Quantitative Effects of Feed Protein Reduction and Methionine on Nitrogen Use by Cows and Nitrogen Emission from Slurry

Abstract

The effects on N use and N volatilization from slurry were investigated in 24 early-lactation Brown Swiss cows (32 kg/d milk) fed four diets with 128, 124, 147 and 175 g/kg DM of crude protein (CP). All diets were supplemented with 0.75 g/kg of rumen-protected Met except for one of the low-protein rations (128 g/kg of CP). The unsupplemented low-protein ration was calculated to be deficient in Met by approximately 20%. No significant treatment effects on performance, water intake and excretion, and slurry quantities were observed. Differences in N intake were closely reflected in the daily excretions of total and urea N via urine, and in urine N as a proportion of total excretory N. These values were higher for the unsupplemented low-protein ration than for the Met-supplemented low-protein ration. The treatment effects on fecal N excretion were generally smaller, and milk N excretion and N balance were not affected. Feed N utilization for milk N excretion increased with decreasing CP content from 27% for the high-protein group to about 35% for the two low-protein groups. Comparing the Met supplemented rations only, ammonia N emission from fresh slurry (excreta:water = 1:0.5) decreased from 231 to 160 and 55 microg/s per square meter of surface with 175, 147 and 124 g/kg of CP, respectively, and the corresponding total N losses during 7 wk of slurry storage declined from 89 to 57 and 25 g/d per cow. Regression analysis demonstrated the basic suitability of milk urea N excretion to estimate urine N excretion and, consequently, potential N emissions.

Nutrient and energy conversion of grass-fed dairy and suckler beef cattle kept indoors and on high altitude pasture

“…Consequently, a low N content of grass, as was analysed in experiment I, is fully sufficient for efficient suckler beef production and any N fertilisation will increase N emission potential. Even in dairy cows a low-protein grass seems to be sufficient as is also suggested [23] by the similar fibre digestibility in both experiments.…”

“…Excessive N is completely excreted, mainly in the form of urine N, thus clearly increasing potential ammonia emissions during storage and application of manure. Accordingly, Kröber et al [23] found a 3.5-fold increase in gaseous N loss from dairy manure when dietary crude protein content of a forage-concentrate diet (1:1) was increased from 125 to 175 g . kg -1 DN, values similar to the herbage types used in experiments I and II.…”

Enteric and manure-derived methane and nitrogen emissions as well as metabolic energy losses in cows fed balanced diets based on maize, barley or grass hay

“…Urinary N is converted to NH 4 much more easily in the slurry than in faecal N, and thus subject to rapid emission (e.g. Van Horn et al, 1996;Krö ber et al, 2000) either as ammonia or nitrous oxide volatilisation or nitrate leaching (Jarvis, 1993). This relationship between urinary N, total NH 4 -N in slurry DM before storage and N losses from slurry during storage was also obvious from the present results (significant at the lower slurry storage temperature).…”

Performance, body nitrogen conversion and nitrogen emission from manure of dairy cows fed diets supplemented with different plant extracts

“…Dairy cow diets are often limited in metabolically available protein rather than in net energy. This may open an important field of application for plant extracts containing secondary plant constituents, either to prevent a protein deficiency thus improving performance or to reduce losses of non-utilized N from the animal and from manure in the form of environmentally hazardous ammonia emissions (Kröber et al, 2000). The latter effects are particularly expected from saponins and tannins, as saponins massively reduce ruminal ammonia formation (discussed in detail by Śliwiński et al, 2002b) and tannins are known to form complexes with protein (Brooker et al, 2002).…”