Have been breeding for many years and only hand breed. Process- I take mare to stallion, keeping mare on lead, only when she is cycling. My current stallions are "wham bam thank you ma'am " types, so we are in and out quickly. With mare in heat, stallion will service pretty much as often as he is given the opportunity. If mare kicks, stallion will retreat and we leave. After doing this thousands of times, I have on a few occasions (this morning being one) where the mare is receptive and the stallion will smell, retreat, pin back ears, lower head in snake like form and rush the mare in "bite" mode. Knows mare and has bred her before. Would appreciate hearing what might bring on this reaction.