Mineralämnen i fullfoder : studier på 20 mjölkkogårdar i Halland

Abstract: In 2003 the recommended phosphorus allowance for dairy cows in Sweden was lowered approximately 10 %. For a cow at a production level of 35 kg ECM it decreased from 0,40 to 0,36 % of dry matter. To investigate if the decrease has been implemented at farm level, analysis of following minerals; P, Ca, Mg, K, Na, S, Se, Cu, Mn and Zn was performed on the TMR at 20 farms in Sweden in the summer of 2004. The purpose was to describe the actual allowance of different minerals as compared to the new recommendations. One hypothesis was that the decrease in recommended allowance of phosphorus would lead to the need of new mineral feeds on the market. Analysis of dry matter and crude protein was also performed to investigate the homogeneity and true recipes of the TMR:s. The study was performed on 20 TMR dairy farms in the province of Halland in Sweden. Pooled samples were taken at 15 of the farms. On five farms three separate samples were taken from the beginning, the middle part and from the end of the feeding table. This was done to investigate the homogeneity of the TMR. Planned allowance and actual allowance were both compared with the recommended allowance. Most of the minerals where given in sufficient amounts but the Na-, Cu-, and Ca-allowances were somewhat below the recommendations on some of the farms. The phosphorus allowance was between 0,35 to 0,55 % in the TMR:s at the 20 farms. The average surplus of phosphorus at the farms was 18,3 g P/cow and day. At a 100-cow farm this will account to 1830 g/day or 668 kg per year. The phosphorus supply can be lowered on 18 of the 20 farms but it should not be done at the expense of the other minerals. If the mineral feed would be excluded from the ration, several of the farms would have serious problems with deficiencies of all minerals with the exception of potassium. Problems with deficiencies of microelements would be especially prevalent. The study shows a need of the new mineral feeds with less phosphorus on the market. The results also show that the mineral content of TMRs estimated from the components of the mix using average values from feed tables and declaration of contents is not completely reliable since the mineral content is not analysed in all raw materials. To make sure to give the cows enough of minerals in the TMR a mineral analysis is recommended. The distribution of the minerals in the mix seems to be good. The mineral content of the samples taken at three places of the feeding table did not differ much and no indication of an uneven distribution of minerals was observed. This report also contains a literature review concerning metabolism, source, recommended supply and effects of surplus and deficiency of minerals. Minerals can be found in the cells and tissues of the body and they have several important functions. It is important for the optimal performance of the animals that recommendations are followed. The balance between the different minerals must also be considered since uptake of some minerals is inhibited by others. The micro minerals are needed in smaller concentrations but are as important as the macro minerals. It is difficult to discover a deficiency of a micro mineral because the symptoms are often indirect and diffuse, as decreased growth, lowered reproduction and impaired capacity of feed conversing.