J. Bertilsson

Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay.

The objective of this study was to investigate the effect of an abrupt change from grass hay (81% DM) to grass silage (36% DM) or grass haylage (55% DM), fed at similar DM intakes, and to compare the effects of silage and haylage on the composition and activities of the colon microflora. The forages were from the same swath harvested on the same day. Four adult colon-fistulated geldings were randomly assigned to diets in a crossover design. The study started with a preperiod when all 4 horses received the hay diet, followed by an abrupt feed change to the haylage diet for 2 horses and the silage diet for 2 horses. All 4 horses then had a new second preperiod of hay, followed by an abrupt feed change to the opposite haylage and silage diet. The periods were 21 d long, and the forage-only diets were supplemented with minerals and salt. The abrupt feed changes were made at 0800 h. Colon samples were taken before the abrupt feed change, 4 and 28 h after the feed change, and 8, 15, and 21 d after the feed change, all at 1200 h. Colon bacterial counts, VFA, pH, and DM concentrations were unchanged throughout the first 28 h after the abrupt feed change from hay to haylage and silage. Also, fecal pH and DM concentrations were unchanged during the first 28 h. During the weekly observations, colon lactobacilli counts increased (P = 0.023) in horses receiving the silage diet and were greater than on the haylage diet at 21 d. Streptococci counts decreased (P = 0.046) in horses receiving the haylage diet and were less than on the silage diet at 15 and 21 d. Total VFA concentrations and colon and fecal pH did not differ between diets and were unchanged throughout the weekly observations. The DM concentration of colon digesta and feces decreased (P = 0.030 and 0.049, respectively) on both diets during the weekly observations. The results suggest that in horses fed at the maintenance level of energy intake, an abrupt feed change from grass hay to grass silage or grass haylage from the same crop does not induce any major alterations in the colon ecosystem during the first 28 h. During the subsequent 3-wk period, colon and fecal DM decreased and there were alterations in the lactobacilli and streptococci bacterial counts. The changes in lactobacilli and streptococci counts need further investigation.

Enteric methane emissions from dairy cows fed different proportions of highly digestible grass silage

Abstract Enteric methane (CH4) emissions were measured from six lactating dairy cows using the sulfur hexafluoride tracer technique. Three diets with different proportions of highly digestible grass silage/concentrates were fed: 500/500, 700/300, or 900/100 g kg–1 dry matter (DM). The average daily CH4 emissions were 282, 300, and 321 g animal–1, respectively and the methane conversion factor (Y m ) from gross energy (GE) ranged from 0.051 to 0.056. However, the statistical power of the study was weak and the differences between diets were not significant (p=0.149 and p=0.293, respectively). A linear regression analysis showed a trend (p=0.08) toward higher enteric CH4 emissions with higher proportion of high quality grass silage in the diet. A definite conclusion is not possible and further studies are needed as a base for concrete advice on how to mitigate enteric CH4 emissions from high yielding dairy cows in Scandinavia.

Feeding Green-cut Forage Contaminated by Radioactive Fallout to Dairy Cows

Grass contaminated by radioactive fallout from the Chernobyl accident was cut with 150 mm (Treatment 1) and 50 mm (Treatment 2) stubble height and fed to 20 dairy cows. The transfer of 137Cs and 131I from the greencut forage to milk was studied during a four-week and a two-week period, respectively. The four-week period was followed by a three-week period with nearly uncontaminated feeds. Cutting with high stubble height significantly reduced the activity concentration in forage compared with low stubble cutting, the average contents kg-1 dry matter being 385 Bq 137Cs and 24 Bq 131I in Treatment 1 versus 6656 Bq 137Cs and 249 Bq 131I in Treatment 2. Apparent treatment effects were also demonstrated by the 137Cs concentration in milk, with maximum weekly means of 23 Bq kg-1 (Treatment 1) and 92 Bq kg-1 (Treatment 2). Single day maximum concentrations of 131I in milk were 4 Bq kg-1 (Treatment 1) and 9 Bq kg-1 (Treatment 2). The mean transfer coefficients (d kg-1) were calculated to be 0.67 X 10(-2) and 0.19 X 10(-2) for 137Cs (weeks 2-4) and 1.8 X 10(-2) and 0.2 X 10(-2) for 131I (week 2) in Treatments 1 and 2, respectively. The lower value for 137Cs might possibly be associated with an enhanced ash content of the forage. Feeding nearly uncontaminated rations rapidly decreased the 137Cs levels in milk in both treatments with calculated effective half-times over the three-week period of 10 and 7 d, respectively.

Methane Production in Dairy Cows Correlates with Rumen Methanogenic and Bacterial Community Structure

Methane (CH4) is produced as an end product from feed fermentation in the rumen. Yield of CH4 varies between individuals despite identical feeding conditions. To get a better understanding of factors behind the individual variation, 73 dairy cows given the same feed but differing in CH4 emissions were investigated with focus on fiber digestion, fermentation end products and bacterial and archaeal composition. In total 21 cows (12 Holstein, 9 Swedish Red) identified as persistent low, medium or high CH4 emitters over a 3 month period were furthermore chosen for analysis of microbial community structure in rumen fluid. This was assessed by sequencing the V4 region of 16S rRNA gene and by quantitative qPCR of targeted Methanobrevibacter groups. The results showed a positive correlation between low CH4 emitters and higher abundance of Methanobrevibacter ruminantium clade. Principal coordinate analysis (PCoA) on operational taxonomic unit (OTU) level of bacteria showed two distinct clusters (P < 0.01) that were related to CH4 production. One cluster was associated with low CH4 production (referred to as cluster L) whereas the other cluster was associated with high CH4 production (cluster H) and the medium emitters occurred in both clusters. The differences between clusters were primarily linked to differential abundances of certain OTUs belonging to Prevotella. Moreover, several OTUs belonging to the family Succinivibrionaceae were dominant in samples belonging to cluster L. Fermentation pattern of volatile fatty acids showed that proportion of propionate was higher in cluster L, while proportion of butyrate was higher in cluster H. No difference was found in milk production or organic matter digestibility between cows. Cows in cluster L had lower CH4/kg energy corrected milk (ECM) compared to cows in cluster H, 8.3 compared to 9.7 g CH4/kg ECM, showing that low CH4 cows utilized the feed more efficient for milk production which might indicate a more efficient microbial population or host genetic differences that is reflected in bacterial and archaeal (or methanogens) populations.

Effects on enteric methane production and bacterial and archaeal communities by the addition of cashew nut shell extract or glycerol—An in vitro evaluation

The objective of the study was to evaluate the effect of cashew nut shell extract (CNSE) and glycerol (purity >99%) on enteric methane (CH4) production and microbial communities in an automated gas in vitro system. Microbial communities from the in vitro system were compared with samples from the donor cows, in vivo. Inoculated rumen fluid was mixed with a diet with a 60:40 forage:concentrate ratio and, in total, 5 different treatments were set up: 5mg of CNSE (CNSE-L), 10mg of CNSE (CNSE-H), 15mmol of glycerol/L (glycerol-L), and 30mmol of glycerol/L (glycerol-H), and a control without feed additive. Gas samples were taken at 2, 4, 8, 24, 32, and 48h of incubation, and the CH4 concentration was measured. Samples of rumen fluid were taken for volatile fatty acid analysis and for microbial sequence analyses after 8, 24, and 48h of incubation. In vivo rumen samples from the cows were taken 2h after the morning feeding at 3 consecutive days to compare the in vitro system with in vivo conditions. The gas data and data from microbial sequence analysis (454 sequencing) were analyzed using a mixed model and principal components analysis. These analyses illustrated that CH4 production was reduced with the CNSE treatment, by 8 and 18%, respectively, for the L and H concentration. Glycerol instead increased CH4 production by 8 and 12%, respectively, for the L and H concentration. The inhibition with CNSE could be due to the observed shift in bacterial population, possibly resulting in decreased production of hydrogen or formate, the methanogenic substrates. Alternatively the response could be explained by a shift in the methanogenic community. In the glycerol treatments, no main differences in bacterial or archaeal population were detected compared with the in vivo control. Thus, the increase in CH4 production may be explained by the increase in substrate in the in vitro system. The reduced CH4 production in vitro with CNSE suggests that CNSE can be a promising inhibitor of CH4 formation in the rumen of dairy cows.

A prediction equation for enteric methane emission from dairy cows for use in NorFor

Abstract A data-set with 47 treatment means (N = 211) was compiled from research institutions in Denmark, Norway, and Sweden in order to develop a prediction equation for enteric methane (CH4) emissions from dairy cows. The aim was to implement the equation in the Nordic feed evaluation system NorFor. The equation should therefore be based on input variables available in NorFor. The best equation to predict CH4 (MJ/d) was based on dry matter intake (DMI, kg/d), and content of (g/kg DM) fatty acids (FA), crude protein (CP), and neutral detergent fiber (NDF). The equation was CH4 = 1.36 (±0.10) × DMI – 0.125 (±0.039) × FA – 0.02 (±0.012) × CP + 0.017 (±0.005) × NDF (RMSE = 3.00 MJ CH4/d; CV = 13.8%; R2 = 0.77), where RMSE is the root mean square error and CV is the coefficient of variation. However, CP was on the borderline of being significant and did not quantitatively explain much variation in CH4 emission. Based on the present research, we concluded, therefore, that the equation CH4 = 1.23 (±0.08) × DMI – 0.145 (±0.039) × FA + 0.012 (±0.005) × NDF (RMSE = 3.10 MJ CH4/d; CV = 14.3%; R2 = 0.75) is most suited for being implemented in NorFor. However, the ability of the proposed equation to predict enteric methane emissions is uncertain until evaluated on an independent data-set.

Effect of dietary proportion of grass silage on milk fat with emphasis on odd- and branched-chain fatty acids in dairy cows

High proportions of forage in diets fed to dairy cows are interesting options in conventional production, and mandatory in organic dairy farming (e.g., within the European Union). The objectives of the present study were to study the milk fatty acid (FA) profiles, with particular focus on the odd- and branched-chain FA (OBCFA) and their association with diet composition, using 3 different proportions of grass silage in the diet. The OBCFA profiles in milk have been suggested to be potential markers to assess nutrient supply to the cows. The study included data from 24 cows in 2008 and 26 cows in 2009, using pooled milk samples from morning and evening milking within 24 h. The 3 diets were composed of the same feeds: grass silage and grain-based concentrate, but the silage component was fed in different proportions, namely 50, 70, and 85% of total dry matter intake. The cows were in late lactation, with a mean of 220 (SD=15) days in milk in 2008, and 216 (SD=35) days in milk in 2009, at the onset of the trial. Increased proportions of grass silage in the diet increased the intake of C18:3n-3, and decreased the intake of C18:2n-6 and intake of total FA. The daily intake of C18:3n-3 and C18:2n-6 was reflected in a similar increase in milk C18:3n-3, whereas the concentration of milk C18:2n-6 decreased with increasing proportion of grass silage in the diet. Increased proportions of grass silage in the diet increased the concentration of conjugated linoleic acid and the linear odd-chain FA C15:0 and C17:0, the branched-chain iso C15:0 and total OBCFA in milk. The concentration of total OBCFA in milk was shown to be positively correlated with dietary content of neutral detergent fiber. This suggests that the concentration of milk OBCFA may be useful in the future to indicate low forage intake in cows under conditions when it is not possible to measure individual forage intake.

Effects of crude protein intake from grass silage-only diets on the equine colon ecosystem after an abrupt feed change

The objective of this study was to investigate the effect of CP intake from 2 grass silage-only diets, differing in CP concentration, fed at similar DMI on the equine colon ecosystem after an abrupt feed change between the diets. Four adult right ventral colon-fistulated geldings were fed one silage-only diet high in CP (HP, 873 g of CP/d) and one diet providing recommended intakes (RP, 615 g of CP/d). An adaptation period of 15 d on either the HP or the RP diet was followed by 2 experimental periods when the diets were fed for 22 d each in a crossover design. Colon samples were taken before and at 4, 12, and 24 h, and at 7, 14, and 22 d after the feed change. During the first 24 h after the abrupt feed change, the concentrations of total anaerobic bacteria and lactobacilli were greater on the HP than the RP diet (7.1 vs. 6.7 log(10) cfu/mL, P = 0.021, 6.0 vs. 5.5 log(10) cfu/mL, P = 0.021, respectively). During the first 24 h post feed change, VFA concentrations did not differ between the diets. From 7 to 22 d, total VFA concentrations were greater on the HP diet than on the RP diet (51.8 vs. 45.1 mmol/L, P = 0.034), and colon pH was lower on the HP diet than on the RP diet (6.9 vs. 7.2, P = 0.035). After an adaptation period of 22 d, N, ammonia, and urea concentrations and osmolality of the colon fluid did not differ between diets. Fecal pH and colon and fecal DM were unchanged throughout the experiment. The results suggest that, in horses fed at the maintenance level of energy intake, a feed change between silages with different CP content may alter the colon bacterial counts within the first 24 h. Moreover, during the subsequent 3 wk, pH decreased slightly and VFA concentrations increased, but no other major alterations occurred in the composition and activities of the colon ecosystem or fecal DM.

Transfer of 137Cs to cow's milk: Investigations on dairy farms in Sweden

Since 1986, the year of the nuclear accident at Chernobyl, 137Cs activity concentrations in cows milk on dairy farms were studied in Sweden. Transfer coefficients, Fm, of 137Cs from pasture and fodder to cows milk were determined on farms in the counties of Uppsala, Gavleborg and Vastmanland in central Sweden for one month on winter-fodder, and for the first month in 1987 and in 1988 on pasture. The average Fm for all investigations (of 10 farms on winter-fodder and 11 farms on pasture in 1987 and 4 farms on pasture in 1988) south of Gavle was estimated to be 0.0055 with a range of 0.0039 to 0.0080. The 137Cs activity concentration in milk decreased with time. In summer 1992 and 1993, 137Cs in milk, on the farms still producing milk, was determined. On these farms, 137Cs activity concentration in milk was found to be < 2–21 Bq kg−1. The effective ecological half-life from 1987 was estimated to be 1.4 ± 0.5 (sd) years for milk from 10 farms with a range of 0.8–2.0 years. One farm where 137Cs in milk decreased at a slower rate, or not at all, used semi-natural and uncultivated pasture, forest meadows. On intensely managed farms, where potassium fertilizer was distributed, ploughing was performed and, in 1986, forage was cut at a higher stubble-height, the decrease of 137Cs in milk was observed to be faster.

Intake and digestion of whole-crop barley and wheat silages by dairy heifers.

The effect of maturity at harvest on the digestibility and intake of large bale silage made from whole-crop barley and wheat when fed to growing heifers was evaluated. Two crops of spring barley (Hordeum distichum cv. Filippa and Kinnan) and 1 of winter wheat (Triticum aestivum cv. Olevin) were harvested at the heading, milk, and dough stages of maturity. The silage was fed to 36 dairy heifers in a balanced crossover experiment with 3 periods and 9 treatments (diets based on 3 crops and 3 stages of maturity), organized into 6 pairs of 3 × 3 Latin squares. No clear relationship was observed between intake and stage of maturity of whole-crop cereal silage, but intake was positively correlated to silage DM content (P < 0.001, r = 0.46) and negatively correlated to NDF content (P < 0.001, r = -0.42). Organic matter digestibility decreased between the heading and milk stages of maturity in all crops (P < 0.001), did not differ between the milk and the dough stages in the 2 barley crops, but increased in the wheat silage (P = 0.034). The NDF digestibility decreased between the heading and milk stages in all crops (P < 0.001), whereas it decreased in 1 barley crop (P < 0.001), increased in the other barley (P = 0.025), and was unchanged in the wheat between the milk and dough stages of maturity. Starch digestibility was less in the 2 barley crops compared with the wheat at the dough stage of maturity (P < 0.001). The feeding value of the whole-crop barley and wheat declined between the heading and milk stages of maturity, but thereafter the effect of maturity on the feeding value was minor.