Abstract

Background and Aim: Weaning is a critical period in calf development, particularly under tropical conditions where nutritional stress and parasitic infestations can precipitate anemia. Anemia compromises growth and survival; yet, few studies have evaluated the effectiveness of hematinic therapy in anemic calves before weaning in tropical systems. This study aimed to assess hematological responses in anemic dairy calves treated with a hematinic complex and to establish anemia thresholds based on hematological indices in healthy calves raised under tropical conditions.

Materials and Methods: A total of 22 Holstein × Zebu calves were studied from January to April 2024 in Tabasco, Mexico. Calves were grouped as healthy (n = 10; hematocrit [HCT] >24%) or anemic (n = 12; HCT <24%). The anemic group received an intramuscular hematinic complex for 5 consecutive days and three additional doses at day 42. Hematological parameters were measured every 21 days using an automated analyzer. Anemia thresholds were defined from the healthy group using mean ± 2 standard deviations. Data were analyzed using a repeated-measures design over time.

Results: Anemia thresholds were determined as HCT <21.3%, hemoglobin (HGB) <7.5 g/dL, and red blood cell (RBC) <5.4 × 106/μL. At baseline, anemic calves exhibited significantly lower HCT (21.4%), HGB (6.9 g/dL), and RBC (5.9 × 106/μL) compared to healthy controls (p < 0.01). Three calves presented with microcytic hypochromic anemia and one with macrocytic anemia. By day 42, hematinic-treated calves surpassed the anemia threshold, reaching an HCT of 25%, and further increased to 30% following the second treatment. HGB and RBC levels also improved, showing no significant differences from healthy calves at study end. Males responded more robustly to treatment than females.

Conclusion: The administration of a hematinic complex effectively restored hematological parameters in anemic calves within 42 days, with sustained improvement following a second application. This intervention is recommended as part of pre-weaning health protocols to mitigate anemia-related growth setbacks in tropical cattle systems.

Keywords: anemia, calves, haematocrit, haemoglobin, hematinic complex, red blood cells, tropical cattle systems.