DIAGNOSTIQUEES AU CANADA. Ontario. Assessment of trace mineral and vitamin E status ... plant in Kitchener, Ontario, and from the University of. Guelph ...
RAPPORT DES MALADIES DIAGNOSTIQUEES AU CANADA
CROSS-CANADA DISEASE REPORT
Ontario Assessment of trace mineral and vitamin E status beef cows in Ontario mineral requirements and assessment of herd mineral status are strong areas of interest for producers and veterinarians. Trace minerals are required for a variety of metabolic functions, including immune response to pathogenic challenges and maintenance of reproduction. Diagnosing and treating a subclinical trace mineral deficiency may have a positive economic impact on beef cattle production. Subclinical mineral deficiencies in cattle may be a larger problem than acute deficiencies, because specific clinical signs are often not evident to allow the producer and veterinarian to recognize the deficiency. Animals with a deficiency status may reproduce or grow at a reduced rate, have decreased feed efficiency, and have a depressed immune system. It has been well documented that several diseases of cattle are caused by or are associated with a deficiency of either selenium (Se) or vitamin E, alone or combined, usually associated with some predisposing factor. Subclinical deficiencies of Se and/or vitamin E are not determined easily and may be associated with other Trace
mineral deficiencies.
The difficulty in diagnosing trace mineral deficiencies is due to a number of factors. The identification of trace mineral deficiencies based on blood (serum) concentrations may be misleading. Serum copper (Cu) levels do not have a high correlation with liver Cu levels and are not considered a reliable indicator of Cu status in cattle. All Cu circulating in the blood is not available to the animal, and serum Cu values can be affected by dietary molybdenum (Mo) and sulfate, infection, trauma, and the stage of gestation. Most of the grain and forages grown in Ontario are deficient in several trace minerals. Young et al (1) sampled grains and forages from various parts of Ontario, and found that 79% of grains and 86% of forages contained less than 0.10 mg/kg of Se, the minimum recommended
dietary requirement for animals. As well, the majority of the forages grown in Ontario do not contain enough Cu, zinc (Zn), or manganese (Mn) to meet the requirements for beef cattle. In a recent survey, our objective was to identify deficiencies in cull beef cows, as well as to try to establish reference intervals for several typical beef herds in Ontario. During 1999-2000, blood and liver samples were collected by convenience from 55 cull beef cows of unknown health status at slaughter from a packing plant in Kitchener, Ontario, and from the University of Guelph, Animal Science facility. The cows represented 45 farms from various parts of Ontario. The vitamin E and trace mineral levels in these samples are presented in Table 1. Blood samples were also collected from cull cows at 5 selected beef herds (10 cows per herd) with no known clinical problems and from various parts of Ontario. These herds were selected by convenience but were considered typical of herds in Ontario. The vitamin E and Se levels of beef cows judged clinically healthy by the herd veterinarian are presented in Table 2. We found very low serum levels of Se, Cu, and Mn in most of the animals tested; the levels of Cu and Mn varied greatly. Ninety-six percent of the cull cows were deficient in blood Se. Seventy-three percent were deficient in Cu, with 51% and 18% being deficient in Mn and iron, respectively. These results suggest that many cull beef cows may be deficient in vitamin E, Se, Cu, and Mn. A larger survey would be needed to confirm the degree of vitamin E and trace mineral deficiency in herds in Ontario. It is interesting to note that the 2 herds receiving sodium selenite mixed with a salt-mineral mix (20 mg/kg salt) were borderline in vitamin E. There can be many signs of deficiency with each deficient element. Cattle may exhibit a wide range of signs depending on the severity of the deficiency and the length of time they have been deficient. Diagnosis of trace mineral deficiencies can be very difficult. Most work has been done with individual elements, and the
Table 1. Vitamin E and trace mineral levels in cull beef cows from Ontario at slaughter (n = 55)
384
Nutritional component
Tissue
Mean
Minimum
Maximum
Vitamin E (pg/mL) Vitamin E/cholesterol Vitamin E (pig/mL) Selenium (pg/mL) Selenium (pg/g) Copper (j.g/g) Iron (pg/g) Manganese (pg/g) Molybdenum (ptg/g) Zinc (pg/g)
Serum Serum Liver Blood Liver Liver Liver Liver Liver Liver
3.13 2.2 11.59 0.09 0.81 100 257 8.55 3.59 127
0.39 0.73 2.10 0.02 0.30 8 105 5.30 2.30 80
8.20 5.1 34.60 0.18 1.40 328 712 13.00 5.40 360
Range of adequate levels (2) 3.0-6.0 2.5-6.0 20-40 0.17-1.2 0.9-3.5 75-300 135-900 7.5-18 0.42-4.2 75-300 Can Vet J Volume 42, May 2001
Table 2. Vitamin E and selenium levels of clinically normal cows in selected beef herds in Ontario Reference herdsa Mean (range) Nutritional component Serum vitamin E
(pg/mL) Vitamin E/cholesterol (ratio) Blood selenium
(p.g/mL)
Herd A (n = 10)
Herd B (n = 10)
Guelph area (n = 10) Mean (range)
Northern Ontario (n = 10) Mean (range)
Western Ontario (n = 10) Mean (range)
AHL range of adequate levels Mean (range)
3.17 (2.49-4.11) 2.59 (1.20-5.21) 0.18 (0.16-0.21)
2.19 (1.90-3.92) 2.26 (1.58-3.03) 0.18 (0.16-0.21)
4.49 (3.13-4.62) 3.11 (2.42-4.68) 0.07 (0.04-0.09)
5.3 (2.98-5.17) 3.61 (2.61-4.55) 0.12
2.73 (2.18-3.90) 2.49 (1.65-3.92) 0.14 (0.05-0.17)
3.0-6.0
(0.09-0.17)
2.5-6.0 0.17-1.20
AHL - Animal Health Laboratories aReference herds were supplemented with selenium in the salt (20 mg/kg salt, for 3 mo)
effects of multiple deficiency problems have received little attention. It is likely that most of the trace mineral deficiency problems experienced by cattle in Ontario are of a subclinical nature. An increase in weaning weight and weight gain in yearlings through trace mineral supplementation has been recorded (3). Improvement in reproductive performance has also been observed with adequate trace mineral supplementation. Recent research has demonstrated that Cu, Zn, Mn, and Se are required for optimum functioning of the immune system in cattle. How much of these trace elements is required to optimize immune function is not known. Some evidence suggests that more Se is required to optimize immune function than is required to prevent white muscle disease, retained placentas, and other problems commonly associated with Se deficiency (4). Producers who have upgraded the trace mineral status of their herds through provision of appropriate supplement have observed improvements in the general health, growth, and reproductive performance of their animals. This is not surprising when one considers that all the animals tested by us were deficient in at least 2 elements, and some in as many as 4. Trace element nutrition of livestock is extremely complicated. Many interactions occur among the trace elements, and between trace elements and other nutrients. These interactions can be very complex and many are
X
not well understood. All trace elements are toxic if fed in excessive amounts. Testing of feed, blood, or tissue levels of trace elements may be warranted from time to time.
Acknowledgment This study was funded in part by the Ontario Cattlemen's Association.
References 1. Young LG, Jenkins KJ, Edmeads DM. Selenium content of feedstuffs grown in Ontario. Can J Anim Sci 1977;57:793-799. 2. Puls R. Mineral Levels in Animal Health. 2nd ed. Clearbrook, British Columbia: Sherpa International, 1994. 3. Marston T. Trace mineral supplementation in beef cattle. Compend Contin Educ Pract Vet 1999;21:S21-S28. 4. Swecker WS, Eversole DE, Thatcher CD, Blodgett DJ, Schurig GG, Meldrum JB. Influence of supplemental selenium on humoral immune responses in weaned beef calves. Am J Vet Res 1989;50: 1760-1763.
Brent Hoff, DVM, DVSc, DipTox, Nick Schrier, MSc, Animal Health Laboratory; Herman Boermans, DVM PhD, Department of Biomedical Sciences, Ontario Veterinary College; Harold Faulkner, PhD, Abdullahi Hussein, Analytical Services Unit, Laboratory Services Division, University of Guelph, Guelph, Ontario.
K20
British Columbia/Colombie-Britannique Cutaneous chytridiomycosis in dwarf aquatic frogs (Hymenochirus boettgeri) originating from southeast Asia and in a western toad (Bufo boreas) from northeastern British Columbia ten dwarf aquatic frogs (Hymenochirus boettgeri)
were procured from a wholesaler in Florida, USA, in September 1998 by the Vancouver Aquarium Marine Science Centre in Vancouver, British Columbia. Shortly after initial receipt and introduction of the stock, 3 frogs died but were not presented for diagnostic evaluation; because they had died soon after their arrival, the Can Vet J Volume 42, May 2001
Aquarium presumptively attributed the cause of death to physiologic stress associated with transit and acclimation. The remaining 7 frogs were housed in a glass aquarium with a silica sand substrate, a corner charcoal filter, and a few aquatic plants consisting of grasses and floating frogbit or duckweed. The animals were maintained on a diet of artemia and thawed blood worms, and the tank water was exchanged once a week. There was no history of clinical disease and the animals had repeatedly exhibited amplexus. During the 2nd week of May 1999, all 7 remaining frogs died suddenly with no apparent clinical signs; 3 were presented to the Animal Health Centre, Abbotsford, British Columbia for diagnostic evaluation. 385
