Estimation of gestational age of lambs based on fleece development

Authors: Orr MB
Publication: New Zealand Veterinary Journal, Volume 33, Issue 6, pp 99, Jun 1985
Publisher: Taylor and Francis

Animal type: Livestock, Production animal, Ruminant, Sheep
Subject Terms: Diagnostic procedures, Pregnancy, Reproduction, Reproduction - female, Integument/skin/wool/hair/fur/feather
Article class: Correspondence

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Abstract: Various techniques are employed to determine the gestational age of foetal lambs. Most are quantitative, based on weight or length measurements. Often crown anus length is used. For more accurate estimates, brain weights have been advocated. The disadvantage of quantitative methods is that they take no account of the smaller size of twins and triplets. A single lamb is usually bigger and heavier than a twin or triplet of the same age. Crown anus length measurements of bloated or malformed lambs may give false age estimates, and brain weights of autolysed foetuses are obviously useless. Variation in size due to breed is a further confounding factor. For practical purposes, a good estimate of the age of foetuses from 105 to 135 days gestation can be made by visual appraisal of the stage of fleece development. Wool fibres are first apparent over the head and neck at about 105 days gestation. Development then proceeds in a posteroventral direction over the rest of the body. At 115 days, wool fibres have just appeared over the rib cage and by 125 days, there is wool over the whole body although it is still short and straight over the haunches. By 135 days, the wool is long enough to have a crimp overall…

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