Forage-concentrate Diets Research Articles

Effects of Dietary Fiber Level and Forage Particle Size on Growth, Nutrient Digestion, Ruminal Fermentation, and Behavior of Weaned Holstein Calves under Heat Stress.

This experiment was designed to investigate the effects of feeding diets with different fiber content and forage particle size on the performance, health, nutrient digestion, rumen fermentation, and behavioral and sorting activity of Holstein dairy calves kept under elevated environmental temperature. Sixty weaned Holstein female calves (age = 96.7 ± 7.62 days old; body weight = 82.4 ± 10.4 kg) were randomly assigned to one of 4 treatments arranged in a 2-by-2 factorial design in a 70-day experiment. Dietary forage content (moderate, 22.5%; or high, 40.0% on DM basis) and alfalfa hay particle size (short, 4.39 mm; or long, 7.22 mm as geometric mean) were the experimental factors, resulting in the following combinations: (1) high-fiber (HF) diets with forage-to-concentrate ratio of 40:60 and long particle-sized alfalfa hay (LPS; HF-LPS); (2) HF diets with short particle-sized alfalfa hay (SPS; HF-SPS); (3) moderate-fiber (MF) diets with forage-to-concentrate ratio of 22.5:77.5 with LPS (MF-LPS); and (4) MF diets with SPS (MF-SPS). The temperature-humidity index averaged 73.0 ± 1.86, indicating that weaned calves experienced a moderate extent of heat stress. Fiber level and AH particle size interacted and affected dry matter intake, with the greatest intake (4.83 kg/d) observed in MF-SPS-fed calves. Final body weight was greater in calves receiving MF vs. HF diets (164 vs. 152 kg; p < 0.01). Respiration rate decreased when SPS vs. LPS AH was included in HF but not MF diet. Lower rectal temperature was recorded in calves fed MF vs. HF diet. Digestibility of dry matter and crude protein was greater in calves fed MF than HF diets, resulting in lower ruminal pH (6.12 vs. 6.30; p = 0.03). Fiber digestibility was greater in calves fed SPS compared with those fed LPS alfalfa hay. Feeding HF compared with MF diet increased acetate but lowered propionate molar proportions. The inclusion of SPS vs. LPS alfalfa hay decreased lying time in HF diet (920 vs. 861 min; p < 0.01). Calves fed MF vs. HF diets spent less time eating but more time lying, which is likely indicative of better animal comfort. Dietary fiber level and forage particle size interacted and affected sorting against 19 mm particles, the extent of which was greater in HF-SPS diet. Overall, dietary fiber level had a stronger effect than forage particle size on the performance of weaned calves exposed to a moderate degree of heat stress as feeding MF vs. HF diet resulted in greater feed intake, final body weight, structural growth measures, nutrient digestion, as well as longer lying behavior. The inclusion of SPS alfalfa hay in MF diets increased feed consumption.

3-Nitrooxypropanol supplementation of a forage diet decreased enteric methane emissions from beef cattle without affecting feed intake and apparent total-tract digestibility.

Supplementation of ruminant diets with the methane (CH4) inhibitor 3-nitrooxypropanol (3-NOP; DSM Nutritional Products, Switzerland) is a promising greenhouse gas mitigation strategy. However, most studies have used high grain or mixed forage-concentrate diets. The objective of this study was to evaluate the effects of supplementing a high-forage diet (90% forage DM basis) with 3-NOP on dry matter (DM) intake, rumen fermentation and microbial community, salivary secretion, enteric gas emissions, and apparent total-tract nutrient digestibility. Eight ruminally cannulated beef heifers (average initial body weight (BW) ± SD, 515 ± 40.5 kg) were randomly allocated to two treatments in a crossover design with 49-d periods. Dietary treatments were: 1) control (no 3-NOP supplementation); and 2) 3-NOP (control + 150 mg 3-NOP/kg DM). After a 16-d diet adaption, DM intake was recorded daily. Rumen contents were collected on days 17 and 28 for volatile fatty acid (VFA) analysis, whereas ruminal pH was continuously monitored from days 20 to 28. Eating and resting saliva production were measured on days 20 and 31, respectively. Diet digestibility was measured on days 38-42 by the total collection of feces, while enteric gas emissions were measured in chambers on days 46-49. Data were analyzed using the mixed procedure of SAS. Dry matter intake and apparent total-tract digestibility of nutrients (DM, neutral and acid detergent fiber, starch, and crude protein) were similar between treatments (P ≥ 0.15). No effect was observed on eating and resting saliva production. Relative abundance of the predominant bacterial taxa and rumen methanogen community was not affected by 3-NOP supplementation but rather by rumen digesta phase and sampling hour (P ≤ 0.01). Total VFA concentration was lower (P = 0.004) following 3-NOP supplementation. Furthermore, the reduction in acetate and increase in propionate molar proportions for 3-NOP lowered (P < 0.001) the acetate to propionate ratio by 18.9% as compared with control (4.1). Mean pH was 0.21 units lower (P < 0.001) for control than 3-NOP (6.43). Furthermore, CH4 emission (g/d) and yield (g/kg DMI) were 22.4 and 22.0% smaller (P < 0.001), respectively, for 3-NOP relative to control. Overall, the results indicate that enteric CH4 emissions were decreased by more than 20% with 3-NOP supplementation of a forage diet without affecting DM intake, predominant rumen microbial community, and apparent total-tract nutrients digestibility.

Evaluation of dehydrated corn silage as the primary forage for lactating dairy cows

The objective was to compare productivity of lactating dairy cows fed dehydrated corn silage with those fed whole-crop barley silage. Twelve multiparous Holstein cows in mid lactation were fed diets containing dehydrated corn silage (DCS) or barley silage with additional grain (BSHG) or without (BSLG) in a 3 × 3 Latin square design, with 21-d periods, balanced for carryover effects. The dietary starch content was similar for DCS and BSHG diets, and dietary forage content was similar for DCS and BSLG diets. Experimental diets did not affect dry matter intake, but cows fed DCS diet decreased milk yield compared with those fed barley silage regardless of the dietary starch content. Apparent total-tract digestibility of starch and crude protein was also lower for cows fed DCS compared with those fed barley silage, and milk urea N content was lowest for cows fed DCS diet, indicating that DCS likely had less protein degradation in the rumen than barley silage. Milk fat content and yield, energy-corrected milk yield, and feed efficiency were not different between cows fed BSHG and DCS diets, but higher for cows fed BSLG than those fed BSHG or DCS diet, which can be attributed to the difference in dietary starch content. Feeding DCS in place of barley silage did not improve productivity of lactating dairy cows in the current study, and further research is warranted to optimize its utilization in dairy diets.

Improving the accuracy of beef cattle methane inventories in Latin America and Caribbean countries

On-farm methane (CH4) emissions need to be estimated accurately so that the mitigation effect of recommended practices can be accounted for. In the present study prediction equations for enteric CH4 have been developed in lieu of expensive animal measurement approaches. Our objectives were to: (1) compile a dataset from individual beef cattle data for the Latin America and Caribbean (LAC) region; (2) determine main predictors of CH4 emission variables; (3) develop and cross-validate prediction models according to dietary forage content (DFC); and (4) compare the predictive ability of these newly-developed models with extant equations reported in literature, including those currently used for CH4 inventories in LAC countries. After outlier's screening, 1100 beef cattle observations from 55 studies were kept in the final dataset (∼ 50 % of the original dataset). Mixed-effects models were fitted with a random effect of study. The whole dataset was split according to DFC into a subset for all-forage (DFC = 100 %), high-forage (94 % ≥ DFC ≥ 54 %), and low-forage (50 % ≥ DFC) diets. Feed intake and average daily gain (ADG) were the main predictors of CH4 emission (g d−1), whereas this was feeding level [dry matter intake (DMI) as % of body weight] for CH4 yield (g kg−1 DMI). The newly-developed models were more accurate than IPCC Tier 2 equations for all subsets. Simple and multiple regression models including ADG were accurate and a feasible option to predict CH4 emission when data on feed intake are not available. Methane yield was not well predicted by any extant equation in contrast to the newly-developed models. The present study delivered new models that may be alternatives for the IPCC Tier 2 equations to improve CH4 prediction for beef cattle in inventories of LAC countries based either on more or less readily available data.

Prediction of enteric methane production and yield in sheep using a Latin America and Caribbean database

Methane (CH4) produced from enteric fermentation in ruminants has a noticeable impact on climate change. Prediction models are an alternative to current laborious and costly in vivo CH4 measurement techniques. The objectives of this study were to: (1) collate a database of individual sheep records from CH4 emission studies conducted in the Latin America and Caribbean (LAC) region; (2) identify key variables for predicting CH4 production (g/d) and CH4 yield [g/kg of dry matter intake (DMI)]; (3) develop and cross-validate these newly-developed models; and (4) compare models’ predictive ability with equations currently used to support national greenhouse gas (GHG) inventories in the LAC region. After removing outliers, the final database retained 219 individual sheep records from 11 studies, 48.2% of the original database. Models were developed using a sequential approach, by incrementally adding different variables with increasing complexity. Production and yield of CH4 were predicted by fitting mixed-effects models with a random effect of study. The predictive accuracy of fitted CH4 prediction models was evaluated using a leave-one-out cross-validation. Overall, increasing model complexity improved the predictive performance of CH4 production and yield equations. Feed intake was the most important predictor of sheep CH4 production. Our best-developed CH4 production models outperformed Tier 2 equations from the Intergovernmental Panel on Climate Change (IPCC) in the growing lambs and mature sheep subsets, whereas they performed slightly worse in the complete subset. Methane yield can be predicted using dietary forage content only, or with an increased complexity model combining body weight, feeding level, and dietary forage content. The use of the newly-developed models rather than IPCC Tier 2 equations can substantially improve the accuracy of GHG inventories from LAC countries.

330 3-nitrooxypropanol Supplementation of a Forage Diet Decreased Enteric Methane Emissions from Beef Cattle Without Affecting Apparent Total-tract Digestibility

Abstract Supplementation of ruminant diets with the investigational methane (CH4) inhibitor 3-nitrooxypropanol (3-NOP; DSM Nutritional Products, Switzerland) is as a promising mitigation strategy. However, most studies have examined high grain or mixed forage-concentrate diets. The objective of this study was to evaluate the effects of supplementing a forage diet with 3-NOP on rumen fermentation, CH4 emissions and apparent total-tract nutrient digestibility. Eight ruminally cannulated beef heifers (BW = 514 kg) were randomly allocated to two treatments in a crossover design with 49-d periods. Dietary treatments were: control, high-forage diet (90% forage DM basis) without 3-NOP; and NOP, control diet supplemented with 150 mg 3-NOP/kg DM. After a 14-d diet adaption, dry matter (DM) intake (DMI) was recorded daily. Rumen contents were collected on days 17 and 28 for volatile fatty acid (VFA) analysis, whereas ruminal pH was continuously monitored from day 20 to 27. Diet digestibility was measured on day 38 to 41 by total collection of feces. Enteric CH4 emissions were measured on days 46 to 49 in chambers. Dry matter intake was lower (P = 0.001) for NOP (10.0 kg/d) as compared with control (10.2 kg/d). However, DM, neutral and acid detergent fiber, and crude protein digestibilities were similar between treatments (P ≥ 0.29). Although total VFA concentration was not affected by treatment (P = 0.19), the reduction in acetate and increase in propionate proportion for NOP lowered (P &amp;lt; 0.001) the acetate to propionate ratio by 18% as compared with control. Mean pH was lower (P = 0.03) for control (6.46) than NOP (6.57). Furthermore, CH4 yield (g/kg DMI) was 21.6% less (P &amp;lt; 0.001) for NOP relative to control (25.5 g/kg DMI). Overall, the results indicate that enteric CH4 emissions were effectively decreased with 3-NOP supplementation of a forage diet without affecting apparent total-tract digestibility of nutrients.

Effect of dietary Thais coronata shell on odour reduction and nitrogen output in rabbit farm

This work investigated the effect of integrated forage-concentrate diets with Thais coronate as additive on reducing odour and nitrogen output in rabbit production. Thais coronate shells were thoroughly washed, dried and ground to 2mm particle size. Forty-five growing rabbits were fed diets comprising 25% forage and 75% concentrate with 0%, 0.25%, 0.50%, 0.75% or 1.0% ofthe shells for two weeks in a completely randomized design (CRD) experiment. The treatments were designated T1, T2, T3, T4 and T5, respectively with 9 rabbits per dietary treatment and replicated thrice with 3 rabbits per replicate. Faeces and urine were collected and odour perception scored by 10-member panel on a 5-point scale. The mean odour perception scores of T1 (urine =4.02, faeces=3.55) represented the strongest (P&lt; 0.05) degree of pungency while T4 (urine=3.05, faeces=2.76) gave the least (P&lt;0.05) pungent odour. Average total nitrogen yield from treatment 1 (2.93g/day) was significantly higher than those from treatments 3 (2.53g/day) and 4 (2.31g/day) but similar to those from treatments 2 (2.74g/day) and 5 (2.70g/day). Inclusion of T. coronata shell at0.75% in a forage-concentrate (T4) diet of rabbit reduces odour in rabbit production and elicits the least yield of nitrogen.&#x0D;

Influence of fiber degradability of corn silage in diets with lower and higher fiber content on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows

The effect of neutral detergent fiber (NDF) degradability of corn silage in diets containing lower and higher NDF concentrations on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows was measured. Eight ruminally cannulated Holstein cows averaging 91 ± 4 (standard error) days in milk were used in a replicated 4 × 4 Latin square design with 21-d periods (7-d collection periods). Dietary treatments were formulated to contain either conventional (CON; 48.6% 24-h NDF degradability; NDFD) or brown midrib-3 (BM3; 61.1% 24-h NDFD) corn silage and either lower NDF (LNDF) or higher NDF (HNDF) concentration (32.0 and 35.8% of ration dry matter, DM) by adjusting the dietary forage content (52 and 67% forage, DM basis). The dietary treatments were (1) CON-LNDF, (2) CON-HNDF, (3) BM3-LNDF, and (4) BM3-HNDF. Data were analyzed as a factorial arrangement of diets within a replicated Latin square design with the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with fixed effects of NDFD, NDF, NDFD × NDF, period(square), and square. Cow within square was the random effect. Time and its interactions with NDFD and NDF were included in the model when appropriate. An interaction between NDFD and NDF content resulted in the HNDF diet decreasing dry matter intake (DMI) with CON corn silage but not with BM3 silage. Cows fed the BM3 corn silage had higher DMI than cows fed the CON corn silage, whereas cows fed the HNDF diet consumed less DM than cows fed the LNDF diet. Cows fed the BM3 diets had greater energy-corrected milk yield, higher milk true protein content, and lower milk urea nitrogen concentration than cows fed CON diets. Additionally, cows fed the BM3 diets had greater total-tract digestibility of organic matter and NDF than cows fed the CON diets. Compared with CON diets, the BMR diets accelerated ruminal NDF turnover. When incorporated into higher NDF diets, corn silage with greater in vitro 24-h NDFD and lower undegradable NDF at 240 h of in vitro fermentation (uNDF240) allowed for greater DMI intake than CON. In contrast, for lower NDF diets, NDFD of corn silage did not affect DMI, which suggests that a threshold level of inclusion of higher NDFD corn silage is necessary to observe enhanced lactational performance. Results suggest that there is a maximum gut fill of dietary uNDF240 and that higher NDFD corn silage can be fed at greater dietary concentrations.

Apparent digestibility, rumen fermentation, digestive enzymes and urinary purine derivatives in yaks and Qaidam cattle offered forage-concentrate diets differing in nitrogen concentration

Abstract Yaks (Bos grunniens) and Qaidam yellow cattle (Bos taurus) are indigenous to the Qinghai-Tibetan Plateau and graze natural pasture all year. Yaks are raised at higher elevations than cattle and are not offered supplementary feed whereas cattle receive supplementary feed and are sheltered at night during winters. We hypothesized that the species differ in metabolism of energy and nitrogen (N) and predicted that the differences would favour yaks to the harsh conditions of the plateau. To test our prediction, we examined nutrient digestibility, rumen fermentation, digestive enzymes and urinary purine derivatives (PD) in yaks and cattle offered forage-concentrate diets differing in N concentration. Four castrated yaks and 4 castrated cattle of similar ages (2.5 years) and body weights (200 kg) were used in two concurrent 4×4 Latin square designs. There was no difference (P > 0.05) between yaks and cattle in apparent digestibilities of dietary nutrients, concentrations of ruminal N components and activities of digestive enzymes (P > 0.05). Crude protein and acid detergent fiber digestibilities increased linearly (P 0.05), and both variables were not affected by dietary N content (P > 0.05). As dietary N increased, ruminal concentrations of ammonia, urea and amino acids increased linearly (all P 0.10) for both species. The activity of carboxymethylcellulase decreased linearly (P 0.10); however, the PD nitrogen index (PNI) was greater in yaks than in cattle for the lowest N diets (linear dietary N × species, P

Effect of dietary crude protein and forage contents on enteric methane emissions and nitrogen excretion from dairy cows simultaneously

The study aimed to examine, simultaneously, the effects of changing dietary forage and crude protein (CP) contents on enteric methane (CH4) emissions and nitrogen (N) excretion from lactating dairy cows. Twelve post-peak lactating Holstein cows (157 ± 31 days postpartum; mean ± s.d.) were randomly assigned to four treatments from a 2 × 2 factorial arrangement of two dietary forage levels [37.4% (LF) vs 53.3% (HF) of DM] and two dietary CP levels [15.2% (LP) vs 18.5% (HP) of DM] in a 4 × 4 Latin square design with four 18-day periods. Alfalfa hay was the sole source of dietary forage. Cows were fed ad libitum and milked twice daily. During the first 14 days, cows were housed in a free-stall barn, where enteric CH4 emissions were measured using the GreenFeed system from Days 8 to 14 in each period. Cows were then moved to metabolic cages, where faeces and urine output (kg/cow.day) were measured by total collection from Days 16 to 18 of each period. No dietary forage by CP interactions were detected for DM intake, milk production, enteric CH4 emissions, or N excretions. There was a tendency for DM intake to increase 0.6 kg/day in cows fed LF (P = 0.06). Milk production increased 2.1 kg/day in LF compared with HF (P &lt; 0.01). Milk fat content decreased in cows fed LF compared with HF (1.07 vs 1.17 kg/day; P &lt; 0.01). Milk contents of true protein, lactose and solid non-fat were greater in cows fed LF (P &lt; 0.01). No difference in DM intake, milk yield and milk contents of true protein, lactose and solid non-fat was found between cows fed HP or LP. However, milk fat content increased 0.16 kg/day in cows fed HP (P &lt; 0.05). Enteric CH4 emissions, and CH4 per unit of DM intake, energy-corrected milk, total digested organic matter and neutral detergent fibre were not affected by dietary CP, but decreased by LF compared with HF (P &lt; 0.01). Milk true protein N was not affected by dietary CP content but was higher for LF compared with HF. Dietary N partitioned to milk true protein was greater in cows fed LF compared with HF (29.4% vs 26.7%; P &lt; 0.01), also greater in cows fed LP compared with HP (30.8% vs 25.2%; P &lt; 0.01). Dietary N partitioned to urinary N excretion was greater in cows fed HP compared with LP (39.5% vs 29.6%; P &lt; 0.01) but was not affected by dietary CP content. Dietary N partitioned to faeces was not affected by dietary CP but increased in cows fed LP compared with HP (34.2% vs 27.8%; P &lt; 0.01). Total N excretion (urinary plus faecal) as proportion to N intake did not differ between HP and LP, but tended to be lower in cows fed LF compared with the HF diet (64.2% vs 67.9%; P = 0.09). Both milk urea N (P &lt; 0.01) and blood urea N (P &lt; 0.01) declined with decreasing dietary CP or forage contents. Based on purine derivative analysis, there was a tendency for interaction between dietary CP and forage content on microbial protein synthesis (P &lt; 0.09). Rumen microbial protein synthesis tended to be lower for high forage and low protein treatments. Increasing dietary forage contents resulted in greater CH4 emission (g/kg of energy-corrected milk) and manure N excretion (g/kg of energy-corrected milk) intensities of lactating dairy cows. Cows receiving reduced CP diets had low manure N outputs and improved milk true protein production efficiencies, regardless of dietary forage content.

Apparent digestibility, rumen fermentation and nitrogen balance in Tibetan and fine-wool sheep offered forage-concentrate diets differing in nitrogen concentration

SUMMARYA comparative study of the effect of dietary nitrogen (N) content [Low: 11·0; Medium-Low (MLow): 16·7; Medium-High (Mhigh): 23·1; High: 29·2 N g/kg dry matter (DM)] on apparent digestibilities, rumen fermentation and N balance was conducted in coarse wool Tibetan sheep and Gansu Alpine fine-wool sheep at Wushaoling in the northeast of the Qinghai-Tibetan Plateau. It was hypothesized that responses would differ between breeds and that responses would favour Tibetan over fine-wool sheep at low N intakes. Eight wethers [four Tibetan sheep and four fine-wool sheep, 20–24 months old; body weight ± standard deviation was 52 ± 3·2 kg] were used in two concurrent 4 × 4 Latin square designs. Dry matter, organic matter, neutral detergent fibre and acid detergent fibre digestibilities were higher in Tibetan than fine-wool sheep when fed the Low, MLow and High N diets while N retention was higher when the animals were fed the Low and MLow N diets. Tibetan sheep had a higher rumen pH than fine-wool sheep; however, total volatile fatty acids were similar between breeds. Molar proportions of acetate were higher but propionate and butyrate lower in Tibetan than fine-wool sheep. In addition, Tibetan sheep had higher concentrations of ruminal free amino acid-N and soluble protein-N than fine-wool sheep. Plasma and saliva urea-N concentrations were higher in Tibetan than fine-wool sheep when supplied with the Low N diet. It was concluded that Tibetan sheep were better able to cope with low N feed than fine-wool sheep because of the higher N retention and higher DM and fibre digestibilities with Low and MLow diets.

Effect of reducing dietary forage in lower starch diets on performance, ruminal characteristics, and nutrient digestibility in lactating Holstein cows

This experiment evaluated the effect of feeding a lower starch diet (21% of dry matter) with different amounts of forage (52, 47, 43, and 39% of dry matter) on lactational performance, chewing activity, ruminal fermentation and turnover, microbial N yield, and total-tract nutrient digestibility. Dietary forage consisted of a mixture of corn and haycrop silages, and as dietary forage content was reduced, chopped wheat straw (0–10% of dry matter) was added in an effort to maintain chewing activity. Dietary concentrate was adjusted (corn meal, nonforage fiber sources, and protein sources) to maintain similar amounts of starch and other carbohydrate and protein fractions among the diets. Sixteen lactating Holstein cows were used in replicated 4×4 Latin squares with 21-d periods. Dry matter intake increased while physically effective neutral detergent fiber (peNDF1.18) intake was reduced as forage content decreased from 52 to 39%. However, reducing dietary forage did not influence milk yield or composition, although we observed changes in dry matter intake. Time spent chewing, eating, and ruminating (expressed as minutes per day or as minutes per kilogram of NDF intake) were not affected by reducing dietary forage. However, addition of chopped wheat straw to the diets resulted in greater time spent chewing and eating per kilogram of peNDF1.18 consumed. Reducing dietary forage from 52 to 39% did not affect ruminal pH, ruminal digesta volume and mass, ruminal pool size of NDF or starch, ruminal digesta mat consistency, or microbial N yield. Ruminal acetate-to-propionate ratio was reduced, ruminal turnover rates of NDF and starch were greater, and total-tract digestibility of fiber diminished as dietary forage content decreased. Reducing the dietary forage content from 52 to 39% of dry matter, while increasing wheat straw inclusion to maintain chewing and rumen function, resulted in similar milk yield and composition although feed intake increased. With the lower starch diets in this short-term study, the minimal forage content to maintain lactational performance was between 39 and 43%.

Meta-analysis of factors affecting milk component yields in dairy cattle.

The objectives of this study were thus to identify most significant factors that determine milk component yield (MCY) using a meta-analysis and, if possible, to develop equations to predict MCY using variables that can be easily measured in the field. A literature database was constructed based on the research articles published in the Journal of Dairy Science from Oct., 2007 till May, 2010. The database consisted of a total of 442 observed means for MCY from 118 studies. The candidate factors that determine MCY were those which can be routinely measured in the field (e.g. DMI, BW, dietary forage content, chemical composition of diets). Using a simple linear regression, the best equations for predicting milk fat yield(MFY) and milk protein yield (MPY) were MFY = 0.351 (±0.068) + 0.038 (±0.003) DMI (R2 = 0.27), and MPY = 0.552 (±0.071) + 0.031 (±0.002) DMI - 0.004 (±0.001) FpDM (%, forage as a percentage of dietary DM) (R2 = 0.38), respectively. The best equation for predicting milk fat content (%) explained only 12% of variations in milk fat content, and none of a single variable can explain more than 5% of variations in milk protein content. We concluded that among the tested variables, DMI was the only significant factor that affects MFY and both DMI and FpDM significantly affect MPY. However, predictability of linear equations was relatively low. Further studies are needed to identify other variables that can predict milk component yield more accurately.

Effect of feeding dried high-sugar ryegrass (‘AberMagic’) on methane and urinary nitrogen emissions of primiparous cows

The objective of the present study was to test the hypothesis that feeding dried grass from a ryegrass cultivar with high water-soluble carbohydrate (WSC) concentration to dairy cows lowers emissions of enteric methane and urinary nitrogen. This dried grass (here the cultivar ‘AberMagic’) was compared as a forage-only diet to dried grass prepared from a low-WSC cultivar (‘Respect’). Six mid-lactating primiparous Holstein-Friesian dairy cows (19kg milk/cow/day) were subjected to a change-over design in two 26-day experimental periods. In the last 8 days of each period, feed intake, milk yield, fecal and urinary excretion were recorded and samples were taken. During 2 days, methane emissions were measured in open-circuit respiration chambers. The dried grass type had no significant effect on feed intake and milk gross composition. Milk yield was lower for cows fed the dried high-WSC grass. Total enteric methane (g/day) did not significantly differ when cows received dried high-WSC grass (279) instead of dried low-WSC grass (315). Methane expressed as g/kg dry matter intake (19.4 and 20.3 for dried high- and low-WSC grass, respectively), and methane conversion rates (Ym; 63kJ/MJ of gross energy for both dried grass types) were similar with both dried grass types. The dried high-WSC grass had a lower crude protein concentration compared to the dried low-WSC grass (158 vs. 255g/kg dry matter) resulting in a correspondingly different urinary N excretion (114 vs. 292g/day) and milk urea concentration. A similar effect was found for urinary N proportion of total excreta N. Fecal N excretion and milk N secretion were higher with the dried high-WSC grass. In conclusion, feeding dried high-WSC ryegrass, where WSC mainly replace crude protein, might be helpful in limiting N emissions from dairy cattle husbandry whereas methane emissions seem to remain unaffected. Further studies have to test whether dried high-WSC grass has the same effect when the WSC replace fiber and to address the extent to which favorable effects can be recovered in mixed forage-concentrate diets.

Dietary fiber content influences soluble carbohydrate levels in ruminal fluids

The soluble carbohydrate concentration of ruminal fluid, as affected by dietary forage content (DFC) and/or ruminally undegradable intake protein content (UIPC), was determined. Four ruminally cannulated steers, in a 4 × 4 Latin square design, were offered diets containing high (75 % of DM) or low (25 % of DM) DFC and high (6 % of DM) or low (5 % of DM) UIPC, in a 2 × 2 factorial arrangement. Zinc-treated SBM was the primary UIP source. Soluble hexose concentration (145.1 μM) in ruminal fluid (RF) of steers fed low DFC diets exhibited a higher trend (P = 0.08) than that (124.5 μM) of steers fed high DFC diets. UIPC did not modulate (P = 0.54) ruminal soluble hexose concentrations. Regardless of diet, soluble hexose concentration declined immediately after feeding and did not rise until 3 h after feeding (P < 0.0001). Cellobiose (≈90 %) and glucose (≈10 %) were the major soluble hexoses present in RF. Maltose was not detected. Soluble glucose concentration (13.0 μM) was not modified by either UIPC (P = 0.40) nor DFC (P = 0.61). However, a DFC by post-prandial time interaction was detected (P = 0.02). Pentose concentrations were greater (P = 0.02) in RF of steers fed high DFC (100.2 μM) than steers fed low DFC (177.0 μM). UIPC did not influence (P = 0.35) soluble pentose concentration. The identity of soluble pentoses in ruminal fluid could not be determined. However, unsubstituted xylose and arabinose were excluded. These data indicate that: (i) soluble carbohydrate concentrations remain in ruminal fluid during digestion and fermentation; (ii) slight diurnal changes began after feeding; (iii) DFC influences the soluble carbohydrate concentration in RF; and (iv) UIPC of these diets does not affect the soluble carbohydrate concentration of RF.

Effect of feeding system on growth and carcass characteristics of Improved Jezersko-Solčava lambs

The objective of this study was to evaluate the effect of feeding system on growth and carcass characteristics of Improved Jezersko-Solčava (JSR) weaned lambs. Thirty-five lambs (25.48 kg) housed in group pens were divided into four groups and offered different diets which consisted of hay and second harvest in the ratio of 40:60 and a supplement of 650 g concentrate (Diet 1), hay and second harvest in the ratio of 40:60 (Diet 2), hay and 650 g of concentrate (Diet 3), and just hay (Diet 4) for 50 days. Daily intake was calculated by weighting the offered amount and leftovers of concentrate and forage. Daily intake per lamb contained 15.56 MJ, 14.38 MJ, 16.57 MJ, and 12.23 MJ ME for the Diet 1, 2, 3, and 4, respectively. Lambs were slaughtered at 30.77 kg of live weight. Lambs fed Diet 1 reached the highest DG (165.5 g/day), followed by Diet 3 (146.89 g/day), Diet 2 (123.55 g/day) and Diet 4 (75.51 g/day). HCW and CCW were higher in Diet 1 and 3, compared to Diet 2 and 4. Lambs fed Diet 3 had the highest DP (45.35%), followed by Diet 1, 2, and 4 with 44.33, 41.10 and 39.51%, respectively. The lowest kidney-pelvic fat was observed in lambs fed Diet 4 (5.64) and the highest in Diet 3 (7.66). These results demonstrate that fattening of weaned JSR lambs fed by forage-concentrate diets produced heavier carcasses than those only fed by forage, without significant effects on carcass fatness or carcass conformation.

Effect of Phenotypic Residual Feed Intake and Dietary Forage Content on the Rumen Microbial Community of Beef Cattle

Feed-efficient animals have lower production costs and reduced environmental impact. Given that rumen microbial fermentation plays a pivotal role in host nutrition, the premise that rumen microbiota may contribute to host feed efficiency is gaining momentum. Since diet is a major factor in determining rumen community structure and fermentation patterns, we investigated the effect of divergence in phenotypic residual feed intake (RFI) on ruminal community structure of beef cattle across two contrasting diets. PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative PCR (qPCR) were performed to profile the rumen bacterial population and to quantify the ruminal populations of Entodinium spp., protozoa, Fibrobacter succinogenes, Ruminococcus flavefaciens, Ruminococcus albus, Prevotella brevis, the genus Prevotella, and fungi in 14 low (efficient)- and 14 high (inefficient)-RFI animals offered a low-energy, high-forage diet, followed by a high-energy, low-forage diet. Canonical correspondence and Spearman correlation analyses were used to investigate associations between physiological variables and rumen microbial structure and specific microbial populations, respectively. The effect of RFI on bacterial profiles was influenced by diet, with the association between RFI group and PCR-DGGE profiles stronger for the higher forage diet. qPCR showed that Prevotella abundance was higher (P < 0.0001) in inefficient animals. A higher (P < 0.0001) abundance of Entodinium and Prevotella spp. and a lower (P < 0.0001) abundance of Fibrobacter succinogenes were observed when animals were offered the low-forage diet. Thus, differences in the ruminal microflora may contribute to host feed efficiency, although this effect may also be modulated by the diet offered.

Corrigendum to: Experimental validation of the Intergovernmental Panel on Climate Change default values for ruminant-derived methane and its carbon-isotope signature

Two aspects regarding the ruminant's contribution to global methane (CH4) emissions were investigated: (i) testing the accuracy of the Intergovernmental Panel on Climate Change default values for dairy cows fed different diet types and differing slurry storage temperatures; and (ii) providing carbon-isotope (C-isotope) signature data to contribute information on the characteristics of ruminant-derived CH4 as global source. The experimental diets, fed to 18 dairy cows, were separated into forage-only (hay, C3 plant) and forage-concentrate diets (barley, C3 plant; maize, C4 plant). Accumulated slurry was stored at either 14 or 27�C. The hay diet had the highest CH4 conversion rate (Ym 7.9%). Negligible amounts of CH4 were emitted from slurries stored at low temperature. No diet effect was found at 27�C (~33 L/kg volatile solids). The isotope ratios of enteric CH4 averaged -67.7‰ (C3 plants) and -57.4‰ (C4; maize). High temperature slurry storage resulted in different enrichment factors εCO2-CH4 for maize (33.2‰) and hay (35.9‰). Compared with the Intergovernmental Panel on Climate Change default values for Ym and slurry CH4 emission the results gained in the present experiment were higher and lower, respectively. Slurry-derived CH4 was less depleted in 13C than enteric CH4, which decreases the usefulness of this signature for global ruminant-derived CH4.

Experimental validation of the Intergovernmental Panel on Climate Change default values for ruminant-derived methane and its carbon-isotope signature

Two aspects regarding the ruminant’s contribution to global methane (CH4) emissions were investigated: (i) testing the accuracy of the Intergovernmental Panel on Climate Change default values for dairy cows fed different diet types and differing slurry storage temperatures; and (ii) providing carbon-isotope (C-isotope) signature data to contribute information on the characteristics of ruminant-derived CH4 as global source. The experimental diets, fed to 18 dairy cows, were separated into forage-only (hay, C3 plant) and forage-concentrate diets (barley, C3 plant; maize, C4 plant). Accumulated slurry was stored at either 14 or 27°C. The hay diet had the highest CH4 conversion rate (Ym 7.9%). Negligible amounts of CH4 were emitted from slurries stored at low temperature. No diet effect was found at 27°C (~33 L/kg volatile solids). The isotope ratios of enteric CH4 averaged −67.7‰ (C3 plants) and −57.4‰ (C4; maize). High temperature slurry storage resulted in different enrichment factors ϵCO2-CH4 for maize (33.2‰) and hay (35.9‰). Compared with the Intergovernmental Panel on Climate Change default values for Ym and slurry CH4 emission the results gained in the present experiment were higher and lower, respectively. Slurry-derived CH4 was less depleted in 13C than enteric CH4, which decreases the usefulness of this signature for global ruminant-derived CH4.

The methanogenic potential and C-isotope fractionation of different diet types represented by either C3 or C4 plants as evaluated in vitro and in dairy cows

The methanogenic potential of two major feed production systems, grassland and arable land, was tested in vitro and in vivo. Diets were differentiated into C3 (grass, cereals) and C4 plants (maize) to determine whether C-isotope fractionation during methane formation differed between the C3 and C4 plant based diets. In the in vitro experiment, four diets consisting of hay, maize, wheat (the latter two straw and grain) and a 1 : 1 mixture of the maize and wheat diet were investigated using the Rusitec system (n = 4 per diet). In the in vivo experiment with 12 lactating cows, diets were basically similar, but barley was used instead of wheat and no maize–cereal mixture was tested (n = 4 per diet). Diets were always iso-energetic and iso-nitrogenous. Methane was either measured by gas chromatography from complete daily collections (in vitro) or by putting cows into respiratory chambers. In vitro, the methanogenic potential of the diets was similar. Methane related to apparently degraded neutral detergent fibre (NDF) was 50% lower in the hay than in the wheat diet, while the other diets ranged in between. The largest C-isotope fractionation between fermentation gases (αCO2 – CH4) was found in the wheat diet. In vivo, methane formation was highest with the barley diet followed by the hay and the maize diet (580, 461 and 453 L/day). Relating methane emission to dry matter intake reduced differences among diets (average 34 L/kg). On average, 118 L of methane were produced per kg digested NDF. Methane conversion rate was higher than the IPCC default value of 6.5% given for diets with less than 90% concentrate. No differences in the C-isotope fractionation were found in vivo. It was shown that forage-only diets, containing higher levels of fermentable fibre, do not necessarily have a higher methanogenic potential than mixed forage-concentrate diets.