Effects of Feeding Different Levels of Flaxseed on Performance, Nutrient Digestibility and Blood Parameters of Pre-Weaning Calves

   In this experiment, we used 15 newborn Holstein male calves that their initial weight was 41 ± 4.5 kg and their age was one week. The experiment was conducted in a completely randomized design with three treatments and five replications. Treatments included: 1- control treatment without flaxseed, 2- treatment containing 5% flaxseed and 3- treatment containing10% flaxseed. Flaxseed replaced corn and soybean meal in the starter diet. The whole experiment period was 60 days. The rations were given as pellets to the calves. To measure nutrient digestibility, fecal and feed intake of calves were sampled for 5 days at the end of the experiment and then the digestibility of the samples was done using an internal marker (acid insoluble ash) in the laboratory. Blood samples were taken to measure blood parameters at the end of the experiment period.  Different levels of flaxseed had no significant effect on performance parameters such as final weight, daily weight gain, daily dry matter intake and feed conversion ratio. Addition of calf seed to starter calves had a significant effect on digestibility of dry matter (p=0.0498), crude protein (p=0.0067), and insoluble fiber in neutral detergent (p=0.0249). Treatments containing 10% and 5% levels had the highest dry matter digestibility, respectively. The highest digestibility of crude protein and digestibility of insoluble fiber in neutral detergent were related to 5% flaxseed treatment. Experimental treatments with different levels of flaxseed had a significant effect on blood urea nitrogen content (p=0.0047), so that the highest urea nitrogen content was obtained for treatments containing 5% and 10% flaxseed, respectively. Due to the fact that treatments on the amount of dry matter, daily weight gain, final weight of calves were not significant and also due to improved digestibility of nutrients in treatments with 5% flaxseed, it is recommended to use 5% of flaxseed as a source of energy and protein in the diet of dairy calves.