| Popis: |
The effect of heat treatment in an aqueous medium with and without subsequent drying on the quality of the protein from lean and fatty fishes in milk replacers for pre-ruminant calves has been studied. Milk protein (dried skim milk, used as a control) had an apparent protein digestibility (PDA) of 0.902 and 0.936 in calves aged 1–3 and 3–5 weeks, respectively. The corresponding values for undried lean fish heated in an aqueous medium for 30 min at 20, 55 and 95°C, respectively, were 0.887 and 0.912, 0.872 and 0.909 and 0.828 and 0.914. Raw lean fish which was freeze dried, spray dried and direct hot-air dried had PDA of 0.861 and 0.937, 0.880 and 0.874 and 0.812 and 0.897, respectively. Spray-dried fatty fish had PDA of 0.778 and 0.860 in calves aged 1–3 and 3–5 weeks. Solvent lipid extraction did not affect PDA. Biological value was not affected by the age of the calves, or by heat treatment or drying of the fish, and was 75.4, 69.9 and 64.5 in milk protein and in protein from lean and fatty fish, respectively. There were no significant differences between diets in the incidence of digestive disorders, but several calves on all diets scoured at the beginning of the trials. |
