Evaluation of two indirect predictors of current dairy milk yield in Dorset ewes

Abstract

Abstract The aim of the four experiments in this paper was to determine if either a 4-h test or udder volume could be used to select Poll Dorset ewes for high daily dairy milk yields. In Experiment 1, milk yields were estimated using a 4-h test in which ewes were injected into the jugular vein with 1 IU oxytocin, and machine-milked after an interval of 4 h (FHT milk yield). The milk volume from the second milking was multiplied by 6 to give 24-h FHT milk yields. There were no relationships between FHT milk yield measured on ewes suckling lambs and subsequent dairy milk yields. There was a correlation (r = 0.46; P = 0.012) between FHT milk yield of machine-milked ewes and daily dairy milk yields measured the previous day. In Experiments 2, 3, and 4, the udder volumes were calculated from measurements of the lateral and longitudinal semicircumferences of the udder. In Experiment 2, the udder volumes were measured before and after milking on 23 hoggets and 28 mature Poll Dorset ewes, which were 55 and 97 day...