One of the first pearls of wisdom I learned from Jenny Cobb back in the early days of my alpaca breeding (1989) was that Sugar Beet aids milk production. I therefore always fed sugar beet to our lactating females in the Winter. A few years ago a group of visiting females with cria at foot arrived for mating to our studs. Both the females and their crias were thin, and so we offered the crias bottles, which they gulped down eagerly – a sure sign that they were hungry. We also started feeding the dams our highly nutritious home-grown haylage, along with alfalfa nuts and rehydrated sugar beet. The females improved and the crias started putting on weight. Then, one weekend, the duty stockperson forgot to give this group their sugar beet. (She left Bozedown shortly afterwards!) Lo and behold the cria weights dropped just over the weekend. With this added proof, I feel very confident when I say that Sugar Beet aids lactation.
P.S. Lactating females need to keep up their liquid intake, so if it gets very cold in Winter, consider giving them warm water to drink – it really aids milk production. They will drink warm water in preference to cold water, and will drink more of it. Warm water improves digestion of hay and feeds, so all your alpacas can gain weight as a result of giving them warm water, even when the amount they eat is not increased.
P.P.S. We waited until all the females above had gained on their body condition scores before we mated them.