Feeding heat-treated colostrum or unheated colostrum with two different bacterial concentrations to neonatal dairy calves

Abstract

The objective of this study was to determine the effects of feeding heat-treated colostrum or unheated colostrum of different bacterial counts on passive transfer of immunity in neonatal dairy calves. First milking colostrum was collected from Holstein cows, frozen at –20°C, and then thawed and pooled into a single batch. One-third of the pooled colostrum was transferred into plastic containers and frozen at –20°C until needed for feeding (unheated-low bacteria). Another third was heat-treated at 60°C for 30min and then frozen at –20°C until needed for feeding (heat-treated). The final third of colostrum was transferred into plastic containers, stored at 20°C for bacteria to grow for 24h (unheated-high bacteria), and then frozen at –20°C until needed for feeding. A total of 30 Holstein bull calves weighing ≥30kg at birth were systematically enrolled into 1 of the 3 treatment groups. Calves were separated from their dams at birth before suckling occurred. Before colostrum was fed, a jugular blood sample was collected from each calf. The first feeding consisted of 3.8L of colostrum containing, on average, 68g of IgG/L using an esophageal feeder between 1.5 and 2h after birth. For the second and third feeding pasteurized whole milk at 5% of birth weight was fed. Blood samples were collected before colostrum feeding and at 24 and 48h of age to determine serum total protein (STP) and IgG concentrations. Heat treatment of colostrum at 60°C for 30min reduced colostrum bacteria concentration yet maintained colostral IgG concentration and viscosity at similar levels to the control treatment. Calves fed heat-treated colostrum had significantly greater STP and IgG concentrations at 24h and greater apparent efficiency of absorption (AEA) of IgG (STP=62.5g/L; IgG=26.7g/L; AEA=43.9%) compared with calves fed unheated-low bacteria colostrum (STP=57.0g/L; IgG=20.2g/L; AEA=35.4%) or unheated-high bacteria colostrum (STP=56.2g/L; IgG=20.1g/L; AEA=32.4%). High bacteria load in colostrum did not interfere with total protein or IgG absorption or AEA.