Estimation of Nitrogen Use Efficiency for Ryegrass-Fed Dairy Cows: Model Development Using Diet- and Animal-Based Proxy Measures

Wumaierjiang Aizimu,Long Cheng,Saranika Talukder,Simon Hodge,Ao Chen,Omar Al-Marashdeh,Guangyong Zhao,Grant R Edwards,Richard J Dewhurst

doi:10.3390/dairy2030035

Abstract

This study aimed to identify suitable predictors of nitrogen (N) use efficiency (NUE; milk N/N intake) for cows that differed in breeds and were fed with ryegrass pasture, using existing data from the scientific literature. Data from 16 studies were used to develop models based on the relationships between NUE and dietary and animal-based factors. Data from a further 10 studies were used for model validation. Milk urea N (MUN) and dietary water-soluble carbohydrate-to-crudeprotein ratio (WSC/CP) were the best and most practical animal- and diet-based proxies to predict NUE. The results indicate that it might be necessary to adopt separate models for different breeds when using WSC/CP to predict NUE but not when using MUN.

Highlights

Prediction of nitrogen (N) use efficiency (NUE; milk N/N intake) of dairy cows at a herd or farm level is essential to support the development of sustainable dairy production, as it relates to the farm productivity, profitability, and environmental footprint [1,2,3,4]
Studies between Friesian and Jersey × Friesian fed with a diet composed of more than 50% perennial ryegrass were selected in this study (Table 1)
The range of animal DMI was slightly larger for Jersey × Friesians (10–19 kg/cow/d) than for Friesians (12–17 kg DM/cow/d); the mean DMI was similar between the breeds (14.4 vs. 14.2 kg DM/cow/d for Friesians and Jersey × Friesians, respectively)

Summary

Introduction

Prediction of nitrogen (N) use efficiency (NUE; milk N/N intake) of dairy cows at a herd or farm level is essential to support the development of sustainable dairy production, as it relates to the farm productivity, profitability, and environmental footprint [1,2,3,4]. In temperate grassland regions (e.g., Ireland), dairy cows are commonly grazed on pastures containing blends of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens), which typically have high levels of N (ranges between 3.0 and 4.8% of DM) relative to dairy cow requirements for milk production [5]. This oversupply of dietary N results in low NUE and high (more than 50% of N intake) urinary N excretion, leading to increased N loss to the environment via nitrate leaching and nitrous oxide emission [5].

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Results

Conclusion