1. Whole-body protein turnover was measured by a single-injection [¹⁵N]glycine method in the euro (Macropus robustus erubescens), wallaroo (M. r. robustus) and goat (Capra hircus). 2. Dietary nitrogen (N) intake was greater (P < 0.05) in the goat (1.17g N/kg⁰·⁷⁵ x day) than in the kangaroo sub-species and greater (P < 0.05) in the wallaroo (1.07 g N/kg⁰·⁷⁵ x day) than in the euro (0.93 g N/kg⁰·⁷⁵ x day). However, N balance was similar (0.29-0.34g N/kg⁰·⁷⁵ x day) among the species. 3. Crude protein (CP) turnover was similar in the euro (14.8 g CP/kg⁰·⁷⁵ x day) and goat (13.8 g CP/kg⁰·⁷⁵ x day) and less (P < 0.05) in the wallaroo (10.4g CP/kg⁰·⁷⁵ x day).

1. Glucose pool size, space, entry rate, and turnover time were estimated from the specific radioactivity vs time curves of [³H] and [¹⁴C]glucose administered as a single injection in the euro (Macropus robustus erubescens) and the sympatric feral goat (Capra hircus). 2. Digestible energy intake was greater (P < 0.05 ± SE) in the goat than in the euro (798 ± 64 vs 624 ± 31kJ/kg⁰·⁷⁵ × day). 3. However, there were no significant differences between the two species in parameters of glucose metabolism. 4. The use of an implantable osmotic infusion pump to deliver isotopic glucose showed promise as a means of avoiding the stress involved with the single injection technique.

Sheep selected for high wool growth were previously shown to exhibit higher microbial protein outflow from the rumen and higher uptake of amino nitrogen in portal blood than those selected for low wool growth. This suggests that genetic selection for wool growth may induce changes in foregut physiology. This study was undertaken to determine whether differences in digesta kinetics, especially mean retention mime (MRT), are associated with differences in fleece production between sheep with low or high estimated breeding values (EBVs) for fleece weight. Twenty mature Merino wethers with uniform EBVs for liveweight were allocated to two groups of 10 animals on the basis of high or low EBVs for yearling fleece weight. Five sheep with low-EBVs and five sheep with high-EBVs for fleece weight groups were allocated in a crossover design to low and high feeding-level treatments, which comprised a blended hay diet fed at maintenance or 1.5 times maintenance. All sheep were given single doses of chromium-mordanted fibre and cobalt-EDTA as inert, non-digestible markers. Digesta kinetics was determined by analysis of the faecal marker excretion patterns using a compartmental model. Higher feed intakes from animals fed 1.5 times maintenance were associated with higher rates of wool growth and higher masses of indigestible fibre in the gut, but reduced MRT of digesta. Although sheep with higher EBVs for fleece weight had higher wool growth rates, there was no indication that these wool growth differences were associated with differences in digesta kinetics. The lack of interaction between feeding level and genotype suggests that MRT did not contribute to genotype differences in wool growth in sheep fed restricted intakes. The differences in wool growth among commercial Merino sheep with divergent fleece weight EBVs achieved by multi-trait selection are not attributable to differences in digesta kinetics, at least when feed is not available 'ad libitum'.

On behalf of the 28th Council I commend this special edition of Animal Production Science to you for it showcases the great work being done by ASAP members on behalf of our farm animal industries. These peer-reviewed papers, along with short papers published by our Society in the companion edition of Animal Production in Australia, were presented to the Society's Biennial Scientific Conference held at the University of New England, Armidale, 11–15 July 2010. We have chosen the Conference theme: "Livestock production in a changing environment". We are witnessing change: in the basis of provision of government funding of R, D and E; a move to open competition between tertiary education institutions for students and the funding that comes with them; farmers grappling with increasing regulation and community expectations and a high Aussie dollar that is hurting their export sales; whilst seemingly everyone in the community has an opinion on whether we are witnessing "man-induced" climate change. It is in this changing environment that the conference committee decided to invite expert speakers to look ahead and present their views on the themes of food security and production, education, extension, and adoption. Progress and looking ahead are also the themes for the traditional ASAP special lectures: the McClymont (Agricultural Systems), Underwood (Livestock Nutrition) and Harry Stobbs (Grazing Management) lectures; and new this conference: the John Barnett lecture (Animal Welfare). We have strived to build on the initiative of the previous Federal Council to attract new members and to ensure that ASAP remains relevant to researchers and producers alike.

The effect on production of supplementing a straw diet with legume forage or rice bran was evaluated in beef steers.

Metabolism studies often require collection of urine for accurate determination of excreted products. Total collection of urine over a period of 24 h or more can be stressful to the animal and is often impractical, especially in grazing situations and when large numbers of animals are involved. Urine spot-sampling, while not as accurate as total collection of urine, can be useful for assessing the metabolic state of an animal if total daily urine output can be calculated. Creatinine is a waste product of muscle turnover and the creatinine concentration of urine spot-samples has been used to estimate daily urine excretion.

Chickens cannot biosynthesise arginine and many studies with other species have shown that immune responses can be influenced by dietary arginine. Additionally, as nutritional status in early life may permanently 'programme' immune functions in later life of humans and other species (Hales and Barker 1992), the present study investigated the carryover effect of short-term dietary arginine in early life on the immune system in chickens. Day-old ISA-Brown cockerels (n = 180) were allocated to 3 treatment groups, each with 6 replicates of 10 birds, and were given an arginine deficient basal diet (6.7 g arginine/kg) supplemented with 0 (control), 2.7 (LA) or 5.4 (HA) g L-arginine/kg for 4 weeks; then all birds were offered a commercial pullet grower feed (8.9 g arginine/kg) for another 8 weeks. The dietary arginine contents of the control, LA and HA diets were equivalent to 70, 100 and 130% respectively of NRC, USA, recommendations. Lymphoid organ weights, serum primary antibody levels against sheep red blood cells (SRBC) and bovine serum albumin (BSA), and cutaneous reactivity of toe-webs to phytohaemagglutinin (PHA)-M as an indicator of T cell responsiveness, were measured at 4 week intervals.