Enteric methane emission and digestion in dairy cows fed wheat or molasses.

The aim of this experiment was to measure enteric methane (CH4) emission and its relation with rumen digestion in dairy cows fed diets rich in 1 of the 2 carbohydrate sources, starch or sugar. The rations were based on late first-cut grass-clover silage supplemented with wheat (Wh), NaOH-treated wheat (Wh+NaOH), sugar beet molasses (Mo), or sugar beet molasses with addition of sodium bicarbonate (Mo+Bic). Wheat and molasses made up 35% of dry matter in the 2 diets with molasses and wheat, respectively. Four cows fitted with ruminal, duodenal, and ileal canulae were used in a 4 × 4 Latin square design. Nutrient digestibility was measured using chromium oxide and titanium oxide as flow markers, and emissions of CH4 and hydrogen were measured via open-circuit indirect calorimetry on 4 consecutive days. Data were analyzed using PROC MIXED of SAS (version 9.4; SAS Institute Inc., Cary, NC) with treatment and period as fixed effects and cow as random effect. Furthermore, orthogonal contrasts were calculated. The cows produced 32.5, 33.6, 36.2, and 35.1 L of CH4/kg of dry matter intake (DMI) on diets Wh, Wh+NaOH, Mo, and Mo+Bic, respectively. The emission of CH4 per day, per kilogram of DMI, and per kilogram of energy-corrected milk as well as daily hydrogen emission were higher on the Mo diet compared with the Wh diet. With the present inclusion of wheat and molasses in the diet, no effects of NaOH treatment of wheat or of sodium bicarbonate supplementation to the Mo diet could be demonstrated on CH4 emission expressed per kilogram of DMI or per kilogram of energy-corrected milk. The duodenal flow of starch was higher when wheat was treated with NaOH. Under the conditions in the present experiment, ruminal NDF digestibility was not affected by carbohydrate source, NaOH treatment of wheat, or bicarbonate supplementation. Total volatile fatty acid concentration in the rumen and the proportions of acetate and propionate were not affected by carbohydrate source, NaOH treatment of wheat, or bicarbonate supplementation. Likewise, we could not show any influence of diet on microbial protein synthesis or efficiency of microbial protein synthesis expressed as grams of microbial protein synthesis per kilogram of true rumen-digested organic matter. We concluded that CH4 emission was increased when wheat was replaced by molasses, whereas no effect of manipulating rumen fermentation by NaOH treatment of wheat or addition of bicarbonate to molasses could be found with a level of approximately 25% of dry matter from starch and sugar, respectively.

Initiating transitional care for adolescents with cystic fibrosis at the age of 12 is both feasible and promising.

AIM: Adolescence is a vulnerable period in cystic fibrosis, associated with declining lung function. This study described, implemented and evaluated a transition programme for adolescents. METHODS: We conducted a single centre, nonrandomised and noncontrolled prospective programme at the cystic fibrosis centre at Copenhagen University Hospital Rigshospitalet from 2010 to 2011, assessing patients aged 12-18 at baseline and after 12 months. Changes implemented included staff training on communication, a more youth-friendly feel to the outpatient clinic, the introduction of youth consultations partly alone with the adolescent, and a parents' evening focusing on cystic fibrosis in adolescence. Lung function and body mass index (BMI) were measured monthly and adolescents were assessed for their readiness for transition and quality of life at baseline and 12 months. RESULTS: We found that 40 (98%) of the eligible patients participated and youth consultations were successfully implemented with no dropouts. The readiness checklist score increased significantly over the one-year study period, indicating increased readiness for transfer and self-care. Overall quality of life, lung function and BMI remained stable during the study period. CONCLUSION: A well-structured transition programme for cystic fibrosis patients as young as 12 years of age proved to be both feasible and sustainable.

Effect of dietary nitrate level on enteric methane production, hydrogen emission, rumen fermentation, and nutrient digestibility in dairy cows.

Nitrate may lower methane production in ruminants by competing with methanogenesis for available hydrogen in the rumen. This study evaluated the effect of 4 levels of dietary nitrate addition on enteric methane production, hydrogen emission, feed intake, rumen fermentation, nutrient digestibility, microbial protein synthesis, and blood methemoglobin. In a 4×4 Latin square design 4 lactating Danish Holstein dairy cows fitted with rumen, duodenal, and ileal cannulas were assigned to 4 calcium ammonium nitrate addition levels: control, low, medium, and high [0, 5.3, 13.6, and 21.1g of nitrate/kg of dry matter (DM), respectively]. Diets were made isonitrogenous by replacing urea. Cows were fed ad libitum and, after a 6-d period of gradual introduction of nitrate, adapted to the corn-silage-based total mixed ration (forage:concentrate ratio 50:50 on DM basis) for 16d before sampling. Digesta content from duodenum, ileum, and feces, and rumen liquid were collected, after which methane production and hydrogen emissions were measured in respiration chambers. Methane production [L/kg of dry matter intake (DMI)] linearly decreased with increasing nitrate concentrations compared with the control, corresponding to a reduction of 6, 13, and 23% for the low, medium, and high diets, respectively. Methane production was lowered with apparent efficiencies (measured methane reduction relative to potential methane reduction) of 82.3, 71.9, and 79.4% for the low, medium, and high diets, respectively. Addition of nitrate increased hydrogen emissions (L/kg of DMI) quadratically by a factor of 2.5, 3.4, and 3.0 (as L/kg of DMI) for the low, medium, and high diets, respectively, compared with the control. Blood methemoglobin levels and nitrate concentrations in milk and urine increased with increasing nitrate intake, but did not constitute a threat for animal health and human food safety. Microbial crude protein synthesis and efficiency were unaffected. Total volatile fatty acid concentration and molar proportions of acetate, butyrate, and propionate were unaffected, whereas molar proportions of formate increased. Milk yield, milk composition, DMI and digestibility of DM, organic matter, crude protein, and neutral detergent fiber in rumen, small intestine, hindgut, and total tract were unaffected by addition of nitrate. In conclusion, nitrate lowered methane production linearly with minor effects on rumen fermentation and no effects on nutrient digestibility.

Dietary Nitrate for Methane Mitigation Leads to Nitrous Oxide Emissions from Dairy Cows.

Nitrate supplements to cattle diets can reduce enteric CH emissions. However, if NO metabolism stimulates NO emissions, the effectiveness of dietary NO for CH mitigation will be reduced. We quantified NO emissions as part of a dairy cow feeding experiment in which urea was substituted in nearly iso-N diets with 0, 5, 14 or 21 g NO kg dry matter (DM). The feeding experiment was a Latin square with repetition of Period 1. Each period lasted 4 wk, with CH emission measurements in Week 4 using respiration chambers. During Period 3, NO concentrations in chamber outlet air were monitored semicontinuously during 48 h. High, but fluctuating, NO concentrations were seen at the two highest NO levels (up to between 2 and 5 µL L), and dynamics were linked with recent feed intake. In Periods 4 and 5, NO concentrations and feed intake were determined from all four respiration chambers during two 7-h periods. Emissions of NO coincided with feed intake, again with NO concentrations in the microliter per liter range at the two highest NO intake levels. Neither feed nor excretion of NO via urine were significant sources of NO, indicating that emissions came from the animals. Leakages due to rumen fistulation could also not account for NO emissions. The possibility that NO is produced in the oral cavity is discussed. Nitrous oxide emission factors ranged between 0.7 and 1.0% except in one case at 21 g NO kg DM, where it was 3.4%. When accounting for NO emissions at the highest NO intake level, the overall GHG mitigation effect in two different animal-diet combinations changed from -47 to -40%, and from -19 to -17%, respectively, due to NO emissions.

Methane production and digestion of different physical forms of rapeseed as fat supplements in dairy cows.

The purpose of this experiment was to study the effect of the physical form of rapeseed fat on methane (CH4) mitigation properties, feed digestion, and rumen fermentation. Four lactating ruminal-, duodenal-, and ileal-cannulated Danish Holstein dairy cows (143 d in milk, milk yield of 34.3 kg) were submitted to a 4×4 Latin square design with 4 rations: 1 control with rapeseed meal (low-fat, CON) and 3 fat-supplemented rations with either rapeseed cake (RSC), whole cracked rapeseed (WCR), or rapeseed oil (RSO). Dietary fat concentrations were 3.5 in CON, 5.5 in RSC, 6.2 in WCR, and 6.5% in RSO. The amount of fat-free rapeseed was kept constant for all rations. The forage consisted of corn silage and grass silage and the forage to concentrate ratio was 50:50 on a dry matter basis. Diurnal samples of duodenal and ileal digesta and feces were compiled. The methane production was measured for 4 d in open-circuit respiration chambers. Additional fat reduced the CH4 production per kilogram of dry matter intake and as a proportion of the gross energy intake by 11 and 14%, respectively. Neither the total tract nor the rumen digestibility of organic matter (OM) or neutral detergent fiber were significantly affected by the treatment. Relating the CH4 production to the total-tract digested OM showed a tendency to decrease CH4 per kilogram of digested OM for fat-supplemented rations versus CON. The acetate to propionate ratio was not affected for RSC and WCR but was increased for RSO compared with CON. The rumen ammonia concentration was not affected by the ration. The milk and energy-corrected milk yields were unaffected by the fat supplementation. In conclusion, rapeseed is an appropriate fat source to reduce the enteric CH4 production without affecting neutral detergent fiber digestion or milk production. The physical form of fat did not influence the CH4-reducing effect of rapeseed fat. However, differences in the volatile fatty acid pattern indicate that different mechanisms may be involved.

Technical note: test of a low-cost and animal-friendly system for measuring methane emissions from dairy cows.

Methane is a greenhouse gas with a significant anthropogenic contribution from cattle production. A demand exists for techniques that facilitate evaluation of mitigation strategies for dairy cows. Therefore, a low-cost system facilitating the highest possible animal welfare was constructed and validated. The system uses the same principles as systems for open-circuit indirect calorimetry, but to lower the costs, the chamber construction and air-conditioning system were simpler than described for other open-circuit systems. To secure the highest possible animal welfare, the system is located in the cow's daily environment. The system consists of 4 transparent polycarbonate chambers placed in a square so that the cows are facing each other. The chamber dimensions are 183 (width), 382 (length), and 245 cm (height) with a volume of 17 m(3). Flow and concentrations of O(2), CO(2), CH(4), and H(2) are measured continuously in the outlet. Flow is measured with a mass flow meter, O(2) with a paramagnetic sensor, CO(2) and CH(4) with infrared sensors, and H(2) with an electrochemical sensor. Chamber inlet is placed in the barn and background concentrations may differ between chambers, but delta values between background and outlet concentrations for all chambers were within instrument tolerance. Average recovery rates of CO(2) and CH(4) were (mean ± SD) 101 ± 4 and 99 ± 7%, respectively. This is within the expected tolerance of the whole system (gas sensors and flow meters). Feed dry matter intakes were not affected by confining the animals in chambers, as dry matter intake before and during chamber stay were similar. It was concluded that the system delivers reliable values, and the transparent construction in combination with the location in the barn environment prevent negative impact on animal welfare and, thereby, data quality.

Methane production and diurnal variation measured in dairy cows and predicted from fermentation pattern and nutrient or carbon flow.

Many feeding trials have been conducted to quantify enteric methane (CH(4)) production in ruminants. Although a relationship between diet composition, rumen fermentation and CH(4) production is generally accepted, the efforts to quantify this relationship within the same experiment remain scarce. In the present study, a data set was compiled from the results of three intensive respiration chamber trials with lactating rumen and intestinal fistulated Holstein cows, including measurements of rumen and intestinal digestion, rumen fermentation parameters and CH(4) production. Two approaches were used to calculate CH(4) from observations: (1) a rumen organic matter (OM) balance was derived from OM intake and duodenal organic matter flow (DOM) distinguishing various nutrients and (2) a rumen carbon balance was derived from carbon intake and duodenal carbon flow (DCARB). Duodenal flow was corrected for endogenous matter, and contribution of fermentation in the large intestine was accounted for. Hydrogen (H(2)) arising from fermentation was calculated using the fermentation pattern measured in rumen fluid. CH(4) was calculated from H(2) production corrected for H(2) use with biohydrogenation of fatty acids. The DOM model overestimated CH(4)/kg dry matter intake (DMI) by 6.1% (R(2)=0.36) and the DCARB model underestimated CH(4)/kg DMI by 0.4% (R(2)=0.43). A stepwise regression of the difference between measured and calculated daily CH(4) production was conducted to examine explanations for the deviance. Dietary carbohydrate composition and rumen carbohydrate digestion were the main sources of inaccuracies for both models. Furthermore, differences were related to rumen ammonia concentration with the DOM model and to rumen pH and dietary fat with the DCARB model. Adding these parameters to the models and performing a multiple regression against observed daily CH(4) production resulted in R 2 of 0.66 and 0.72 for DOM and DCARB models, respectively. The diurnal pattern of CH(4) production followed that of rumen volatile fatty acid (VFA) concentration and the CH(4) to CO(2) production ratio, but was inverse to rumen pH and the rumen hydrogen balance calculated from 4×(acetate+butyrate)/2×(propionate+valerate). In conclusion, the amount of feed fermented was the most important factor determining variations in CH(4) production between animals, diets and during the day. Interactions between feed components, VFA absorption rates and variation between animals seemed to be factors that were complicating the accurate prediction of CH(4). Using a ruminal carbon balance appeared to predict CH(4) production just as well as calculations based on rumen digestion of individual nutrients.