Establishing Tolerable Ergot Levels for Weaned Pigs
Ergot is a fungal disease that primarily affects wheat, barley, triticale and rye. It is most often seen in years where wet weather prevails in the spring and early summer or during the flowering stage of cereal crops. An ergot infection may not necessarily reduce grain yield but it will definitely have an impact on grain quality. As a result of the infection, the grain kernels are replaced with poisonous alkaloid-containing ergot sclerotia, hardened bodies that are formed by the fungus.
The effect of feeding ergot-contaminated grain to pigs is not consistent, and ultimately depends on both the ergot content and the alkaloid concentration. The Canadian Grain Commission currently allows 0.02% ergot by weight in the highest grade wheat to 0.10% for the lowest grade of most wheat classes. When pork producers are considering their options, whether to sell contaminated wheat or to keep it for feeding to their herd, questions arise as to the acceptable level of ergot in swine diets. Although it is technically possible to remove ergot from cereal grains, complete removal may be impossible or impractical in a commercial setting. As a result, it would be very useful to define safe upper limits for the use of ergot-contaminated grain in swine diets.
Ergotism is generally associated with poor performance in pigs and alkaloids are generally thought to inhibit the secretion of certain hormones that may interfere with the development of the mammary glands and lactation. Since so little information exists to help producers make sound decisions on safe feeding levels of wheat containing ergot to swine, researchers at the Prairie Swine Centre set out to investigate the problem. The objectives of the experiment were to define the quantity of ergot and ergot alkaloids that may be included in the diet of weaned pigs without negatively affecting performance, and to identify clinical signs that may be used to identify low-level ergo-toxicity.
For the experiment, wheat ergot sclerotia were isolated and added on a weight basis to a basal diet at 0.00 (control), 0.05, 0.10, 0.25, 0.50, and 1.00% and fed to 192 weaned pigs for 28 days, beginning 7 days post-weaning. The ergot sclerotia used in the experiment contained 1880 mg/kg total alkaloids, with a range of 110 to 755 mg/kg for the five individual alkaloids measured. (Refer to Table 1 for the itemized levels of ergot and associated alkaloids included in each dietary treatment.) In addition to tracking performance parameters throughout the experiment, pigs were also monitored daily for abnormal behaviour and any signs of ergotism, such as gangrenous lesions on the extremities (snout, ears, eyelids, and limbs).
The performance results are summarized in Table 1. Pigs fed the 1.00% diet gained 37% less than the control. Ergot alkaloids decreased average daily intake by 10% and feed efficiency by 29% over the entire period although average daily intake was not affected during the initial 14 days of the trial. The researchers suggest that it is reasonable to conclude that the reduction in feed consumption during that last 2 weeks of the experiment was a result of an overall increase in the intake of alkaloids as a proportion of body weight. The results suggest that the maximum tolerable ergot level in the diet was 0.10 and 0.05% based on average daily gain and average daily feed intake, respectively, corresponding to 2.07 mg and 1.04 mg alkaloid/kg diet.
The researchers also measured prolactin concentrations from blood samples taken from the pigs. Prolactin is a hormone that is necessary in normal development of mammary glands in gilts and the expression of maximum milk potential in lactating sows. Ergot alkaloid consumption severely reduced serum prolactin concentrations by an average of 43% for all treatments compared to the control. The researchers suggest that, until further data is available on the impact of consuming ergot-contaminated feed on future reproductive performance of gilts, feed containing ergot may not be suitable for pigs that are destined to enter the breeding herd. The long-term effects on reproductive development are simply unknown.
Consumption of up to 1.00% ergot by piglets did not show any external symptoms of ergotism. As the results suggest, reduced feed intake may not necessarily be apparent during low-level ergo-toxicity in the weaned pig. Increased intake of ergot-contaminated feed caused a severe reduction in the growth performance of weaned pigs with or without an effect on feed intake. This indicates that low levels of ergot in feed, although it may not result in overt symptoms, will impair growth rate and days to market. The negative impacts may ultimately be seen in the inefficient use of facilities, lower productivity and, potentially, higher susceptibility to disease. At 1800 mg alkaloid/ kg ergot, piglets cannot tolerate more than 0.10% ergot sclerotia in their diet. A safer level would be 0.05% based on feed intake.
a 0.25% dietary ergot and above differ from the control
Source: Oresanya, T.F., Patience, J.F., Zijlstra, R.T., Beaulieu, A.D., Middleton, D.M., Blakley, B.R., and Gillis, D.A. 2003. Defining the tolerable level of ergot in the diet of weaned pigs. Can. J. Anim. Sci. 83: 493-500.
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