1. Effect of natural feed additive APC RZ2000 on performance of high yielding Holstein cows

2. Materials and Methods n The trial was done between 02.08.2004- 11.09.2004 in the Gale Khaje Farm, Iran under the control of the University of Isfihan! n Two groups of multiparous early lactation cows were randomly assigned to two treatments, either fed APC (n=106 cows) or served as control (n=109 cows) n For control and APC-fed cows, mean lactation number were 2.9 and 3.1, DIM were 59.5±21 and 65.3 ± 26 and milk yield at last 3 days before the commencement of the trial were 37.36 and 38 kg/d, respectively n The experiment lasted for 6 wk with 14 d of adaptation and 28 d for data collection

3. Materials and Methods n Mean ambient temperature throughout the trial was 36.7° C, hence cows were experiencing severe heat stress n Cows were offered TMR 4 times daily at 0600, 1400, 1800 and 2200h and milked 3 times at 0500, 1300 and 2100h by a semi-automated milking system n DMI were calculated based on average consumption of each group and difference between feed offered and refused each day n Weekly samples of TMR, silage and refusals were obtained and DMI adjusted based on DM changes

4. Materials and Methods n Milk yield of individual cows were recorded automatically and then averaged by group n For the analysis of milk composition, all cows were sampled at 1st week, sampling was continued randomly on 24, 36 and 48 cows of each group at wk 2, 3 and 4 respectively. Milk composition was analyzed with Milko-scan by IR n Approximately 4 hours after feeding, 20 cows were randomly milk sampled for 3 consecutive Monday and milk urea nitrogen was analyzed calorimeterically to test the effect of treatment on N balance