Effects of inclusion of a high-fat extruded pellet mixed with a conventional pellet in rearing calves

Calf rearing systems are moving toward greater milk allowances (≥20% birth weight in L/d), driven by their benefits for later life performance. However, higher milk allowances can lead to a reduction in solid feed intake before, during and even after weaning, resulting in lower energy in-take. Therefore, fat inclusion in the starter pellets can increase energy den-sity of the feed, but it might negatively influence rumen development. The objective of this study was to evaluate the effect of supplementing a high-fat extruded pellet mixed with a conventional starter on feed and energy intake, and performance in calves. Forty Holstein bull calves were blocked by serum IgG (2451 ± 109 mg/dL) and date of arrival (2.5 ± 0.5 d of age). Within each block, calves were randomly assigned to 1 of 2 treatments: a pelleted low fat control starter (LFP; 3.2% fat) or the LFP mixed in a ratio of 90:10 with an extruded feed high in hydrogenated palm free fatty acids (HPFFA; 6.8% fat for the mixture). Calf milk replacer (MR: 24.4% CP, 19.6% CF) was provided twice daily until 42 d of age, followed by a gradual weaning period of 7 d. Starter treatments, straw and water were available ad libitum throughout the study (2 to 112 d of age). Measure-ments included intake, BW, and blood parameters. Data were analyzed by PROC MIXED in SAS accounting for the fixed effects of treatment, time (week), and their interaction, plus the random effect of block. Measure-ments over time entered the model as repeated measures. No differences were observed between LFP and HPFFA calves on BW or ADG until 49 d of age. From weaning (d50) until d 112, HPFFA calves had a greater BW (P < 0.05) than LFP animals (140.0 vs. 131.5 kg). Moreover, HPFFA calves had the highest starter, straw, calculated metabolizable energy and CP intakes after weaning (P < 0.05). No differences were present in blood B-hydroxybutyrate, glucose or IGF-1 concentrations between treatments. In conclusion, the high-fat extruded pellet in at 10% mixed with a conven-tional starter improved BW, solid feed and energy intake after weaning