Abstract
This study aimed to evaluate the effects of dietary supplementation with increasing levels of a polyherbal phytogenic additive (PPA) on growth performance, health parameters, and blood metabolites of dairy calves. Forty female Holstein calves (43.35 ± 2.41 kg body weight and 25.1 ± 2.2 d of age) were housed in individual pens and randomly assigned to four treatments (n = 10) with increasing levels of PPA: 0 (CON), 2 (PPA2), 3 (PPA3), and 4 (PPA4) g PPA/d for 67 d. Compared to the CON treatment, supplementation with the PPA2 treatment increased (quadratic effect p = 0.02) the average daily gain and final body weight of the dairy calves. Also, a higher starter intake (SI), and intake of milk + milk replacer was observed (linear and quadratic effect p = 0.0001) in response to supplementation with the PPA2, PPA3, and PPA4 treatments. The evaluated treatments did not affect (p > 0.05) the feed conversion ratio, or the number of cases of diarrhea, pneumonia, and otitis. The evaluated treatments did not affect (p > 0.05) most of the hematological and biochemical blood parameters. However, compared to the CON treatment, supplementation with the PPA2 treatment increased (quadratic effect p < 0.05) the blood concentration of the segmented neutrophils and plasma protein. Likewise, the serum glucose concentration decreased (linear effect p < 0.05) with supplementation of the PPA2, PPA3, and PPA4 treatments. Compared with the CON treatment, the PPA4 supplementation decreased the serum urea concentration (linear effect p = 0.04). In conclusion, supplementation with 2 g/d of PPA can be used as a natural alternative to improve the growth rate and stimulate starter and milk + milk replacer intake in dairy calves without adverse effects on health parameters or blood metabolites.