Following a small survey of milk constituents in 5 lactating alpacas in south-eastern Australia, it was revealed that the average milk fat content was 4.4%, the average milk protein content was 4.2% and the average milk sugar (lactose) content was 5.8%. Constituents in alpaca milk can vary depending on age of dam, number of days post-partum, nutrition and genetics. Accordingly, alpacas and llamas exhibit small ranges for milk fat (2.7-4.9%), milk protein (3.4-4.5%) and milk sugar (lactose; 5.6-7.4%) in the scientific literature.
Alpaca milk is very similar to other domestic livestock with respect to milk constituents. For example, cows average 3.6-4.2% milk fat, 3.2-3.5% milk protein and 4.6-5.0% for milk sugar (lactose).
Do not overthink what you should supplement crias that have been orphaned or require a top up if the dam is not producing much milk. Remember that the milk sugar, lactose, is present in alpaca milk and crias have the enzyme necessary to digest it (for you budding biochemists out there, lactase in the gut of the cria snips the disaccharide lactose into monosaccharides glucose and galactose for absorption and use by the cria for energy). For more information, have a look at the recently updated Cria Genesis PDF Note on supplementing crias.