Delays in oral motor skills can affect feeding and speech development. These skills develop side by side and one builds on the other. A child with poor oral motor skills will have feeding difficulties in certain areas and speech delays.
The following links and articles may be helpful:
NDSC Resource Guide to Oral Motor Skill Difficulties in Children with Down Syndrome by Libby Kumi
Oral Sensitivities and Low Tone in Children with Down Syndrome - Ark Therapeautic Services Inc.
Fussy Baby Clinic - Melbourne Paediatric Specialists
Down Syndrome Education Resource Centre - The development of oral motor control and language by Katie Alcock
Marinet Janse van Vuren, from the Down Syndrome Centre has also written some very helpful articles on the topic. There are many more on a wide range of topics too so it is well worth a visit to their site!