Investigation concerning the nutrient and mineral supply of beef suckler herds in extensive pasture management

Die komplette Dissertation im pdf-Format (1.109.045 Bytes): teroe.pdfThe purpose of the present investigation was to demonstrate the nutrient and mineral supply of beef suckler herds in extensive pasture management. The investigation was carried out with five herds with an average of 100 sucklers and their calves during the grazing period in 1995. The performance data included food intake, mineral feed intake, live weight and weight gain. The pasture data like botanical composition and yield capacity were raised and the green roughage was analysed for the energy, nutrient and mineral contents. These data enabled the calculation for the total daily intake. * All five surveyed pastures showed a high botanical variety caused by the extensive pasture management. Differences in the botanical composition between the pastures were mainly due to the different impact of low intensive pasture management. * The pasture yield reached 75 dt TS/ha and was relatively high, even after five years of extensive pasture management. This shows a high natural productivity of those locations. * The cows with an average bodyweight of 510 kg had a daily dry matter intake of 2% of their bodyweight and a milk yield of approximately ten liters. * The calves had a daily weight gain of 0,77 - 0,85 kilogrammes per day. This correlated well with the calculated daily energy and nutrient supply through milk and green roughage. * The daily intake of mineral supplements ranged between 17 and 47 grammes per animal/day. The reason for this difference could be either a deficient acceptance or problems in the herd management. * Cows with a low productivity status (pregnancy, low lactation at the end of lactation period) were oversupplied with energy and protein, whereas cows in the first weeks of lactation with a high energy and nutrient requirement were undersupplied with energy and protein. * The decreasing energy supply of the cows of one herd was mainly due to problems in pasture management such as an insufficient pasture yield in relation to the herd density, long grazing periods and low growing periods. * The calculated water intake of cows was higher than suggested by the relevant literature and the reported requirement of four liters per kg dry matter uptake plus four liters per liter milk given by various investigators may be called into question. * The cows were adequately provided with major elements. The analyses of sodium concentration in saliva showed a deficient sodium supply in cows in July. This was in contrast to the calculated supply and the reason might have been the bad potassium-sodium-ratio. * High sulphur contents in green roughage and drinking water as well as high molybdenum concentration in green roughage were found. An antagonism on the copper and selenium absorption can be taken into account. This can be concluded from the increasing copper and selenium concentration in green roughage, because both elements were excreted in large amounts and thus found in the analyses. * The drinking water of some locations had high contents of sodium, potassium and magnesium. The reason for this is the connection of the drainagesystem to the Baltic Sea. Only by water intake the animals had a high input of those three elements, which had a major influence on the mineral supply. * Analysing the serum concentration of various trace elements a marginal zink supply and a deficiency in copper and selenium were found. The reason for the zinc deficiency was the marginal content in the green roughage in the spring as well as a bad calcium-zinc-ratio all through the year. The deficiency of copper could not be explained by the daily intake but a high molybdenum and sulphur intake had a major influence. The low selenium intake with green roughage, antagonisms between selenium on the one hand and trace elements and sulphur on the other were responsible for the selenium deficiency. * Calves younger than ten weeks, that fed mainly on milk were deficient in all minerals with the exception of sodium and potassium. As soon as they started feeding additionally on grass the intake of major elements was sufficient. The intake of trace elements improved with increased grazing but the copper, selenium and cobalt intake was still insufficient. * The calculated marginal or deficient supply of sodium, potassium, selenium and zinc can have a negative effect on reproductive efficiency and breeding periods. * The deficient major and trace element supply of calves can for example lead to a reduction in feed intake and therefore to a decreasing weight gain and a deficiency in the immune system. A deficient selenium and copper supply can also lead to anaemia as well as depressed sexual development and it could be the reason for the high mortality of calves which exists