Abstract #330

# 330
A meta-analysis of starch concentration in dairy calf feeds on growth and digestibility.
W. Hu1, T. M. Hill*1, F. X. Suarez-Mena1, T. S. Dennis1, J. D. Quigley1, R. L. Schlotterbeck1, 1Nurture Research Center, Provimi, Brookville, OH.

There are limited published studies evaluating the concentration of starch in a dry starter diet on growth and digestibility in Holstein dairy calves through 16 wk of age. Our objectives were to improve this understanding using a database developed from published studies from our lab that included 4 trials from 0 to 8 wk of age (10–43% starch), 8 trials from 8 to 16 wk of age (19–50% starch), and 3 digestibility trials from 6 to 16 wk of age (13–50% starch). A meta-analysis was conducted to examine potential relationships between starch concentration in the starter (% dry matter, DM; STA) and ADG (kg/d), hip width change (cm/d; HWC), or DM digestibility (%; DMD). Factors such as ME intake (Mcal/d), CP intake (g/d), DM intake (% of body weight), and ambient temperature, which might have influences on the responses to STA, were also evaluated using mixed-effects models. Milk replacers (4.7–4.8 Mcal ME/kg) were fed at an equal rate among starter treatments within a trial. Chopped grass hay (5%) was blended with the starter from 8 to 16 wk. Starters were 18–20% CP and 2.8–3.0 Mcal ME/kg. Within a trial, starters were equal in CP with a high starch (>38%) control. Depending upon the trial, one or more low starch ingredients (cottonseed hulls, soybean hulls, wheat middlings, distillers dried grains with solubles) replaced corn to reduce the starch and ME concentrations of the feed. Linear relationships were: 0–8 wk HWC = 0.000262 × STA + 0.0562 (P = 0.01; R2 = 0.75); 0–8 wk ADG = 0.001345 × STA + 0.4817 (P = 0.13; R2 = 0.42); 8–16 wk HWC = 0.000724 × STA + 0.7432 (P < 0.0001; R2 = 0.76); 8–16 wk ADG = 0.00575 × STA + 0.8608 (P = 0.003; R2 = 0.61); 6–16 wk DMD = 0.2777 × STA + 69.988 (P = 0.02; R2 = 0.89). Increasing intake of ME (P < 0.001) improved ADG from 8 to 16 wk along with STA. Intake of CP and DM and ambient temperature did not impact growth or digestibility. From this, changing a feed from 20 to 38% starch (within a typical range in the US industry) was predicted to increase DMD from 6 to 16 wk by 6%, HWC from 0 to 8 wk of age by 7%, and HWC from 8 to 16 wk of age by 14%. Increasing starch concentration of feeds increased digestibility and calf growth through 16 wk of age.

Key Words: calf, formulation, starch