UK DIAGNOSTIC ROUNDS (CONT.)
able intravenous solutions labeled for hypomagnesemia are prescription only and have “CMPK” in the name as these products contain calcium, magnesium, phosphorous and potassium. If unable to treat in the vein, a 10% magnesium sulfate solution given under the skin (SQ) or as an enema is a useful alternative therapy because the large intestine can absorb Mg rapidly. Response to therapy depends on the length of time between onset of symptoms and treat- ment. Cattle that do recover take at least an hour to return to normal. Many will relapse and require additional Mg treatment within 12 hours. Administering oral magnesium or CMPK gel or drenching with magnesium oxide or mag- nesium sulfate solutions once the animal has regained good swallowing reflexes will reduce the rate of relapse. If grass tetany has occurred within a herd, an effort should be made to immediately increase the intake of magnesium to other herd members to prevent further cases.
Prevention of grass tetany is based on maintaining consis- tent intake of soluble magnesium to be absorbed in the ru- men of susceptible cattle when conditions for grass tetany exist. Highly susceptible groups include lactating cows or cows in late pregnancy, especially older, over-conditioned cows. Tese groups should be provided supplementary di- etary sources of magnesium, commonly magnesium oxide. Te average beef cow reaches peak lactation at 6-8 weeks post-partum which is also her highest demand for magne- sium.
References: 1. Goff JP. Calcium and Magnesium Disorders. Vet Clin North Am Food Anim Pract 2014;30:359-381.
2. Jefferson PG, Mayland HF, Asay KH, et al. Variation in mineral concentration and grass tetany potential among Russian wildrye accessions. Crop Science 2001;41:543-548.
3. Martens H, Leonhard-Marek S, Rontgen M, et al. Magnesium homeostasis in cattle: absorption and excretion. Nutr Res Rev 2018;31:114-130.
4. Martens H, Schweigel M. Pathophysiology of grass tetany and other hypomagnesemias. Implications for clinical management. Vet Clin North Am Food Anim Pract 2000;16:339-368.
5. McCoy MA. Hypomagnesaemia and new data on vitreous humour magnesium concentration as a post-mortem marker in ruminants. Magnes Res 2004;17:137-145.
6. Niles GA. Toxicoses of the Ruminant Nervous System. Vet Clin North Am Food Anim Pract 2017;33:111-138.
7. Odette O. Grass tetany in a herd of beef cows. Can Vet J 2005;46:732-734.
8. Primefact 785; Grass tetany in Cattle-Predicting its Likelihood. Mac Elliott, Livestock Officer. New South Wales Department of Primary Industries (
www.dpi.nsw.gov.au). June 2008
9. Smith BP. Large animal internal medicine. Fifth edition. Missouri:- Mosby, 2009: 1374-1375.
10. Sutherland, RJ; Bell, KC; McSporran, KD; Carthew, GW. A com- parative study of diagnostic tests for the assessment of herd mag- nesium status in cattle. New Zealand Veterinary Journal, 1986; 34
(8): pp. 133-135. Winter 2023 39
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