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HYPOCALCEMIA AND HYPOMAGNESEMIA PREVALENCE IN A GRAZING JERSEY, GUERNSEY AND HOLSTEIN HERD IN COSTA RICA
The aim of this study was to determine the prevalence of hypocalcemia and hypomagnesemia in Jersey, Guernsey and Holstein cows at parturition under the same feeding, management and environmental conditions. The study was conducted on a dairy farm located in Cartago, Costa Rica during a nine months period and comprised a total of 152 cows (62 Jersey, 41 Guernsey and 49 Holstein). During the close up period cows grazed intensively managed kikuyu grass (Kikuyuocloa clandestina)(14.8% DM, 23.4% CP, 54% NDF, 0.35% Ca, 0.31% Mg and 3.50% K) and were supplemented with 4 kg/animal/d of a concentrate mixture low in Ca (14% CP, 31% NDF, 0.2% Ca, 0.42% Mg and 1.38% K) and 1 kg of hay (82.3% DM, 5.1% CP, 61.4% NDF, 0.4% Ca, 0.35% Mg and 1.8% K)/ d. Cows were fed 1 kg of concentrate (18.6% CP, 0.90% Ca, 0.42% Mg and 1.38% K)/ 2.5 to 3.0 kg of milk during lactation. Blood samples were taken from the coccygeal vessels at peripartum (calving ±1d) and were analyzed for Ca and Mg. The blood thresholds to classify cows as clinically or sub clinically hypocalcemic were less than 5.5 and 5.5 to 8.0 mg/dl of Ca, respectively. A value of 1.8 mg/dl of Mg or lower was set as criterion to classify cows as hypomagnesemic. Results are shown in Table 1.
Table 1. Blood calcium and magnesium concentration and prevalence of clinical and subclinical hypocalcemia and hypomagnesemia according to breed. |
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Breed |
Ca (mg/dl) |
Mg (mg/dl) |
Hypocal.(%) |
Hypomag.(%) |
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Mean |
95% CI |
Mean |
95% CI |
Clin. |
Subcl. |
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Jersey |
7,49 |
7,11-7,87 |
2,78a |
2,64-2,92 |
13 |
50 |
2 |
Guernsey |
8,09 |
7,63-8,56 |
2,35b |
2,18-2,52 |
0 |
44 |
12 |
Holstein |
7,85 |
7,42-8,28 |
2,37b |
2,22-2,53 |
4 |
55 |
0 |
a, b Means in the same column not sharing a common superscript are different (P < 0.05) |
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Jersey cows were more prone to develop clinical hypocalcemia during peripartum than Holstein cows in this herd (OR=3.48, 95% CI: 0.76-15.9) and Guernsey cows were more likely to suffer hypomagnesemia than Jersey cows during the same period (OR=8.47, 95% CI: 1.30-55.2). These results suggest that Jersey grazing cows are more susceptible to clinical hypocalcemia and Guernsey to hypomagnesemia. High prevalence of subclinical hypocalcemia found in this study in Jersey, Guernsey and Holstein cows could comprise cow health and productivity and more research should be done to better understand Ca metabolism during the transition period in grazing cows.
Keywords: Grazing dairy cows, hypocalcemia, hypomagnesemia,