Undernutrition of the Merino sheep and its sequelae. II. The influence of finite periods of arrested growth on the subsequent wool growth, fleece development, and utilization of feed for wool production of lambs

Abstract

Five groups of Merino lambs were subjected to contrasting nutritional regimes during a preparatory period of 400 days. All animals were then restored to a normal diet and during the subsequent 27 months the sequelae to the experimental treatments were measured in terms of wool growth, fleece development, and the utilization of feed for wool production. The most rigorous treatment (growth arrested for 400 days at 15 kg weight) had as its sequel a less dense wool follicle population (adjusted to a standard body weight) and a reduced growth rate of wool during the early recovery period. Total fibre numbers and wool growth per unit of feed intake were also depressed but not significantly so. Fibre diameter, fibre weight, and the ratio of secondary to primary follicles were not affected. The less severe treatments (growth restrictions for 200 days (a) at 15 kg and (b) at 30 kg) influenced none of the parameters under study once a normal diet had been restored. It is concluded that only with extreme under nutrition from early in post-natal life is the wool-producing potential of young sheep likely to be impaired.

A comparison of wool follicle development of New Zealand Romney lambs at two stocking levels

“…This trial is therefore comparable to those of Henderson (1953), Schinckel (1953), Ryder (1955), Wildman (1958Wildman ( , 1965, and Doney and Smith (1964). The imposed effects are much less severe than those reported by Schinckel and Short (1961) and Allden (1968). It is reasonable to assume from the work of many authors (reviewed by Fraser and Short 1960) that all primary follicles are fully developed before birth.…”

“…Any delay is transient. Because of the capacity of young sheep to undergo long periods of under-nutrition without impairing wool production in later life (Allden 1968), a situation in which permanent changes in the follicle population could be induced would be extremely rare for Romney sheep under New Zealand grazing conditions.…”

“…The nutritional status of the Merino ewe has been shown to influence the pattern of follicle development of her offspring (Schinckel and Short 1961;Everitt 1967;Allden 1968). It is generally suggested for nonMerino breeds that a restriction in maternal nutrition slows the rate of secondary initiation and maturation (Henderson 1953;Ryder 1955;Wildman 1958Wildman , 1965Doney and Smith 1964).…”

Feeding and Nutrition

“…7 In addition, they possess the ability to reduce urine and fecal water losses during times of water deprivation. In general, only very young animals are affected.…”

Near-real time financial assessment of the Queensland wool industry on a regional basis

“…Secondly, net efficiency is the gross efficiency of wool production at maintenance, or the genetic potential for wool growth efficiency. Allden (1979) concluded that high wool producers within a flock consume both more feed and utilise this feed more efficienfiy than low wool producers, whereas differences between strains and breeds of sheep reflects differences in feed intake rather than differences in the gross efficiency of conversion of feed to wool. Pritchard (1988) also showed high producing sheep had higher intake of digestible organic matter and were better able to utilise apparenfiy digested protein for wool production than low wool producing sheep.…”