Blood metabolites, Dairy calves, Performance, Probiotic, Skeletal growth indices

Antibiotics have long been widely used to stimulate growth and prevent disease in animals. But, concerns about bacterial resistance and gastrointestinal malformations have prompted nutritionists to look for alternatives. Probiotics and ruminal growth promoter are among them. Probiotics are viable microorganisms that their use by ruminants has beneficial effects on the growth and microbial population balance of the rumen and will improve animal performance by improving feed conversion ratio. Calves are exposed to a variety of stressful events at birth due to defects in the immune system and underdevelopment of the digestive tract. Because of this, stimulation of rumen development, microbial population balance, and transfer of calves from the single gastric to the ruminant state are necessary. This study was conducted in order to investigate the effect of probiotic additive and ruminal growth promoter on feed intake, weight gain, skeletal growth indices, health, and blood metabolites of young dairy calves.

in this study, twenty four Holstein female calves immediately after birth, were used in a completely randomized design (4 treatments and 6 replicates). Calves after birth were randomly assigned into one of four treatments as follow: 1) control (milk without any probiotic or ruminal growth promoter), 2) calves receiving probiotic additive, 3) calves receiving or ruminal growth promoter and 4) calves receiving probiotic additive + ruminal growth promoter. Measurement of dry matter intake and fecal scoring were done daily. Calves were weighed once every15 days. Blood smples were taken at 21 and 45 days of age, 3 hours after morning feeding. Ruminal fluid was collected 4 hours after morning feeding on days 21 and 45 to measure pH and ammoniacal nitrogen. Skeletal growth indices were measured every 15 days up to 90 days. The data obtained from this study were analyzed according to completely randomized design and repeated measurements.

Results showed that probiotic and ruminal growth promoter supplementation had no significant effect on body weight, body weight gain changes and average body weight gain (P>0.05). There was no significant difference between control calves and those fed with probiotic and ruminal growth promoter in terms of skeletal growth indices (P>0.05). Fecal consistency score was higher in control than other treatments (P<0.05). Probiotic and ruminal growth promoter supplementation decreased ammoniacal nitrogen concentration on days of 21 and 45 (P<0.05). Treatments had no significant effect on blood concentration of glucose, cholesterol, urea and BHBA (P>0.05). However, concentration of triglyceride, total protein and albumin was different among the treatments (P<0.05).

Totally, The results of this study showed that Probiotic and ruminal growth promoter supplementation had no noticeable effect on the studied traits.