I think it's a lot to expect cattle to cycle and breed in the type of weather we've been having, even when they're left to take care of business on their own! It's very difficult to catch cattle in heat and time artificial insemination with much success during hot summer months. Some females may not cycle, and a lot of them may show little to no signs even if they do. And to compound the frustration, just because an animal tries to mount another one time, that may not mean either of them is actually in heat. Cows are known to exhibit that kind of behavior occasionally just because... All those factors can make heat detection during summer time super frustrating to me.
For the most success, I think you have a couple of options...
1) Turn a bull out with those cows! Sure, everybody prefers an AI calf, but isn't A calf a better alternative than NO calf? A lot of small breeders think they can handle the business of breeding cattle without having a bull on the place, and all I can say to that is good luck. I guess if you're not real particular about breeding seasons or cows calving every 15-18 months, then it's not a big deal. I'm pretty good at AI, and I'm realistic enough to know I'm not gonna get 100% of them bred. And I'm not willing to sacrifice a good cow because something didn't go right in the AI barn. We try to calve for 60 days in the spring and 60 days in the fall, and I would say 98% are within that window. If we have a straggler one year, she has the next year to catch up, but that means we don't even try to AI her...she goes straight out with the bull. We AI for 3 weeks starting March 20th and another 3 weeks starting on Thanksgiving, and we own the best clean up bull we can afford. If you can't afford to own a good bull, figure out some way to lease one.
2) Think about a shift in your calving season. I don't understand late spring and summer born calves...I never have. Our spring cows used to calve February through April, and we had the same problems...we were STARTING our breeding season right when the weather was getting hot. And cows were calving right when grass was coming up, meaning extra rich milk and big bags at calving time. We had more calf sickness and more problems in general. When we started having some early calves for whatever reason, they always did better. We pushed our breeding season earlier each year, and now we start calving around New Years Day, with most of the calves being on the ground before the end of January. The calves are big enough to eat grass when it starts coming in March, and the cows are gaining weight, cycling like crazy and ready to breed when we bring em in. Early born commercial calves are heavier when the market typically hits a high in August--compare average calf prices for the last however many years...February and August are the highs. The market will be flooded in the fall...
Personally, what's worked for us is to adopt BOTH these practices, and I feel confident it's made our program a lot more manageable. I understand some parts of the world have different weather and other factors to deal with, but summer seems to be hot everywhere. January may not be a good time to calve cows out where ever you are, but I would look at some time of year so you're not trying to get cows bred in July. Cattle like cold weather better than hot, and they do better in cold than they do in heat in most cases. The toughest calving season besides summer heat is when it's wet...you'll have more scours and lose more calves in wet weather than you will in cold weather if you can keep em relatively dry.