title: Biological implications of longevity in dairy cows: 2. Changes in methane emissions and efficiency with age.
abstract: Previous studies indicated that absolute CH4 emissions and CH4 yield might increase and that milk production efficiency might decrease with age in cattle. Both would make strategies to increase longevity in dairy cattle less attractive. These aspects were experimentally determined in Brown Swiss cattle distributed continuously across a large age range. Thirty lactating dairy cows (876-3,648 d of age) received diets consisting of hay, corn silage, and grass pellets supplemented with 0 or 5kg of concentrate per day. Twelve heifers (199-778 d of age) received hay only. Cows and heifers were members of herds subjected to the 2 different feeding regimens (with or without concentrate) for the past 10 yr. Methane emissions were measured individually for 2 d in open-circuit respiration chambers, followed by quantifying individual feed intake and milk yield over 8 d. Additional data on digestibility, rumination time, and passage time of feed of all experimental animals were available. Regression analyses were applied to evaluate effects of age and feeding regimen. Body weight, milk yield, and the hay proportion of forage dry matter intake were considered as covariates. Methane emissions per unit of intake, body weight, and milk yield were significantly related to age. Their development in the cows with age was characterized by an increase to maximum at around 2,000 d of age, followed by a decline. This response was not accompanied by corresponding age-related changes in intake, chewing activity, digesta passage time, and digestibility of organic matter, which would have explained shifts in CH4. However, fiber digestibility showed a similar change with age as methane emissions, resulting in quite stable methane emissions per unit of digestible fiber. As expected, methane emissions intensity per unit of milk produced was greater by 8% without concentrate than with concentrate, but no difference was noted in the response to age when the animals were subjected to different feeding regimens. The efficiency of milk production was only marginally influenced by age and diet, and no different response was observed for age in the 2 dietary regimens. In conclusion, life cycle analyses of milk production systems focusing on longevity should consider changing methane yields with age in addition to the variation in environmental costs for replacements of culled cows.
authors.affiliation: ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, 8092 Zurich, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Grandl
authors.affiliation: ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, 8092 Zurich, Switzerland.
authors.forename: S L
authors.initials: SL
authors.lastname: Amelchanka
authors.affiliation: Agricultural Education and Advisory Centre Plantahof, Kantonsstrasse 17, 7302 Landquart, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Furger
authors.affiliation: University of Zurich, Vetsuisse Faculty, Clinic for Zoo Animals, Exotic Pets and Wildlife, Winterthurerstrasse 260, 8057 Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Clauss
authors.affiliation: Justus-Liebig-University Gießen, Institute of Animal Nutrition and Nutritional Physiology, Heinrich-Buff-Ring 26-32, 35392 Gießen, Germany.
authors.forename: J O
authors.initials: JO
authors.lastname: Zeitz
authors.affiliation: ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, 8092 Zurich, Switzerland. Electronic address: michael.kreuzer@inw.agrl.ethz.ch.
authors.forename: M
authors.initials: M
authors.lastname: Kreuzer
authors.affiliation: ETH Zurich, Institute of Agricultural Sciences, Universitaetstrasse 2, 8092 Zurich, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Schwarm
mesh_terms: D000367:Age Factors; D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004032:Diet / Q000662:veterinary*; D019587:Dietary Supplements / Q000032:analysis; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism; D005247:Feeding Behavior; D005260:Female; D008697:Methane / Q000378:metabolism*
chemical_list: D008697:Methane
keywords: feed efficiency; forage-based diet; greenhouse gas; lactation number; residual feed intake