Live mass, carcass and wool growth responses to supplementation of a roughage diet with sources of protein and energy in South African Mutton Merino lambs

The effect of supplementing a diet of wheat straw plus urea with either 0, 100 or 200 g/d cottonseed oilcake meal .(CSM) in combination with either 0, 100 or 200 g/d  whole maize on wool and carcass growth of SA Mutton Merino lambs was studied. Voluntary intake of wheat straw was increased by CSM and decreased by maize (P < 0,01). Feed conversion ratio was improved by both supplements (P < 0,01). Although growth rate was increased by both supplements (P < 0,01), the response to CSM supplementation was almost double that for maize. The proportion of fat in the carcass was doubled by maize (P < 0,01), but was not affected by CSM. The proportion of fat in viscera was increased by both supplements (P < 0,01). Wool growth rate was increased by 89% and 226% when 100 or 200 g/d CSM werefed respectively, and by 46% and 96% when corresponding amounts of maize were fed. Wool fibre diameter was increased by 26% with 200 g/d CSM and by 6% with 200 g/d maize. Acetate clearance rate was not significantly increased by maize or CSM (P > 0,05). An interaction between treatment effects for feed conversion ratio suggests that responses to protein supplementation will depend on the level of energy supplied.Die invloed van katoensaadoliekoekmeel (KOK) teen peile van 0, 100 of 200 g/d in kombinasie met heel mielies teen 0, 100 of 200 g/d as byvoeding tot 'n dieet van koringstrooi plus ureum vir SA Vleismerino-lammers is ondersoek. Vrywillige inname van koringstrooi is verhoog deur KOK, maar verlaag deur mielies (P < 0,01). Voeromsetverhouding is deur albei bronne verbeter (P < 0,01). Alhoewel groeitempo deur albei bronne verhoog is (P < 0,01), was die respons tot KOK bykans dubbel die van mielies. Persentasie vet in die karkas is verdubbel deur mielies (P < 0,01),maar is me deur KOK bei'nvloed me. Persentasie vet in die ingewande is egter deur albei bronne verhoog (P < 0,01). Wolgroeitempo is met 89% en 226% verhoog met 100 en 200 g/d KOK onderskeidelik en met 46% en 96% deur ooreenstemmende hoeveelhede mielies. Wolveseldikte is met 26% verhoog met 200 g/d KOK en met 6% met 200 g/d mielies. Asetaatverdwyningstempo is nie deur mielies of KOK verhoog me (P > 0,05). 'n Interaksie tussen behandelingseffekte vir voeromsetverhouding dui daarop dat die invloed van protei'enbyvoeding deur die vlak van energiebyvoeding bei'nvloed mag word

Amino acid metabolism and whole-body protein turnover in lambs fed roughage-based diets: 2. Methionine metabolism and a comparison of estimates of whole-body protein turnover derived from lysine, leucine and methionine kinetics1

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Amino acid metabolism and whole-body protein turnover in lambs fed roughage-based diets: 1. Lysine and leucine metabolism1

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Acetate clearance rate as a potential index of the availability of glucogenic precursors in ruminants fed on roughage-based diets

Three experiments were conducted to investigate interactions between acetate and glucose metabolism in sheep fed on roughage-based diets, and to establish whether the clearance rate of an intravenous acetate load would provide a valid index of the dietary acetate:glucogenic precursors ratio. In Expt 1 lambs were fed on a basal diet of wheat straw and supplemented with propionate and protein. Both supplements increased glucose irreversible loss rate (ILR) although not to the same degree. Acetate clearance rates were increased by protein and propionate supplementation and were positively related to glucose ILR irrespective of precursor. In Expt 2 the effects of an increased dietary load of acetate given with or without propionate were investigated. Glucose ILR did not respond to acetate supplementation, but was increased when propionate was fed in addition to acetate. This was reflected in an unchanged ability to clear an intravenous acetate load from the blood when acetate alone was added, but an increased acetate clearance rate when propionate was fed in addition to acetate. In Expt 3 the effects of supplementation with various propionate: Acetate ratios were investigated. Acetate clearance was consistently increased by an increased propionate: Acetate ratio. These results show that the metabolism of excess acetate is responsive to the dietary supply of glucose precursors, and provide support for the concept that additional glucose precursors are necessary for the efficient utilization of acetate when roughage diets low in protein are fed

Allocation of greenhouse gas production between wool and meat in the life cycle assessment of Australian sheep production

'Purpose' Australia is the largest supplier of high-quality wool in the world. The environmental burden of sheep production must be shared between wool and meat. We examine different methods to handle these co-products and focus on proportional protein content as a basis for allocation, that is, protein mass allocation (PMA). This is the first comprehensive investigation applying PMA for calculating greenhouse gas (GHG) emissions for Australian sheep production, evaluating the variation in PMA across a large number of farms and locations over 20 years. 'Materials and methods' Inventory data for two superfine wool Merino farms were obtained from farmer records, interviews and site visits in study 1. Livestock GHG emissions were modelled using Australian National GHG Inventory methods. A comparison was made of mass, protein mass and economic allocation and system expansion methods for handling coproduction of wool and sheep meat. In study 2, typical crossbred ewe, Merino ewe and Merino wether flocks in each of the 28 locations in eight climate zones were modelled using the GrassGro/GRAZPLAN simulation model and historical climatic data to examine the variation in PMA values for different enterprise types. 'Results and discussion' Different methods for handling coproducts in study 1 changed allocated GHG emissions more than fourfold, highlighting the sensitivity to method choice. In study 2, enterprise, climate zone and year and their interactions had significant effects on PMA between wool and liveweight (LW) sold. The wool PMA (wool protein as proportion of total protein sold) least square means (LSM) were 0.61 ± 0.003 for wethers, 0.43 ± 0.003 for Merino ewes and 0.27 ± 0.003 for crossbred ewe enterprises. The wool PMA LSM for the main effect of Koppen climate zone varied from 0.39 to 0.46. Two zones (no dry season/warm summer and distinctively dry and hot) had significantly lower wool PMA LSM, of 0.39 and 0.41, respectively, than the four other climate zones. 'Conclusions' Effects of superfine wool production on GHG emissions differed between regions in response to differences in climate and productivity. Regarding methods for handling co-production, system expansion showed the greatest contrast between the two studied flocks and highlighted the importance of meat from wool production systems. However, we also propose PMA as a simple, easily applied allocation approach for use when attributional life cycle assessment (LCA) is undertaken