Pre Treatment Levels Two Hours After Treatment example essay topic

! SSA review of research articles dealing with the potential effects of ergot alkaloids on the growth and reproductive performance of beef cattle grazing fescue. !" By Pia A. Herring September 20, 2001 Assignment #2 A GSC 514 Introduction Due to the enormous amounts of money that are lost yearly to tall fescue toxicosis, there have been numerous studies conducted to try and discover the specific mechanisms of action that the toxins present in the fungus Neotyphodium follow. Researchers have looked at the effect of the alkaloids at the cellular level, as well as observing the effects of the alkaloids on physiological responses and hormonal changes. All in an effort to try and better understand the different ways that the toxins affect susceptible animals. It is believed that if the mechanisms of action are better understood, that it would be easier to determine ways to counteract the effects of the toxins, and decrease the large amounts of money lost every year to tall fescue toxicosis. Discussion One of the studies that have been conducted to discover the mechanisms of action that the toxins follow looked at the mechanism from a cellular level.

Larson et al. (1999) took commercially available, acid amides, and alkaloids, N-acetyl and N-, and added them to cellular cultures of rat D 2 Dopamine receptors to see if they would bind to the receptor sites. The D 2 Dopamine receptors were chosen, because they regulate prolactin release; which if inhibited is a biological indicator of toxins present from the consumption of endophyte infected tall fescue. The D 2 Dopamine receptors have also been implicated in cardiovascular, thermo regulatory, nervous, and adrenal functions, as well as H 2 O intake.

What they found was that the ergo peptide and acid amides acted like endogenous dopamine and did bind to the receptor sites; as well as inhibiting cyclic AMP production. While at the same time the alkaloids, N-acetyl and N-, did not have an effect on the receptor sites or on cyclic AMP production. In another study, the interaction of ergo valine with 5-HT 2 A, 5-HT 1 B/1 D, and alpha 1 receptors in isolated arteries of the rat and guinea pig was looked at (Schoning et al., 2001). They found that the ergo valine had a powerful constrictor effect on vascular tissues, due its mediation from the activation of 5-HT 2 A, 5-HT 1 B/1 D receptors. And it is this vascular constriction that affects the thermo regulatory response problems that animals having fescue toxicosis exhibit. If you take what was learned from these two studies about the interactions of the alkaloid toxins at the cellular level, you will see that the toxins are capable of binding to important receptor sites in the body.

And some of these receptor sites are implicated in controlling functions that are know to be affected when fescue toxicosis is present. Studies have also been conducted to look at the effects of the alkaloid toxins at an overall systems level. Browning and Leite-Browning (1997), looked at the effect of ergot amine tart ate (ergot amine) and maleate on thermal regulation and cardiovascular function. Both of these alkaloids were separately administered intravenously (i. v.) along with saline, in a manner that would allow for each animal to be exposed to each of the treatments. What they found was that the administration of the saline produced no change in measured physiological responses.

The ergot amine caused respiration rates and blood pressure to rise, and plasma prolactin concentrations to decrease by 75%. The also caused a rise in respiration and blood pressure and a 38% decrease in plasma prolactin concentrations. In a similar study done by Osborn et al. (1992) it was found that the ergot amine added to an endophyte free diet produced similar responses to those found in cattle that consume endophyte infected fescue. The feed intake (FI), average daily gain (ADG), heart rate (HT), and peripheral temperatures (ear canal, ear tip, pastern, coronary band, & tail tip) all decreased for the endophyte infected and ergot amine / endophyte free diets for the first experiment. In the second experiment, the ergot amine / endophyte free diet FI was decreased by almost 49%, when compared to the endophyte free diet.

HT was also decreased by 23 beats / min, while peripheral temperature also decreased. A rise in respiration rates and rectal temperature was also noticed for the ergot amine / endophyte free diet. But then it was thought that maybe animals that were better suited for tropical climates, or heat-tolerant breeds, would not suffer from the symptoms of tall fescue toxicosis, when feed a diet containing the alkaloids. Browning (1999) took Brahman cattle (Bos indic us) feed them a fescue free diet and gave them i. vs. injections of ergot amine, placed them under a heat challenge (HC) and then compared them to Hereford cattle (Bos taurus) that were placed on the same treatments. It was discovered that the Brahman cattle responded similarly to the Hereford cattle with respect to the ergot amine injections and HC. In other studies that have been carried out, the researchers decided to look at the effect of the alkaloids on hormone levels in treated cattle.

In one such study the plasma concentrations of glucagon, insulin, cortisol, and (T 3) were looked at when the cattle were given injections of ergot amine. Browning et al. (2000 a), found that the glucagon and insulin levels changed in response to the ergot amine. In the first experiment they found that cortisol levels after the ergot amine treatment were higher than the saline treatment and pre-treatment levels for a three-hour period following ergot amine administration. Then for the next three hours the ergot amine levels were similar to those of the saline. T 3 levels were higher for two hours following the ergot amine treatment, than for the saline treatment or pre-treatment levels.

When the insulin levels were examined, it was found that these levels were lower than pre-treatment levels for both treatments. For the saline, the insulin levels were gradually lowered throughout the treatment. And for the ergot amine the insulin levels were lower for all eight hour following the treatment, when compared to the pre-treatment levels. As well as being lower than the saline levels for two of the eight hours. Glucagon levels following the ergot amine treatment went up one hour after treatment, fell to pre-treatment levels two hours after treatment, then gradually increased to higher than pre-treatment levels three to four hours after treatment. The decrease in the glucagons levels one hour following ergot amine treatment, may be accounted to the oxytocin that was administered one hour after the beginning of both treatments.

During hour six of observation following treatments, glucagon decreased to levels similar to those prior to the addition of the oxytocin, and to pre-treatment levels in hour seven of the observation. In experiment two, respiration rates were higher for ergot amine during the first seven hours of observation, while there was no change after the saline treatment. Cortisol levels were higher than pre-treatment levels for five hours following treatment with ergot amine, but were lower than pre-treatment levels during the sixth hour after the saline treatment. Two hours after the ergot amine treatment, T 3 levels were also higher than pre-treatment levels. In another study done to examine the effects of ergot amine and on the plasma concentrations of thyroid hormones and cortisol (Browning et al. 1998 a), there was evidence found of T 3 and (T 4) changes due to interactions with the alkaloids.

In experiment one it was shown that in steers given i. vs. injections of ergot amine that levels of T 3 increased in the first hour of observation, but returned to pre-treatment levels two to four hours after treatment. T 4 showed no signs of interaction, and plasma cortisol levels showed no significant changes. When these steers were given i. vs. injections of, T 3 increased after the first hour, but returned to pre-treatment levels during the two to four hour period after treatment. T 4 again showed no signs of interaction, but cortisol levels increase significantly during the four-hour observation period.

Saline injections were also given and showed no signs of interaction with T 3, T 4, or with cortisol levels. In the second experiment the i. vs. injections of ergot amine, , and saline were given to cows that were nursing calves. The results of this second experiment showed that two hours after the administration of the ergot amine, that T 3 was increased, but returned to pre-treatment levels three to four hours after treatment. T 4 also increased, while there were no significant changes in cortisol levels.

Two hour after the was given, there was a noticeable increase in T 3, but once again, three to four hours after treatment began the T 4 returned to pre-treatment levels. But in this second experiment there was a three-hour increase in cortisol levels, then a return to pre-treatment levels for the remainder of the observation period. This experiment indicated that there was a definite response e in cortisol levels to the treatment, in both the steers and the nursing cow. Other studies have looked at the hormones that are linked to important performance traits in cattle. In one such study Browning et al. (1997), examined the effects of ergot amine, , and saline on the plasma concentrations of prolactin, growth hormone, and hormone (LH).

After the administration of the saline it was found that the respiration rates were lower at two hundred-ten minutes after treatment, while there was a rise in prolactin levels. The LH levels did not change, but the growth hormone increased above pre-treatment levels, between one hundred-twenty minutes and two hundred-forty minutes. When the ergot amine was given there was a sharp increase in the respiration rates at thirty minutes, but a decrease back to levels similar to those at pre-treatment, in the rates at two hundred-ten minutes. Prolactin levels decreased at thirty minutes, differed from at one hundred-five minutes, then returned to pre-treatment levels by one hundred-twenty minutes, and were similar to saline levels at one hundred-eighty minutes.

Growth hormone increased after thirty minutes, and after sixty minutes levels were similar to those found prior to treatment; while LH levels had intermediate changes, differing from both the saline and levels. The treatment caused an increase in respiration after thirty minutes, but was not as large of a difference as that seen after ergot amine. Prolactin was consistently lower throughout the two hundred-forty minutes after treatment, while growth hormone increased after thirty minutes, and returned to pre-treatment levels seventy-five minutes after treatment. The LH decreased to levels lower than those found prior to treatment, and during the saline and ergot amine treatments. One other important performance trait is reproduction; this above all others might be the most important. So some researchers have begun to focus their attentions on this area, and the effect that the alkaloids can have on reproductive functions.

Browning et al. (1998 b), found that the reproductive hormonal response to ergot amine dramatically lowered prolactin concentrations and keep them lower over the four-hour observation period. The ergot amine also elevated the respiration rates for two to four hours after treatment. They also found that after the treatments that prolactin was lowered for one to two hours after treatment, but returned to pre-treatment levels after three to four hours. In another study done by Browning et al.

(2001), the effects of an acute ergot amine challenge on reproductive hormones in follicular phase heifers and progestin-treated cows was examined. What they found in experiment one, was ergot amine reduced prolactin levels one to four hours after treatment and increased F 2 f~N (PGFM) concentrations for two to five hours after treatment. Oxytocin was also given to the heifers, four hours after the administration of the ergot amine, but the PGFM did not show a response. In the second experiment the progestin-treated cows were also given ergot amine injections. The prolactin response to the ergot amine exhibited a decline in concentrations by one hundred-twenty minutes after treatment, with a return to pre-treatment levels by two hundred minutes after treatment. These cows also exhibited higher PGFM concentrations after ergot amine, compared to the PGFM concentrations after the saline treatment from one hundred-twenty minutes to two hundred-forty minutes after treatments.

Although both treatments showed a similar increase in PGFM concentrations, the increase in the second experiment was after (GnRH) was given. The LH and follicular stimulating hormone (FSH) concentrations increased one hundred to one hundred-twenty minutes after treatment with GnRH, then returned to pre-treatment levels two hundred minutes after treatment. In another study conducted by Browning (2001), an acute ergot amine challenge was initiated to examine its effect on reproductive hormones in follicular phase heifers and progestin-treated cows. In experiment one, the ergot amine reduced the prolactin levels from one to four hours after treatment, and increased PGFM concentrations two to five hours after treatment. While a PGFM response to oxytocin was not detected. In experiment two, the ergot amine reduced the prolactin concentrations one hundred-twenty minutes after, with a return to pre-treatment levels two hundred minutes after initial treatment.

Cows that were given the ergot amine showed higher PGFM concentrations as compared to the saline treated cows, one hundred-twenty to two hundred-forty minutes after treatments. While both show similar increases in PGFM after oxytocin was given. Plasma LH and FSH concentrations increased one hundred to one hundred-twenty minutes after GnRH was given for both ergot amine and saline, although the LH response to GnRH was greater for those given ergot amine. The ergot amine lowered prolactin concentrations and elevated PGFM concentrations in follicular phase heifers and cows on therapy. Ergotamine also increased the LH response to exogenous GnRH. The data collected, highlighted the potential of alkaloids to affect reproduction through altered endocrine function.

One other study done examined the effect of the alkaloids on the development of pregnancy and endocrine foetal-placenta function in goats. This study done by Engeland et al. (1998), showed that the alkaloids raised a key PGF 2 f~N level in goats. And they surmised that this hormone disturbed the formation of the placenta and its function. And this in turn would have led to the abortions and the birth of the weak kids. The also found that the goats showed classic signs of toxicity: a decrease in feed intake and weight gain, depression, and a raised rectal temperature.

The information that can be taken from all of the studies discussed in this section, show that the ergot amine and can have adverse effects on the reproductive hormones and abilities of both cattle and goats. Implications The information that was presented in this paper, shows the importance of controlling the alkaloids found in the tall fescue. All of these studies showed the short-term effects of the alkaloids on FI, ADG, HT, peripheral and rectal temperatures, plasma concentrations of glucagon, insulin, cortisol, T 3, T 4, LH, FSH, prolactin, growth hormone, GnRH, and PGFM. But I believe that a more relevant study would be to look at the long-term effect of the alkaloids on cattle performance, reproduction, and hormone levels. Since most farmers in the southeast use tall fescue as a major forage for their animals on pasture, it would be of better service to them to conduct a study on the long term effects on the animals. Cited Literature Browning, R. Jr., F.N. Schrick, F.N. Thompson, T. Wakefield, Jr.

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