Grass Pellets Research Articles

Enteric methane emissions and nitrogen utilisation efficiency for two genotype of hill hoggets offered fresh, ensiled and pelleted ryegrass

Thirty-six 12-month-old hill hoggets were used in a 2 genotype (18 Scottish Blackface vs. 18 Swaledale×Scottish Blackface)×3 diet (fresh vs. ensiled vs. pelleted ryegrass) factorial design experiment to evaluate the effects of hogget genotype and forage type on enteric methane (CH4) emissions and nitrogen (N) utilisation. The hoggets were offered 3 diets ad libitum with no concentrate supplementation in a single period study with 6 hoggets for each of the 6 genotype×diet combinations (n=6). Fresh ryegrass was harvested daily in the morning. Pelleted ryegrass was sourced from a commercial supplier (Aylescott Driers & Feeds, Burrington, UK) and the ryegrass silage was ensiled with Ecosyl (Lactobacillus plantarum, Volac International Limited, Hertfordshire, UK) as an additive. The hoggets were housed in individual pens for at least 14 d before being transferred to individual respiration chambers for a further 4 d with feed intake, faeces and urine outputs and CH4 emissions measured. There was no significant interaction between genotype and forage type on any parameter evaluated. Sheep offered pelleted grass had greater feed intake (e.g. DM, energy and N) but less energy and nutrient apparent digestibility (e.g. DM, N and neutral detergent fibre (NDF)) than those given fresh grass or grass silage (P<0.001). Feeding pelleted grass, rather than fresh grass or grass silage, reduced enteric CH4 emissions as a proportion of DM intake and gross energy (GE) intake (P<0.01). Sheep offered fresh grass had a significantly lower acid detergent fibre (ADF) apparent digestibility, and CH4 energy output (CH4-E) as a proportion of GE intake than those offered grass silage (P<0.001). There was no significant difference, in CH4 emission rate or N utilisation efficiency when compared between Scottish Blackface and Swaledale × Scottish Blackface. Linear and multiple regression techniques were used to develop relationships between CH4 emissions or N excretion and dietary and animal variables using data from sheep offered fresh ryegrass and grass silage. The equation relating CH4-E (MJ/d) to GE intake (GEI, MJ/d), energy apparent digestibility (DE/GE) and metabolisability (ME/GE) resulted in a high r2 (CH4-E=0.074 GEI+9.2 DE/GE−10.2 ME/GE−0.37, r2=0.93). N intake (NI) was the best predictor for manure N excretion (Manure N=0.66 NI+0.96, r2=0.85). The use of these relationships can potentially improve the precision and decrease the uncertainty in predicting CH4 emissions and N excretion for sheep production systems managed under the current feeding conditions.

Biological implications of longevity in dairy cows: 1. Changes in feed intake, feeding behavior, and digestion with age

Milk production strategies focusing on longevity and limited use of concentrate are receiving increasing attention. To evaluate such strategies, knowledge of the development with age of animal characteristics, particularly digestion, is indispensable. We therefore investigated the development of feed intake, chewing activity, and digestion in 30 lactating Brown Swiss cows (876–3,648 d old) and 12 heifers (199–778 d old). We also studied whether age effects were exhibited differently in animals selected from herds subjected for 11 yr either to a forage-only or to a forage-concentrate feeding regimen. Forages consisted of grass hay (the only feed for heifers), corn silage, and grass pellets. Measurements lasted for 8 d, where amounts and composition of feeds, feces, and milk were recorded and analyzed. Ruminal pH data and eating and rumination activity were assessed by pH sensors put into the rumen and halter-mounted noseband sensors. The mean retention time of feed particles was assessed using Cr-mordanted fiber and data were used to calculate dry matter gut fill. Data were subjected to regression analyses with age and feeding regimen as explanatory variables, and body weight, milk yield, and proportion of hay in forage as covariates. This allowed separating age-related changes of body weight and milk yield from independent age effects and correcting for differences in preference for individual forages. In cows, organic matter intake increased with age (from slightly below to above 20kg/d), as did mean retention time and gut fill. Digestibility of organic matter did not show a clear age dependency, but fiber digestibility had a maximum in cows of around 4 to 6 yr of age. Ruminal pH and absolute eating and rumination times did not vary with cow age. Young and old cows chewed regurgitated boluses more intensively (60–70 times) than middle-aged cows (about 50 times). Effects of feeding regimen were small, except for fiber intake and rumination time per unit of intake, owing to the different fiber content of the diets. No significant interactions between age and feeding regimen were found. Heifers spent more time eating and ruminating per unit of feed than cows, which resulted in a high fiber digestibility. Irrespective of the feeding regimen tested, older cows maintained intake and digestion efficiency with longer retention times and chewing rumination boluses more intensively. The results support efforts to extend the length of productive life in dairy cows.

Biological implications of longevity in dairy cows: 2. Changes in methane emissions and efficiency with age

Previous studies indicated that absolute CH4 emissions and CH4 yield might increase and that milk production efficiency might decrease with age in cattle. Both would make strategies to increase longevity in dairy cattle less attractive. These aspects were experimentally determined in Brown Swiss cattle distributed continuously across a large age range. Thirty lactating dairy cows (876–3,648 d of age) received diets consisting of hay, corn silage, and grass pellets supplemented with 0 or 5kg of concentrate per day. Twelve heifers (199–778 d of age) received hay only. Cows and heifers were members of herds subjected to the 2 different feeding regimens (with or without concentrate) for the past 10 yr. Methane emissions were measured individually for 2 d in open-circuit respiration chambers, followed by quantifying individual feed intake and milk yield over 8 d. Additional data on digestibility, rumination time, and passage time of feed of all experimental animals were available. Regression analyses were applied to evaluate effects of age and feeding regimen. Body weight, milk yield, and the hay proportion of forage dry matter intake were considered as covariates. Methane emissions per unit of intake, body weight, and milk yield were significantly related to age. Their development in the cows with age was characterized by an increase to maximum at around 2,000 d of age, followed by a decline. This response was not accompanied by corresponding age-related changes in intake, chewing activity, digesta passage time, and digestibility of organic matter, which would have explained shifts in CH4. However, fiber digestibility showed a similar change with age as methane emissions, resulting in quite stable methane emissions per unit of digestible fiber. As expected, methane emissions intensity per unit of milk produced was greater by 8% without concentrate than with concentrate, but no difference was noted in the response to age when the animals were subjected to different feeding regimens. The efficiency of milk production was only marginally influenced by age and diet, and no different response was observed for age in the 2 dietary regimens. In conclusion, life cycle analyses of milk production systems focusing on longevity should consider changing methane yields with age in addition to the variation in environmental costs for replacements of culled cows.

Accumulation of polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls in livers of young sheep

A major part of sheep livers contains levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) above the former but to some extent also the new maximum levels (MLs) in the EU. In order to investigate the relationship between the intake of these contaminants and their accumulation in livers, kidney fat and meat, young blackhead sheep were fed with grass pellets containing PCDD/Fs at 2.5 times the maximum level. Levels of PCDD/Fs in livers were already quite high at the start of the exposure but increased 3-fold within 56d, exceeding the new product based MLs. Levels in meat and fat also increased but did not exceed the MLs. Although less elevated in the grass, both dl- and ndl-PCB levels also increased in liver and fat. Their kinetics in the tissues was less clear, potentially caused by increased levels in the straw given to the sheep during the whole experimental period.There was a clear difference in the behavior of the various congeners, the PCDFs and especially the higher chlorinated PCDFs and PCDDs showing a higher accumulation in the liver. In the case of the PCBs, this was particularly true for PCB 126.When switched to clean grass after 56d, the levels in livers and other tissues decreased to about the levels in the control sheep within 56d. This offers a potential solution for decreasing the intake of consumers.

Characterization of Emissions from Grass Pellet Combustion

Emission factors of pollutants from combustion of five different types of grass pellets with ash content ranging from 3% to 13% were measured and compared to a premium type wood pellet with ash content 0.6% at low and high loads, respectively. The effects of fuel properties on the grass pellet combustion emissions were also studied. Criteria pollutants including PM2.5, NOx, SO2, and CO were continuously monitored using an EPA CTM-039 dilution sampling system. PM10 emissions from grass combustion were found to be higher when compared to wood pellet emissions at both low and high loads (26–40 and 36–60 mg MJ–1, respectively). The PM2.5 emissions were strongly correlated to the ash content of the fuel (R2 = 0.939). CO emissions were found to be higher for grass combustion indicating an incomplete combustion. PM2.5 samples collected on Teflon and quartz substrates were analyzed for ions and trace elements. About 60–75% of the PM2.5 fraction was recovered that included K of about 20–30%, sulfate about 16–25%, and chloride of about 10–15%. Semivolatile organic compounds collected on quartz and polyurethane foam (PUF) were also analyzed for molecular markers, PAHs and PCDD/Fs. PAH emissions were strongly correlated to the CO (r2 = 0.80). The PCDD/F emissions were clearly a function of chlorine content of the fuel (r2 = 0.98). A strong correlation exists between emitted levoglucosan and PM2.5 indicating levoglucosan, a molecular marker for cellulose combustion (r2 = 0.87). All of the emissions were found to be higher for grass pellets compared to wood pellets and are higher at high loads than at low loads.

Residential-Scale Biomass Boiler Emissions and Efficiency Characterization for Several Fuels

Detailed particulate and gaseous emission characterizations were conducted on six commercially available residential-scale wood pellet boilers. The objective of the study was to define emission factors for these six different appliances burning wood pellets, grass pellets, and a blend of grass pellets and corn as fuels under low and high loads. Continuous monitoring of criteria pollutants, including PM2.5, NOx, SO2, and CO, was conducted using an EPA CTM-039 dilution sampling system. The PM10 emissions with wood as the fuel ranged between 14 and 17 mg/MJ and between 16 and 21 mg/MJ at low and high loads, respectively. The PM10 emissions from grass were found to be higher for all of the appliances compared to wood pellets at both low and high loads (28–33 and 37–44 mg/MJ, respectively). CO emissions, an indication of combustion efficiency, were found to be higher for the grass pellets, indicating less complete combustion. NOx and SO2 emissions were also higher for grass and grass/corn blends, attributable to the higher fuel N and S. PM samples collected on Teflon and quartz substrates were analyzed for ions and trace elements. Semi-volatile organic compounds collected on quartz and polyurethane foam (PUF) plugs were also analyzed. Levoglucosan, a molecular marker for wood combustion, was the predominant organic compound found in the grass combustion PM2.5 and ranged between 6 and 100 μg/MJ for grass and between 9 and 130 μg/MJ for wood. Polycyclic aromatic hydrocarbon (PAH) emissions were relatively higher for grass combustion ranging from 10 to 700 μg/MJ than for wood combustion ranging from about 5 to 200 μg/MJ. Dioxin and dibenzofuran emissions were found to be substantially higher for grass pellet emissions compared to wood pellet emissions at both high and low loads for all of the appliances.

An experimental study of combustion and emissions of biomass pellets in a prototype pellet furnace

This study presents combustion and emission results obtained using a prototype pellet furnace with 7–32kW capacity (designed for burning high ash content pellet fuels) for four biomass pellets: one grass pellet and three wood pellets. Fuel property, gas emissions and furnace efficiency are compared. In regard to fuel properties, proximate analysis, ultimate analysis and heating values are determined and emissions of carbon monoxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), nitrogen oxides (NOx) and sulfur dioxide (SO2) are measured and compared. Scanning electron microscopy (SEM) was used for ash analysis. No ash agglomeration was observed and ash discharge was in the form of powder instead of lumped particles, which are usually observed for high ash biomass fuel. The results suggest that grass pellets can successfully be combusted with similar performance and emissions to that of other wood pellets if burned in appropriate combustion installations.

Grass pellet Quality Index: A tool to evaluate suitability of grass pellets for small scale combustion systems

US renewable fuels policy strongly encourages biomass crop production, which should lead to expansion of biomass heating scenarios. Chemical composition of grass biomass can be extremely variable, depending on species, soil fertility, and harvest management. Biomass quality concerns have hindered the development of grass biomass for residential combustion, with no comprehensive evaluation system for grass pellet quality. Quality labeling will strengthen the fledgling grass biomass heating market, gain consumer confidence, and help to control combustion related emissions. The proposed system sums qualitatively different parameters into one Quality Index for relative evaluation and ranking of grass pellets for residential combustion potential. Parameters were selected and weighted for their relative importance based on available literature. Weighting was accomplished by adjusting the compositional working range for each parameter. A limit also was established for each parameter, beyond which the pellet lot was considered as unacceptable for residential combustion, regardless of the total Quality Index score. The model structure allows for effective evaluation and ranking of grass pellet lots regardless of the specific values ultimately chosen for acceptable limits and working ranges by the industry. Applying the Quality Index to a range of grass pellet types resulted in a reasonable ranking of pellets based on physical characteristics and composition.

Kinetics of switch grass pellet thermal decomposition under inert and oxidizing atmospheres

Grass pellets are a renewable resource that have energy content similar to that of wood. However, the higher ash and chlorine content affects combustion. Thermal degradation analysis of a fuel is useful in developing effective combustion. Thermogravimetric analysis (TGA) of the thermal degradation of grass pellets under inert (nitrogen) and oxidizing (air) atmospheres was conducted. Non-isothermal conditions were employed with 4 different heating rates. Kinetic parameters (activation energy and pre-exponential factors) were estimated using the iso-conversional method. Both pyrolysis and oxidative atmospheric thermal degradation exhibited two major loss process: volatilization of cellulose, hemicelluloses and lignin and burning or slow oxidation of the residual char. The activation energy and pre-exponential factors were high for the oxidizing environment. During pyrolysis, major decomposition occurred with 40% to 75% conversion of the mass to gas with an activation energy of 314kJ/mol. In air the decomposition occurred with 30% to 55% conversion with an activation energy of 556kJ/mol. There was a substantial effect of heating rate on mass loss and mass loss rate. The TG shifted to higher temperature ranges on increasing the heating rate. In both pyrolyzing and oxidizing conditions, average combustion and devolatilization rates increased. Enhanced combustion takes place with higher activation energy in oxidizing atmosphere compared to the inert atmosphere due to presence of air.

Influence of Maternal Nutrient Restriction during the Period of Embryonic and Maximal Placental Growth on Organ Development in the Adult Sheep

Objective: It is apparent that maternal under nutrition at specific period during pregnancy has differential effects on placental and fetal development, such that the resulting offspring is programmed to be at risk of disease in later life. The study investigated the influence of restricted maternal nutrition during the period of embryonic and maximal placental growth (i.e. 0 &ndash; 95 days gestation; term &asymp;147 days) on the developmental and programming of mitochondrial voltage dependent anion channel (VDAC) and cytochrome c in the lung of the resulting ovine adult. Materials and Methods: Singleton bearing ewes were nutrient restricted between 0 and 95 days of pregnancy and lung weight, the abundance of VDAC and cytochrome c were determined in the resulting adult at 3 years of age, using immunoblotting. Nutrient restricted ewes were fed 50% of their metabolisable energy (ME) requirements (4.0 MJ/day), and diet consisted of 250g hay/day and 210g/day of dried grass pellets (2.2 MJ/day). All diets contained adequate amount of vitamins and minerals. Results: Maternal nutrient restriction had no effect on lung weight, protein and total mitochondrial protein; but caused a significant reduction (P&lt;0.05) in VDAC and cytochrome c abundance. Kidney weight was not affected but cytochrome c abundance was significantly (P&lt;0.05) down regulated. Liver weight was significantly (P&lt;0.05) reduced by nutrient restriction, but no effect on VDAC and cytochrome c abundance. Conclusion: Although maternal nutrient restriction over the period of embryonic and maximal placental growth has no effect on lung weight, it reduces the production of mitochondrial VDAC and cytochrome c at 3 years of age and this may affect the adaptation of the adult sheep.Key words: Maternal, nutrient restriction, pregnancy, placenta, organ, development, Sheep

Effects of dam breed and dietary source of n-3 polyunsaturated fatty acids on the growth and carcass characteristics of lambs sourced from hill sheep flocks

The objectives of this study were to investigate the effect of dietary lipid source on the growth and carcass characteristics of lambs sourced from a range of crossbred hill ewes. Over a 2-year period, 466 lambs representing the progeny of Scottish Blackface (BF × BF), Swaledale (SW) × BF, North Country Cheviot (CH) × BF, Lleyn (LL) × BF and Texel (T) × BF ewes were sourced from six commercial hill flocks and finished on one of four diets: grass pellets (GP), cereal-based concentrate (CC), CC enriched with oilseed rape (CR) and CC enriched with fish oil (CF). Dry matter intake (DMI) was highest (P < 0.001) in lambs offered GP; however, carcass weight gain (CWG) and feed conversion efficiency were higher (P < 0.001) in lambs fed concentrate-based diets. For lambs offered concentrate-based diets, DMI and live weight gain were lower (P < 0.001) for CF than CC or CR. Lambs with T × BF dams achieved a higher (P < 0.05) daily CWG and CWG/kg DMI than BF × BF, SW × BF or LL × BF dams. When lambs were slaughtered at fat score 3, CH × BF, LL × BF and T × BF dams increased carcass weight by 0.8 to 1.4 kg (P < 0.001) and conformation score (CS) by 0.2 to 0.4 units (P < 0.001) compared with BF × BF or SW × BF dams. However, breed effects on carcass conformation were reduced by 50% when lambs were slaughtered at a constant carcass weight. Diets CC and CR increased carcass weight by 0.8 to 1.6 kg (P < 0.001) and CS by 0.1 to 0.3 units (P < 0.001) compared with GP and CF. Both, dam breed and dietary effects on carcass conformation were associated with an increase (P < 0.001) in shoulder width of the lambs. Lambs fed CF and slaughtered at a constant carcass weight had more subcutaneous fat over the Longissumusdorsi (P < 0.05), Iliocostalisthoracis (P < 0.001) and Obliquus internusabdominis (P < 0.001) compared with those fed CC. However, these effects were removed when lambs were slaughtered at a constant fat score. At both endpoints, lambs from T × BF dams contained less (P < 0.05) perinephric and retroperitoneal fat than SW × BF or LL × BF dams fed GP or CC, respectively. The results from this study show that using crossbred ewes sired by CH, LL or T sires will increase carcass weight and improve carcass conformation of lambs sourced from hill flocks. Inclusion of oilseed rape in lamb finishing diets had only minor effects on performance compared with a standard CC but feeding fish oil or GP impacted negatively on lamb growth and carcass quality.

Effects of genotype and plane of nutrition on growth and carcass characteristics of lambs from hill sheep systems

The objective of this study was to determine the effect of lamb genotype and plane of nutrition on post-weaning lamb growth, and carcass characteristics in hill sheep systems. The lamb genotypes compared were as follows: purebred Scottish Blackface, Swaledale × Scottish Blackface, Cheviot × Scottish Blackface, Lleyn × Scottish Blackface and Texel × Scottish Blackface lambs. During the finishing period, lambs were allocated to a (i) low plane of nutrition (LP), based on a fixed allowance of dried grass pellets representing a grass-based system; (ii) high plane of nutrition (HP-cereal), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate offered ad libitum; (iii) high plane of nutrition (HP-cereal/oil), with a diet consisting proportionately of 0.20 dried grass pellets : 0.80 cereal-based concentrate containing oilseed rape offered ad libitum. There were significant genotype × diet interactions for dry matter (DM) intake (P < 0.001), live weight gain (P < 0.05) and carcass gain (P < 0.05). On the LP diet, carcass gains were higher for Texel cross compared to Blackface and Swaledale cross lambs (P < 0.05). On both HP diets, carcass gains were lower in Blackface and Swaledale crosses compared with the Cheviot, Lleyn and Texel cross lambs (P < 0.01). Feed conversion efficiency, expressed in terms of carcass gain per unit of DM, was highest for Texel cross and Cheviot cross, lowest in Swaledale cross and Blackface and intermediate for Lleyn cross lambs (P < 0.001). Conformation classification was lowest for Swaledale cross (P < 0.05) and highest for Texel cross lambs (P < 0.001), whilst those of Blackface, Cheviot and Lleyn cross lambs were similar. Carcasses from Blackface and Lleyn cross lambs had higher fat classifications than Texel and Cheviot cross lambs (P < 0.01). Feed conversion efficiency was lowest with the LP diet compared with the HP diets, resulting in a 5-week longer finishing period and lower carcass weights, fat scores, dressing proportions and subcutaneous fat depth measurements. These results indicate that crossbreeding can have a major effect on lamb performance in the hill sheep sector. Feeding a HP increased lamb growth rates, particularly for high growth-potential genotypes, improved feed efficiency, shortened the finishing period but increased carcass fatness. Including oilseed rape in concentrate-based diets did not affect performance.

Changes in food intake and circulating leptin due to gastrointestinal parasitism in lambs of two breeds1

A reduction in food intake is a prominent feature of many infectious diseases. However, the underlying mechanisms of parasite-induced anorexia in sheep are poorly understood. Here, we tested the hypotheses (a) that the degree of parasite-induced anorexia in lambs is influenced by their growth potential and (b) that nematode infection results in elevated plasma leptin concentration in lambs. The hypotheses were tested with Suffolk x Greyface (S) and Scottish Black-face (B) lambs that are known to differ in their growth potential (S lambs are of greater growth potential than B lambs). During a primary parasite infection, 24 out of 48 lambs per breed were trickle-infected with 7,000 infective Teladorsagia circumcincta larvae per day, 3 d/wk, for a period of 12 wk (experiment I). The lambs were then dewormed, and after a 2-wk interval, half of the 24 lambs per breed that were previously infected were reinfected for another 12 wk with the same parasite and dose as used in the primary infection (experiment II). In both experiments, infected lambs were fed grass pellets for ad libitum intake, whereas noninfected lambs were fed grass pellets for either ad libitum or restricted intakes. The S lambs were more susceptible than B lambs to nematode infection, as judged from the differences in fecal egg counts (P = 0.007). Parasitized lambs of the more susceptible breed (S) showed anorexia [i.e., a decrease in intake of 13% compared with uninfected controls (P = 0.01)], whereas no significant reduction in food intake was observed in lambs of the more resistant breed (B). Reexposure to nematode infection of previously infected animals tended to result in renewed anorexia in S lambs but not in B lambs (P = 0.08) in a similar extent as during primary infection. Plasma leptin concentrations did not differ between ad libitum-fed infected and control lambs but were greater in infected than in noninfected lambs at a similar level of food intake during both the primary (P = 0.02) and the secondary parasitic infection (P = 0.004) in both breeds. The results show that leptin may be involved in the response of lambs to infection but that it is unlikely that leptin alone is responsible for the parasite-induced anorexia in lambs.

High quality biofuel pellet production from pre-compacted low density raw materials

In this study, pre-compaction was evaluated as a method to enhance stable reed canary grass pellet production. An experimental design of the factors raw material moisture content, steam addition, raw material bulk density, and die temperature was used to find production conditions for high quality pellets by multiple linear regression modelling of responses. Response variables being modelled were variability of pelletizer current (as a measurement of uneven production), pellet bulk density, and pellet durability. By pre-compacting the raw material from a bulk density of 150 kg/m3 to 270kg/m3, continuous production could be obtained at minimum raw material moisture content of 13.8%. Bulk density and durability were both highly correlated to raw material moisture content, but showed different optima. Multiple response optimization was used to target process settings for production of high quality reed canary grass pellets with bulk density >650kg/m3 and durability >97.5%.

Effects of toasting blue lupins, soybeans or barley as supplement for high-yielding, organic dairy cows fed grass-clover silage ad libitum

The effect of toasted supplement on milk production was examined in three experiments on an organic study farm during the winter 2004/2005. Three types of iso-energetic supplement feed, toasted or untreated, were examined in each experiment, with an untreated cereal mixture as control. The supplement under investigation was: lupins in experiment 1, barley in experiment 2 and soybeans in experiment 3. The same forage mixture of grass-clover silage (84% of DM), grass pellets (11% of DM) and straw (5% of DM) was fed ad libitum in all the experiments.Toasting decreased effective rumen protein degradability determined in situ for all three supplements. Compared to untreated lupins toasting of lupins tended (P=0.10) to increase milk yield, whereas toasting of soybeans did not affect milk yield. Toasting of lupins decreased (P=0.03) milk protein content (32.2 versus 32.7 g/kg), whereas toasting of soybeans did not affect milk protein content. ECM yield was significantly higher (P=0.002) for cows fed toasted soybeans than for cows fed untreated soybeans (28.1 versus 26.4 kg ECM) whereas there was no significant effect on ECM yield from toasting lupins or barley. It can be concluded that the potential of toasting to increase the supply of metabolisable protein under organic feeding conditions is variable between feeds.

Prototyping of Organic Dairy Production Systems Self-sufficient with Feed—Consequences on Productivity, Economy and Nutrient Balance

ABSTRACTIn 2005, it became obligatory to feed all organic dairy cows in the EU 100% organically. To create a better understanding of the possible effects this would have on the whole farming system, six production strategies were formulated and the effects on productivity, economy and nutrient balance were analysed. The strategies differed with respect to type of concentrated feed, level of fresh grass-clover in the ration and length of the calving interval. It was found that supplementation with cereals, rapeseeds/cereals or grass pellets as well as increased level of grazing gave very similar productivities and financial results, but supplementation with rapeseed cakes reduced crop production and the financial result. On the assumption of a positive effect on milk yield persistency and feed intake per cow, prolonged calving interval had a positive effect on the productivity and the financial result of the organic dairy farm. Due to lower inputs a self-sufficient system offers opportunities for reducing N surpluses, but also indicates the risk of P and K deficits and the need for additional fertilizer inputs.

Organic dairy production based on rapeseed, rapeseed cake or cereals as supplement to silage ad libitum

This experiment presents the effect of 100% organic feed rations grown at an equal area per cow on milk production performance and metabolic responses. A total of 174 Danish Holstein cows were included in two experiments on two commercial organic dairy farms during the winter 2000/2001. Three types of supplementary feed were examined: 5 kg cereals, 3 kg rapeseed/cereal pellet or 1 kg rapeseed cake fed with a mixture of clover grass silage, whole crop silage and grass pellets ad libitum. The supplement of rapeseed/cereal pellet compared with cereals tended to decrease both milk fat and protein content, whereas fat and protein yield were unaffected. Milk yield was increased by supplement of rapeseed/cereal pellet compared with cereals in experiment 1, but unaffected in experiment 2. Consequently, energy corrected milk yield tended to be increased in experiment 1 but decreased in experiment 2. The supplement of rapeseed cake compared with cereals changed neither milk composition nor yield. The risk of subclinical ketosis based on metabolic parameters and other metabolic disorders was not affected by the different feedings.

Differing effects of forage and concentrate diets on the oleic acid and conjugated linoleic acid content of sheep tissues: the role of stearoyl-CoA desaturase.

Feeding sheep concentrate-based diets increases the oleic acid content of their tissues, whereas the cis-9, trans-11 conjugated linoleic acid (CLA) content is increased by feeding forage diets. Both these metabolic transformations could be attributable to increased activity of stearoyl-CoA desaturase (SCD). Therefore, the effect of forage or concentrate feeding regimens on the fatty acid composition of sheep tissues were investigated to determine whether any changes are related to an alteration of SCD mRNA levels. Twenty-four ewe lambs were randomly allotted to one of three dietary treatment groups: 1) dehydrated grass pellets, 2) concentrate diet fed to achieve a growth rate similar to that of the dehydrated grass pellets, and 3) the same concentrate diet approaching ad libitum intake. As expected, animals fed ad libitum concentrates grew at a greater (P = 0.001) rate (280 g/d) than those fed either of the other two diets (180 g/d), which were similar. In samples of liver and the three adipose tissue depots studied, the concentration of oleic acid from sheep fed either level of the concentrate diet was greater (P < 0.001) than from animals fed forage. This was associated with an increase (P < 0.05) in the ratio of SCD to acetyl-CoA carboxylase mRNA in adipose tissue and liver. Compared with concentrate-fed, the forage-fed lambs had increased (P < 0.05) levels of the cis-9, trans-11 isomer of CLA and C18:1, trans-11 in all their tissues, although the levels of SCD mRNA were lower. It therefore seems that the increased oleic acid content of sheep tissues in response to concentrate-rich diets is associated with an increase in SCD gene expression. By contrast, the increased concentration of CLA in animals fed forage-based diets is associated with an increase in substrate (C18:1 trans-11) availability.

Assessing dominance in sheep in a competitive situation: level of motivation and test duration

The dominance structure in an established group of sheep is often difficult to determine in the field, because of the low frequency of agonistic interactions, often resulting in some pairs of animals not interacting at all in the observation period. A solution to this problem is to test each pair separately in a competitive situation. The most frequently used test involves competition for food after a specific period of food deprivation, but to date, there is no agreement as to the optimum length of time the animals should go without food. In this experiment, we compared competitive behaviour at different lengths of time after a meal. The experimental animals were a group a of 10 1-year-old, female Scottish Blackface sheep (45 dyads), who had access to dry grass pellets twice daily, from 07:00 to 08:00 h and from 19:00 to 20:00 h. They were tested in pairs for 5 min immediately after and 2, 4, 6 and 8 h after the end of the morning meal. In the test arena ( 4.5 m×4.5 m) a feed hopper provided access to feed to only one sheep at a time. We recorded aggressive interactions, such as blocking, threats and butts, as well as non-aggressive interactions (nudges), the time spent at the feeder, and the number and type of displacements (aggressive or non-aggressive). The number of displacements was also recorded in the home pens during ten 45-min periods of group feeding. Blocking behaviour showed the clearest difference between the two sheep in a pair and was, therefore, used as the main indicator of dominance. Its occurrence increased as the time since the morning meal was increased and decreased in the course of the 5 min tests. Consistency between pair-tests and group observations was greatest in the test 8 h after the previous meal, but the difference in consistency between the 2 and 8 h tests was small. Recording the behaviour for more than 2 min of the 5-min test did not increase the consistency of the data. We suggest that a period of at least 2 h of food withdrawal is necessary to generate sufficient motivation for a competition test and to mask differences in feeding motivation between individuals. While the performance of dominance-relevant behaviour increased with time since the last meal, a period of 4 h may be sufficient to provide high-quality data. We also suggest that the test duration can be reduced to 2 min.

Concentrate Mixture, Grass Pellets, Fodder Beets, or Barley as Supplements to Silage ad libitum for High-yielding Dairy Cows on Organic Farms

In Denmark, organic feeding is typically based on homegrown feed with a high proportion of roughage. Which crop to grow and use as supplementary feed is investigated in this paper. In three experiments, barley (B) was compared with another type of supplementary feed: a concentrate mixture (C), grass pellets (G), or fodder beets (F). The concentrate mixture resulted in a higher (P=0.002) milk yield (25.9 vs. 23.7 kg), a tendency of a lower (P=0.07) fat content (4.08 vs. 4.25%), and a higher (P=0.006) ECM yield (25.7 vs. 24.1 kg) compared to feeding barley as supplement at the same energy level. Grass pellets resulted in a lower (P=0.01) milk fat content (3.74 vs. 4.07%), a tendency of a lower (P=0.12) protein content (3.14 vs. 3.23%), but no different milk or ECM yield compared to feeding barley as supplement at the same dry matter level. Fodder beet tended to decrease (P=0.12) the milk yield (20.7 vs. 22.0 kg), and the ECM yield (P=0.05) was lower (21.5 vs. 22.9 kg) whereas the composition of the milk was unaffected compared to the total mixed ration with barley.