Incorporation of abomasal and intravenous doses of [³⁵S]cystine and [³⁵S]methionine into wool

Abstract

SummaryThe fate of abomasal and intravenous doses of [35S]cystine and [35S]methionine was investigated in sheep to determine their relative efficacy as supplements for wool growth.Administration of L-[35S]cystine and L-, DL- and D-[35S]methionine via the abomasum produced similar patterns of 35S labelling in blood plasma. Only 10–16% of the administered 35S was excreted in urine over 7 days and 22–32% of the dose was incorporated into wool over 21 days. All isomers were utilized by the sheep with similar efficiency and it was concluded that D- and L-methionine and L-cystine are equally effective as supplements for wool growth at optimal dose rates. Abomasal supplementation with a large amount of methionine (10 g/day) resulted in the excretion of a high proportion of the 35S in urine (55% of the dose over 7 days) and low incorporation into wool.A comparison of the extent of incorporation of 35S into wool from intravenous doses of L-[35S]cystine and L-[35S]methionine in the same sheep, and in sheep from flocks selected for high and low wool production, showed that incorporation from methionine averaged 80% of that from cystine. It was concluded that, at moderate (2–3 g/day) methionine availability, methionine is utilized for synthesis of wool with about 80% of the efficiency of cystine, conversion of methionine to cysteine occurring via the transulphuration pathway.

Effect of sex and rearing system on the quality and mineral content of fiber from raeini cashmere goats

“…Both zinc and copper are indispensable micronutrients for fast growing tissues such as fiber-producing follicles [30]. Copper deficiency results in impaired keratinization of hair and wool and physical properties of wool like crimp that are dependent on disulfide groups.…”

“…Copper deficiency results in impaired keratinization of hair and wool and physical properties of wool like crimp that are dependent on disulfide groups. Thus, sheep exposed to sulfur deficiencies have shown lower sulfur content in their wool compared with a nutritionally adequate group [30,31]. …”

“…Variable effects of dietary sulfur on zinc content in cashmere fiber of Raeini kids have been shown [30]. A decreased cashmere zinc content of 0.01165 to 0.01015% was reported with diets containing 0.22 or 0.14% sulfur [30].…”

“…A decreased cashmere zinc content of 0.01165 to 0.01015% was reported with diets containing 0.22 or 0.14% sulfur [30]. In addition, a negative linear relationship between dietary sulfur and cashmere copper was reported so that at dietary levels of 0.4 and 0.14% sulfur, cashmere copper levels were 24.9 and 22.3 mg/kg, respectively [30]. The ranges of sulfur, copper and zinc in cashmere fibers of Raeini kids were 1.8 to 7%, 10 to 15 mg/kg and 75 to 299 mg/kg, respectively.…”

Wool production and blood supply to skin and other tissues in sheep

“…Details of wool growth studies of the animals in our study have been reported by Reis et al (1989). Mean wool growth rate per unit area of skin in the Fleece plus group was more than twice that in the Fleece minus group; there was no significant difference in mean follicle density (total or secondary), but fiber diameter (primary) and fleece depth (distance between skin and outer fleece surfaces) were greater in Fleece plus sheep (Table 1).…”