The use of chromium sesquioxide to measure the digestibility of carotene by goats and cows

Abstract

The digestibility of carotene in dried grass was measured by the Cr₂O₃method in both cows and goats. In the goats the direct method was simultaneously used for comparison with the Cr₂O₃method.The main conclusions were:1. When mixed with the concentrate portion of the ration of lactating goats, Cr₂O₃was recovered in the faeces in four experiments in amounts equal to 100·0, 99·1, 99·1 and 96·0% of the amount ingested.2. The apparent digestibility of carotene in the goat was measured both directly by the use of metabolism crates and indirectly by using Cr₂O₃as an indicator of equivalence of faeces and food. By the former method digestibilities of carotene in four goats were 68·7, 62·7, 61·8 and 59·6%. The corresponding digestibilities obtained from the same faeces samples by the Cr2O3 method were 67·4, 62·9, 61·8 and 58·9%.3. In six cows, on the diet similar to that of the goats, the Cr₂O₃method showed that 59·3, 54·0, 54·4, 54·4, 57·1 and 55·5% of carotene was apparently digested.4. Reasons for preferring the use of added Cr₂O₃to natural constituents of the food as a marker are discussed.5. The individual results from cows and goats have been statistically analysed to partition the various sources of variance, and it has been shown that fewer animals for a longer time give a more reliable result than more animals for a shorter time.