Use of partial mixed rations in pasture-based dairying in temperate regions of Australia

Abstract

There is a growing diversity and complexity of dairy farming systems in Australia. Feeding systems based on the provision of mixed rations to dairy cows grazing perennial pastures (termed partial mixed rations or PMR systems) have emerged and present the dairy industry with opportunities for improved production and feed efficiency, but also with significant challenges. Early research results are beginning to define the situations in which PMR systems are profitable and the mechanisms responsible for the improved milk responses. This review focuses on the role of PMR feeding systems in temperate dairying regions of Australia, highlights initial research findings, and identifies some of the gaps in current knowledge that warrant further research. The key findings were that, when very low allowances of pasture are offered to cows, milk production responses were driven mostly by increases in dry matter (DM) intake, and there appeared to be a minimal contribution to increased energy supply from improved whole tract DM digestibility. Differences in milk responses became apparent when >10 kg of total supplement DM was consumed (0.75 : 0.25 concentrate to forage) as PMR. There was a consistent maintenance of milk fat concentration when increasing amounts of concentrates were consumed as PMR, in contrast with supplements consumed in the dairy. There was also a consistent finding that replacing some wheat in the PMR with canola meal resulted in cows consuming more grazed pasture despite the limitations of very low pasture allowances (10–15 kg DM/cow.day, expressed to ground level). This was accompanied by further increases in energy-corrected milk yield. The potential to improve DM intake was further highlighted when pasture allowance was increased, with intake increasing from 3.6% to 4.5% of liveweight (from 20 to 25 kg DM/day for a 550-kg cow). There was also an indication that ~50% of the milk production benefit from PMR can be captured by providing the concentrate supplement as a grain mix in the dairy. There did not appear to be negative impacts of PMR systems on the social and grazing behaviour or health of cows.

Diet change from a system combining total mixed ration and pasture to confinement system (total mixed ration) on milk production and composition, blood biochemistry and behavior of dairy cows

“…These results are in agreement with the available information on the advantages of the system in confinement, where cows consuming TMR diet produce more milk than cows grazing or in mixed systems, which is associated with an increase in DMI and greater availability of energy (Bargo et al, 2002;Fajardo et al, 2015;Kay, Mackle, & Auldist, 2002;Kolver & Muller, 1998;Meikle, Adrien, Mattiauda, & Chilibroste, 2013;Vibart, Fellner, Burns, Huntington, & Green, 2008;Wales et al, 2013). In addition, the change from a mixed system to a single system in confinement with TMR improved the production and composition of milk in a short period of time, evidenced from one week before the change to one week after.…”

“…For example, in summer, high environmental temperatures and humidity (heat stress) affects the production and milk composition, health and reproduction (Bernabucci et al, 2010(Bernabucci et al, , 2015Cowley, Barber, Houlihan, & Poppi, 2015;Jordan, 2003). Thus, due to the fluctuation in the availability of forage that occurs at different times of the year (Bargo, Muller, Delahoy, & Cassidy, 2002;Chilibroste, Soca, Mattiauda, Bentancur, & Robinson, 2007;Wales et al, 2013) and adverse weather conditions (heat stress), confinement system with access to shade is used as an alternative management in dairy cattle to reduce the negative effects on milk production and improve animal welfare (Charlton & Rutter, 2017;Schütz et al, 2010;). In this sense, total mixed ration (TMR) has been strategically incorporated to increase total dry matter (DMI) and energy intake to ensure an adequate balanced supply of nutrients in quality and quantity throughout the year.…”

Ryegrass pasture combined with partial total mixed ration reduces enteric methane emissions and maintains the performance of dairy cows during mid to late lactation

“…The milk production of cows that received supplementation with a partial TMR in pasture-based systems was increased compared with that of cows that consumed solely a pasture diet (O'Neill et al, 2012;Miguel et al, 2014). Further per-cow advantages have also been found during periods of low pasture accumulation rate or in areas with low grazing availability (Wales et al, 2013). Additionally, a mixed diet, including grazed pasture + partial TMR, improved the DMI and milk production of high-producing dairy cows compared with supplementation with concentrate (Bargo et al, 2002).…”

Metabolic Adaptations Due to the Inclusion of Pasture in the Diet of Dairy Cows Fed Total Mixed Ration during Early Lactation

“…Although this decrease could accompany the normal decline in the lactation curve around the peak of milk production [17], as it was only observed in Post-TMR cows, it was probably associated to a restriction in DMI and/or increased in energy requirements after the change of the diet [6]. It has been reported that not only characteristics of the pasture, but also its management can limit DMI of grazing animals [4] [18].…”

“…However, the quantity and quality of the pasture offered is variable throughout the year, determining an imbalance between nutrient supply and demand at various stages of the production cycle of the modern dairy cow [2]. Thus, the inclusion of concentrates and silages in the dairy cow diet has increased to meet the requirement of the milking herd [3] [4]. In this regard, the use of a total mixed ration (TMR) in early lactation allows dairy cows achieve maximum performance in times of reduced pasture dry matter (DM) production, determining an increase in milk yield, cow body condition score (BCS), metabolic status and reproductive performance [5] [6] [7].…”