Effects of nitrogen fertilisation rate and maturity of grass silage on methane emission by lactating dairy cows. (12th August 2015)

• Record Type: Journal Article
• Authors: Warner, D.; Hatew, B.; Podesta, S. C.; Klop, G.; van Gastelen, S.; van Laar, H.; Dijkstra, J.; Bannink, A.
• Is Part Of: Animal. Volume 10:Number 1(2016:Jan.)
• Page Start: 34
• Page End: 43
• Publication Date: 2015-08-12
• Subjects: nitrogen fertilisation, -- grass maturity, -- ryegrass, -- methane, -- dairy cow; Animal breeding -- Periodicals; Animal genetics -- Periodicals; Animal nutrition -- Periodicals; Animal physiology -- Periodicals; Environmental sciences -- Periodicals; 636.005
• DOI: 10.1017/S1751731115001640
• Languages: English
• ISSNs: 1751-7311

Abstract

Abstract : Grass silage is typically fed to dairy cows in temperate regions. However, in vivo information on methane (CH4 ) emission from grass silage of varying quality is limited. We evaluated the effect of two rates of nitrogen (N) fertilisation of grassland (low fertilisation (LF), 65 kg of N/ha; and high fertilisation (HF), 150 kg of N/ha) and of three stages of maturity of grass at cutting: early maturity (EM; 28 days of regrowth), mid maturity (MM; 41 days of regrowth) and late maturity (LM; 62 days of regrowth) on CH4 production by lactating dairy cows. In a randomised block design, 54 lactating Holstein–Friesian dairy cows (168±11 days in milk; mean±standard error of mean) received grass silage (mainly ryegrass) and compound feed at 80 : 20 on dry matter basis. Cows were adapted to the diet for 12 days and CH4 production was measured in climate respiration chambers for 5 days. Dry matter intake (DMI; 14.9±0.56 kg/day) decreased with increasing N fertilisation and grass maturity. Production of fat- and protein-corrected milk (FPCM; 24.0±1.57 kg/day) decreased with advancing grass maturity but was not affected by N fertilisation. Apparent total-tract feed digestibility decreased with advancing grass maturity but was unaffected by N fertilisation except for an increase and decrease in N and fat digestibility with increasing N fertilisation, respectively. Total CH4 production per cow (347±13.6 g/day) decreased with increasing N fertilisation by 4% and grass maturity by 6%. The smaller CH4 production with advancing grass maturity was offset by a smaller FPCM and lower feed digestibility. As a result, with advancing grass maturity CH4 emission intensity increased per units of FPCM (15.0±1.00 g CH4 /kg) by 31% and digestible organic matter intake (33.1±0.78 g CH4 /kg) by 15%. In addition, emission intensity increased per units of DMI (23.5±0.43 g CH4 /kg) by 7% and gross energy intake (7.0±0.14% CH4 ) by 9%, implying an increased loss of dietary energy with advancing grass maturity. Rate of N fertilisation had no effect on CH4 emissions per units of FPCM, DMI and gross energy intake. These results suggest that despite a lower absolute daily CH4 production with a higher N fertilisation rate, CH4 emission intensity remains unchanged. A significant reduction of CH4 emission intensity can be achieved by feeding dairy cows silage of grass harvested at an earlier stage of maturity.