Abstract
Simple SummarySix main fatty acids measured by gas-chromatography of four types of milk samples, fresh products, by-products, and ripened cheeses were used for predicting enteric methane yield per kg of feed consumed and intensity per kg of milk produced. Methane yield and intensity can be predicted from single milk samples with good accuracy. Cream, ricotta, and ripened cheese could be used only taking into account the possible overestimation of emissions and increasing the number of samples analyzed to improve the precision. Among by-products, whey could be a possible alternative source of information for predicting methane emission, whereas scotta showed low precision. Ripened cheeses were found to be less valuable sources of information to predict methane emission. This method could be used for monitoring the ecological footprint of different farms, dairy and feeding systems, and processing units.Enteric methane emissions (EME) of ruminants contribute to global climate change, but any attempt to reduce it will need an easy, inexpensive, and accurate method of quantification. We used a promising indirect method for estimating EMEs of lactating dairy cows based on the analysis of the fatty acid (FA) profile of their milk. The aim of this preliminary study was to assess milk from four single samplings (morning whole, evening whole, evening partially skimmed, and vat milks) as alternatives to reference whole milk samples from two milkings. Three fresh products (cream, cheese, and ricotta), two by-products (whey and scotta), and two long-ripened cheeses (6 and 12 months) were also assessed as alternative sources of information to reference milk. The 11 alternative matrices were obtained from seven experimental cheese- and ricotta-making sessions carried out every two weeks following the artisanal Malga cheese-making procedure using milk from 148 dairy cows kept on summer highland pastures. A total of 131 samples of milk, dairy products, and by-products were analyzed to determine the milk composition and to obtain detailed FA profiles using bi-dimensional gas-chromatography. Two equations taken from a published meta-analysis of methane emissions measured in the respiration chambers of cows on 30 different diets were applied to the proportions of butyric, iso-palmitic, iso-oleic, vaccenic, oleic, and linoleic acids out of total FAs to predict methane yield per kg of dry matter ingested and methane intensity per kg of fat and protein corrected milk produced by the cows. Methane yield and intensity could be predicted from single milk samples with good accuracy (trueness and precision) with respect to those predicted from reference milk. The fresh products (cream, cheese and ricotta) generally showed good levels of trueness but low precision for predicting both EME traits, which means that a greater number of samples needs to be analyzed. Among by-products, whey could be a viable alternative source of information for predicting both EME traits, whereas scotta overestimated both traits and showed low precision (due also to its very low fat content). Long-ripened cheeses were found to be less valuable sources of information, although six-month cheese could, with specific correction factors, be acceptable sources of information for predicting the methane yield of lactating cows. These preliminary results need to be confirmed by further study on different dairy systems and cheese-making technologies but offer new insight into a possible easy method for monitoring the EME at the field level along the dairy chain.
Highlights
Enteric methane (EME) emitted by lactating cows [1] makes the greatest contribution to greenhouse gas (GHG) emissions out of the entire animal sector, and has the greatest impact on climate change [2].The direct quantification of GHG using respiration chambers requires facilities, tools, resources, and knowledge that are available in only a few research centers [3] and make it impossible to testGHG emissions in the field with a large number of farms and cows
Two equations taken from a published meta-analysis of methane emissions measured in the respiration chambers of cows on 30 different diets were applied to the proportions of butyric, iso-palmitic, iso-oleic, vaccenic, oleic, and linoleic acids out of total fatty acid (FA) to predict methane yield per kg of dry matter ingested and methane intensity per kg of fat and protein corrected milk produced by the cows
Methane yield and intensity could be predicted from single milk samples with good accuracy with respect to those predicted from reference milk
Summary
Enteric methane (EME) emitted by lactating cows [1] makes the greatest contribution to greenhouse gas (GHG) emissions out of the entire animal sector, and has the greatest impact on climate change [2].The direct quantification of GHG using respiration chambers requires facilities, tools, resources, and knowledge that are available in only a few research centers [3] and make it impossible to testGHG emissions in the field with a large number of farms and cows. Among the different proxies that have been proposed for indirectly measuring EME in dairy cattle [4], the analysis of fatty acid (FA) profiles of milk and a proper combination of FAs constitute an easy-to-use method for use in the field [5,6,7], as it requires only the collection of milk samples and analysis of them in the laboratory [8] This method exploits the complex relationships between feed characteristics, rumen microbial activity, methane production, the production and metabolism of volatile and non-volatile fatty acids, and their absorption and transportation to the udder, de novo synthesis of fatty acids in the mammary gland, and, lastly, fat globule excretion in milk [5,9,10]. A similar meta-analysis was carried out recently [13] for predicting daily methane production (dCH4 ) per cow
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