Nitrogen Intake and Its Partition on Urine, Dung and Products of Dairy and Beef Cattle in Chile

Ignacio E Beltran,Ruben G Pulido,Ivan Calvache,Marta Alfaro,Alvaro Morales,Rocio Cofre,Juan P Keim,Francisco Salazar

doi:10.3390/agronomy12010015

Abstract

Nitrogen that is excreted through the urine and dung of cattle is an important source of nitrous oxide and ammonia emissions. In Chile, several studies have evaluated nitrogen (N) intake and its partitioning into urine and dung from beef and dairy cattle, however, there are no studies collating all data into one central database, which would allow an estimation of N excretion and its key variables to be developed. The aim of this study was to determine the N partition (milk or meat, urine and dung) and variables influencing the nitrogen use efficiency (NUE) and urinary N excretion of cattle based on a database generated from Chilean studies. The search of studies was carried out using a keyword list in different web-based platforms. Nitrogen excretion into urine and dung was calculated using equations reported in the literature for beef and dairy cattle. Mixed models were used to identify variables influencing the N partitioning. Nitrogen intake and its partitioning into the animal product, urine and dung were higher for dairy compared to beef cattle. For dairy cattle, NUE was influenced by milk yield, the non-fibrous carbohydrates (NFC)/crude protein ratio, acid detergent fiber intake and milk urea N (MUN), while urinary N excretion was influenced by milk yield, MUN and NFC intake. For beef cattle, N intake and its excretion were greater for grazing compared to the confined system, while NUE was greater for confined animals. This database supplies new information on N intake and its partitioning (milk, meat, urine and dung) for dairy and beef cattle, which can be used for the estimation of greenhouse gas emissions from pasture-based livestock in Chile. Additionally, our study supplies new information on nutritional variables determining NUE and urinary N excretion for dairy cattle, which can be used by farmers to reduce N excretion into the environment.

Highlights

It was observed that production systems may importantly affect nitrogen (N) partitioning and nitrogen use efficiency in the animal ( NUE), the latter ranging between13 and 31% in grazing systems and 40 to 45% under confinement systems with balanced rations [1,2]
This grass species is characterized by a high crude protein (CP) content, ranging between 15 and 28% depending on the season and the phenological stage [6], which often exceeds the N requirements of dairy [7] and beef cattle [8,9]
Urinary urea is the main pathway of N excretion for ruminants, which is more readily available for soil microorganisms compared to dung N, it is quickly volatilized as ammonia (NH3 ) or nitrous oxide (N2 O)

Summary

Introduction

It was observed that production systems may importantly affect nitrogen (N) partitioning and nitrogen use efficiency in the animal ( NUE), the latter ranging between13 and 31% in grazing systems and 40 to 45% under confinement systems with balanced rations [1,2]. It was observed that production systems may importantly affect nitrogen (N) partitioning and nitrogen use efficiency in the animal ( NUE), the latter ranging between. In humid temperate regions, such as southern Chile, most of the livestock production systems are based on pasture [4], where the most common pasture species (80%) used in grazing systems is Lolium perenne L. This grass species is characterized by a high crude protein (CP) content, ranging between 15 and 28% depending on the season and the phenological stage [6], which often exceeds the N requirements of dairy [7] and beef cattle [8,9]. Concern regarding N2 O emissions is of increasing global importance due to its high warming potential, which is 265 times greater than that of carbon dioxide [11], while NH3 emissions could contribute to ecosystem degradation and indirect emissions of N2 O [12,13]

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Conclusion