I grew up with a "western" or "cowboy" influence on my horse training. We would bring youngsters in for handling a set amount of time and then they would get turned out again. In the west, on large ranches, some of those youngsters were on hundreds of acres - truly no different than the actual wild american mustangs.
Mares often foaled on pastures - albeit closer to the Home ranch area. They could be checked on that way, foals could be monitored etc. Yes, there was some loss - but compared to what I hear and see now, not anything like the rates of today (big or small equine). Mares and younsters were often culled (sold, moved to a working string or even ... euthanized, depending on the situation), based on their production records or how well they matured. Occasionally, one would be made into a "pet" or "babied"... Mares & foals could be called into the "barn yard" and they would have access to feed and hay. Foals were often lightly handled when they were in. Hooves would be trimmed, shots & worming done, haltering & leading lessons, tying and bathing. At weaning, mares would be removed and go to different broodmare winter pastures. The weanlings stayed in the barn pasture for a while, then would be split by sex (s) and go out again in different pastures. They wintered out - and again, some times there was loss. It wasn't every year and usually weren't many. In truly bad weather, hay and feed was provided on/in the snow and they sometimes had shelters (depending on the ranch) that were built rather than natural. The following year, when most of the youngsters were "long yearlings" - they'd be brought in for 30 -60 days. They'd be introduced to saddles and ground driving and if the trainers/handler/day cowboy in charge felt that that youngster was mentally and physically capable, they'd actually be started under saddle. Often, on these type ranches, it wasn't a big beefy, mean cowboy that started those colts - but the "horse savy" son or daughter of the owner, foreman or other employee. They were often tiny/small so it wasn't an issue weight or size wise - plus even the small horses on these types of set ups were beefy youngsters. It was a common practice - and worked well with people in charge that had compassion and understanding. Other ranches the horses ran out until they were 4 or 5 with little handling - the problem is that they were then needed for working and their training was often hurried and the horse sure didn't appreciate it. Some were truly "broken" and others became true "outlaws".
Over the years with ponies, I've often utilized a combo of the same management/training techniques with my own added in. SOO, we too, have often harnessed and/or had saddles on youngsters as early as 4/5 months of age. It doesn't mean they were "worked into the ground" nor were they upset or stressed over it. Often, it gave intelligent and bored, who then became dangerously mischievous, ponies a job. I've found that the foals worked with this way were easier to actually start riding, or to fully start driving. They weren't spooking over "every day" things. The years that we didn't have many foals or number of ponies I DID have to be careful not to overwork with a youngster - because it gave ME something to do. Now, I have the opposite - a lot of ponies with a full time job (for the first time in years!) and not enough time to do the individual work with the ponies plus maintenance on the "farm". It's been very interesting...
When my children were small - both the oldest and the youngest enjoyed "starting" the ponies. Soon the oldest outgrew them, but the youngest had great fun being our "pony jock" for many years. Because i followed the techniques I grew up around, she often started riding our youngsters before they were a full 2 yrs old - around 20 months of age. ALL of those ponies are in their mid to late teens now and are still going strong with both children and adult handlers/riders. Some are still competitive (4 at "A" rated hunter/jumper shows, 2 @ major driving events, the mare I just sold will go on to do H/J but not sure at what level they will compete to), others are used as lesson ponies and general riding mounts. Only one or two of 30+ have been used for breeding.
They were truly started lightly and not overworked. They weren't ridden for hours at a trot or lope/canter - on hard ground or in nothing but circles - though most of the riding did occur on a simple, flat 3 acre pasture. Though all learned thru lounging and started being lounged as early as 3 months of age - I've never had any of the problems so many pony/mini folk cry "foul" over. I often had not only my 3 daughters but up to 4 or 5 more kids (very few boys) "hanging out" in our pasture. We had few amenities (no heat in winter, no air in summer, no potty - though for smaller children I had a potty chair and for me I had a "campers' toilet" and tissue and wipes) but we had water, gatorade and soda plus snacks. The kids had "races" with the ponies - all the way down to the foals. The ponies got used to kids running (tho I did discourage that) around them and occasionally falling. YES, sometimes the kid got stepped on or even kicked - often they rolled out of the way and were up and gone again. The ponies learned to lead - walk, trot & gallop. The kids got treats for the winner in who got to the horse trailer first & got their pony loaded - w/o dragging or whipping. At least once - had kids out there with a pony in each hand jogging from the round pen to the trailer and hopping in w/ the ponies. I really regret that I don't have many pics and the ones I do have aren't on the computer(s) at this time.
For two years, I often rode the one mare 2 miles with up to 4 ponies in tow beside/behind me. All but the last would have a kids saddle on and a headstall w/ a bit. They would be tied to the gullet/pommel of the saddle in front of them. When we got to the "barn" (actual owner of the pasture I leased) - they would all be tied up, and I'd work with them 1 on 1 - leading, lounging and ground driving them around this boarding barn - thru ditches, water, thru the cleared tree area, between pastures with BIG horses, around farm equipment I didn't have at our "place", over jumps. The youngest baby I was ponying would be the weanling or suckling from the mare I was riding who would be at the "tail" of my line. W/i a couple of weeks, the oldest would then have either Skye or Sierra in the saddle for the first time...
Since I've gotten back into the ponies, I haven't had this availability of "pony jocks". However, on occassion, both the oldest and youngest still hop in and will work with a pony or two. The pony will get several short sessions of "work" or training. Sierra had a couple that she put time in with harness and even ground driving as weanlings and early yearlings. Wasn't everyday, nor for hours on end. The ponies were well adjusted, happy and not sore. I can tell the difference when I've gone on to work those "babies" as 2 or 3 yr olds getting ready to drive!
AND I miss having that kind of "help". THOSE ponies are awesome!!