Environmental Impact Of Milk Production Research Articles

Lactation modeling and the effects of rotational crossbreeding on milk production traits and milk-spectra-predicted enteric methane emissions

Rotational crossbreeding has not been widely studied in relation to the enteric methane emissions of dairy cows, nor has the variation in emissions during lactation been modeled. Milk infrared spectra could be used to predict proxies of methane emissions in dairy cows. Therefore, the objective of this work was to study the effects of crossbreeding on the predicted infrared proxies of methane emissions and the variation in the latter during lactation. Milk samples were taken once from 1,059 cows reared in 2 herds, and infrared spectra of the milk were used to predict milk fat (mean ± SD; 3.79 ± 0.81%) and protein (3.68 ± 0.36%) concentrations, yield (21.4 ± 1.5 g/kg dry matter intake), methane intensity (14.2 ± 2.0 g/kg corrected milk), and daily methane production (358 ± 108 g/d). Of these cows, 620 were obtained from a 3-breed (Holstein, Montbéliarde, and Viking Red) rotational mating system, and the rest were purebred Holsteins. Milk production data and methane traits were analyzed using a nonlinear model that included the fixed effects of herd, genetic group, and parity, and the 4 parameters (a, b, c, and k) of a lactation curve modeled using the Wilmink function. Milk infrared spectra were found to be useful for direct prediction of qualitative proxies, such as methane yield and intensity, but not quantitative traits, such as daily methane production, which appears to be better estimated (450 ± 125 g/d) by multiplying a measured daily milk yield by infrared-predicted methane intensity. Lactation modeling of methane traits showed daily methane production to have a zenith curve, similar to that of milk yield but with a delayed peak (53 vs. 37 d in milk), whereas methane intensity is characterized by an upward curve that increases rapidly during the first third of lactation and then slowly till the end of lactation (10.5 g/kg at 1 d in milk to 15.2 g/kg at 300 d in milk). However, lactation modeling was not useful in explaining methane yield, which is almost constant during lactation. Lastly, the methane yield and intensity of cows from 3-breed rotational crossbreeding are not greater, and their methane production is lower than that of purebred Holsteins (452 vs. 477 g/d). Given the greater longevity of crossbred cows, and their lower replacement rate, rotational crossbreeding could be a way of mitigating the environmental impact of milk production.

Global contributions of milk to nutrient supplies and greenhouse gas emissions

Globally, ruminant production systems used to synthesize meat and milk differ tremendously in terms of their efficiency, productivity, and environmental impacts. Regardless of this variability, milk has been repeatedly identified as an essential source of nutrients for humans. The objective of this work was to characterize global contributions of fluid milk to human food and nutrient supplies, greenhouse gas emissions, and water withdrawal. Data were leveraged from the United Nations Food and Agriculture Organization to estimate global supplies of agricultural products. Trade of agricultural products and waste of those products, along with use of human food for livestock feed were accounted for before estimating human nutrient supplies. The contributions of milk to human-edible nutrient supplies were then enumerated in terms of their proportion of total nutrients supplied by the agricultural system and in terms of the human population's requirement for that nutrient. We identified that fluid milk provides over 10% of consumable supplies of vitamin B12, vitamin A, riboflavin, and calcium available for humans globally. In terms of human nutrient requirements, milk provides sufficient vitamin B12 to meet the needs of over 60% of the global population, riboflavin to satisfy 50% of the population, and calcium and phosphorus for over 35% of the population. Compared with other foods, milk ranked among the highest in terms of nutrient-to-calorie ratio for numerous amino acids, phosphorus, calcium, and riboflavin. Conditional dependencies were identified between greenhouse gas emissions and ruminant milk and meat, but not between water withdrawal and milk production. When evaluating the trade-offs in nutrient use versus nutrient provision for producing milk or producing all ruminant products, the production of ruminants worldwide was associated with both net increases and net decreases of several key nutrients. Continued work focusing on strategies to reduce the environmental impact of milk production will improve the utility of milk for feeding the growing global population.

Feeding lower-protein diets based on red clover and grass or alfalfa and corn silage does not affect milk production but improves nitrogen use efficiency in dairy cows

Reducing the dietary crude protein (CP) concentration can decrease the financial cost and lower the environmental impact of milk production. Two studies were conducted to examine the effects of reducing the dietary CP concentration on animal performance, nutrient digestibility, milk fatty acid (FA) profile, and nitrogen use efficiency (NUE; milk N/N intake) in dairy cows fed legume silage-based diets. Thirty-six multiparous Holstein-Friesian dairy cows that were 76 ± 14 (mean ± SD) days in milk and 698 ± 54 kg body weight were used in a 3 × 3 Latin square design in each of 2 studies, with 3 periods of 28 d. In study 1, cows were fed diets based on a 50:50 ratio of red clover to grass silage [dry matter (DM) basis] containing 1 of 3 dietary CP concentrations: high (H) = 175 g of CP/kg of DM; medium (M) = 165 g of CP/kg of DM; or low (L) = 150 g of CP/kg of DM. In study 2, cows were fed 175 g of CP/kg of DM with a 50:50 ratio of alfalfa to corn silage (H50) or 1 of 2 diets containing 150 g of CP/kg of DM with either a 50:50 (L50) or a 60:40 (L60) ratio of alfalfa to corn silage. Cows in both studies were fed a total mixed ration with a forage-to-concentrate ratio of 52:48 (DM basis). All diets were formulated to meet the MP requirements, except L (95% of MP requirements). In study 1, cows fed L ate 1.6 kg of DM/d less than those fed H or M, but milk yield was similar across treatments. Mean milk protein, fat, and lactose concentrations were not affected by diet. However, the apparent total-tract nutrient digestibility was decreased in cows fed L. The NUE was 5.7 percentage units higher in cows fed L than H. Feeding L also decreased milk and plasma urea concentrations by 4.4 mg/dL and 0.78 mmol/L, respectively. We found no effect of dietary treatment on the milk saturated or monounsaturated FA proportion, but the proportion of polyunsaturated FA was increased, and milk odd- and branched-chain FA decreased in cows fed L compared with H. In study 2, DM intake was 2 kg/d lower in cows receiving L50 than H50. Increasing the alfalfa content and feeding a low-CP diet (L60) did not alter DMI but decreased milk yield and milk protein concentration by 2 kg/d and 0.6 g/kg, respectively, compared with H50. Likewise, milk protein and lactose yield were decreased by 0.08 kg/d in cows receiving L60 versus H50. Diet had no effect on apparent nutrient digestibility. Feeding the low-CP diets compared with H50 increased the apparent NUE by approximately 5 percentage units and decreased milk and plasma urea concentrations by 7.2 mg/dL and 1.43 mmol/L, respectively. Dietary treatment did not alter milk FA profile except cis-9,trans-11 conjugated linoleic acid, which was higher in milk from cows receiving L60 compared with H50. We concluded that reducing CP concentration to around 150 g/kg of DM in red clover and grass or alfalfa and corn silage-based diets increases the apparent NUE and has little effect on nutrient digestibility or milk performance in dairy cows.

Environmental impact of milk and electricity production from dairy farms with biogas plants of different size and feeding system

Anaerobic digestion is an effective method to decrease the environmental impact of milk production and to generate renewable energy. A dairy farm with an annexed biogas plant produces three outputs, milk, meat and electricity, and should be considered as a single system for the evaluation of the environmental impact. The aim of this study was to investigate to what extent the size and feeding methods of the biogas plants in three dairy farms with different features affect the environmental impact related to the milk and electricity produced. The first farm was characterized by a biogas plant of 300 kW fed only with cattle manure, the second farm had a plant of 526 kW fed with cattle manure, maize silage and waste of maize grain production, while the third farm had a biogas plant of 999 kW fed with cattle and poultry manure, maize and triticale silage, and fats from slaughterhouse waste. The Life Cycle Assessment involved the environmental impact of Fat Protein Corrected Milk (FPCM), in the first instance with meat and electricity from biogas considered with an economic allocation, and then considered a credit. Successively, the environmental consequences of electricity were evaluated considering milk and meat as credits. With the economic allocation, Carbon Footprint (CFP) of one kg of FPCM was 0.82, 0.85 and 0.72 kg CO2 eq in the first, second and third farm, respectively. In all the three farms, electricity generation from biogas determined a reduction in the environmental impact of milk production thanks to a credit of emissions provided by the production of renewable energy. Milk CFP in the three farms was 0.82, 0.91 and 0.13 kg CO2 eq respectively, with mitigation from biogas of 11%, 11% and 85%. The best performances were obtained in the third farm thanks to higher levels of electricity generation, covered digestate storage and the large use of agri-industrial waste. Electricity CFP in the farms was −0.74, −0.68 and −0.06 kg CO2 eq/kWh respectively. Environmental consequences of electricity production from biogas plants were compensated in all the farms thanks to the credits provided by milk; this compensation was as greater as the ratio between milk and electricity production and the first farm reached better outcomes. In the context of reducing the environmental impact of animal foods and implementing an ecological transition to reach national and European goals for renewable energy production, the work could be beneficial to assess which combination between dairy and energy products should be promoted.

Environmental impacts of cow's milk in Northern Italy: Effects of farming performance

A Life Cycle Assessment was conducted on 55 dairy farms located in Northern Italy to investigate the effect of dairy farming performance on the environmental impact of milk production. Feeds used in diet formulation were analyzed for nutrients contents by near-infrared reflectance technique, and the real composition was used to estimate methane emissions from enteric fermentation and manure handling. The functional unit was 1 kg of fat and protein corrected milk at the farm gate. The results were expressed according to the Product Environmental Footprint (PEF) method version 2.0 for 19 impact indicators through SimaPro® software v9.0.35. Five main data categories were considered: water used on the farm, off-farm feeds, energy resources, on-farm feeds, and bedding materials. Dairy farms were ranked into high-, mid-, and low-performing herds according to the average milk yield (>32.6; 25.4–32.6; <25.4 kg milk/cow/d; respectively). Statistical analysis between groups of herds was performed using JMP (JMP® Pro 15.2.0). The environmental impacts of indicators were lower (P < 0.05) in high-performing herds compared with low-performing herds and lower (P < 0.05) for climate change, climate change-biogenic, climate change-fossil, photochemical ozone formation human health (POCP), and eutrophication terrestrial when compared with mid-performing herds. Similar values among groups were observed for acidification, ionizing radiation human health, and ozone depletion potential indicators. The off-farm and on-farm feeds categories had the highest share of value of impact indicators. The enteric fermentation and manure handling significantly contributed to greenhouse gas emissions, whereas particulate matter formation and POCP were mainly related to barn management. Results from this research could be helpful in the dairy sector through the completeness of the expected impact indicators evaluated by the PEF method. • Environmental impacts of fifty-five dairy farms in Northern Italy were assessed at farm gate. • Product Environmental Footprint guidelines were used to express results for nineteen impact indicators. • Dairy farms were ranked into high-, mid- and low-performing herd groups. • A low environmental impact characterized high-performing herds. • The off-farm and in-farm feeds data categories were most responsible for impact indicators values.

Partial replacement of soybean meal with soybean silage and responsible soybean meal in lactating cows diet: part 2, environmental impact of milk production

Soybean meal, the main protein source for livestock in Italy, is associated with high environmental impact in terms of land use change. Thus alternative protein sources are advisable. The study aimed to evaluate through a Life Cycle Assessment (LCA) approach the environmental impact of milk production systems characterised by different diets of lactating cows including different sources of soybean. Four scenarios were identified: (1) conventional soybean meal (CON), (2) conventional soybean meal and soybean silage (SBS), 3) responsible soybean meal defined by the FEFAC guidelines (CON + RSM), (4) soybean silage and responsible soybean meal (SBS + RSM). Inventory data were derived from a previous in vivo trial on lactating cows and farmer interviews. Secondary data were obtained from the ECOINVENT® and the Agri-footprint databases. The LCA was performed using the SimaPro V 8.3. Soybean silage showed higher global warming potential (GWP), marine eutrophication and human toxicity compared with lucerne hay, the most utilised self-produced protein feed, due to the high contribution of mechanical operations in the field. The GWP of milk (kg CO2eq/kg FPCM) decreased from 1.38 of the CON scenario to 1.17 of SBS and 1.13 of CON + RSM; the best result was obtained by combining soybean silage with responsible soybean meal: 1.01. Furthermore, the scenarios using RSM reduced agricultural land occupation and natural land transformation. The inclusion of SBS and RSM is an interesting option to reduce environmental impact of milk production, maximising yields of DM and CP per hectare and representing an alternative protein source. HIGHLIGHTS The ration of dairy cows represents one of the main causes of the environmental impact of the livestock sector due to the impact for feed production (forage and concentrate) Feeding soybean meal as protein source has high environmental impact since it is linked with deforestation in South America Alternative protein sources like soybean silage and soybean meal produced sustainably could reduce the environmental impact of the sector

Milk production and efficiency of utilization of nitrogen, metabolizable protein, and amino acids are affected by protein and energy supplies in dairy cows fed alfalfa-based diets

Alfalfa has a lower fiber digestibility and a greater concentration of degradable protein than grasses. Dairy cows could benefit from an increased digestibility of alfalfa fibers, or from a better match between nitrogen and energy supplies in the rumen. Alfalfa cultivars with improved fiber digestibility represent an opportunity to increase milk production, but no independent studies have tested these cultivars under the agroclimatic conditions of Canada. Moreover, decreasing metabolizable protein (MP) supply could increase N use efficiency while decreasing environmental impact, but it is often associated with a decrease in milk protein yield, possibly caused by a reduced supply of essential AA. This study evaluated the performance of dairy cows fed diets based on a regular or a reduced-lignin alfalfa cultivar and measured the effect of energy levels at low MP supply when digestible His (dHis), Lys (dLys), and Met (dMet) requirements were met. Eight Holstein cows were used in a double 4 × 4 Latin square design, each square representing an alfalfa cultivar. Within each square, 4 diets were tested: the control diet was formulated for an adequate supply of MP and energy (AMP_AE), whereas the 3 other diets were formulated to be deficient in MP (DMP; formulated to meet 90% of the MP requirement) with deficient (94% of requirement: DMP_DE), adequate (99% of requirement: DMP_AE), or excess energy supply (104% of requirement; DMP_EE). Alfalfa cultivars had no significant effect on all measured parameters. As compared with cows receiving AMP_AE, the dry matter intake of cows fed DMP_AE and DMP_EE was not significantly different but decreased for cows fed DMP_DE. The AMP_AE diet provided 103% of MP and 108% of NEL requirements whereas DMP_DE, DMP_AE, and DMP_EE diets provided 84, 87, and 87% of MP and 94, 101, and 107% of NEL requirements, respectively. In contrast to design, feeding DMP_EE resulted in a similar energy supply compared with AMP_AE, although MP supply has been effectively reduced. This resulted in a maintained milk and milk component yields and improved the efficiency of utilization of N, MP, and essential AA. The DMP diets decreased total N excretion, whereas DMP_AE and DMP_EE diets also decreased milk urea-N concentration. Reducing MP supply without negative effects on dairy cow performance is possible when energy, dHis, dLys, and dMet requirements are met. This could reduce N excretion and decrease the environmental impact of milk production.

ENVIRONMENTAL PERFORMANCE OF SEMI-CONFINEMENT AND PASTURE-BASED SYSTEMS FOR DAIRY COWS

Two dairy farms (one a semi-confinement system and the other a pasture-based system) in the same region of Spain were chosen for comparison from a life cycle assessment perspective. In both cases, cattle feeding was found to be the main contributor to environmental impact in most categories. Additionally, cow emissions to air were the principal contribution to the global warming, fine particulate matter formation and terrestrial acidification categories. Although cow productivity in the pasture-based farm was almost half that obtained in the semi-confinement farm, the impact per 1 kgFPCM in the pasture-based system was notably lower in 12 of the 18 categories analysed, mainly due to the fact that the relative amount of milk and surplus calves and culled cows sold for meat production was higher in the pasture-based farm. Finally, it should be noted that given the scarcity and variability of the data found in the literature, this LCA study contributes much needed knowledge about the effect of the degree of confinement of cows on the environmental impact of milk production.

Environmental impact of milk production from samples of organic and conventional farms in Lombardy (Italy)

In 2016, eight conventional and six organic dairy farmers from the Lombardy Plain were interviewed about their farm technical and economical outcomes in 2015. Environmental performances were assessed according to the life cycle assessment (LCA) approach. The environmental effects investigated were global warming potential (GWP), acidification potential (ACP), and eutrophication potential (EUP). The functional units were 1 kg of fat protein corrected milk (FPCM) and 1 ha of occupied area. The calculations were performed with a version of LatteGHG model, updated to take into account carbon sequestration, ACP and EUP. Herd sizes did not differ between the conventional and organic farms, but the variability in organic herd size (CV 0.88) was larger than that in conventional herd size (CV 0.35). FPCM production was significantly (P < 0.05) higher in the conventional than in the organic farms (9004 vs. 7736 kg/cow per year, respectively). The GWP, ACP and EUP, with no allocation per kilogram of FPCM, for conventional vs. organic farms were 1.24 vs. 1.37 kg CO2eq, 0.025 vs. 0.026 kg of SO2eq, and 0.011 and 0.013 kg of PO43−eq, respectively, and showed no significant differences between conventional and organic farms. When considering 1 ha of occupied area, GWP, ACP, and EUP were significantly higher in the conventional than in the organic system (25.8 vs. 11.5 t CO2eq; 507 vs. 225 g SO2eq; 210 vs 117 g PO43−eq, respectively). Average milk production was found to be a significant driver of GWP per mass produced and per unit of land occupied in both production systems. Correlations between consumption of inputs per cow or kilograms of milk are controversial. In this study, there was no significant difference in the contribution of sources of GHG, with the exception of inputs for cropping, which was significantly higher in the conventional system. The main contributor of ACP were the emissions of NH3 and NOx from manure management and application, with a significant difference between the conventional and organic systems (82.2% vs. 92.9%, respectively). The main source of EUP was the emissions of NH3, N2O and P from manure management and application, which was significantly higher in the organic system than in the conventional system (62.9% vs. 67.8%, respectively). These results suggest that organic systems should improve milk productivity, and act as an effective contributor in tackling the environmental problems examined in this study. The study further suggests that there are organic farms with cows producing as much milk as the cows in conventional farms.

Opportunities to improve sustainability on commercial pasture-based dairy farms by assessing environmental impact

For pasture-based dairy farming to become more sustainable, the negative environmental impacts associated with milk production must be minimized. These negative impacts include eutrophication, ammonia emissions and greenhouse gas (GHG) emissions. Two tools, a nutrient budget and a carbon footprint calculator, allow farm-level assessments of these negative impacts. In this study, a nutrient budget was used to calculate the efficiency of nitrogen and phosphorous use, and a carbon footprint calculator was used to calculate GHG emissions. Farm system descriptors were used to identify the farm systems that had the lowest environmental impact. Soil carbon was measured as an indicator of soil health, and the link between soil health, nutrient use efficiency and GHG emissions was examined. Nitrogen and phosphorous were not efficiently utilized on the farms included in this study, with a large excess of nutrients imported onto the farms each year. The average use efficiency was 29% for nitrogen, and 36% for phosphorous. The GHG emissions per liter of milk production were higher on the farms included in this study than found in previous studies on dairy farms, with an average of 1.39 kg of carbon dioxide equivalents emitted per kilogram of energy-corrected milk. Farm systems which optimized milk production on the available land, while applying the least amount of fertilizer and feeding the least amount of purchased feeds per milk produced, had the lowest environmental impact. Farms with higher soil carbon levels had higher nitrogen use efficiencies and lower GHG emissions. This is the first South African research to examine environmental impact on pasture-based dairy farms in this manner. It is possible for pasture-based dairy farmers to reduce the environmental impact of milk production by adopting some of the principles identified in this study.

Farm characteristics and management routines related to cow longevity: a survey among Swedish dairy farmers

BackgroundLongevity is an important trait for increasing the profitability of dairy production. Long cow longevity is also essential to reduce the environmental impact of milk production, and to maintain positive consumer attitude. Genetic selection for increased longevity has been effective, but the phenotypic trend of longevity in Swedish dairy cows has not been improved. The objective of this study was to identify herd characteristics and management routines that are associated with the average cow longevity in a herd. To obtain this information, a questionnaire was developed and sent out to 661 Swedish dairy farmers.ResultsThe response rate was 35%. Seventeen of the 62 characteristics investigated had either a univariable association with the outcome (days from birth to culling) at P < 0.15, or were identified as confounders in the causal diagram and were therefore considered as candidates for the multivariable analysis. Multiple imputation was used to fill in the missing data from the questionnaires, and this increased the number of usable observations in the multivariable modeling from 156 to 228. Only a few of the investigated herd characteristics and management routines were associated with average cow longevity. The results demonstrated that using herd health advisory services shortened the average longevity, while using breeding advisory services prolonged the average longevity in the herd. Furthermore, having a greater interest in animal breeding (i.e. genetic selection) decreased the longevity, and calling the veterinarian when discovering an unhealthy cow increased the average longevity. Higher age of the farmer was also associated with longer average herd longevity.ConclusionsThe herd average cow longevity was only associated with some of the farm characteristics and management routines studied. The results demonstrate that the use of advisory services and farmers’ attitudes could be targeted for increasing the herd longevity. Further, the results indicate that other e.g. qualitative factors influencing farmers’ decisions play an important role.

Life cycle analysis of raw milk production in Tunisia

Life Cycle Assessment (LCA) is a tool to calculate greenhouse gas (GHG) emissions of dairy production. A survey was conducted in 20 dairy farms at the governorate of Sousse. The present study aimed to evaluate environmental impact of milk production at the farm regarding GHG emission and energy consumption. In the 20 dairy farms total GHG emissions resulted in a mean of 0.63 +/- 0.2 kg CH4/kg ECM and forage can contribute with a means 0.35 Le kg CO2eq/DM. The main reductions in GHG emissions per kg of FPCM started from 2,347 kg per cow per year and then the reduction slowed down to stabilize at around 6,127 kg FPCM per cow per year.

Environmental impact of milk production across an intensification gradient in Ethiopia

Abstract This paper quantifies environmental performances of milk production systems differing in degree of intensification in the Mekelle milkshed area, Ethiopia. Life Cycle Assessment (LCA) methodology was used to estimate Land Use (LU), Fossil Energy Use (FEU) and Global Warming Potential (GWP) of the cattle sub-system in 8 large-scale, 8 (peri-)urban and 8 rural farms. The large-scale farms owned considerably more and other types of cattle (35.0 cattle units (cu); mainly Friesians) than the (peri-)urban (6.3 cu; mainly crossbreds) and rural farms (4.1 cu; mainly local breeds). The milk production per average cow per year was much lower in rural farms (730 kg) than in large-scale (2377 kg) and (peri-)urban farms (1829 kg). Milk was the main contributor to the economic benefits of the large-scale (90%) and (peri-)urban (80%) farms, whereas milk (sold and consumed at home) contributed only about 40% to the economic benefits in the multifunctional rural farms. The environmental impacts per cu, reflecting the absolute impacts of cattle keeping, were considerably higher in the large-scale and (peri-)urban farms than in the rural farms. LU and FEU were for the great majority caused by the land use for hay, straws and grasses, and harvesting, transport and processing of feeds, in particular wheat bran. On-farm emissions from enteric fermentation and manure storage were the main contributors to GWP. The impacts per kg milk did not differ significantly between the three systems. The LU per kg milk estimates (9.4, 11.2 and 8.8 m2 in the large-scale, (peri-)urban and rural farms, respectively) were relatively high compared to LCA studies of milk production in developed countries due to large amounts of low-quality forages and wheat bran fed, whereas the FEU values per kg milk (7.5, 11.1 and 6.6 MJ in the large-scale, (peri-)urban and rural farms, respectively) were relatively low compared to studies of milk production systems in developed countries. The GWP estimates per kg milk (1.75, 2.25 and 2.22 kg CO2-equivalents per kg milk in the large-scale, (peri-)urban and rural farms, respectively) were slightly higher than GWP values for the same types of farms in other developing countries, due to the relatively large amounts of low quality feeds fed. The quality of cattle management practices seems more important than the choice for a specific cattle keeping system in reducing environmental impacts of milk production.

Environmental impact assessment of different cropping systems of home-grown feed for milk production

Animal feeding is a critical point in terms of both production efficiency and environmental impact for the livestock sector and farmer choices about home-grown feed can have great influence on environmental impact of milk production. The aim of the study was to assess the environmental performances of the most common home-grown fodder crops in Northern Italy and to analyse the impacts of different cropping system scenarios for milk production, through a Life Cycle Assessment (LCA) approach. The environmental impact of the most common home-grown feeds was calculated from cradle-to-the-animal’s mouth expressing the different categories per hectare and per unit of net energy for lactation and protein digested in the small intestine when rumen-fermentable nitrogen is the limiting factor (PDIN). Moreover four scenarios (BASE, HAY, SILAGE, PROTEIN) characterized by different cropping systems were hypothesized to assess the environmental impact of milk production from cradle to farm gate in an intensive farming system. Primary data were collected by direct interviews in 134 dairy farms located in Lombardy Region (Northern Italy).Among the most common fodder crops grown in Northern Italy, alfalfa preserved as silage and, although with a lesser extent, the double cropping system “whole plant maize silage-Italian ryegrass hay” showed the best environmental performances especially when the impact are expressed per unit of net energy for lactation or digestible protein in the intestine. Alfalfa showed also the lowest values of acidification and eutrophication when they were expressed as unit of land. The high variability of forage quality suggests a great room for improvement in terms of mitigation potentials.The analysis of alternative cropping system scenarios for milk production showed that the cropping system based on alfalfa and grass hays (HAY scenario) had the lowest self-sufficiency in terms of DM and the highest values of all impact categories per kg of fat and protein corrected milk (FPCM). The PROTEIN scenario, characterized by the introduction in the cropping system of protein rich crops (whole plant soy silage and alfalfa hay) can be considered the best one in a global perspective. In fact, the PROTEIN scenario showed the lowest potentials for acidification, eutrophication and non-renewable fossil energy use per kg FPCM and a reasonable value in terms of GWP. Moreover, the PROTEIN scenario had the higher feed self-sufficiency in terms of both DM and CP. Thanks to their capability to fix atmospheric nitrogen increasing the cultivation of legume such as alfalfa and soy in the cropping system of Northern Italy can reduce the utilization of chemical nitrogen fertilization and, consequently, the environmental impact. Moreover, considering that the main part of soybean consumed in Italy is cultivated in South America, a higher farm self-sufficiency in terms of protein feeds could decrease the emissions of CO2 linked to land use change generated by the cultivation of soybean.

Impact of diet and fertility on greenhouse gas emissions and nitrogen efficiency of milk production

Nutrition affects the environmental impact of milk production through its direct influence on enteric fermentation and excretion of undigested and excess nutrients, especially nitrogenous compounds, in manure and its indirect influence on daily level of milk output per cow and fertility. The higher the level of milk production and fertility, the lower the emissions intensity, or carbon footprint, of a dairy herd. Increasing feed efficiency reduces greenhouse gas emissions per litre of milk because emissions are spread over higher product output per cow. Nitrogen use efficiency and cow fertility can be increased and diet carbon footprint reduced by altering diet formulation to utilise by-product raw material feeds of low carbon footprint.

Dietary options to reduce the environmental impact of milk production

SUMMARYA range of options was explored to test the hypothesis that diets for dairy cows could be formulated to reduce the carbon footprint (CFP) of feed, increase efficiency of conversion of potentially human-edible feed into milk, increase nitrogen use efficiency (NUE) and reduce methane (CH4) emissions per kg milk. Diets based on grazed grass, grass silage, maize silage or straw, supplemented with raw material feeds, were formulated to meet requirements for metabolizable energy and metabolizable protein for a range of daily milk yields. At similar levels of milk yield, NUE, predicted CH4emissions and diet CFP were generally higher for diets based on maize silage than for those based on grazed grass, grass silage or straw. Predicted CH4emissions and human-edible proportion decreased, while NUE increased with the increasing level of milk yield. It is concluded that there is potential to reduce the environmental impact of milk production by altering diet formulation, but the extent to which this might occur is likely to depend on availability of raw material feeds with low CFPs.

Anaerobic digestion and milking frequency as mitigation strategies of the environmental burden in the milk production system

The aim of the study was to assess, through a cradle to farm gate Life Cycle Assessment, different mitigation strategies of the potential environmental impacts of milk production at farm level. The environmental performances of a conventional intensive dairy farm in Northern Italy (baseline scenario) were compared with the results obtained: from the introduction of the third daily milking and from the adoption of anaerobic digestion (AD) of animal slurry in a consortium AD plant. The AD plant, fed only with animal slurries coming also from nearby farms. Key parameters concerning on-farm activities (forage production, energy consumptions, agricultural machines maintenance, manure and livestock management), off-farm activities (production of fertilizers, pesticides, bedding materials, purchased forages, purchased concentrate feed, replacement animals, agricultural machines manufacturing, electricity, fuel) and transportation were considered. The functional unit was 1kg fat and protein corrected milk (FPCM) leaving the farm gate. The selected environmental impact categories were: global warming potential, acidification, eutrophication, photochemical oxidation and non-renewable energy use. The production of 1kg of FPCM caused, in the baseline scenario, the following environmental impact potentials: global warming potential 1.12kg CO2 eq; acidification 15.5g SO2 eq; eutrophication 5.62g PO43− eq; photochemical oxidation 0.87g C2H4 eq/kg FPCM; energy use 4.66MJeq. The increase of milking frequency improved environmental performances for all impact categories in comparison with the baseline scenario; in particular acidification and eutrophication potentials showed the largest reductions (−11 and −12%, respectively). In anaerobic digestion scenario, compared to the baseline one, most of the impact potentials were strongly reduced. In particular the most important advantages were in terms of acidification (−29%), global warming (−22%) and eutrophication potential (−18%). The AD of cow slurry is confirmed as an effective strategy to mitigate the environmental impact of milk production at farm level.

Breakeven prices for recording of indicator traits to reduce the environmental impact of milk production.

A breeding scheme using genomic selection and an indicator trait for environmental impact (EI) was studied to find the most effective recording strategy in terms of annual monetary genetic gain and breakeven price for the recording of indicator traits. The breakeven price shows the investment space for developing a recording system for an indicator trait. The breeding goal consisted of three traits – milk production, functional trait and environmental impact – with economic values of €83, €82 and €-83, respectively. The first scenario included only breeding goal traits and no indicator traits (NoIT). The other scenarios included all three breeding goal traits and one indicator trait (IT) for EI. The indicator traits were recorded on a large scale (stayability after first lactation and stature), medium scale (live weight and greenhouse gases (GHG) measured in the breath of the cow during milking) or small scale (residual feed intake and total enteric methane measured in a respiration chamber). In the scenario with stayability, the genetic gain in EI was over 11% higher than it was in NoIT. The breakeven price of recording stayability was €8 per record. Stayability is easy to record in the national milk recording system, and its use as an indicator trait for EI would not generate any additional recording costs. Therefore, stayability would be a good indicator trait to use to mitigate EI. The highest genetic gain in EI (23% higher compared to NoIT) was achieved when the GHG measured in the breath of the cow was used as indicator trait. The breakeven price for this indicator trait was €29 per record in the reference population. Ideally the recording of a specific indicator trait for EI would take place when: (i) the genetic correlation between the IT and EI is high; and (ii) the number of phenotypic records for the indicator trait is high enough to achieve a moderately high reliability of direct genomic values.

Factors affecting life cycle assessment of milk produced on 6 Mediterranean buffalo farms

This study quantifies the environmental impact of milk production of Italian Mediterranean buffaloes and points out the farm characteristics that mainly affect their environmental performance. Life cycle assessment was applied in a sample of 6 farms. The functional unit was 1kg of normalized buffalo milk (LBN), with a reference milk fat and protein content of 8.3 and 4.73%, respectively. The system boundaries included the agricultural phase of the buffalo milk chain from cradle to farm gate. An economic criterion was adopted to allocate the impacts on milk production. Impact categories investigated were global warming (GW), abiotic depletion (AD), photochemical ozone formation (PO), acidification (AC), and eutrophication (EU). The contribution to the total results of the following farm activities were investigated: (1) on-farm energy consumption, (2) manure management, (3) manure application, (4) on-farm feed production (comprising production and application of chemical fertilizers and pesticides), (5) purchased feed production, (6) enteric fermentation, and (7) transport of purchased feeds, chemical fertilizers, and pesticides from producers to farms. Global warming associated with 1kg of LBN resulted in 5.07kg of CO2 Eq [coefficient of variation (CV)=21.9%], AD was 3.5×10−3 kg of Sb Eq (CV=51.7%), PO was 6.8×10−4 kg of C2H4 Eq (CV=28.8%), AC was 6.5×10−2 kg of SO2 Eq (CV=30.3%), and EU was 3.3×10−2 kg of PO43− Eq (CV=36.5%). The contribution of enteric fermentation and manure application to GW is 37 and 20%, respectively; on-farm consumption, on-farm feed production, and purchased feed production are the main contributors to AD; about 70% of PO is due to enteric fermentation; manure management and manure application are responsible for 55 and 25% of AC and 25 and 55% of EU, respectively. Methane and N2O are responsible for 44 and 43% of GW, respectively. Crude oil consumption is responsible for about 72% of AD; contribution of CH4 to PO is 77%; NH3 is the main contributor to AC (92%); NO3− and NH3 are responsible for 55 and 41% of EU, respectively; contribution of P to EU is only 3.2%. The main characteristics explaining the significant variability of life cycle assessment are milk productivity and amount of purchased feed per kilogram of LBN. Improvement of LBN production per buffalo cow is the main strategy for reducing GW and PO; improvement of the efficiency of feed use is the strategy proposed for mitigating AD, PO, AC, and EU.

How can farming intensification affect the environmental impact of milk production?

The intensification process of the livestock sector has been characterized in recent decades by increasing output of product per hectare, increasing stocking rate, including more concentrated feed in the diet, and improving the genetic merit of the breeds. In dairy farming, the effects of intensification on the environmental impact of milk production are not completely clarified. The aim of the current study was to assess the environmental impacts of dairy production by a life cycle approach and to identify relations between farming intensity and environmental performances expressed on milk and land units. A group of 28 dairy farms located in northern Italy was involved in the study; data collected during personal interviews of farmers were analyzed to estimate emissions (global warming potential, acidification, and eutrophication potentials) and nonrenewable source consumption (energy and land use). The environmental impacts of milk production obtained from the life cycle assessment were similar to those of other recent studies and showed high variability among the farms. From a cluster analysis, 3 groups of farms were identified, characterized by different levels of production intensity. Clusters of farms showed similar environmental performances on product basis, despite important differences in terms of intensification level, management, and structural characteristics. Our study pointed out that, from a product perspective, the most environmentally friendly way to produce milk is not clearly identifiable. However, the principal component analysis showed that some characteristics related to farming intensification, such as milk production per cow, dairy efficiency, and stocking density, were negatively related to the impacts per kilogram of product, suggesting a role of these factors in the mitigation strategy of environmental burden of milk production on a global scale. Considering the environmental burden on a local perspective, the impacts per hectare were positively associated with the intensification level.