Search

Addition of fats to the diets of ruminants has long been known to result in a reduction in enteric methane emissions. Tannins have also been used to reduce methane emissions but with mixed success. However, the effect of feeding fat in combination with tannin is unknown. Eight ruminally cannulated Holstein-Friesian cows were fed four diets in a double Latin-square, full crossover sequence. The treatments were 800 ml/day of water (CON), 800 g/day of cottonseed oil, 400 g/day of tannin, and 800 g/day of cottonseed oil and 400 g/day of tannin in combination (fat- and tannin-supplemented diet). Methane emissions were measured using open-circuit respiration chambers. Intake of basal diets was not different between treatments. Cows fed cottonseed oil had greater milk yield (34.9 kg/day) than those fed CON (32.3 kg/day), but the reduced concentration of milk fat meant there was no difference in energy-corrected milk between treatments. Methane yield was reduced when either cottonseed oil (14%) or tannin (11%) was added directly to the rumen, and their effect was additive when given in combination (20% reduction). The mechanism of the anti-methanogenic effect remains unclear but both fat and tannin appear to cause a reduction in fermentation in general rather than cause a change in the type of fermentation. [ABSTRACT FROM AUTHOR]

• Challenging learning environments demand improved pedagogical practices. • Learner-centred interactive pedagogy promotes students' active engagement in learning. • Dialogic teaching is one pedagogical response to Eritrea's learner-centred interactive pedagogy policy. • The seeds of interactive teaching methods are clouded by teacher-led instruction. • Changes in pedagogical approaches stimulate teacher professional development. Learner-centred interactive pedagogy (LCIP) emphasises skills, such as enquiring, analysing, evaluating, problem-solving and critical thinking which require students to interact and participate in classroom discourses by drawing on their own experiences. This study focuses on the manifestations LCIP in promoting teacher-student classroom interaction in Eritrean secondary classrooms and explores the seeds of dialogic interaction in fostering LCIP. In 2003, the Ministry of Education in Eritrea (MoE) reformed the traditional learning approaches and developed new pedagogical practices guided by LCIP. In response to the educational reform, various learning strategies including group- and pair work activities, generating open questions, student presentation and some features of dialogue have been employed by teachers to develop LCIP in classrooms, although little research has explored how teachers implement LCIP in practice. The research reported here is based on twelve video-recorded lessons from secondary schools in two regions of Eritrea. The lessons were analysed to explore the different forms of interaction present in Eritrean classrooms. Despite teachers' effort in practicing LCIP, the findings suggest that teachers have still continued with more conventional teaching. Nevertheless, the findings also reveal the presence and potential of dialogic moments indicating the value of developing LCIP with dialogic interaction through more and active student involvement to enhance classroom interaction. The findings suggest that knowledge of LCIP and dialogic interaction support experience of learning in Eritrea and are an important means to invigorate teacher education and professional development programs for improving the quality of education. [ABSTRACT FROM AUTHOR]

Highlights • This study outlines the value of reflective sketchbooks as a forum for fostering different forms of reflection. • The importance of vicarious reflection is highlighted in this study. • this study suggests a broader conceptualization of dialogic space drawing on the material mediation of reflective practices. • This study highlights that value of combining the sensuous and cognive as part of reflective practice. Abstract This study addresses the crucial relationship between theory and practice as a key feature of professional learning in initial teacher education. The context for the study is an EU-funded intensive programme drawing on different dimensions of insideness and outsideness and arts-based pedagogies in response to the diversity of education today. The data for the study comes from self-selected pages from preservice teacher participants' reflective sketchbooks. As a methodological approach that unifies the sensuous and cognitive this study suggests that reflective sketchbooks document the dialogic encounters of students whilst also providing a material space that can itself become a form of dialogic space for critical reflection. The main findings of the study outline critical ways in which preservice teachers transform theoretical inputs into individual expressions as well as conceptualise theory in relation to lived experience. [ABSTRACT FROM AUTHOR]

Background IL-13 has an important role in atopic dermatitis (AD) pathogenesis. Tralokinumab is a fully human mAb that potently and specifically neutralizes IL-13. Objective We sought to evaluate the efficacy and safety of tralokinumab in adults with moderate-to-severe AD. Methods In this phase 2b study (NCT02347176), 204 adults were randomized 1:1:1:1 to receive 45, 150, or 300 mg of subcutaneous tralokinumab, or placebo, every 2 weeks for 12 weeks with concomitant topical glucocorticoids. Coprimary end points were change from baseline in Eczema Area Severity Index score and percentage of participants with an Investigator's Global Assessment response (0/1 score and reduction of ≥2 grades from baseline) at week 12. Results At week 12, 300 mg of tralokinumab significantly improved change from baseline in Eczema Area Severity Index score versus placebo (adjusted mean difference, −4.94; 95% CI, −8.76 to −1.13; P =.01), and a greater percentage of participants achieved an Investigator's Global Assessment response (26.7% vs 11.8%). Greater responses were found in participants with greater concentrations of biomarkers of increased IL-13 activity. Participants treated with 300 mg of tralokinumab demonstrated improvements in SCORAD, Dermatology Life Quality Index, and pruritus numeric rating scale (7-day mean) scores versus placebo. Upper respiratory tract infection was the most frequent treatment-emergent adverse event reported as related to study drug in the placebo (3.9%) and pooled tralokinumab (3.9%) groups. Conclusions Tralokinumab treatment was associated with early and sustained improvements in AD symptoms and an acceptable safety and tolerability profile, thereby providing evidence for targeting IL-13 in patients with AD. [ABSTRACT FROM AUTHOR]

Wheat is the most common concentrate fed to dairy cows in Australia, but few studies have examined the effects of wheat feeding on enteric methane emissions, and no studies have compared the relative potencies of wheat, corn, and barley for their effects on enteric methane production. In this 35-d experiment, 32 Holstein dairy cows were offered 1 of 4 diets: a corn diet (CRN) of 10.0 kg of dry matter (DM)/d of single-rolled corn grain, 1.8 kg of DM/d of canola meal, 0.2 kg of DM/d of minerals, and 11.0 kg of DM/d of chopped alfalfa hay; a wheat diet (WHT) similar to the CRN diet but with the corn replaced by single-rolled wheat; a barley diet (SRB) similar to the CRN diet but with the corn replaced by single-rolled barley; and a barley diet (DRB) similar to the CRN diet but with the corn replaced by double-rolled barley. Individual cow feed intakes, milk yields, and milk compositions were measured daily but reported for the last 5 d of the experiment. During the last 5 d of the experiment, individual cow methane emissions were measured using the SF6 tracer technique for all cows, and ruminal fluid pH was continuously measured by intraruminal sensors for 3 cows in each treatment group. The average DM intake of cows offered the CRN, WHT, SRB, and DRB diets was 22.2, 21.1, 22.6, and 22.6 kg/d. The mean energycorrected milk of cows fed the WHT diet was less than that of cows fed the other diets. This occurred because the milk fat percentage of cows fed the WHT diet was significantly less than that of cows fed the other diets. The mean methane emissions and methane yields of cows fed the WHT diet were also significantly less than those of cows fed the other diets. Indeed, the CRN, SRB, and DRB diets were associated with 49, 73, and 78% greater methane emissions, respectively, compared with the emissions from the WHT diet. Methane yield was found to be most strongly related to the minimum daily ruminal fluid pH. This study showed that although the inclusion of wheat in the diet of dairy cows could be an effective strategy for substantially reducing their methane emissions, it also reduced their milk fat percentage and production of milk fat and energy-corrected milk. [ABSTRACT FROM AUTHOR]

Variation in the composition of microorganisms in the rumen (the rumen microbiome) of dairy cattle (Bos taurus) is of great interest because of possible links to methane emission levels. Feed additives are one method being investigated to reduce enteric methane production by dairy cattle. Here we report the effect of 2 methanemitigating feed additives (grapemarc and a combination of lipids and tannin) on rumen microbiome profiles of Holstein dairy cattle. We used untargeted (shotgun) massively parallel sequencing of microbes present in rumen fluid to generate quantitative rumen microbiome profiles. We observed large effects of the feed additives on the rumen microbiome profiles using multiple approaches, including linear mixed modeling, hierarchical clustering, and metagenomic predictions. The effect on the fecal microbiome profiles was not detectable using hierarchical clustering, but was significant in the linear mixed model and when metagenomic predictions were used, suggesting a more subtle effect of the diets on the lower gastrointestinal microbiome. A differential representation analysis (analogous to differential expression in RNA sequencing) showed significant overlap in the contigs (which are genome fragments representing different microorganism species) that were differentially represented between experiments. These similarities suggest that, despite the different additives used, the 2 diets assessed in this investigation altered the microbiomes of the samples in similar ways. Contigs that were differentially represented in both experiments were tested for associations with methane production in an independent set of animals. These animals were not treated with a methane-mitigating diet, but did show substantial natural variation in methane emission levels. The contigs that were significantly differentially represented in response to both dietary additives showed a significant enrichment for associations with methane production. This suggests that these methane-mitigating diets have altered the rumen microbiome toward naturally low methane-emitting microbial profiles. The contig sequences are predominantly new and include Faecalibacterium spp. The contigs we have identified here are potential biomarkers for low-methane-emitting cattle. [ABSTRACT FROM AUTHOR]

This study examined effects on milk yield and composition, milk fatty acid concentrations and methane (CH4) emissions when dairy cows were offered diets containing different amounts of algal meal. The algal meal contained 20% docosahexaenoic acid (DHA) and cows were offered either 0, 125, 250, or 375 g/cow per d of algal meal corresponding to 0, 25, 50, or 75 g of DHA/cow per d. Thirty-two Holstein cows in mid lactation were allocated to 4 treatment groups, and cows in all groups were individually offered 5.9 kg of dry matter (DM) per day of concentrates [683 g/kg of cracked wheat (Triticum aestivum), 250 g/kg of cold-pressed canola, 46 g/kg of granulated dried molasses, and 21 g/kg of mineral mix] and ad libitum alfalfa (Medicago sativa) hay. The algal meal supplement was added to the concentrate allowance and was fed during the morning and afternoon milking, whereas the alfalfa hay was fed individually in pens. Cows were gradually introduced to their diets over 7 d and then fed their treatment diets for a further 16 d. Dry matter intake and milk yield were measured daily, and milk composition was measured on a sample representative of the daily milk yield on Thursday of each week. For the last 2 d of the experiment, cows were individually housed in respiration chambers to allow measurement of CH4 emissions. Dry matter intake, milk yield and milk composition were also measured while cows were in the respiration chambers. Cows ate all their offered concentrates, but measured intake of alfalfa decreased with increasing dose of DHA by 16.2, 16.4, 15.1, and 14.3 kg of DM/d, respectively. Milk yield (22.6, 23.5, 22.6, and 22.6 kg/ cow per d) was not affected by DHA dose, but milk fat concentrations (49.7, 37.8, 37.0, and 38.3 g/kg) and, consequently, milk fat yields (1.08, 0.90, 0.83, and 0.85 kg/d) decreased with addition of DHA. The feeding of algal meal high in DHA was associated with substantial increases in the concentrations of DHA (0.04, 0.36, 0.60, and 0.91 g/100 g of milk fatty acids) and conjugated linoleic acid C18:2 cis-9,trans-11 (0.36, 1.09, 1.79, and 1.87 g/100 g of milk fatty acids). Addition of DHA did not affect total emissions of CH4 (543, 563, 553, and 520 g/cow per d), nor emissions in terms of milk production (24.9, 22.1, 24.3, and 23.4 g of CH4/kg of milk), but emissions were increased with respect to total intake (22.6, 23.5, 24.5, and 24.4 g of CH4/kg of DM). These findings indicate that CH4 emissions were not reduced when dairy cows were fed a forage-based diet supplemented with DHA from algal meal. [ABSTRACT FROM AUTHOR]

Abstract: Quantitative assessment of pancreatic insulin secretion rate in individuals may help advance our understanding and treatment of diabetes. We describe for the first time the application of a long-established numerical deconvolution procedure in which a prescribed input function is used to represent first-phase pancreatic secretion response to an intravenous glucose challenge (intravenous glucose tolerance test [IVGTT]) in individual subjects. We identify that C-peptide secretory response to an IVGTT can be described by a basal secretion rate (S b) (picomoles per liter per minute) and a first-phase secretory response characterized by a Gaussian function. The Gaussian function contains 3 parameters: P 1 (picomoles per liter per minute), which represents the peak rate secretion; P 2 (per square minute), which is related to the inverse of peak width at half-peak height; and P 3 (minutes), which is the time of the peak secretion rate. When applied to data from 8 healthy Chinese subjects, the estimated parameter values (mean ± SD) were 19.2 ± 12.9 pmol L−1 min−1, 1548 ± 1143 pmol L−1 min−1, 1.09 ± 1.21 min−2, and 2.94 ± 1.13 minutes for S b, P 1, P 2, and P 3, respectively. The Gaussian input functions are shown to have similar shapes and to be highly concordant in magnitude with secretory responses estimated by means of the method of Eaton et al (1980) and by the ISEC computer program. In conclusion, we have presented a simple, integrated, validated, and easily implemented method suitable for quantifying pancreatic C-peptide and insulin secretion in individual human subjects. The superiority of our method in comparison with other methods is that it uses as an input function the Gaussian, which has been experimentally verified as describing in vivo the profile of pulsatile insulin secretion. The particular strength of our method is that the Gaussian parameters and simple indices derived from them provide a standardized and interpretable means for carrying out comparative investigations aimed at quantifying how pancreatic secretory responses to an IVGTT differ in various demographic groups or in response to therapeutic treatments. [Copyright &y& Elsevier]

Previously observed relationships between dietary composition and production of a small number of individual milk fatty acids were the motivation to examine whether equations could be developed to predict production of all the major individual milk fatty acids. Such equations could be incorporated into ration formulation programs and used to examine factors that influence milk fat composition. Data from 29 published experiments on Holstein cows that provided 120 dietary treatments were entered into CPM-Dairy to obtain estimates of amounts of individual long-chain fatty acids (LCFA) absorbed from the intestines. These derived data and other dietary and animal data including the reported fatty acid composition of milk fat were entered into a spreadsheet. Descriptors of diet included daily intake of dry matter, total fermentable carbohydrate, total fatty acids, and profile of dietary fatty acids, intake of neutral detergent fiber, supplemental fish-oil, buffer, and magnesium oxide. Cow data included body weight and days in milk/DIM). Multiple linear regression was used to develop equations to predict the production (g/d) of each of 26 major LCFA. The equations developed generally had R² values in excess of 0.5. Production (g/d) of total de novo fatty acids (C4:0 to C15:0) (PTdenovo/was found to be positively related to the intake of fermentable carbohydrate, and negatively related to the intake of fish oil fatty acids and the estimated total amount of unsaturated fatty acids absorbed from the intestines. The PTdenovo was greater in pasture-fed cows than total mixed ration-fed cows and was negatively related to the square root of DIM. Production of each individual de novo fatty acid was described by a fixed proportion of PTdenovo. These proportions were 0.12 ± 0.006 (C4:0), 0.083 ± 0.0039 (C6:0), 0.0516 ± 0.0025 (C8:0), 0.111 ± 0.003 (C10:0), 0.134 ± 0.0037 (C12:0), 0.441 ± 0.007 (C14:0), 0.046 ± 0.0024 (C14:1), and 0.0432 ± 0.0017 (C15:0). Separate independent equations were developed to describe the daily production of C16:0, C16:1, and the main individual preformed fatty acids (>C16). The productions of each of the main individual preformed fatty acids were generally strongly related to the corresponding estimated amount (g/d) of specific fatty acids absorbed from the intestines. Percentage estimates for the direct transfer of the major absorbed LCFA to their corresponding LCFA in milk were 42% (C16:0); 9.5% (C18:0); 47.5% (cis-9 C18:1); 16.1% (all isomers of trans-C18:1), 38% (cis-9, cis-12 C18:2); and 31% (cis-9, cis-12, cis15 C18:3). High dietary intake of fish oil fatty acids was negatively associated with the production of all of the major individual preformed fatty acids with the exception of C20:5 and C22:6. In some instances, particular dietary factors were found to have positive influences on production of one fatty acid and negative influences on another. For example, high levels of dietary magnesium oxide were positively associated with production of C17 fatty acids but negatively associated with production of C18:0 and cis-9, trans-11 C18:2 (conjugated linoleic acid). This analysis quantified effects of major dietary and cow factors on production of individual fatty acids in milk. [ABSTRACT FROM AUTHOR]

Previous investigations into ruminal lipolysis of triacylglycerol and ruminal biohydrogenation (BH) of unsaturated long-chain fatty acids have generally quantified these processes with either zero-order or first-order kinetics. This investigation examined if Michaelis-Menten and other nonlinear kinetics might be useful for quantifying these processes. Data from 2 previously published in vitro experiments employing rumen fluid from sheep to investigate the lipolysis of trilinolein, the BH of cis-9, cis-12 linoleic acid (LA), and the BH of fatty acids derived from the lipolysis of trilinolein were used for the development of a multi-compartmental model. The model described the lipolysis of triacylglycerol well. The model also provided a good mathematical description of the resulting production of nonesterified fatty acids, the isomerization of nonesterified LA, and subsequent production of rumenic acid (RA), vaccenic acid (VA), and stearic acid (SA). However, the model described poorly the patterns of the concentrations of LA, RA, VA, and SA after incubation of trilinolein in rumen fluid. The model is consistent with known stoichiometry and biochemistry and is parsimonious in that it employs a minimal number of parameters to describe all of the major aspects of lipolysis and BH. The first step in the lipolysis of trilinolein was described by Michaelis-Menten kinetics (Vmax = 529 ± 16 mg/L per h; Km= 698 ± 41 mg/L). Both subsequent lipolysis steps were approximated by a first-order (linear kinetics) rate constant (k = 2.64 ± 0.041/h). Isomerization of LA to RA was modeled by simple Michaelis-Menten kinetics (Vmax = 2,421 ± 83 mg/L per h; Km = 440 ± 22 mg/L). The kinetics of the BH of RA to VA was described by a Michaelis-Menten-type process involving competitive inhibition by VA (Vmax = 492 ± 6.5 mg/L per h; Km = 1 mg/L). The final step, the BH of VA to SA, was modeled by a quasi-first-order process (k = 0.533 ± 0.021/h), but as the concentration of VA increased, its BH appeared to be self-inhibited such that when the concentration of VA acid exceeded 517 ± 10.4 mg/L, BH was completely inhibited. The major new insights and benefits afforded by this model are 1) lipolysis and BH are described by nonlinear kinetics; 2) high concentrations of VA appear to inhibit its own BH; and 3) BH of RA appears to proceed at a much greater rate when triglyceride is present in the incubation medium. This model provides a conceptual framework for researching ruminal lipolysis and BH. [ABSTRACT FROM AUTHOR]

Data from 29 published experiments on Holstein cows, providing 120 dietary treatments, were collated to obtain means, standard deviations, and ranges for the concentrations (mg/g) of 26 major individual fatty acids in bovine milk fat. The influence of diet type (total mixed ration- vs. pasture-based diet) on concentrations of individual fatty acids was examined. Pairwise correlations for concentrations (g/kg) of individual fatty acids in milk showed that almost all of the individual de novo fatty acids were significantly correlated with each other and with the total concentration of de novo fatty acids. Concentrations of individual unsaturated preformed fatty acids were generally positively correlated with each other but were negatively correlated with concentrations of total de novo fatty acids. Substantial variation was found in the concentrations of individual milk fatty acids and, apart from those synthesized de novo, concentrations of individual fatty acids did not vary in concert. The adequacy of literature data for the development of a model to predict the production of the major individual fatty acids in milk is discussed. The limitations associated with the currently available studies that may be used in a predictive model are 1) failure of many publications to adequately describe dietary details, 2) reporting poorly defined milk fatty acids, 3) aggregating a number of closely related fatty acids under a single category, and 4) the selective reporting of only those fatty acids that are present in milk fat in appreciable quantities. Despite these limitations, the data are sufficient to enable development of a model to predict the concentrations and production of major individual fatty acids in milk fat. The extreme variability in concentrations of individual milk fatty acids and the complex matrix of positive and negative correlations among the concentrations of many individual fatty acids suggest that separate equations will be needed to predict the production of each individual milk fatty acid. [ABSTRACT FROM AUTHOR]

Introduction: A new nonradiographic craniofacial imaging technique is described and evaluated. The Sydney diagnostic system (SDS) image is formed from a standardized lateral head digital photograph and a standardized digital photograph of the study models. The SDS image was designed for orthodontic diagnosis and treatment planning without a lateral cephalogram. Methods: Measurements from the composite facial and study model images of 35 randomly selected patients were compared with the same measurements from cephalograms to assess their validity and reliability. The measurements involved soft-tissue profile landmarks, landmarks on the ear, and hard-tissue landmarks identified on the study models including Point A, Point B, and dental landmarks. Results and Conclusions: The new imaging technique is reliable and valid for orthodontic treatment planning when compared with a lateral cephalogram if the inherent distortion between images is considered. Most soft-tissue measurements were more reliable than hard-tissue measurements, but some soft-tissue landmarks were less reliable. The ear was a reliable soft-tissue landmark. Maxillary incisor edge was the most reliable hard-tissue landmark, and neither Point A nor Point B could reliably be found on the study model images. [Copyright &y& Elsevier]

Recently, a fat sub-model was introduced into the Cornell-Penn-Miner Dairy model (CPM-Dairy; Moate et al., 2004). The principal aim of the work reported here was to validate this fat sub-model in terms of its accuracy in predicting the apparent absorption (intake -- feces) of total long-chain fatty acids (LCFA) in lactating dairy cows. The fat sub-model in CPM-Dairy was used to predict the amounts (g/d) of total LCFA apparently absorbed from 63 diets described in 14 published experiments. These predicted amounts (PLCFA) were regressed against the amounts reported to be apparently absorbed (RLCFA). The regression equation was: PLCFA = -24.8 ± 25.2 + 1.011 x 0.029 x RLCFA; R² = 0.95, RMSE = 55.2 g/d. The results show that for a diverse range of diets, the fat model in CPM-Dairy can accurately predict apparent absorption of dietary total LCFA. [ABSTRACT FROM AUTHOR]

This experiment investigated the metabolic response of dairy cows undergoing an extended lactation to a frequently sampled intravenous glucose tolerance test. The experiment used 12 multiparous Holstein cows that calved in late winter in a seasonally calving pasture-based system and were managed for a 670-d lactation by delaying rebreeding. In each of four 5-wk experimental periods commencing at approximately 73, 217, 422, and 520 (±9.1) days in milk (DIM), cows were offered a diet of perennial ryegrass (73 and 422 DIM) or pasture hay and silage (217 and 520 DIM) supplemented with 1 kg of DM grain (control; CON) or 6 kg of DM grain (GRN) as a ration. Daily energy intake was approximately 160 and 215 MJ of metabolizable energy/cow for the CON and GRN treatments, respectively. At all other times, cows were managed as a single herd and grazed pasture supplemented with grain to an estimated minimum daily total intake of 180 MJ of metabolizable energy/cow. Cows were fitted with an indwelling jugular catheter during the final week of each experimental period. The standard intravenous glucose tolerance test using 0.3 g of glucose per kilogram of body weight was performed on each cow at approximately 100, 250, 460, and 560 DIM. Plasma concentrations of glucose, insulin, and nonesterified fatty acids (NEFA) responses were measured. Milk yield, milk solids yield, body weight, and basal plasma glucose were greater in the GRN compared with the CON treatment. The area under the plasma response curve relative to baseline (AUC) for glucose, insulin, and NEFA and their apparent fractional clearance rates indicated varied whole body responsiveness to insulin in terms of glucose metabolism throughout the 670-d lactation. The glucose AUC 0 to 20 min postinfusion was increased at 560 DIM, indicating reduced utilization of glucose by the mammary gland at this stage of lactation. The NEFA clearance rate, 6 to 30 min postinfusion, was greater at 460 and 560 DIM. These data indicated an increase in lipogenic activity or a decrease in lipolysis as lactation progressed, suggestive of an overall increase in responsiveness to insulin in terms of whole body lipid metabolism as lactation progressed. These observations are consistent with decreased priority of lactation beyond 300 DIM. Cows in the GRN treatment had decreased whole body responsiveness to hyperglycemia compared with CON cows in terms of glucose clearance and AUC for the glucose response. Variation in the response curves of plasma glucose, NEFA, and insulin was predominantly a result of stage of lactation and not diet. This may be due to changes in mammary gland uptake of glucose that is independent of insulin and the responsiveness of peripheral tissues to the actions of insulin at different stages of the lactation that are independent of diet. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined the effect of a reduction in the dietary cation-anion difference before calving and increase calcium intake after calving on the incidence of periparturient hypocalcaemia and milk production in pasture-based dairy cows. Materials and methods; Results; Discussion; Conclusions.

Compares a range of dietary cation-anion difference (DCAD) on a perennial ryegrass and pasture hay diet before calving. Method used to alter the DCAD; Measurement of blood and urine parameters and mineral concentrations and urine hydroxyproline; Result of the addition of anions to the diet to produce a negative DCAD.

Determines the effects of altering the dietary cation-anion difference (DCAD) of a perennial ryegrass and cereal grain diet of dairy cows. Effects on milk production, acid-base balance and blood and urine parameters of dairy cows in early lactation; Effect of a range of DCAD on urine; Factor attributed to the lack of a significant difference in milk yields.

Effective pasture supplementation is critical to the efficiency of resource management in milk production. We understand a great deal about ruminal and metabolic processes in dairy cattle that control efficiency but we need to improve our ability to predict effects of practical feeding strategies based on the basic biological processes of the cow. Therefore, a large-scale pasture supplementation study was used to explore the details of both practical management and the underlying biological principles and processes involved. This included a multiple lactation study coupled with shorter-term experiments that tested the type and rate of supplementation. Basal supplementation strategies were (1) pasture allowance [14 kg of dry matter (DM)/d per cow] supplemented with milled barley grain fed twice daily in the milking parlor and pasture silage provided in the paddock; the ratio of grain:forage fed as supplement was 0.75:0.25 (control; DM basis); (2) the same pasture allowance plus the same amounts of milled barley grain and pasture silage, but the supplements were mixed and chopped before being fed immediately after each milking; and (3) the same pasture allowance and offered a partial mixed ration comprising barley (25%) and corn grain (30% of DM), corn silage (20% of DM), and alfalfa hay (25% of DM) after each milking. In late lactation (227 d in milk), a short-term experiment was done feeding the same pasture allowances but with the 3 supplements offered at 6, 8, 10, and 12 kg of DM/d for an 11-d measurement period following adaptation to the diet to each of the 3 long-term supplementation groups. Production responses were recorded and ruminal volatile fatty acids (VFA) and pH were measured in a subset of animals. Model descriptions of yields of milk and milk constituents as well as mean concentrations of ruminal fluid VFA and ruminal fluid pH were compared with measured values resulting when dairy cows were fed 12 different pasture-based diets with different levels and types of dietary supplement. Inputs into the model were measured dry matter intake and feed composition on the 12 combined treatments as well as initial body weight and composition. The model described milk and milk component production within 1 standard deviation of the treatment means (less than 5% of the mean as measured in the root mean square error). The simulated proportions of ruminal acetate, propionate, and butyrate were consistent with observed effects of supplemental treatments and rate of supplementation; however, the error analysis showed room for improvement. The model described, to a general extent, the changes in ruminal pH; however, this investigation showed that the equations that describe ruminal pH need to be improved or modified. These results show that the fundamental knowledge of ruminal and organ metabolism in this mechanistic model is sufficient to describe the qualitative responses to complicated dietary strategies, but our quantitative understanding of the parameters involved such as degradation and absorption kinetics and ruminal pH still demands more specific research. [ABSTRACT FROM AUTHOR]

The objective of this study was to compare 2 commonly used techniques for measuring methane emissions from ruminant animals: the GreenFeed (GF) system and the sulfur hexafluoride (SF6) technique. The study was part of a larger experiment in which a methane inhibitor, 3-nitrooxypropanol, fed at 4 application rates (0, 40, 60, and 80 mg/kg of feed dry matter) decreased enteric methane emission by an average of 30% (measured by both GF and SF6) in a 12-wk experiment with 48 lactating Holstein cows fed a total mixed ration. The larger experiment used a randomized block design and was conducted in 2 phases (February to May, phase 1, and June to August, phase 2), with 2 sets of 24 cows in each phase. Using both GF and SF6 techniques, methane emission data were collected simultaneously during experimental wk 2, 6, and 12 (phase 1) and 2, 9, and 12 (phase 2), which corresponded to a total of 6 sampling periods. During each sampling period, 8 spot samples of gas emissions (staggered over a 3-d period) were collected from each cow using GF, as well as 3 × 24-h collections using the SF6 technique. Methane emission data were averaged per cow for the statistical analysis. The mean methane emission was 373 (standard deviation = 96.3) and 405 (standard deviation = 156) g/ cow per day for GF and SF6, respectively. Coefficients of variation for the 2 methods were 25.8 and 38.6%, respectively; correlation and concordance between the 2 methods were 0.40 and 0.34, respectively. The difference in methane emission between the 2 methods (SF6 - GF) within treatment was from 46 to 144 and 24 to 27 g/d for phases 1 and 2, respectively. In the conditions of this experiment, the SF6 technique produced larger variability in methane emissions than the GF method. The overall difference between the 2 methods was on average about 8%, but was not consistent over time, likely influenced by barn ventilation and background methane and SF6 concentrations. [ABSTRACT FROM AUTHOR]

Effects of different strategies for feeding supplements to grazing dairy cows on the composition and coagulation properties of milk and the subsequent yield and quality of Cheddar cheese were measured. The experiment used milk from 72 Holstein-Friesian cows, averaging 45 d in milk, fed according to 1 of 3 feeding strategies: (1) cows grazed a restricted allowance of perennial ryegrass pasture [approximately 14 kg of dry matter (DM)/cow per day, to ground level] supplemented with milled wheat grain fed in the milking parlor and alfalfa hay offered in the paddock (control); (2) same pasture and allowance as control, supplemented with a formulated grain mix containing wheat grain, corn grain, and canola meal fed in the parlor and alfalfa hay fed in the paddock (FGM); or (3) same pasture and allowance as control, supplemented with a partial mixed ration comprising the same formulated grain mix but mixed with alfalfa hay and presented on a feed pad after each milking (PMR). For all strategies, supplements provided the same metabolizable energy and grain:forage ratio (78:22, DM basis). Within each feeding strategy, milk was sampled from cows receiving either 8 or 16 kg (DM) of supplement/cow per day. There were 2 replicated groups of 6 cows per supplement amount per dietary strategy; approximately 250 L of milk was sampled from each for analyses of composition and coagulation properties and the manufacture of Cheddar cheese. The experiment had a 14-d adaptation period and a 14-d measurement period. For cows fed according to the control strategy, those fed 16 kg/cow per day produced milk with lower concentrations of milk fat than cows fed 8 kg/cow per day. This effect was not observed for cows fed according to the FGM and PMR strategies. Milk from cows fed 16 kg of DM/cow per day according to the control strategy yielded less Cheddar cheese than milk from cows fed according to the PMR strategy, with cheese yields from FGM cows being intermediate. Amount of supplement offered had minor effects on percentages of some fatty acids. We observed few other effects of feeding strategy on milk composition, types of milk protein, milk coagulation properties, or the composition and quality of the resultant Cheddar cheese. These data show that, compared with the traditional control strategy, feeding PMR or FGM may increase milk fat concentration and the subsequent yield of Cheddar cheese without compromising cheese composition or quality. [ABSTRACT FROM AUTHOR]

An experiment was conducted to quantify the changes in energy partitioning resulting from grain supplementation in herbage-fed dairy cows at 4 stages during a 670-d lactation. The experiment used 16 lactating Holstein-Friesian cows, with a control and a grain treatment being randomly allocated to 8 cows each. During 4 measurement periods (each of 4 d in a metabolism stall and 3 d in an indirect calorimeter) beginning at approximately 110, 270, 450, and 560 d in milk (DIM), the energy balance of each cow was measured. Cows in both groups were individually offered freshly cut ryegrass pasture (Lolium hybridum L.) in periods 1 and 3 and ryegrass pasture silage and alfalfa (Medicago sativa L.) hay in periods 2 and 4. In all periods, cows in the grain group were offered an additional 4.4 to 5.0 kg of dry matter of cereal grain/cow per day. Adding grain to the diet increased yields of fat and protein and tended to increase yields of milk and lactose, but did not affect milk composition. Gross energy intake (GEI) declined as lactation progressed. Adding grain to the diet decreased the percentage of GEI in feces and urine, but the extent of these reductions did not change as lactation progressed. Adding grain to the diet similarly reduced the percentage of GEI lost to heat, but again the extent of the reduction remained similar as lactation progressed. The magnitude of the increase in milk energy resulting from grain supplementation did not change with advancing lactation, but tissue energy retention was greater in the first 300 DIM compared with after 300 DIM. For herbage-based diets, CH4 emissions ranged from 6.2 to 7.6% of GEI, which corresponds to 24.0 to 25.8 g of CH4/kg of dry matter intake. For diets supplemented with cereal grains, CH4 emissions ranged from 6.3 to 7.3% of GEI, which corresponds to 21.6 to 25.2 g of CH4/kg of dry matter intake. It was concluded that, for cows producing <24 kg of milk/d and consuming herbage-based diets supplemented with grain, the efficiency of utilizing the additional energy in the grain, as measured by the loss of energy in heat, and its partitioning to milk, did not change as lactation progressed from 110 to 560 DIM. [ABSTRACT FROM AUTHOR]

Predictable release of sulphur hexafluoride (SF6) tracer gas from permeation tubes into the reticulo-rumen is necessary to estimate methane emissions from ruminants using the SF6 tracer technique. Any discrepancy between the laboratory determined rate of SF6 release from permeation tubes and the actual rate of release in the reticulo-rumen would bias calculated methane emissions. The purpose of this investigation was to determine the effect of temperature, submersion and orientation on the rate of SF6 release from permeation tubes. Four experiments were undertaken. Experiment 1 determined that release of SF6 increased by 2.5±0.14% per degree Celsius increase in temperature between 37 and 41°C (P<0.001). Experiment 2 determined that the Arrhenius equation can be used to describe the temperature dependence of SF6 release rate from permeation tubes between 0 and 70°C, consistent with a change in release rate of 2.3±0.08% per degree Celsius change in temperature. Experiment 3 determined that submersion of permeation tubes in water did not affect the rate of SF6 release (P=0.13). Experiment 4 determined that SF6 release rate was not influenced by permeation tube orientation (P=0.42). In addition we determined the activation energy of permeation, Ep, describing the overall temperature dependence of SF6 permeation flux from permeation tubes, to be 18,424±680J/mol. This research implies that the short-term release rate of SF6 from permeation tubes within the reticulo-rumen will vary in response to temperature change due to animal, diet and/or environmental factors. A short term decrease in temperature of reticulo-rumen contents, induced by drinking cold water, is expected to have a larger influence on the accuracy of estimated methane emission derived from time-averaged sampling periods less than 24h. Use of the SF6 technique to detect differences in enteric methane emissions due to diet or between animal species may be confounded by diet or genetic effects on body temperature. Unless the effect of temperature is managed through careful implementation of the technique, substantial errors could be caused as illustrated by the following example: a +2°C error in calibration temperature (41°C), and a -2°C discrepancy between the actual (37°C) and assumed reticulo-rumen temperature (39°C), could bias estimated methane emissions by approximately +10%. [ABSTRACT FROM AUTHOR]