Effect ofin ovofeeding of dextrin-iodinated casein in broilers: II. Hatch window and growth performance
Studies were conducted using a commercial InovojectTM system to determine effects of in ovo feeding of dextrin and iodinated casein (IC) on hatch and posthatch growth in broilers. At ˜18.5 d embryonic development, eggs were treated with 0, 240, or 480 μg IC/mL in saline (Cont, IC240, and IC480) or dextrin (Dext, DextIC240 and DextIC480). The Dext solution consisted of 18% maltodextrin and 10% potato starch dextrin; saline was the vehicle used by the company for in ovo vaccination. The volume for all in ovo treatments was 50 μL/injection. Eggs in Experiment 1 were transferred to a commercial hatcher unit whereas eggs in Experiments 2 and 3 were transferred to a research hatcher unit to assess effects of treatments on timing of hatch. At hatch, chicks were randomly selected and placed in floor pens and grown to 6 wk. In Experiment 1, there were no differences in hatch weights, but broilers provided Dext IC240 in ovo were heavier (P < 0.05) at 6 wk compared to other treatments with the exception of the Dext IC240 group. In Experiment 2, hatch weights were heavier (P < 0.05) in chicks receiving IC240 and DexIC480 treatments compared to Controls. At 6 wk, broilers in all treatments were heavier (P < 0.05) than Cont with the exception of IC480. In Experiment 3, hatch was stimulated by IC240 (in saline), but was delayed by Dext IC240. Serum analysis of β-hydroxybutyrate (μM/mL), as an indicator of ketone accumulation from fat metabolism of chicks held in chick boxes for 24 h posthatch (to simulate delay in placement after hatch), indicated that chicks in the IC240 group (that hatched earlier) had higher blood ketones compared to chicks that received Dext or DextIC240 in ovo (that hatched later). We conclude dextrin and iodinated casein (240 μg/mL) provided in ovo (˜18.5 d of embryonic development) has the potential to improve chick quality and posthatch body weight by delaying or narrowing hatch window.