Years ago I read an article in Countryside & Small Stock Journal about the many uses for apple cider vinegar. One of them was to put it in your goats' water during breeding season. This was said to cause the nannies to produce more female offspring. I tried this out and guess what? It seems to be true.
The first year that I consistently gave apple cider vinegar during the breeding season, I had five nanny goats. All had twins, giving 10 offspring. Eight were nanny kids, only two were males. Each male had a female twin, and both were among the first sets of twins born. With an 80% success rate, that indicates that the apple cider vinegar may be useful.
The amount I use was not carefully measured, I just poured some in out of the one-gallon jug of store-bought apple cider vinegar. I would guess the amount was 1 to 2 cups, in a water bucket with a five-gallon capacity. I used real apple cider vinegar and not the apple cider flavored vinegar they sell now in the large jugs.
In other years I fed some apple cider vinegar, but not consistently, and did not keep track of the results. There was only one other year that I fed it consistently enough to get results. (In other words, gave it every day starting a few days before the breeding session began.) I don't have the exact records of that year, but again I had a bumper crop of female twins, with only a few males born, and those all had female twins.
I have never tried this with my Shetland sheep. For one thing, they drink much less water, so should be less affected. But this year during breeding season I may well try it.
I won't be able to run an effective test on this with my goats this year. I had to put my Boer billy with the nannies early because he broke out of his pen. When the pen is repaired, this breeding session will be done. There will be a second breeding session in the fall, in which I may use the apple cider vinegar, but if Warlock has done his job the first time around there may not be enough births to be a good test.
The best use of the apple cider vinegar is with the rare/endangered breeds, such as my soon-arriving Arapawa goats. Since one buck can service quite a number of females, one doesn't need as many males, and extra females are a blessing. And since apple cider vinegar is also generally healthy for goats, it won't do any harm.
This year, I won't be testing the method on the Arapawas, since my only breeding-age female, Rose, will be bred when I get her. But next year, when I will have 3 does to breed, I'm definitely trying it, with the intention of increasing my population of Arapawa breeding females. After that is accomplished, I may eliminate the use of apple cider vinegar most years in order to ensure that I get enough buck kids to have a good selection.