A comparison of some laboratory techniques for the estimation of the digestibility of the organic matter in forage samples.

The 194 samples of forage were of 6 groups; grass or other forage dried, fresh or ensiled. Workers from 5 institutes analysed some of the samples by their usual methods, 10 methods altogether. Digestibility estimated with sheep was regressed on the other results and correlation coefficients and residual standard deviations were calculated; those were closer for groups of forages than for all forages together. The least accurate predictor of digestibility in vivo was crude fibre content, which is much used in the Netherlands. The best method for each fodder group was the method of Tilley and Terry (NAR 34, 156) as modified by Koelen, Kemmink and Dijkstra (De bepaling van de voederwaarde van ruwvoeders met behulp van de in vitroverteerbaarheid. Internal Report, Institute for Animal Feeding and Nutrition Research 'Hoorn' (1969), No. 27, available in English). It took least work but required sheep rumen fluid. For all groups together, the cell-wall constituents method of Gaillard and Nijkamp (NAR 38, 8034) was better for 54 samples but the residual standard deviation was higher than within groups; it required more labour, but not rumen fluid. (Abstract retrieved from CAB Abstracts by CABI’s permission

Between-animal variation in the amount of energy required for the maintenance of cows

To measure any between-animal differences in requirement of energy for maintenance of cows 38 metabolic balance trials were performed with 13 dry Friesian cows in their 7th month of pregnancy, on the same rations. For 6 of the cows measurements were also taken in the 9th month of pregnancy. A detailed description was given of new respiration chambers used and of techniques. The results of 237 balance trials with cattle with an energy balance between + 4000 and - 4000 kcal. described in the literature, were analysed statistically. In this material between-animal variation in metabolizable energy for maintenance, corrected to the same bodyweight, reached about 11 % and within some breeds 8- 10 %. In the author's trials, variation in Friesians was 4-8 % similar to results of published trials. For both sets of data a reliable figure for between-animal variation needed exclusion of such factors as differences in ration, date of measurement and pregnancy. From the author's trials utilisation of metabolizable energy for growth of foetus, foetal membranes and udder was about half of that for fattening if it was assumed that pregnancy had no influence on maintenance requirement