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South African Journal of Animal Science

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Homeorhetic hormones, metabolites and accelerated growth

A.L. Marais, J.G. van der Walt

Abstract


Six newly weaned karakul ewes, three with fat tails and three without tails, were used to investigate the metabolic and hormonal changes during accelerated growth. Two lambs acted as controls, while the remaining four were SUbjected to a maintenance diet for two weeks. The subsequent resumption of ad lib feeding caused a period of accelerated growth for approximately four days before the normal growth pattern resumed.Blood samples were drawn from surgically implanted  catheters in the caudal aorta and vena cava during normal growth, maintenance (zero) growth and accelerated growth.These samples were assayed for glucose, free fatty acids, glycerol, alanine, lysine, growth hormone, insulin and thyroxine. It was found that during the period of accelerated growth, glucose concentrations decreased after feeding while free fatty acids and glycerol concentrations increased after feeding. This is the inverse of the normal growth pattern. The uptake of lysine was doubled during accelerated growth, while alanine concentrations did not change significantly. Growth hormone concentrations dropped during accelerated growth and increased dramatically during the subsequent normal growth phase, while insulin concentrations increased during accelerated growth. Thyroxine concentrations increased during accelerated growth and dropped during the subsequent normal growth phase.

Ses pas gespeende karakul ooie, drie met sterte en drie sonder sterte is gebruik om die moontlike veranderings in metaboliete en hormone waar te neem, tydens versnelde groei. Twee skape is as kontroles gebruik, terwyl die oorblywende vier blootgestel is aan 'n dieet wat net genoegsaam is vir onderhoud vir twee weke. Daaropvolgens is 'n ad lib dieet gegee wat 'n periode van versnelde groei veroorsaak het vir ongeveer vier dae, voordat normale groei weer in werking getree het. Bloedmonsters is getrek uit kateters wat deur chirurgiese metodes in die kaudala aorta en vena cava ingeplant is. Bloed is getrek tydens drie fases: normale groei, onderhoud en versnelde groei. Hierdie monsters is ontleed vir glukose, vry vetsure, gliserol, alanien, Iisien, groeihormoon, insulien en tiroksien. Gedurende die periode van versnelde groei is gevind dat glukosekonsentrasies verminder na voeding terwyl vetsure en gliserolkonsentrasies vermeerder. Dit is die teenoorgestelde patroon van die van normale groei. Die opname van lisien was dubbeld gedurende versnelde groei terwyl alanienkonsentrasies nie beduidend verander het nie. Groeihormoonkonsentrasies val gedurende versnelde groei maar vermeerder dramaties gedurende die daaropvolgende normale groeifase, terwyl insulienkonsentrasies vermeerder gedurende versnelde groei. Tiroksienkonsentrasies vermeerder gedurende versnelde groei en val dan weer in die daaropvolgende normale groeifase.

Keywords: Karakul ewes, accelerated growth, growth hormone, free T4, glucose, free fatty acids, glycerol, alanine, lysine




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