Most of the world’s arable area is sown to grains or oilseeds and with a reduced demand for ethanol and biodiesel, the profitability of crops for human and animal consumption will be the most important pressures on global cropping-area supply. Protein crops will likely be favoured in the future as countries become wealthier and more animal products are consumed. Therefore, we should see a contraction in cereal crops and growth in oilseeds as the demand for feed becomes the main driver for global agriculture.

Current animal nutrition systems based on nutrient supply and animal characteristics may predict performance but are inadequate to predict retail yield and composition. The relationship between oxygen uptake, visceral and muscle protein mass, and energy expenditure can be used to explain variation in animal growth and composition with regard to nutritional changes over time. This paper explores independent evidence supporting an existing model linking protein metabolism to animal performance and body composition, and identifies data gaps for future research.

Mitigating the impact of swine production on the environment is needed to ensure the sustainability of the industry. Enhancing the dietary amino acid (AA) balance for lactating sows is an effective approach to improve nitrogen (N), AA and energy efficiency, and to reduce N excretion and ammonia emission into the environment. A near-ideal AA balance allows to estimate individual maximum biological efficiency values of AA for milk protein production which are needed to predict their requirements.

Metabolisable protein in ruminants is derived from dietary protein that is not degraded in the rumen and protein synthesised by rumen microbes that passes to the duodenum. Mechanistic rumen models have been developed in an attempt to improve the prediction of metabolisable protein for ration formulation. These models are more complex than are simple empirical models and their accuracy is limited by the availability of data to parameterise them. This article discusses the limitations of mechanistic models for the prediction of metabolisable protein in ruminants.

Whole-grain and exogenous phytase inclusions have been widely accepted by the chicken-meat industry. Whole-grain feeding increases gizzard weights, reduces gizzard pH and enhances gizzard functionality. The majority of phytate degradation by phytase takes place in the gizzard. Therefore, whole-grain inclusion should increase the rate of phytate degradation and any interactions that may arise from this combined supplementation are of potential importance. Therefore, recent investigations into the effects of whole-grain feeding and phytase in combination merit consideration.

The interrelationships between the structure and function of the gastrointestinal tract, the stress response at weaning, and subsequent production are critical in pork production. Weaning is a major challenge to young pigs and the gastrointestinal tract can be severely compromised, with different impacts for male and female pigs. The development and implementation of various nutritional and management strategies can assist in alleviating the stress responses associated with weaning.

Pelleting is the widely employed thermal process in the manufacture of broiler diets and is used to enhance the growth performance of birds and achieve their genetic potential. However, the magnitude of pelleting-induced benefits on broiler performance and feed utilisation depends on the dietary nutrient density, nutrient digestibility, grain type and processing variables such as particle-size reduction and pelleting temperature. To maximise pelleting benefits, it is critical to identify manufacturing techniques to create high-quality pellets that are highly digestible.

Improving the sustainability of animal nutrition for human food consumption is of paramount importance to secure water, land and nutrient resources of current and future generations. This review outlines the benefits, advantages and opportunities of feeding insects and their products to pigs and poultry, and summarises the implications of their usage to the current insect-breeding industry. This information allows for the critical appraisal of using insects as a feed ingredient.

Animal products (meat, milk and fibre) contribute a valuable (and increasing) source of nutrients for humans; however, consumers are concerned with the environmental impact of food production. Thus, production-animal enterprises must develop sustainable production methods. Insects are rapid growing, have low water and feed requirements, have a high FCE and are highly nutritious; and can contribute to human food and animal-feed sources. The present review will discuss the current state of mass-rearing of insects as a food and feed source.

In free-range or barn-housed facilities, hens can be of different bodyweight, health and reproduction status, but receive all the same diet. This review summarises the knowledge about the individual nutritional needs of hens and hen clusters and outlines the technical opportunities to improve the current feeding strategies. Adopting new technologies will allow for improved hen husbandry as well as a more efficient and sustainable use of feed resources.

Horse owners commonly overfeed proteins and this practice has consequences on the environment and sustainability of equine operations, in particular, in increasingly urbanised areas and areas close to waterways. Nutritionists and scientists require more data on how equids utilise dietary proteins, so as to make recommendations on best feeding practices. A conceptual prediction model of nitrogen and amino acid requirements for equids is proposed. The need to generate more knowledge on protein quality of feed ingredients and the efficiency of N and AA utilisation is highlighted.

Recently, the topic of reducing the protein in broiler diets has been of interest to the meat-chicken industry. This stems from economic, environmental, health and welfare concerns with current meat-chicken production. However, reducing dietary protein is likely to negatively affect performance. Research has extensively examined amino acid supplementation; however, there is a further need to investigate other dietary compositional changes that occur as these may also affect performance. This will enable the successful adoption of reduced-protein diets for meat-type chickens in the poultry industry.

The microbial fermentation in the forestomach of ruminants allows them to utilise low-protein fibrous diets and also endogenous urea recycled (returned) to the rumen to support microbial growth. This review evaluated information on the magnitude and the physiological control of this urea recycling. Optimal control of urea recycling is important for production efficiency of ruminants on low-protein diets and to minimise nitrogen excretion and, thus, the environmental impact of ruminants.