Three experiments, involving a total of 294 Israeli Holstein cows, were carried out to study aspects of the grouping of cows in relation to timing of changes and the type of complete diet given. In Expt 1, 40 cows were changed from a high energy diet to a medium energy diet either at 60 or at 180 days post calving. The results indicated a larger reduction in milk and FCM yield following the later than the earlier change of diet.
Experiment 2 involved 64 cows subjected to two treatments, one involving a ‘uniform’ diet (25:75 forage to concentrate D.M. ratio) and the other a ‘step’ treatment where the same diet as in treatment 1 was given for approximately 74 days and then changed to a diet of 35:65 forage to concentrate ratio. The results showed that it is not necessary to adopt different feeding systems according to the potential yield of the cow and that cows could be given rather lower energy diets within the range offered without loss of efficiency.
In Expt 3, involving 190 cows, the cows were divided into one of two feeding treatments, ‘uniform’ and ‘step’ similar to Expt 2 and the effect of potential yield and parity was considered. The results emphasized the importance of potential yield rather than feeding system in relation to yield. The results showed a shorter period from calving to conception for the ‘uniform’ treatment.
A strategy for efficient cow feeding is outlined.