the response to cycling heat stress. Once this study was completed in early July 1999, all steers were moved to the MU South Farm feedlots for further testing. Animals were followed from July through August, and exposed to sun with limited access to shade during the initial portion of this time. We continuously recorded core body temperature (Tcore) and ambient conditions (i.e., air (Ta) and black globe (BG) temperatures, percent relative humidity) throughout the period In late July, all animals were used for several weeks in a collaborative study with the above groups to test and quantify the
benefit of shade. We were fortunate to have a significant heat wave in mid-Missouri during this period, and were able to collect data on both animals and environment during this critical time. In the field study, linear increases in Tcore occurred above 23.5C (Ta) and 31.8C (BG). Correlation coefficients above these critical temperatures for relationships of Tcore to Ta and BG were 0.74 (P<.001) and 0.72 (P<.001), respectively. Temperature-humidity indices (THI, BGTHI) are often used as measures of potential heat stress. While all indices showed linear responses, Ta was the better indicator for thermal stress. However, BGTHI compared to THI showed a higher level of correlation with Tcore, especially at lower levels of stress. Further studies using continuous monitoring methods, will quantify the effect of solar radiation on performance for improved prediction of the impact of heat stress on performance.
Impacts
Further analysis of the data from these studies is in progress. Studies of feedlot cattle exposed to a heat wave, such as experienced this summer, have been able to quantify the benefit of shade. Provision of shade for cattle is a simple, inexpensive action which could save lives and, in the long-term, diminish the reduction in productivity.
Publications
- No publications reported this period
|
Progress 01/01/98 to 12/31/98
Outputs
OBJECTIVES: 1)To develop tests that can be used to identify genetic differences in animal response to thermal stress conditions; 2)To determine the thermoregulatory profile for mice containing the metallothionein/bovine growth hormone transgene. PROGRESS: 1) A collaborative study was conducted with Cornell University, USDA-ARS MARC, and the University of Nebraska to determine changes in heat exchange compartments for Simmental heifers during heat stress, and test "field-test" devices for continuous recording of rectal temperature and respiration rate. Animals were tested in the Brody Climatology Laboratory at 18, 28, 30, and 32C to determine convective, radiative, and evaporative exchanges, and at the University of Missouri South Farm. The results of this study are now being analyzed. 2) Nontransgenic and transgenic mice with the metallothionein/bovine growth hormone transgene were tested to determine resting metabolic rate (RMR), cold-induced thermogenesis, and
beta-agonist stimulated nonshivering thermogenesis. Although RMR tended to be lower in transgenics compared to nontransgenic mice, both groups maintained the same colonic temperature (Tco) at 31C, but Tco decreased more in transgenic relative to nontransgenics at cold Ta. For each degree decrease in Ta between 31 and 17C, nontransgenic mice increased heat production by 1.03 watt/kg, whereas transgenic mice increased it by only .56 watt/kg, indicating that the thermogenic response of transgenics to cold Ta was inferior. The magnitude of the maximal increase in Tco after beta-agonist stimulation was similar for both groups, but the response rate was slower in transgenics. It is suggested that mean body mass and substrate availability for shivering thermogenesis are reduced in transgenics relative to total body weight, and they allow Tco to decrease at low Ta to conserve energy.
Impacts
(N/A)
Publications
- Moura, A.S.A.M.T. , D.E. Spiers, and W.R. Lamberson. 1998. Thermogenic activity of growth hormone transgenic mice. Growth, Development and Aging (Submitted).
- Moura, A.S.A.M.T. , W.R. Lamberson , and D.E. Spiers. 1998. Cold-induced thermogenic response in MT-bGH transgenic mice. In: Reuniao Anual da Sociedade Brasileira de Zootecnia., 35, Botucatu. Proceedings ... Botucatu, SBZ, 4:40-42.
- Moura, A.S.A.M.T. , W.R. Lamberson , and D.E. Spiers. 1998. Beta-agonist stimulated thermogenesis in MT-bGH transgenic mice. In: Reuniao Anual da Sociedade Brasileira de Zootecnia., 35, Botucatu. Proceedings ... Botucatu, SBZ, 4:43-45.
|
Progress 01/01/97 to 12/31/97
Outputs
Bovine/rodent models were used to determine responses to growth promotants during heat stress. Studies have shown that bovine growth hormone (bGH) is superior to bovine placental lactogen (bPL) in stimulating growth and lactation. Likewise, bGH has greater somatogenic activity in different age groups and thermal environments. Initial studies of bPL analog T188 suggest that its lactogenic potential is superior to bGH. Effective experimental models have now been developed and tested for analysis of new bPL analogs. An additional study was conducted to determine growth promotant activity of recombinant bovine prolactin (bPRL) as a function of age and ambient temperature (Ta). In prepubertal rats, bPRL treatment did not alter body weight gain or feed intake. Fat free mass, total body water and liver mass were not affected by bPRL, but were decreased in heat-stressed rats. Reproductive tract but was increased in rats receiving bPRL compared to control rats. Adult rats
treated with bPRL increased body weight above control level only under TN condition. Fat free mass and total body water were lower in HC rats compared to TN rats, but not affected by rBPRL treatment. This growth promotant has age- and Ta-dependent effects in rats, but is a less effective stimulant of growth than either bovine growth hormone or placental lactogen.
Impacts
(N/A)
Publications
- Eichen,P.A.,Spiers,D.E.,Westhoff,K.E. and Byatt,J.C. 1997. Recombinant bovine prolactin effects in prebubertal and adult rats at different ambient temperatures.J. Anim. Sci. 75 (Suppl. 1): 158.
- Becker,B.A. 1997. Endocrine and thermoregulatory responses to acute thermal exposures in six-month-old pigs reared in different neonatal environments.J. Therm. Biol. 22:87-93.
- Wilson,S.J.,Marion,R.S.,Spain,J.N.,Spiers,D.E.,Keisler,D.H. and M.C. Lucy,M.C. 1997. Effects of heat stress on ovarian function in dairy cattle.I.Lactating cows.J. Dairy Sci.,In press.
|
Progress 01/01/96 to 12/30/96
Outputs
Bovine/rodent models were used during this period to examine responses to heat stress and/or growth promotants in situations related to animal production function. Holstein dairy cows in early lactation were exposed to 28.5C under controlled conditions, before and during fan cooling. Telemetric temperature transmitters were used to measure core body temperature (Tcore) throughout the study. Tcore peaked prior to midnight under thermoneutral conditions and shifted to early morning hours during heat challenge. Fan cooling produced a rapid 0.5C reduction of Tcore. In a separate study, recombinant bovine placental lactogen (rBPL) was given daily to 50 and 100 day-old female rats to determine activity at thermoneutral (TN; 21C) and heat-challenge (HC; 31C) temperatures. Body weight at 50 days was unaltered by rBPL in HC rats, but increased in TN rats. Daily food intake was not affected by rBPL. At 100 days, body weight of rBPL rats surpassed controls in TN and HC rats.
Daily food intake relative to body mass was greater for rBPL than control TN rats, but not different for HC rats. Although rBPL rapidly increased growth in adult rats at different ambient temperatures, it was only slightly effective in prepubertal rats.
Impacts
(N/A)
Publications
- SPIERS, D. E., ET.AL. 1996.. Recombinant bovine placental lactogen stimulation ofgrowth in adult rats at different ambient temperatures. J. Anim. Sci. 74(Suppl. 1): 154.
- EICHEN, P.A. ET.AL. 1996. Recombinant bovine placental lactogen stimulation of growth in prepubertal rats at different ambient temperatures. J. Anim. Sci. 74(Suppl. 1): 155.
- SPAIN, J. and SPIERS, D.E. 1996. Effects of Supplemental Shade on Thermoregulatory Response of Calves to Heat Challenge in a Hutch Environment. J.Dairy Sci.79: 639-646.
- SPIERS, D. E., ET.AL. 1996.. Ethanol Effect on Activation and Maintenance of ColdStress Response in Immature Rats. Pharmacol. Biochem. Behav.54: 555-564.
- DICOSTANZO, A., ET.AL. 1996.. Nicotinic Acid Supplementation for Lactating Holstein Cows Under Heat Stress Conditions. J. Dairy Sci.(in press).
- BECKER, B. A., ET.AL. 1996. Endocrine and Thermoregulatory Responses to Acute Thermal Exposures in Six Pigs Reared in Different Neonatal Environments. J. Thermal Biology (in press).
- SPIERS, D. E., ET.AL. 1996. Treatment of adult rat with recombinant bovine somatotropin increases growth during heat challenge. FASEB J. 10: A113.
|
Progress 01/01/95 to 12/30/95
Outputs
Bovine/rodent models were used during the period to examine responses to heat stress in situations related to animal production/function. One emphasis was to define the action of toxins found in endophyte-infected tall fescue that might contribute to fescue toxicosis. Darily injection of Angus yearlings with ergovaline during heat stress resulted in an increase in core body temperature that was more pronounced at night, and attributed to reduction in peripheral heat loss. Repeat injection of rats for 6 days with ergovaline disrupted circadian rhythm of core body temperature. There was no indication that such treatment resulted in adaptation to this toxin. A second emphasis has been to determine the effectiveness of recombinant bovine somatotropin(BST) as a growth promotant during heat stress. Female rats, 50 and 100 days of age, received 10 day injection of BST. Both heat-stressed age groups on BST increased growth rate to that of rats at thermoneutrality, and double
that of heat-stressed control rats. Treatment with BST did not result in increased feed intake. Fat free mass was increased by BST treament at 100 daysof age but not at 50 days of age. There were indication that BST treatment during heat stress results in an increase in energetic efficiency of young and adult rats. Both areas of emphasis over the last year have increased our understanding of how animals respond to heat stress,and genereated new approaches to reduce its effect on performance.
Impacts
(N/A)
Publications
|
Progress 01/01/94 to 12/30/94
Outputs
Studies have concentrated on developing both rat and cattle models of the interaction between toxins, derived from endophyte-infected tall fescue, and exposure to heat stress. Dose-response relationships for ergovaline (i.e., the primary toxin) effect on thermoregulatory ability were developed for thermoneutral and heat challenge conditions. Ergotamine (i.e., a secondary toxin) was found to be half as potent as ergovaline. Studies are now underway to determine if repeat treatment with ergovaline alters circadian rhythm for body temperature and results in adaptation to the toxin. Cattle exposed to controlled heat challenge condition exhibited a significant alteration in circadian rhythm for body temperature. Consumption of endophyte-infected tall fescue during this period resulted in an additional increase in peak daily core body temperature. Future studies will examine potential treatment or management protocol which might effectively reduce symptoms associated with
fescue toxicosis.
Impacts
(N/A)
Publications
- WARNER, D., SPAIN, J., BATEMAN, G., and SPIERS, D. 1994. Physiological responses of young calves housed in hutches with or without supplemental shade during summer. Proc. of Third International Dairy Housing Conference. Amer. Soc. of Agr.
- ZHANG, Q., SPIERS, D. E., ROTTINGHAUS, G. E., and GARNER, G. B., 1994. Thermoregulatory effects of ergovaline isolated from endophyte-infected tall fescue seed on rats. J. Agric. Food Chem. 42:954-958.
- LOPEZ, J., GOODBAND, R. D., JESSE, G. W., NELSSEN, J. L., TOKACH, M. D., SPIERS, D. E., and BECKER, B. A., 1994. The effects of diets formulated on an ideal protein basis on growth performance, carcass characteristics, and thermal balance.
- SPIERS, D., AL-HAIDARY, A., and GARNER, G., 1994. Fescue toxicosis and heat stress in cattle. Missouri Beef Cattleman, May, 1994.
- NESBITT, M., and SPIERS, D. E., 1994. Modification of thermoregulator ability in the rat following long-term heat exposure. J. Anim. Sci. 72:154. (Abstract).
|
Progress 01/01/93 to 12/30/93
Outputs
All studies conducted during this period were designed to determine the effects of environmental stress on animal function and performance. Rodent and bovine models were used to examine mechanisms by which endophyte-infected tall fescue impairs animal response to environmental stress. Thermoregulatory ability was measured following administration of ergovaline (i.e., the principle toxin), either directly or in diet form, under controlled environmental conditions. Studies continued with the Agricultural Research Service to define the stress tolerance ability of the young pig, with concentration on regional differences in body temperature during long-term adaptation to selected ambient temperatures. An environmental test chamber is being developed for the young pig that will allow for sophisticated studies of thermal balance under controlled conditions. Also, a rat model of long-term adaptation to heat stress has been developed, and studies are now being performed to
assess the involvement of an endogenous opioid, (beta)-endorphin, in mediating this adaptive process. Field studies were conducted during the last year to evaluate the thermoregulatory ability of calves during hot summer months in mid-Missouri, and determine the effectiveness of polyethylene hutches in reducing thermal stress under these conditions. A total of 3 graduate students were involved in these projects.
Impacts
(N/A)
Publications
|
Progress 01/01/92 to 12/30/92
Outputs
Several projects related to thermoregulatory response to environmental stress were initiated and one project was terminated during this period. The completed project dealt with the effect of ethanol on thermoregulatory ability at an early age. Studies concentrated on ethanol-induced changes in heat production and loss in cold and warm environments. A comparison of heat stress responses in tropical (Romo sinuano) and temperate (Angus) breeds of Bos taurus cattle were also made to determine the potential benefits derived from crosses of these strains. Studies were initiated in cooperation with the ARS to determine the effects of thermal stress applied before and after birth on growth and development of the young pig. The first project has been to identify regional differences in body temperature of the young pig and measure the change that occurs as a function age at different environmental temperatures. In conjunction with this work, studies were begun using a rat model
to determine the effects of heat stress on early development. Evaluations of differences in temperature control, body composition, and endocrine status are being performed as a part of this study. A final study was conducted to examine the energy metabolism of a transgenic mouse line that expresses the bovine growth hormone gene.
Impacts
(N/A)
Publications
|
Progress 01/01/91 to 12/30/91
Outputs
We are constructing a laboratory which will use indirect calorimetric, techniques to determine how young animals respond and adapt to environmental stress. Once the test equipment is assembled we will be able to measure both thermogenic and thermolytic responses of mammals (rats, mice) and birds (chickens, turkeys, quail) to controlled thermal stress. Heat production determinations will include measurements of oxygen consumption for estimation of metabolic heat production, plus quantitation of nonshivering and shivering thermogenic abilities. Heat loss determinations will include measurements of evaporative heat loss, cutaneous heat flux, plus skin and rectal temperatures. The information gathered in this laboratory will be used to construct heat balance equations for each group of animals, and allow for the identification of mechanisms used for the maintenance of homeothermy. Our first project is to determine the early changes in thermoregulatory ability and endocrine
function of rats following perinatal exposure to heat stress. Animals will be continuously exposed either in utero or in the litter to heat stress conditions, followed by testing in the laboratory to assess changes in function. A primary objective is to determine if there are critical periods during early development when the mammal is extremely sensitive to heat stress. The information gathered from this study will be an important contribution to piglet studies being conducted by the Agricultural Research Service.
Impacts
(N/A)
Publications
- SPIERS, D.E. and L.E. FUSCO. 1991. Age-dependent differences in the thermoregulatory response of the immature rat to ethanol. Alcoholism: Clin. Exp. Res. 15:23-28.
- SPIERS, D.E. and S.C. BAUMMER. 1991. Thermal and metabolic responsiveness of Japanese quail embryos following periodic exposure to 2450-MHz microwaves. Bioelectromagnetics 12:225-239.
- ADAIR, E.R., D.E. SPIERS, L.E. FUSCO, B.W. ADAMS and S.K. HARTMAN. 1991. Microwave incubation of the newborn mammal:A feasibility study. Presented at the 13th Annual Meeting of the Bio-electromagnetics Society, Salt Lake City.
|
|