Animal weight is an important tool in livestock research and management. The most direct method of measuring liveweight (LW) is using a calibrated electronic or mechanical scale. However such equipment is usually costly and not readily available to poor rural livestock keepers. Farmers and livestock traders have been found to underestimate or overestimate the weights of the cattle by an average of 46 and 25% respectively of their true L W (Machila et al 2008). Linear body measurements, in particular heart girth are useful predictors of liveweight in livestock. However, the predictive ability of models developed from these measurements is influenced by body condition, age, breed and sex (Lesosky et al 2012; Ozkaya and Bozkurt 2009). The present study tested the accuracy of linear body measurements for predicting L W of crossbred dairy cattle of different genotypes in smallholder farms in Kenya and developed predictive equations appropriate to this context.

Merino ewe liveweight represents an objective measure shown to have a profound effect on production outcomes and therefore research into technology that provides accurate and timely feedback of ewe liveweight change is warranted. Most sheep in Australia are not individually identified and therefore management of sheep is on a flock or 'mob' basis. Mob-based walk-over weighing (MBWOW) is a remote weighing concept for sheep flocks whereby animal weights are collected as they pass freely over a strategically placed weighing platform. The weights are then collected by the livestock manager, analysed and interpreted to aid nutritional decision making on a whole-flock basis. The hypothesis tested in this study was that data from MBWOW systems is comparable to data from static weighing sessions. At three sites, MBWOW data was collected simultaneously with monthly static weighing sessions. Raw data from MBWOW from each site was manipulated through a series of methodologies that were compared according to their relationship with the static weight data. All forms of MBWOW data showed a significant relationship with static weighing data (P < 0.05). Using a 25% filter (data within 25% of a predetermined central weight kept) and grouping data into 5-day groups strengthens the relationship between MBWOW data and static weighing data. In 1-day groupings, MBWOW data with a 25% filter and subjectively chosen central weight showed the strongest relationship (R² = 0.89) with static weighing data. In 5-day groupings, MBWOW data with a 25% filter and reference weight from a previous weighing event as a central weight showed the strongest relationship (R² = 0.88) to static weighing data. The former MBWOW data manipulation methodology had the least mean numerical difference (±s.d.) between MBWOW data and static weighing data (1.86 ± 0.85 kg), yet the latter had the least mean numerical difference in change-in MBWOW data and change-in static weighing data (1.51 ± 0.39 kg), and as change-in liveweight has the most application to industry, it is recommend as the preferred data manipulation technique. These findings suggest that although MBWOW is not fully congruent with static weighing, a strong relationship (R2 > 0.8) between the two and low mean numerical difference in change-in liveweight indicates that MBWOW has potential to be used to established liveweight profiles for Merino ewes that aid nutritional management.

Measurement of intake of individual grazing animals remains one of the fundamental challenges to improving efficiency of livestock production. The use of wireless sensor networks (WSN) shows potential for this purpose and requires benchmark data to underpin the necessary algorithm development. This study aimed to provide benchmark data and enable improved precision in estimating pasture intake when pasture availability is low and declining. Each of 10 Angus steers with a mean liveweight ± s.d. of 326 ± 46 kg was randomly allocated to an individual grazing plot. The plots comprised a monoculture of Italian ryegrass ('Lolium multiflorum' cv. Surge), with estimated initial pasture biomass availability ≤1100 kg DM/ha, provided at three levels of pasture availability (low, medium and high), achieved by varying plot sizes (0.2, 0.3 and 0.4 ha). Pasture intake was estimated using two pasture disappearance-based techniques (risingplate meter and capacitance meter) using regression equations of daily pasture biomass estimates over an 11-day pasture intake period, and two chemical marker-based techniques (dosed 'n'-alkanes and chromic oxide). Both pasture disappearance-based techniques showed high variability in estimating pasture biomass, with mean coefficients of variation between repeated-measurements of 28% for the capacitance meter and 44% for the plate meter, although daily biomass measurements over the duration of the study using the two devices were highly correlated ('r' = 0.82). Mean pasture intake estimates across all four techniques ranged from 3.4 to 10.7 kg DM/day. The estimates of pasture intake differed between techniques but not between biomass availability treatments. Mean of pasture intake estimates made using the plate meter were consistently higher than for the other three techniques. The correlation coefficients between the intake estimates determined using the pasture disappearance-based techniques, and between their rankings, were 0.61 and 0.58, respectively. Intake estimates obtained using pasture disappearance and the chemical marker methods were not correlated apart from between chromic oxide and the plate meter ('r' = 0.51). Further refinement of these techniques and more studies over a wider range of pasture conditions are needed. It is critical to understand the limits within which each of the pasture intake methodologies will produce reliable results that can then be used as benchmark data for the development of predictive algorithms using WSN.

Supplementing low-quality straw with protein meal, fresh tropical grass or legume forage improves dry matter intake (DMI), digestion and live weight gain in cattle (Doyle et al., 1986). Smallholder cattle farmers in Cambodia mostly use rice ('Oryza sativa') straw as a basal diet, especially during feed shortages. Supplementation of such diets with C4 grasses such as Mulato II hybrid ('Brachiaria' spp.) increases the intake and digestibility of rice straw, but mixed diets of grass and rice straw may still be deficient in rumen degradable N (RDN), especially if the grass is mature when cut. Inclusion of a tropical legume such as Stylo CIAT 184 ('Stylosanthes guianensis') as a source of RDN may further increase microbial activity and DMI. Our objective was to measure the effect of adding Stylo 184 forage to a mixed diet of rice straw and C4 grass fed to cattle in terms of DMI, digestibility, microbial crude protein (MCP) production and live weight gain.

In Cambodia, seasonal flooding of land each year by the Mekong river limits the availability of feed for cattle. To alleviate this feed shortage, the concept of forage banks was developed by CIAT (2003-05) and feed banks are being exploited in our current ACIAR project (AH/2003/008). 'Brachiaria' mulato II hybrid (CIAT 36087) is a promising grass for these fodder banks but its nutritive value for cattle when used as a supplement with rice straw has not been widely investigated. The aim of this study was to provide basic information on the in situ rumen digestibility of mulato II hybrid relative to rice straw and to determine the effect of the animal's diet on rumen degradability estimated by the in situ method. In situ evaluations of dried samples of rice straw and sun-dried, first-cut mulato were made using 3 fistulated steers (c. 2.5 years, 248 ± 38kg). In Expt 1, bags were placed in steers ingesting 30% fresh-cut mulato II and 70% rice straw and, in Expt 2, the steers ingested only freshly cut mulato ad libitum. In Expt 1, feed bins were emptied each morning and then filled with rice straw followed by half of the daily ration of fresh mulato; the second half was given in the evening. Both feeds were cut to 2 mm, placed in nylon bags (pore size 40 μm) and incubated (in triplicate) for 3, 12, 24, 36, 48, 72 and 96 h in all three steers. All bags were removed together and washed with 9 additional bags, similarly prepared but never placed in the rumen (to give washing loss). Results for loss of OM (Y) during the incubation period (t) were fitted to a curve, Y=A+B(1-e⁻ct) where A, B, c and lag time are as described by Dhanoa et al. (1996). Rumen NH₃ was also determined (Beecher and Whitten 1970). Effective degradability of both feeds was higher (P<0.05) when steers were ingesting 100% mulato, and lag time (the period before there was net loss of OM) was shorter by 3-4 h (P<0.05), indicating that rumen digestion was markedly inferior when the diet was 70% rice straw and only 30 % mulato (Table 1). Effective degradability of OM, washing loss and rate of degradation of B were higher (P<0.05) and lag time was shorter (P<0.05) for mulato than for rice straw. The degradable OM percentage, excluding washing loss (WL) was similar for mulato and rice straw but with WL included, total potential degradability was higher (P<0.05) for mulato. Thus, the main reason that mulato hybrid exhibited a higher nutritive value than rice straw was its higher washing loss (higher level of soluble components) and its apparently more rapid colonisation by rumen microorganisms.

Effective university level education in animal nutrition requires both research-led teaching and motivated students (Brew, 1999). With the aim of providing both of these requirements, we established the "State of Origin Chicken Challenge" competition. This annual event capitalises on Australian students' love of sporting competition (albeit linked to sport in name only) and incorporates this into the teaching of animal nutrition. Practical activities involving diet formulation and the effects of different diets on chicken growth have been part of the traditional animal nutrition curriculum at most universities. The basis of the current competition was that students at the University of New England, Armidale (UNE) and The University of Queensland, Gatton (UQ) would formulate diets and subsequently feed these diets to chickens at both campuses. The competition winner is the university that grows the greatest weight of chicken per dollar of feedstuff.

The ability to monitor average liveweight of a sheep flock provides livestock managers the opportunity to nutritionally manage their flock for higher productivity. Mob-based walk-over weighing (MBWOW) is a remote weighing concept for sheep flocks whereby liveweights are collected as the animals pass freely over a strategically placed weighing platform. We tested the hypothesis that the repeatability and frequency of MBWOW data are sufficient to generate sheep flock average liveweight estimates with a 95% confidence interval (CI) of <2 kg over a 5-day time period. These criteria were considered reasonable, in terms of accuracy and timeliness, for application in a commercial context. Radio frequencyidentifiedWOWdata were obtained from four sheep flocks in south-eastern New South Wales, representing a mix of age and breeds, as sheep traversed a remote weighing platform to and from some form of incentive. The repeatability and frequency of three forms of radio frequency-identified WOW data, being raw (unfiltered), course-filtered (filtered to remove all sheep weights outside the flock weight range) and fine-filtered (filtered to remove all sheep weights outside a 25% range of a recent flock average reference weight), were used in a simulation to test the 95% CI of 1- and 5-dayM BWOW liveweight capture periods (samples). All data-filtering approaches over a 5-day sample generated flock average liveweight estimates with 95% CI of <2 kg, thus meeting the hypothesis criteria. One-day samples generated flock average liveweight estimates with 95% CI of >2 kg and data filtering, although reducing the 95% CI, did not bring it below the hypothesis criteria. Thus, when the appropriate data handling technique is used, MBWOW may provide information suitable for sheep management decisionmaking in a commercial context.

This communication describes the application of calculations for estimating basal metabolic rate (BMR) and metabolisable energy requirement to sheep exposed to hot climatic conditions. Graham et al. (1974) studied animal factors that affect BMR and found that the BMR of weaned sheep of up to 27 months of age was well described by the following equation. BMR (MJ/d) = 0.257 × FW0.75exp(–0.08A) + 2.8G + 0.046DE where FW is fasted live weight (kg), A is age in years, G is growth rate (kg/d) in the 2–4 weeks before fasting and DE is intake of digestible energy (DE, MJ/d) before fasting.

Vitamin D metabolites and the major mammalian minerals phosphorus (P) and calcium (Ca) have a complex and detailed relationship. The relationship, especially for Ca, is delicately controlled by a range of hormones and is largely dependent on the animal's physiological state. Studies have identified that Vitamin D metabolites given in supraphysiological doses to cattle can manipulate Ca and P metabolism. Furthermore, large doses of the metabolite 25-hydroxy vitamin D (25-vitD) can replace the actions of active vitamin D, 1,25-dihydroxy vitamin D (1,25-vitD) and initiate increased absorption of both Ca and P from the digestive tract in mice. These findings led to the hypothesis that 25-vitD could be used to favorably manipulate the metabolism of both Ca and P in cattle. The studies undertaken within this thesis are focused on the use of 25-vitD in both the beef and dairy industries. A group of beef breed steers were recruited and trained to halter, stand in metabolism crates and spend extended periods of time in individual pens. For studies concerning Ca, urine was the most important measurement. An increase in urinary Ca excretion demonstrated that there has been an increase in available Ca, either from the diet or skeletal reserves. With P studies faecal P excretion and plasma P were important guides to changes in P metabolism. The results of the metabolism studies undertaken in the thesis identify that Ca and P homeostasis is manipulated by 25-vitD and the majority of the increase in availability of both Ca and P originates from the diet. This is further supported by the absence of bone degradation. Thus, the inclusion of 25-vitD in a typical anionic transition diet will increase Ca absorption prior to parturition, enabling labile bone Ca stores to remain intact and available for immediate use at parturition whilst increasing the amount of Ca available to the animal from both bone and diet. Furthermore, the combination of 25-vitD and anionic salts has physiological implications that allow sufficient generation of extracellular Ca at parturition. An increase in plasma 25-vitD concentrations, to approximately 375 ng/ml, facilitated an increase in the concentration of plasma P and a reduction in faecal P, which indicates that dietary P absorption was increased.

Liveweight is a widely accepted proxy for the energy status of sheep at a particular point in time. Fleece- and conceptus-free ewe liveweight and liveweight change influence the productivity of the ewe and optimisation may increase whole-farm profitability. Despite this, it is uncommon for producers to monitor ewe liveweight regularly and objectively. The current review discusses why ewe liveweight is important, identifies and assesses available technologies for monitoring sheep liveweight, and highlights future research priorities. The common theme in the literature is that while there are options that could possibly be used to monitor the liveweight of sheep in extensive grazing systems, few of them offer realistic solutions, especially in regard to timeliness of data collection. Thermal and stereo imaging, body measurements and plasma hormonal assays are unlikely to be commercially viable, while visual assessment, although widely practised, offers a surprisingly poor indication of sheep liveweight. Alternatively, assessment of body condition (condition scoring) or fat (fat scoring) offers viable methods of assessing sheep energy status; however, like conventional static weighing, they are performed infrequently and therefore contribute little to the day-to-day tactical management of sheep flocks. Walk-over weighing systems offer a feasible alternative for regular monitoring of sheep liveweight. Such systems are fully automated, and may be operated remotely. Currently, there are challenges associated with monitoring the liveweight of individual animals using such systems and hence there is little commercial opportunity for individual animal management. Mob-based walk-over weighing, which generates flock average liveweight estimates, offers greater potential in the short term, although the technology would benefit from further research and development, primarily to increase the frequency and repeatability of liveweight capture.