I can share anecdotal info. 3 years in a row we would pick the date for our girls to camp out with our buck. The day would arrive and we move them in and note the calendar date. Boy goes wild, girls become flirts. 21-22 days later - nothing, nada, zip. Blood test at 45 days - yep pregnant. First girl starts stringy stuff - into the kidding pen. She starts hollering and delivering kids and the other girl (her mom) starts hollering - yep, she's in labor. I'm going back and forth between the two pens, across the barn from each other. Both deliver, both are happy. 3 years in a row that happened. Last few years- the younger doe is generally a month ahead of her mom - but she's also a bigger flirt and will get the job done through a cattle panel if we're not careful. Not sure about this year yet - could be any day now.