Abstract
Ruminal gases, particularly methane, generated during the fermentative process in rumen, represent a partial loss of feed energy and are also pointed to as an important factors in greenhouse effect. This study aimed at quantifying methane (CH4) emission rates from lactating and dry cows and heifers, 24 month-old in average, on pasture under Southeast Brazil tropical conditions, using the tracer gas technique, sulphur hexafluoride (SF6), four animals per category, distributed in four blocks. Measurements were performed in February and June, 2002, with Holstein and Brazilian Dairy Crossbred (Holstein ¾ x Gir (Zebu) ¼), maintained on fertilized Tanzania-grass (Panicum maximum Jacq. cv. Tanzania) and fertilized Brachiaria-grass (Brachiaria decumbens cv. Basilisk) pastures. Heifers of both breeds were maintained on unfertilized Brachiaria-grass to simulate conditions of extensive cattle farming systems. CH4 and SF6 levels were measured with gas chromatography. Differences in CH4 emissions were measured (p < 0.05) for genetical groups. Holstein produced more methane (299.3 g day-1) than the Crossbred (264.2 g day-1). Lactating cows produced more methane (353.8 g day-1) than dry cows (268.8 g day-1) and heifers (222.6 g day-1). Holstein, with greater milk production potential, produced less CH4 (p < 0.05) per unit of dry matter intake (19.1 g kg-1) than the Crossbred (22.0 g kg-1). Methane emission by heifers grazing fertilized pasture (intensive system) was 222.6 g day-1, greater (p < 0.05) than that of heifers on unfertilized pasture (179.2 g day-1). Methane emission varied as function of animal category and management intensity of production system.
Highlights
Ruminal gases yield are correlated to the microbial activity in rumen, and methane, a gas generated during the fermentative process in rumen, represents a partial loss of feed energy, with an accepted mean value of 6.5% of the ingested gross energy (IPCC, 2006), varying from 2% by animals feeding on highgrain diets, to 12% when low quality forage is fed (Johnson & Johnson, 1995; Johnson et al, 2007)
Experimental design consisted of four randomized blocks, represented by consecutive weeks, main plots represented by two breeds - Holstein and Holstein 3⁄4 × Gir (Zebu) 1⁄4 - Crossbred - and three categories: lactating cows, dry cows and heifers; seasons represented subplots in time, and treatments consisted of genetic groups: heifers, dry cows and dairy cows, one animal per treatment
When variables related to dry matter intake (DMI), organic matter intake (OMI) and digestible organic mater intake (DOMI) were analyzed, differences occurred between breeds and among categories, and their interaction
Summary
Ruminal gases yield are correlated to the microbial activity in rumen, and methane, a gas generated during the fermentative process in rumen, represents a partial loss of feed energy, with an accepted mean value of 6.5% of the ingested gross energy (IPCC, 2006), varying from 2% by animals feeding on highgrain diets, to 12% when low quality forage is fed (Johnson & Johnson, 1995; Johnson et al, 2007). When the objective is weight gain, daily methane production by animal would be greater than in systems targeting production per hectare. These differences occur partially because of variation in forage availability in both systems. Considering methane emission by product unit (milk yield or weight gain per animal) values would be lower where gains per animal are greater, but methane yield by surface area will be larger (Kurihara et al, 1999)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
