Inclusion of tallow and soybean oil to calf starters fed to dairy calves from birth to four months of age on calf performance and digestion.

Energy demands for calves can increase during periods of heat and cold stress. One way to potentially increase energy intake is to increase the energy density of the feed with fat. Trial 1a compared a control starter with no added fat or oil (CON) to starters with 2% tallow (TAL) and 2% soybean oil (SBO). Starters were 20% crude protein (CP) and 45 to 47% starch. Male Holstein calves that were initially 3 to 5d of age were fed a 27% CP, 17% fat milk replacer at 0.66kg of dry matter daily and fully weaned by 42d of a 56-d trial. Trial 1b estimated the digestion of the diets (employed chromic oxide as an indigestible digesta flow marker) using a subset of 5 weaned calves per treatment between d 52 and 56. Trial 2 used Holstein calves initially 59 to 61d of age fed starters CON and SBO blended with 5% chopped grass hay over a 56-d trial. Trial 3 used Holstein calves initially 59 to 61d of age fed starters CON and TAL blended with 5% chopped grass hay over a 56-d trial. Treatments were compared using repeated measures (where appropriate) in a completely randomized design. In trials 1a and 1b, preplanned contrasts compared CON versus TAL and CON versus SBO. Compared with CON, calves fed SBO had reduced starter intake, average daily gain, and digestion of dry matter, organic matter, and CP before 8wk of age. Compared with CON, calves fed SBO had reduced average daily gain and change in hip width from 2 to 4 mo of age. Compared with CON, calves fed TAL had reduced average daily gain and tended to have reduced change in hip width from 2 to 4 mo of age. Calculated metabolizable energy intake was not increased in any trial by added fat or oil. Tallow and soybean oil inclusion at 2% of the starter feed was not advantageous for calf growth before 4 mo of age.