growth performance, immune response, and rumen/blood parameters of suckling calves when using different fat sources

Calf rearing from birth to weaning is a critical and sensitive period in dairy farming, as it determines the future of a herd. The objective of this research was to examine the impact of various fat sources on growth performance, immune response, and both ruminal and blood parameters in suckling calves. To achieve this goal, 40 female Holstein calves with an average weight of 40 kg and a body score of 3 were studied from birth to weaning (at 3 to 75 days of age) in a completely randomized design with four treatments and 10 replicates. Experimental treatments were i) a starter diet with no fat source (control), ii) a starter diet with coconut oil containing saturated fatty acids (2% of the diet), iii) a starter diet with flaxseed oil containing linoleic acid (2% of the diet), and iv) a starter diet plus safflower oil containing linoleic acid (2% of the diet). 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. The findings indicate that the safflower oil treatment exhibited the highest feed intake after a duration of 10 weeks, with a statistically significant difference observed when compared to 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 did not yield statistically significant differences in fecal scores throughout the duration of the study (p > 0.05). Additionally, the influence of the experimental treatments was not significantly correlated with the pH levels of the calves' rumen fluid during the experimental period. However, the total volatile fatty acid concentration was significantly influenced by the treatment at the conclusion of the experimental period (p < 0.01). Furthermore, the blood parameters, including glucose, protein, and urea levels, as well as the counts of red blood cells and immunoglobulin G in the calves, were significantly affected by the treatment (p < 0.05). The findings of this study indicate that the incorporation of various fat sources, particularly those rich in unsaturated fatty acids such as linoleic and linolenic acid, in the starter diet of female Holstein calves significantly enhanced growth performance, immune response, and rumen/blood parameters when compared to the other experimental groups.