Increasing milk production efficiency from pasture-based diets

Michael Dineen, Teagasc, presented this research at the National Dairy Conference 2022 which took place on Tuesday December 6th, Rochestown Park Hotel, Cork and Thursday December 8th, Mullingar Park Hotel, Co. Westmeath.

Summary

• Ruminant production systems must maximise their use of human inedible feeds
• Lower pre-grazing yields and including white clover increases milk production efficiency
• Concentrate supplementation should be used to fill feed

Introduction

Our global population surpassed 8 billion people on the 15th of November 2022 and is projected to peak at 10.4 billion by 2100. As a result, the world will have to produce more food in the next 50 years than we have produced in the thousands of years since civilization began. While global demand for dairy products will increase, the demand for human- edible plant resources will also concurrently rise, potentially reducing the availability of these resources and the associated arable land for livestock production. Therefore, to maintain a significant contribution to net food production, ruminant production systems should maximise their reliance on the unique ability to convert human inedible resources into human edible food. To achieve this, a clear focus on pre-grazing yield, the inclusion of white clover (WC) into grazing swards and optimizing concentrate supplementation is required.

Pre-Grazing Yield

Organic matter digestibility (OMD; i.e. the amount of nutrients digested) is a crucial factor affecting milk production efficiency from pasture. Pastures with high OMD have high metabolisable energy and metabolisable protein value and can often lead to increased dry matter intake. Experiments performed at Teagasc Moorepark have indicated that lower pre-grazing yield results in higher OMD (Fig 1.) with a more marked effect being demonstrated as the grazing season progresses. Lower pre-grazing yield swards that have higher OMD have also been associated with higher milk yield, milk protein production and milk protein concentration. Therefore, by maintaining optimal pre-grazing yield, through management practices such as grassland measurement, increased milk production efficiency from pasture can be achieved.

Figure 1. The effect of pre-grazing yield on organic matter digestibility (Garry, 2018)

White Clover

The inclusion of WC into perennial ryegrass (PRG) swards can dramatically reduce the system’s reliance on chemical nitrogen (N) fertilisers (-100 kg of N/ha) while simultaneously increasing milk production efficiency (+48 kg of milk solids/cow) and economic profitability (+€305/ha), when sward clover content is >20%. Experiments utilising lactating dairy cows in France and sheep in Ireland have demonstrated increased OMD when WC is included in the sward. Increased dry matter intake (DMI), when cows consume PRG-WC swards, has also been widely observed.

Concentrate Supplementation

In pasture-based systems, when growth rate is lower than herd demand, concentrate supplementation is required to fill the feed deficit. In addition, the use of concentrate supplementation has been adopted to increase the milk production of pasture-fed cows. In the latter scenario, the economic effectiveness of concentrate supplementation can be variable, as a wide range of milk response (calculated as the difference in milk produced between non-supplemented and supplemented treatments divided by supplement DMI) has been reported in the literature (0.3 to 2.4 kg of milk/kg of supplement DM). Linear increases in milk production up to 10 kg of concentrate supplemented per day have been reported, whereas other studies have reported diminishing responses at levels greater than 3 kg/day. Factors such as pasture allowance, pasture chemical composition, level of pasture substitution, concentrate level, concentrate ingredients, negative associated effects, stage of lactation and genetic merit of the cows have been suggested to contribute to this variation in milk response. Ultimately, milk response is a crucial factor influencing the profitability of concentrate supplementation. In an economic analysis ranging across a number of different scenarios and prices, the most profitable pasture-based system generally fed circa 500-600 kg of concentrate/cow/year. Thus nationally, there are opportunities to reduce concentrate supplementation while at the same time increase the profitability of milk production. This will also maintain Ireland’s ability to produce nutritionally superior dairy products from home-grown pasture and further increase the proportion of human inedible feeds in the lactating dairy cow’s diet.

Conclusion

High pasture inclusion levels in dairy cow diets can support an environmentally friendly system of milk production and a resilient business model for the producer. Maintaining lower pre-grazing yields, including white clover into swards and optimizing concentrate supplementation are key factors to increase the milk production efficiency of pasture- based systems.

Read the full National Dairy Conference 2022 publication here