Abstract :
[en] Introduction: In ruminants, the main documented clinical manifestation of aluminium (Al) intoxication is similar to grass tetany, both caused by a hypomagnesemia [1,2]. Nevertheless, it is not known whether the ingestion of doses lower than those inducing grass tetany can provide a chronic influence in cattle, and this case-report is described in this context. Case history: On a Belgian farm with 50 dairy cows, a farmer reported excessive uterine bleeding at calving and decreasing in milk production (from 8000L to 7000L of milk/cow/year). Dairy cows received a total mixed ration consisting of grass silage, energy corrector (1/3 wheat, 1/3 corn, 1/3 barley), overpressed beet pulp and a mineral supplement. A protein corrector and alfalfa pellets are distributed individually. In the milking parlour, the cows receive an additional protein concentrate (18% crude protein). The basic ration had the following characteristics in terms of energy and protein: 0.87 UFL/kg DM; 85g PDI/kg DM; 97g PDI/UFL. A mineral analysis of the ration was carried out (Table 1). Blood and urine were sampled randomly from 10 cows among the sick animals and were compared with a group of 10 healthy cows (ULiege, pedagogic herd, Table 1). The sick cows had anaemia, marginal hypozincemia, hypomagnesemia and 4/10 of subclinical ketosis. Their urine analysis revealed high Al/creatinine concentrations. Recommendations: It was advised to determine the soil pH and lime the grassland if the soil had an acid pH (<5) [1]. Moreover, it was advisable to add salts to the ration, such as MgO, CaCO3, NaHCO3 to cause precipitation of Al in the rumen. Finally, it was suggested to support cows with mineral supplements (zinc, magnesium, phosphore), and propylene glycol. Follow-up: A monitoring visit was carried out after 2 years. Within this period, the status of trace elements was checked regularly and animals with deficiencies were supplemented with boluses. The visit highlighted an overall improvement of the situation, but all of examined animals presented subclinical ketosis. Al content of the grass silage remains high (700 ppm DM), just as the presence of butyric acid (BA; 11.22g/kg DM). Discussion and conclusion: Al could be incriminated at different levels, in particular in micronutrients deficiencies, anaemia and negative energy balance [3,4,5]. However, given the levels of Fe and BA in the silage, Al was probably not the only culprit [5]. This case report is a concern for future years in these areas due to droughts and scarcity of forage [6].
