Dr. Brian Sloan is the Director of Ruminant Business at Adisseo, bringing over 36 years of industry experience. He began his academic journey in biological sciences, shifting to agricultural biochemistry for his undergraduate degree and completing a Ph.D. working with dairy cow trials at Newcastle University. Dr. Sloan’s expertise in ingredients, agribusiness, and agriculture has significantly advanced ruminant nutrition globally. He leads strategic initiatives and innovations in the amino acid business, contributing to sustainable and efficient farming practices.
This presentation builds on earlier work by examining how different energy and protein supplements interact with perennial ryegrass (PRG) diets in pasture-based dairy systems. The central challenge addressed is that while PRG provides high crude protein and sugar concentrations, much of the protein is extensively degraded in the rumen. As a result, cows become heavily dependent on microbial amino acid supply, which can limit milk yield and composition. Supplementation strategies are therefore essential to balance metabolizable energy (ME) and metabolizable protein (MP) supply.
Several experiments are reviewed. In one paddock trial with 80 dairy cows, treatments included PRG alone, PRG plus citrus pulp and urea, PRG plus rumen-protected soybean meal (RP-SBM), and a mix of citrus pulp and RP-SBM. Results showed that supplementation increased milk yield, energy-corrected milk (ECM), and milk solids compared with pasture-only diets. RP-SBM in particular improved milk protein yield, while citrus pulp enhanced dry matter intake. The combination of energy and protein sources produced the greatest improvements, highlighting the importance of balancing both nutrients.
A second study compared starch-, fiber-, and sugar-based supplements with pasture in New Zealand conditions. Starch-based concentrates increased milk protein yield, while fiber-based concentrates boosted milk fat yield. Sugar supplementation had little effect. These findings demonstrate that the type of supplement not only influences overall milk yield but also alters milk composition, with starch favoring protein synthesis and fiber supporting fat production. Importantly, supplementation was modeled using the CNCPS framework to ensure diets supplied adequate ME and MP for target milk yields.
The presentation also outlines updates in CNCPS version 7, which introduces a dynamic gastrointestinal model, disaggregates fiber into fast and slow pools, incorporates protozoa metabolism, and refines nitrogen recycling. These advances allow more precise predictions of nutrient flows and support better feeding strategies in pasture-based systems.
In conclusion, the research underscores that pasture alone, despite its high crude protein, cannot fully support optimal milk production. Strategic supplementation with energy sources such as starch or fiber, and protein sources like RP-SBM, is necessary to maximize rumen efficiency and milk output. The choice of supplement should be guided by production goals — whether prioritizing milk protein or fat — and by economic considerations such as feed costs and milk pricing. By integrating CNCPS modeling with targeted supplementation, producers can achieve higher yields, improved milk composition, and more sustainable pasture-based dairy systems
NZARN members a copy of the presentation is available below if you are logged in.
Non-members looking for more information are encouraged to use our ‘contact a nutritionist’ form and ‘member directory’ to find a member who can help them answer their questions.
If you are a Rural Professional interested in joining the NZARN please see our ‘membership’ section.
