The effect of sulphur-containing amino acids on growth performance and hair production in vivo and in vitro by Angora and Cashmere goats

Major conclusions of each experiment are as follows:- Experiment 1: • Under experimental conditions described in Chapter 3 Cashmere and Angora goats, on average, exhibited similar values for LWG. • Differences between two genotypes were noted in superior values of apparent digestibility of DM and CP although there were lower values of nitrogen retention in Cashmere than Angora goats; this result suggested that nitrogen utilisation was more efficient in the Angora goats. • In response to dietary rumen-protected methionine, nitrogen retention and LWG were improved in both genotypes. However total fibre yield and diameter were increased only in the Angora goats. Experiment 2: • The supply of rumen-protected methionine increased the total weight and protein and water concentration of carcass and non-carcass components of Angora goats. • Methionine supply had no effect on the proportion of dietary nitrogen partitioned between mohair and other body components. • Dietary methionine supplementation changed the amino acid composition of mohair (increased cyst(e)ine and reduced phenylalanine) and muscle samples (increased methionine, phenylalanine and lysine) in addition to producing increases in total weight of mohair and LWG. Experiment 3: • The presence of both methionine and cyst(e)ine was required to support maximum growth of isolated anagen mohair and cashmere secondary hair follicles in vitro. • The presence of methionine, but not cyst(e)ine when methionine was present, was essential for maintaining growth and viability of isolated hair follicles of Angora and Cashmere goats. Experiment 4: • Epidermal growth factor (EGF) at low concentration (1 μg/l) increased DNA concentration, protein deposition and elongation in anagen mohair secondary hair follicles. • At high concentration (10 μg/l) EGF produced a club-hair like structure which was associated with stimulation of cell proliferation in outer root sheath and inhibition in matrix cells. These changes resembled those occurring in anagen to catagen transition.