Developmental modification of fleece structure by adverse maternal nutrition

Abstract

As part of a series of investigations on the factors influencing the development of the secondary follicle population during foetal and early post-natal life of lambs, the influence of severe restriction of the feed intake of ewes throughout pregnancy is recorded. Adverse maternal nutrition reduced the body weight and secondary: primary (S/P) fibre ratio of lambs a t birth but had little effect on the S/P follicle ratio. Although the post-partum feeding of ewes was ad libitum, the restricted nutritional regime during gestation had a delayed impact on the post-natal growth of lambs, presumably due to a reduced milk production; this resulted in restricted final S/P ratios and number of fibres per unit area of skin in the offspring of the poorly fed ewes. At 200 days of age, the offspring of ewes well fed and poorly fed during gestation had attained the same mean body weights and had produced the same amount of clean wool per head and per unit area of skin. Lambs with fewer mature follicles per unit area of skin grew fibres both longer and coarser than lambs with higher fibre densities. This evidence supports previous observations that wool production per unit area of skin is independent of fibre density, and further substantiates the hypothesis of competition between follicles for the precursors of wool keratin.