This goes for the actual food and ammunition supply for the command + control elements of non-motorized or partly motorized units, but not for the actual act of issuing orders or spreading infos.
The HQ of a non-motorized inf regiment had a similar amount of Krad messengers, if compared to a (partly) motorized inf rgt HQ and even to an HQ of a Panzer regiment, in addition to the usual number of radios.
Its (horse-drawn) signal platoon established regular radio and telephone services to keep in touch with its Bns and the parent division.
In 1943, a Pz Rgt just had 3 Krad messengers, while the 3 Kübelwagen and 2 "medium" passenger cars were meant to chauffeur the officers, but some of these cars/drivers could be assigned for messenger missions, if necessary/possible.
The 1941 Panzer Rgt layout listed 5 Krad messengers but only 2 medium passenger cars.
The new 1943 layout of a non-motorized Inf Rgt listed 3 messengers on 3 horses, 3 additional messengers (2 on bikes) and 3 Krad messengers. The 3 chauffeurs of the HQ had 3 Kübelwagen at their disposal, but they could be employed as messengers, too.
While the officers (rgt. CO, adjutant, aide-de-camp and veterinary surgeon) were supposed to use their horses, they probably often used 1 of the cars in urgent cases, instead.
