Different sources of fat in starter and its effect on growth performance, blood parameters and immune system of calves

Calf rearing from birth to weaning is a critical and sensitive period in dairy farming, as it determines the future of a herd. The aim of this work was to investigate the effects of different fat sources on growth performance, immune response and rumen and blood parameters in suckling calves. Forty female Holstein calves (average weight 40 kg, body score 3) were studied from birth to weaning (3 to 75 days). A completely randomized design with 4 treatments (10 replicates each) was used: i) control (no fat source), ii) coconut oil (2 % saturated fat), iii) flaxseed oil (2 % linoleic acid), and iv) safflower oil (2 % linoleic acid). Calf performance was evaluated weekly and feces were examined daily. Rumen parameters (volatile fatty acids and pH), blood parameters (glucose, protein, urea and cholesterol) and immune response (white and red blood cells and immunoglobulin G) were assessed at the end of the trial. According to the results, the highest feed intake after 10 weeks was recorded in the safflower oil treatment, which differed significantly from the control treatment (p < 0.05). The highest weight gain of calves fed diets containing unsaturated fats was observed in the 8th, 9th and 10th weeks, which was significantly higher than in the control and treatment containing coconut oil (p < 0.05). The height of experimental calves was affected by fats, except in the 1st and 2nd weeks. The experimental treatments were not significantly different in terms of fecal scores during the entire experimental period (p > 0.05). The effect of the experimental treatments was not significantly dependent on the pH of the calves' rumen fluid during the experimental period. The total volatile fatty acid content was significantly affected by the treatment (p < 0.01) at the end of the experimental period. Blood parameters (glucose, protein and urea), red blood cells and immunoglobulin G of the calves were significantly affected by the treatment (p < 0.05). The results of this study show that the use of different fat sources, especially those with unsaturated fatty acids containing linoleic and linolenic acid, in the starter diet of calves improved growth performance, immune response and rumen/blood parameters in female Holstein calves compared to the other groups.