Essam S. Soliman1*, Ahmed E. Mahmoud2

Abstract | Calf health was prioritized as one of the most important issues facing the dairy industry. The in-vitro antimicrobial and the in-vivo prophylactic actions of tulathromycin in dairy heifers exposed to harsh macroclimate concerning hematological, biochemical, and bacteriological profiles were evaluated. Tulathromycin 15, 20, and 25* mg were tested against Streptococcus pneumonie, Streptococcus pyogenes, Haemophilus influenzae, Pasteurella multocida (1.8 × 108 CFU/ml), and E. coli O6 (3.5 × 109 CFU/ml) at 0.25, 0.5, 1.0, and 2.0 h using minimal inhibitory concentration procedures. Experimental 30 dairy heifers with an average body weight of 30 kg were divided into two groups, the first was injected with 2.5 ml tulathromycin 25* mg, and the second was kept as control. A total number of 690 samples including 240 in-vitro samples (bacterial- tulathromycin mixes) and 450 in-vivo samples (150 whole blood samples, 150 sera, and 150 nasal swabs) were collected.The in-vitro study revealed that tulathromycin 25* mg achieved highly significant (P<0.01) efficiency with 100% killing against Streptococcus pneumonie, Streptococcus pyogenes, Haemophilus influenzae, Pasteurella multocida, and E. coli O6 at 1.0, 1.0, 0.5, 0.5, and 0.5 h, respectively. In-vivo measured hematological and biochemical parameters revealed no significant differences between the injected and control heifers with significant (P≤0.05) declines in alanine aminotransferase and triglycerides, as well as, significant (P≤0.05) increases in total cholesterol at the 4th-week post-injection. The bacteriological assessments revealed highly significant (P<0.01) declines of total bacterial, Enterobacteriaceae, Streptococcus, Haemophilus, and Pasteurella counts in injected dairy heifers compared to the control. Temperature and humidity revealed non-significant weak correlations with hematological and biochemical parameters. The study concluded an efficient in-vitro antimicrobial, as well as, protective and preventive in-vivo activities of tulathromycin without any modifications in the hematological and biochemical parameters of dairy heifers exposed to cold macroclimatic conditions.

Keywords | Antimicrobial, Cold Stress, Dairy Heifers, Macroclimate, Tulathromycin, Preventive.