Effect of milk replacer feeding rate and functional fatty acids on dairy calf performance and digestion of nutrients

Calves fed large amounts of milk replacer (MR) gain more body weight preweaning than calves fed less MR; however, postweaning growth may be reduced because of impaired digestion of nutrients. This was explored in the current research, as was the inclusion of functional fatty acids (NT) that could ameliorate some poor growth and digestion issues in calves fed large amounts of MR. Two MR rates [moderate (MOD) or aggressive (AGG)] with and without NT were compared using 48 male Holstein calves initially 3 d old (43 ± 1.5 kg of body weight) randomly assigned to treatments. The MOD rate was fed at 0.66 kg of dry matter (DM) for 49 d. The AGG rate was fed for 4 d at 0.66 kg of DM, 4 d at 0.96 kg of DM, then 34 d at 1.31 kg of DM, followed by 0.66 kg of DM for the last 7 d. Calves were completely weaned at 49 d. The MR contained 27% crude protein and 17% fat. The textured starter was 20% crude protein. Starter and water were fed free-choice for the first 56 d when calves were housed in individual pens. From 56 to 112 d, calves were grouped (4 calves/pen), maintaining the same MR rate and NT treatments, and fed starter blended with 5% chopped grass hay free-choice with free-choice water. Digestibility was estimated from fecal collections made on d 19 to 23, 40 to 44, and 52 to 56. Data were analyzed as a completely randomized design with a factorial arrangement of MR rate and NT using repeated measures with a mixed procedure. Fiber and starch digestion increased with age and was lower for AGG versus MOD. Calf average daily gain and hip width change were greater before approximately 6 wk of age for AGG versus MOD, but this was reversed from approximately 6 to 16 wk. Calves fed AGG had lower average daily gain per unit intake of DM, crude protein, and metabolizable energy from 8 to 16 wk than calves fed MOD. Preweaning starter intake was less for calves fed AGG versus MOD. Calves fed AGG had greater body weight gain than MOD over 112 d, but hip width change did not differ. Feeding NT improved digestibility of organic matter, DM, neutral detergent fiber, and acid detergent fiber (over 50% improvement for neutral detergent fiber and acid detergent fiber), which resulted in 10.7 kg (13%) more body weight gain and 1.4 cm (16%) more hip width change over 112 d. This was a greater improvement in growth than the difference in AGG and MOD programs over 112 d.