Christian Swensson

Variation in carbon footprint of milk due to management differences between Swedish dairy farms

To identify mitigation options to reduce greenhouse gas (GHG) emissions from milk production (i.e. the carbon footprint (CF) of milk), this study examined the variation in GHG emissions among dairy farms using data from previous CF studies on Swedish milk. Variations between farms in these production data, which were found to have a strong influence on milk CF, were obtained from existing databases of 1051 dairy farms in Sweden in 2005. Monte Carlo (MC) analysis was used to analyse the impact of variations in seven important parameters on milk CF concerning milk yield (energy-corrected milk (ECM) produced and delivered), feed dry matter intake (DMI), enteric CH4 emissions, N content in feed DMI, N-fertiliser rate and diesel used on farm. The largest between-farm variations among the analysed production data were N-fertiliser rate (kg/ha) and diesel used (l/ha) on farm (CV = 31% to 38%). For the parameters concerning milk yield and feed DMI, the CV was approximately 11% and 8%, respectively. The smallest variation in production data was found for N content in feed DMI. According to the MC analysis, these variations in production data led to a variation in milk CF of between 0.94 and 1.33 kg CO2 equivalents (CO2e)/kg ECM, with an average value of 1.13 kg CO2e/kg ECM. We consider that this variation of ±17%, which was found to be based on the used farm data, would be even greater if all Swedish dairy farms were included, as the sample of farms in this study was not totally unbiased. The variation identified in milk CF indicates that a potential exists to reduce GHG emissions from milk production on both the national and farm levels through changes in management. As milk yield and feed DMI are two of the most influential parameters for milk CF, feed conversion efficiency (i.e. units ECM produced/unit DMI) can be used as a rough key performance indicator for predicting CF reductions. However, it must be borne in mind that feeds have different CF due to where and how they are produced.

Analyses of mineral element balances between 1997 and 1999 from dairy farms in the south of Sweden

Mineral balances, especially nitrogen balances, are analysed for 138 dairy farms over 3 consecutive years, 1997, 1998 and 1999, together with analyses of annual changes in strategy concerning the use of mineral fertiliser at the farm scale. Information was obtained from mineral balance sheets of dairy farmers who shipped milk to the dairy plant Dairy Skane. The mineral balance sheets for N, P and K were constructed using the farm gate model and a balance was calculated for the whole farm. Arable land was approximately 65 hectares and the annual milk delivery per hectare was around 6800 kg. Nitrogen surplus per hectare among dairy farms in the south of Sweden is lower than that found in the intensive milk production regions in Western Europe. Dairy farms that had an output of both crop and animal products had a lower N surplus and a higher N efficiency. The N surplus among the investigated dairy farms decreased between 1997 and 1999. Input of N from purchased mineral fertiliser decreased significantly from the first year.

Characterization of Influence of Manure Handling System and Feeding on the Level of Ammonia Release Using a Simple Method in Cow Houses

The effects of manure handling system and feeding of dairy cows were studied using a simple method to analyse the level of ammonia release in cow stables. Two ratios based on the balances of ammonia and sensible heat, and ammonia and carbon dioxide, respectively, in animal houses were determined and considered to give characteristic levels of the release of ammonia in relation to the animal density independently of the ventilation rate. This required measurements of ammonia, carbon dioxide and temperature with hand-held instruments in the buildings and in outside air. In total, 34 dairy herds were investigated in the south of Sweden. The results clearly demonstrated higher release of ammonia from free stall barn with liquid manure than from conventional tie stall barn with solid manure. There was a clear effect of the content of crude protein, gram per kg dry matter, in the total feed ration on ammonia release in tie stall barn with liquid manure.

Plant development, agronomic performance and nutritive value of forage maize depending on hybrid and marginal site conditions at high latitudes

Abstract The objectives of this investigation were to study the effects of marginal site conditions and hybrid on plant development, agronomic performance and nutritive characteristics of forage maize (Zea mays L.) at high latitudes. Field experiments were conducted in 2008 and 2009 at three experimental sites, Kristianstad, Skara and Västerås, at increasing latitudes from 55°–60° N. Experimental design used two replicated randomized complete blocks at each site with three maize hybrids, Avenir (FAO 180), Isberi (FAO 190) and Burli (FAO 210), which were continuously assessed for plant development and harvested at various levels of maturity. The chemical composition and nutritional characteristics of harvested plant materials were analysed and hybrid responses to advancing maturity in terms of yield and nutritional qualities were evaluated. Results showed that maize hybrids required different numbers of accumulated thermal units at sites on varying latitudes to achieve developmental stages. Lowest thermal unit requirements among hybrids were observed for hybrid Avenir, and for sites it was highest for plants grown in the most northern site, Västerås. The most southern site, Kristianstad, was the only site at which all hybrids reached the dent stage (c. 450 g kg−1 kernel DM), a recommended maturity for ensiling. The DM yields of early maturing hybrid Avenir were consistently lower than those for Isberi and Burli at all the sites. Results also revealed nutritional differences among maize hybrids at a given maturity (DM, g kg−1), indicating that the effects of maturation should be factored into design of hybrid performance trials. This study highlights the effects of marginal site conditions and hybrids on plant development, agronomic performance and nutritional characteristics of maize hybrids at high latitudes. Further studies on marginal sites are recommended to enlighten the understanding of interaction between environmental and genetic factors on the performance of forage maize.

Effect of manure handling system, N fertilizer use and area of sugar beet on N surpluses from dairy farms in southern Sweden

Nitrogen balances from 283 conventional dairy farms situated in southern Sweden were investigated using the farm gate method. Nitrogen balances were determined for 1997 and 1998. Three N balances were calculated; for the whole farm, for crop production and for milk production. The aims of the investigation were to study if factors such as manure handling system, the amount of N obtained from mineral fertilizer per hectare and the proportion of sugar beet have an influence on the N balance. There was no significant effect of manure handling system on the N surplus per hectare or on N efficiency. The results showed that N efficiency was significantly improved by including sugar beet in the crop rotation and was negatively correlated with milk yield per hectare and fertilizer N per hectare. The N surplus per hectare was positively correlated with milk yield per hectare and fertilizer N per hectare. The comparison did not find a strong relationship between the amounts of N obtained from mineral fertilizer per hectare and supplied as manure. The latter was calculated theoretically. There was a weak, but significant, negative correlation between N from manure in 1997 and N from mineral fertilizer in 1998.

Impact of cultivation strategies and regional climate on greenhouse gas emissions from grass/clover silage

Abstract More than half the annual dry matter intake (DMI) of feed by dairy cows can be roughage. Its production and storage constitute a significant part of the life cycle greenhouse gas (GHG) emissions from milk production. This study estimated and analysed the impact of grass/clover silage production practices in five climatically different dairy production regions in Sweden on emitted GHG. GHG emissions calculated by the life cycle assessment method were 0.46–0.54 and 0.48–0.63 kg carbon dioxide equivalents per kg silage DMI for normal and higher silage nutrient quality, respectively. Crop cultivation for higher nutrient quality through an extra cut and increased nitrogen fertilisation rates increased GHG emissions by up to 16%. Varying the yield level by +/–20% decreased (11%)/increased (15%) GHG emissions per kg DMI. Improved management practices can reduce GHG emissions feed production, but accurate estimates of yield levels and feed losses are needed to reduce uncertainties.

Responses in dairy cows to increased inclusion of wheat in maize and grass silage based diets

Abstract The effects of including wheat in the total mixed rations of dairy cows were evaluated using a 4×4 Latin square dose response experiment with 28 dairy cows (Swedish red). The animals were averaging 150 days in milk at the start of the experiment. Diets consisted of mixtures of maize and grass silage with wheat grain at four levels (8, 16, 24 and 32% of dry matter (DM)). The animals consumed 17.8, 19.7, 21.1 and 23.8 kg of DM and produced 28.1, 29.1 29.6 and 30.2 kg of energy corrected milk, respectively. Digestibility of DM and neutral detergent fibre (NDF) was determined using indigestible NDF (iNDF) as a marker. DM digestibility, feed intake and milk and protein yields increased with increasing wheat content while the milk fat concentration, the digestibility of NDF and the feed efficiency of the diets decreased.

Protein efficiency in intensive dairy production: A Swedish example

BACKGROUND Animal agriculture has been criticised in terms of its sustainability from several perspectives. Ruminants such as dairy cows can transform inedible, low-quality protein in roughage and by-products from the food industry into the high-quality protein found in milk and meat. Evaluation of the protein conversion efficiency of dairy production from a sustainability and resource perspective must be based on the proportion of the animal feed edible to humans. A relevant metric is thus edible feed protein conversion ratio (eFPCR), i.e. human-edible protein output in cows milk per unit human-edible protein input in feed. In this study, eFPCR was calculated for five regionally adapted and realistic feed rations fed to Swedish dairy cows producing different annual milk yields typical for high-yielding, intensive dairy production. RESULTS All scenarios except one showed a protein efficiency ratio of >1 for human-edible protein. Thus, depending on the composition of their diet, most Swedish dairy cows can convert human-inedible protein into edible, high-value protein. However, higher milk yield led to a decrease in eFPCR, regardless of diet. CONCLUSION Dairy cows in high-yielding, intensive production systems such as those used in Sweden have the capacity to convert low-value inedible protein into high-value edible protein. However, a minor part of the dairy cow diet is edible for humans and this fraction must be minimised to justify dairy production. These results are in line with previous findings on protein conversion efficiency and add scientific input to the debate on sustainable food systems and sustainable diets.

Prediction of nutritive values, morphology and agronomic characteristics in forage maize using two applications of NIRS spectrometry

ABSTRACT This study evaluates nutritive, morphological and agronomic characteristics of forage maize predicted by using a high-quality near-infrared (NIR) spectrometer and an NIR hyperspectral-imaging technique using partial least squares (PLS) regression models. The study includes 132 samples of dried milled whole-plant homogenates of forage maize with variation in maturity, representing two growing seasons, three locations in Sweden and three commercial maize hybrids. The samples were measured by a classical sample cup NIR spectrometer and by a pushbroom hyperspectral-imaging instrument. The spectra and a number of variables (crude protein, CP, neutral detergent fibre, starch, water soluble carbohydrates (WSC) and organic matter digestibility), morphological variables (leaves, stems & ears) and crop yield were used to make PLS calibration models. Using PLS modelling allowed the determination of how well maize variables can be predicted from NIR spectra and a comparison of the two types of instruments. Most examined variables could be determined equally well, by both instruments, but the pushbroom technique gave slightly better predictions and had higher analytical capacity. Predictions of CP, starch, WSC and the proportions of ears in the maize gave robust. The findings open new possibilities to further utilise the technology in plant breeding, crop management, modelling and forage evaluation.

Effects of morphological fractions on estimated milk yields in forage maize depending on growing site and plant maturity

Abstract This study was undertaken to determine the effects of the morphological fractions of forage maize for milk production as predicted by the spread sheet model called MILK 2006. The plants were harvested at increasing maturities at three different sites in Sweden and separated into stems, leaves, kernels and cobs. Chemical and in vitro analyses of the plant fractions as specified in the MILK 2006 model for predicting estimated milk yields Milk Mg−1 dry matter (DM) and Milk ha−1 were undertaken. Partial least squares regression analysis was used to evaluate the impact of the proportions and qualities of the fractions on Milk Mg−1 DM and Milk ha−1. Estimated milk yields could not be predicted based on the proportions of the fractions and their nutritional values. The most important parameters for determining Milk ha−1 was the DM yield, and for the estimated Milk Mg−1 were the concentrations of starch and the fibre digestibility of the whole crop.