Comparative clinical evaluation of Holstein calves fed with waste milk, pasteurized waste milk, or saleable milk

The use of waste milk (WM) as a liquid diet is a common practice in calf-rearing systems, primarily to reduce rearing costs. It is widely accepted that feeding calves with WM promotes the selection of bacteria resistant to antimicrobials, although its impact on calf health is controversial. The objective of this study was to evaluate the effect of three different sources of liquid diet on the health and development of suckling calves: WM, pasteurized waste milk (PWM), and saleable milk (SM). The study was conducted at the Calf Research Laboratory, where 30 male Holstein calves were housed and distributed into three experimental groups: SM (n=10), WM (n=10), and PWM (n=10). The calves underwent daily health assessments using a scoring system for diarrhea and bovine respiratory disease (BRD). Development assessments were performed weekly, measuring weight with a thoracic tape and evaluating wither height and ischial width using an anthropometric ruler. Venous blood and fecal samples were collected at five-time points: D7, D21, D35, D49, and D63, for complete blood count, blood gas analysis, and fecal dry matter (FDM) determination. Statistical analyses were performed using SAS software (version 9.0, 2002). The occurrence of neonatal diarrhea was affected by the treatments, with a lower percentage of FDM in the WM group, systemic consequences detected in complementary tests, and a greater need for clinical intervention. Although the SM group presented a higher proportion of severe diarrhea, the animals did not develop clinical alterations, with a 21% lower chance of being dehydrated compared to the PWM group (OR: 0.21; CI: 0.04 - 0.99; P = 0.048; SM × PWM). Calves in the SM group had a 48% lower chance of developing BRD compared to PWM (OR: 0.48; CI: 0.25 - 0.90; P = 0.02; SM × PWM). The WM and PWM groups had lower mean PO2 and SO2 levels in blood gas tests. Calves in the WM and PWM groups showed higher mean absolute lymphocyte counts than the SM group. The liquid diet also influenced potassium concentrations, with ...