Global demand for food is increasing, and use of large amounts of potentially human-edible feedstuffs for dairy cows is an important concern. The present study examined whether feeding a by-product-based concentrate combined with high-quality grass silage to high-producing dairy cows affected feed intake and milk production compared with a conventional diet, as well as the effect on efficiency of human food production. In a changeover experiment with four 21-d periods, 24 dairy cows in mid-lactation were offered 9.6 kg of dry matter per day with 1 of 4 concentrates and high-quality grass silage ad libitum. The control concentrate was based on cereal grain (wheat, oat, and barley) and soybean meal, whereas the 3 by-product-based concentrates contained sugar beet pulp in combination with mainly heat-treated rapeseed meal, distillers grain, or a mixture of both. All diets were formulated to be isoenergetic and isonitrogenous. The cows had 10-fold higher starch intake when fed the control diet than when fed the by-product-based concentrates. Silage intake (13 kg of dry matter/d) and milk production (33 kg of energy-corrected milk/d) were not affected by the change in diet. Therefore, replacing cereals and soybean meal with human-inedible by-products in a high-quality forage diet to dairy cows increased net food protein production substantially without lowering milk production.

The development of future food systems will depend on normative decisions taken at different levels by policymakers and stakeholders. Scenario modeling is an adequate tool for assessing the implications of such decisions, but for an enlightened debate, it is important to make explicit and transparent how such value-based decisions affect modeling results. In a participatory approach working with five NGOs, we developed a future food vision for the Nordic countries (Denmark, Finland, Norway and Sweden) through an iterative process of defining the scenario, modeling, and revising the scenario, until a final future food vision was reached. The impacts on food production, land use, and greenhouse gas emissions, and the resulting diets in the food vision, were modeled using a mass flow model of the food system. The food vision formulated was an organic farming system where food is produced locally and livestock production is limited to “leftover streams,” i.e., by-products from food production and forage from pastures and perennial grass/clover mixtures, thus limiting food-feed competition. Consumption of meat, especially non-ruminant meat, was substantially reduced compared with current consumption in the Nordic countries (− 81%). An estimated population of 37 million people could be supplied with the scenario diet, which uses 0.21 ha of arable land and causes greenhouse gas emissions of 0.48 tCO₂e per diet and year. The novelty of this paper includes advancing modeling of sustainable food systems by using an iterative process for designing future food visions based on stakeholder values, which enables results from multidisciplinary modeling (including agronomy, environmental system analysis, animal and human nutrition) to be fed back into the decision-making process, providing an empirical basis for normative decisions and a science-based future vision of sustainable food systems.

A dairy farmer's decision to cull or keep dairy cows is likely a complex decision based on animal health and farm management practices. The present paper investigated the relationship between cow longevity and animal health, and between longevity and farm investments, while controlling for farm-specific characteristics and animal management practices, by using Swedish dairy farm and production data for the period 2009 to 2018. We used the ordinary least square and unconditional quantile regression model to perform mean-based and heterogeneous-based analysis, respectively. Findings from the study indicate that, on average, animal health has a negative but insignificant effect on dairy herd longevity. This implies that culling is predominantly done for other reasons than poor health status. Investment in farm infrastructure has a positive and significant effect on dairy herd longevity. The investment in farm infrastructure creates room for new or superior recruitment heifers without the need to cull existing dairy cows. Production variables that prolong dairy cow longevity include higher milk yield and an extended calving interval. Findings from this study imply that the relatively short longevity of dairy cows in Sweden compared with some dairy producing countries is not a result of problems with health and welfare. Rather, dairy cow longevity in Sweden hinges on the farmers' investment decisions, farm-specific characteristics and animal management practices.

Methane emissions from ruminant digestion contribute significantly to global anthropogenic greenhouse gas emissions. Members of the phylum Rhodophyta (red algae), particularly Asparagopsis sp., have shown promising results in reducing methane emissions in ruminants, due to their high content of halogenated methane analog compounds. However, knowledge is lacking regarding the effects of red algae on animal performance and metabolism. This study investigated the effects of dairy cow diet supplementation with Asparagopsis taxiformis on enteric methane performance, metabolism of bromine and iodine, and health status of the cows. Thirty lactating Nordic Red dairy cows fed a total mixed ration, were blocked according to parity and days in milk, and randomly assigned to one of 3 diets: a control diet with no Asparagopsis taxiformis (CON), a diet with 0.15% Asparagopsis taxiformis on an organic matter (OM) basis (L-AT), and a diet with 0.3% Asparagopsis taxiformis on an OM basis (H-AT). The cows were fed the experimental diets continuously for 13 weeks, beginning with a baseline week (wk 0), which served as covariate by week where all cows received the basal diet. Individual feed intake and milk yield were recorded automatically throughout the experiment. Milk composition was determined by collecting milk samples during each milking session on 2 consecutive days every experimental week. While enteric methane and hydrogen levels were measured continuously by the GreenFeed system. Feces grab samples were collected as spot samples from a subset of 6 cows per treatment after milking during sampling wk 0, 2, 4, 8, and 12. Urine spot samples were collected from the same subset of cows during the same weeks as fecal samples. One urine sample was taken per day on 2 consecutive days, and the samples were analyzed for wk 12. Rumen fluid was collected after morning milking using a stomach tube in wk 0, 2, 4, and 12. We observed a 30% reduction in methane production in the H-AT group, with a concomitant increase in hydrogen production by 383%. However, the interaction between treatment and week showed that the AT effect on methane reduction began to diminish by wk 9 of the experiment. In the L-AT group, methane was reduced by 7.6% and hydrogen production was increased by 70%. However, dry matter intake (DMI) was 7% lower and energy-corrected milk (ECM) yield was 2% lower in the H-AT group compared with the other 2 groups. Total concentration of volatile fatty acids in rumen fluid was lower in the H-AT group compared with CON, with a reduction in acetate concentration and an increase in propionate, butyrate and valerate in the H-AT group. Bromine concentration was 5-fold higher and iodine concentration was 9-fold higher in milk from the H-AT group compared with CON. Bromine concentration in feces and urine samples from H-AT cows was approximately 4-fold and 9-fold higher, respectively, than in samples from CON cows. Metabolic profiling revealed a reduction in cholesterol levels and a decrease in the ferric-reducing ability of plasma in the H-AT treatment group compared with the CON group, as well as an increase in plasma magnesium concentration in the H-AT group. In conclusion, using 0.3% Asparagopsis taxiformis as an additive in dairy cow feed rations can mitigate enteric methane emissions, but this reduction was observed only during the first 8 weeks of the experiment, with no effect on methane emissions from wk 9 to 12. Additionally, it may have negative effects on DMI and ECM yield. Further long-term studies on red algae as methane inhibitor is needed to examine its sustained inhibitory effects over time and its impact on various metabolic processes. The effects appear to decline after wk 8 and influence several metabolic mechanisms.

Ruminants can produce meat and milk from fibrous feed and byproducts not suitable for human consumption. However, high-yielding dairy cows are generally fed a high proportion of cereal grain and pulses, which could be consumed directly by humans. If high production of dairy cows could be maintained with ingredients of low human interest, the sustainability of dairy production would improve. In the present study, 37 multiparous [Holstein (n = 13) and Swedish Red (n = 24)] dairy cows were followed over a whole lactation. A low-concentrate diet of up to 6 kg concentrate per day (6kgConc) was fed to 27 cows, whereas 10 cows were fed a high-concentrate diet of up to 12 kg concentrate per day (12kgConc). The concentrate was mainly based on byproducts (sugar beet pulp, wheat bran, rapeseed meal, distiller's grain). Grass-clover silage of high digestibility was offered ad libitum. Over the whole lactation, cows on the 6kgConc diet had lower dry matter intake and higher forage intake than cows on the 12kgConc diet. Milk yield and energy balance were not influenced by dietary treatment. However, the cows on the 6kgConc diet numerically produced 2.4 kg less energy-corrected milk than cows on 12kgConc diet. The study lacked the statistical power to identify treatment effects on daily yield below 2.8 kg of milk due to low number of animals per treatment. Feed efficiency (as energy-corrected milk yield/dry matter intake or residual feed intake), body weight change, body condition change, milk fatty acid concentration in total milk fatty acids, plasma nonesterified fatty acids, glucose, β-hydroxybutyrate, and fertility measurements were not affected by diet, supporting the energy balance results. However, higher plasma concentrations of insulin-like growth factor-1 and insulin were observed in cows fed the 12kgConc diet. These findings show that cows can adapt to a high-forage diet virtually without human-grade ingredients, without compromising feed efficiency or energy balance, thereby contributing to sustainable food production.

The longevity of dairy cows is mainly determined by farmers' subjective culling decisions and can be linked to the environmental impact of dairy production and to the social acceptance of the industry. Still, the economic impacts of dairy cow longevity are not well understood. The aim of this study was therefore to examine how herd average dairy cow longevity is related to the farm economic outcome. We used 3 indicators of economic outcome: technical efficiency, profitability and average milk yield per cow. We used 2 indicators of dairy cow longevity: average herd length of life and average herd length of productive life. The study was based on a unique and detailed data set from Swedish dairy agriculture, where herd management data from the national dairy herd recording scheme were combined with farm level economic variables, the Swedish farm accountancy survey, for a total of 1,959 observations over the time period 2010 - 2018. The regression results highlight that both measures of average herd dairy cow longevity have an overall positive and statistically significant association with farm level economic performance. These associations had an inverted U-shape which implies that the association is first positive and then declines. Descriptive statistics indicate that the point where the maximum economic performance is attained varied across the economic indicators. Our results are relevant for individual dairy farmers and their advisors who are interested in understanding how herd average longevity relates to economic performance on the farms. Our results are also important from a greater sustainability perspective: linking them to previous knowledge about the positive environmental and social sustainability benefits from keeping cows longer, highlights there may be dairy cow longevity-associated tradeoffs between those benefits and the farm economic outcomes.