Precision in the measurement of dairy feed fractions based on particle size.

The aim of this research note is to evaluate the variability of the physical measurements obtained by a separator of feeds for dairy cows based on particle size. Fresh samples of total mixed ration (TMR) and corn silage were collected from four dairy units and were immediately fractionated using a particle separator (NASCO®, Pennsylvania State University) com- posed of two sieves (diameters of 19 and 8 mm) and a collector on the bottom. Repeatability expressed as standard devi- ation was similar between fractions (>19, 8-19 and <8 mm fractions: +1.9, +1.4 and +2.2% for TMR samples; +2.0, +1.7 and +1.5% for corn silages), but when expressed as coefficient of variation there were, for both samples, large dif- ferences between the values for fraction exceeding 19 mm (44.7 and 35.1 %, respectively for TMR and corn silages) and the middle (3.9 and 2.5 %, respectively for TMR and corn silages) and bottom fractions (3.7 and 5.6 %, respectively for TMR and corn silages). The between operator reproducibility was very close to repeatability and this indicates that the operator’s contribution to the overall variability is marginal in comparison with residual variability. In conclusion, differ- ent operators properly trained in the use of the NASCO® separator can produce satisfactory repeatable and reproducible values for the middle and the bottom fractions

Impact of NDF content and digestibility of diets based on corn silage and alfalfa on intake and milk yield of dairy cows

A meta analysis (22 studies, 83 dietary treatments) evaluated the impact of neutral detergent fiber (NDF) content and whole tract NDF digestibility (NDFD) on dry matter intake (DMI) and milk yield (MY) in high producing dairy cows fed corn silage and alfalfa based diets. Experimental diets were ingested at high levels to support high MY (24.1 and 37.3 kg/d, respectively of DM and MY). The average NDFD was of 42.9% (range: 20.0-68.0 %; within study standard error: ±4.0 %). DMI was negatively related with the dietary NDF (e.g. ± 1.0 % of NDF caused ±160 g/d of DMI;r2=0.51; P<0.01), while NDFD and NDF were positively related (r2=0.74; P<0.01; ±1.0 % of NDF caused approximately ±1.0 % of NDFD). MY was not influenced by dietary NDF. Considering a subset of 5 studies, the regression between NDFD and corn silage:alfalfa ratio in the diet (r2=0.84; P<0.01) allowed to estimate the NDFD of diets containing only alfalfa hay (55%) or corn silage (44%). In conclusion, the dietary NDF concentration influences the NDFD and this has implications both for DMI and MY of cows. Diets based on alfalfa hay have higher NDFD than those based on corn silage

Precision and accuracy of the NDF rumen degradability of hays measured by the Daisy fermenter

An inventory of 162 hay samples from Austrian permanent grasslands was used to obtain information about the precision of the in vitro NDF degradability (NDFd) measured by the Daisy fermenter and its accuracy to predict in situ NDFd. The within forage standard error of the in vitro NDFd triplicate, obtained in five consecutive incubations, was equal to 2.8%, while the effect of the four jar positions in the fermenter was not significant. The cutting frequency had a great impact on the in situ effective NDFd of hays, which ranged (P<0.01) from values of 32.9, 43.1 and 48.3% in hays obtained from 2, 3 and 4 cuts/season, respectively. The regression analysis between the in vitro and in situ NDFd values (measured at 48h and effective, k=3%/h) allowed to obtain medium degrees of correlation (r2 = 0.69 – 0.71; P<0.01) and low levels of accuracy (RSE = 4.0 -4.6 %)

Chemical composition, including secondary metabolites, and rumen fermentability of seeds and pulp of Californian (USA) and Italian grape pomaces

This study determined the chemical composition and metabolizable energy (ME) value for ruminants of seeds and pulps from grape pomaces (GP), which were produced from white and red Vitis vinifera cultivars in Italy and California (USA). Six Italian (i.e., three white and three red) and five California red cultivarswere collected after the crush of grape juice had been completed and were ensiled in micro-silos for 45 d. Fresh and ensiled sampleswere manually sieved to separate seeds from the pulp plus skin fraction and an overall inventory of 44 samples was obtained from the 24 Italian and 20 California samples (i.e., seeds and pulp fractions, fresh or ensiled from 6 or 5 cultivars, respectively). Both in seeds and pulp, the red Italian samples had higher organic matter (P<0.01), ether extract (P<0.05), neutral detergent fiber (aNDF, P<0.01), acid detergent fiber (ADF, P<0.01), lignin(sa, P<0.01) and Cu (P=0.02 and P<0.01, respectively) relative to the California red samples. In addition, K (P<0.01), Fe (P<0.01) and Zn (P=0.03 and P<0.01, respectively in seeds and pulps) were higher in red samples from California versus those from Italy. Italian white samples had higher saponins in pulp (SAP, P<0.05) and tended to have higher total extractable phenolics both in seeds and pulps (P=0.07 and P=0.10, respectively) than did Italian reds. Both in seeds and pulps, ensiling increased concentrations of aNDF (P<0.01 and P=0.08, respectively), ADF (P<0.01) and lignin(sa) (P<0.01 and P=0.03, respectively), had no impact on mineral levels and decreased concentrations anthocyanins (P=0.05) and SAP (P=0.01), respectively in seeds and pulp. Samples were fermented in diluted rumen fluid to measure in vitro rumen fermentability in terms of gas production, which was used to predict ME. Gas production from seeds of different origin were similar, with the exception of higher values at 48 h in red California cultivars with respect to those from Italy (19.2 ml versus 18.0 ml, P<0.05). In pulps, Italian reds did not differ from Italian whites, but had lower gas production than the red California samples (9.2 ml versus 12.2 ml, 16.6 ml versus 21.3 ml, 26.3 versus 32.7, P<0.01, at 4, 24 and 48 h respectively). Ensiling reduced gas production in seeds at 24 and 48 h of incubation (P<0.01) and in pulps at 48 h (P=0.09). Seeds from Italian red samples were lower (P<0.01) in ME than Italian whites (6.23 MJ/kg DM versus 6.89 MJ/kg DM, P<0.01) and higher (P<0.01) than the California samples (5.58 MJ/kg DM). There were no differences between ME of the groups of pulps, but ensiling reduced estimated ME content in seeds (5.94 MJ/kg DM versus 6.54 MJ/kg DM, P<0.01), but not in pulps. On the basis of our results, and in agreement with other recent papers and/or textbook data, the potential to use de-seededGP as a feed in diets of high producing ruminants is limited

Feeding finishing heavy pigs with corn silages: effects on backfat fatty acid composition and ham weight losses during seasoning

The effect of diets containing corn silages (whole ear or high cut whole plant corn silages, WECS and HCCS, respectively) on fatty acid composition of back fat and the weight loss of thighs during the seasoning process were examined in Italian heavy pigs (from 90 to 160 kg of live weight). Two trials were conducted in the same farm, following an identical experimental protocol. In both trials, a control diet, based on dry corn, barley, wheat, extracted soybean meal, wheat bran and supplement (47, 23, 10, 9, 8 and 3% dry matter (DM), respectively) was compared with a diet containing 30% DM of WECS (trial 1) or 20% DM of HCCS (trial 2) in substitution of bran and part of the corn. The initial fresh weight of thighs was very homogeneous between the two trials and only at the end of seasoning the hams from pigs fed the corn silage diets were slightly lighter (of about 0.5 kg, p < .05). The dietary inclusion of corn silages determined a significant increase of the saturated fraction of the back fat (from 40.6 to 41.9%, p < .05), mainly due to the increase of the C 18:0 fatty acid (from 14.3 to 15.2%, p < .05). Overall, the calculated iodine value was favourable for the fat of pigs fed silages (62.63 vs. 64.24, p = .05). In conclusion, feeding corn silages to heavy pigs has limited impact on seasoning ham losses and can slightly improve backfat quality, in terms of fatty acid composition

Impact of NDF degradability of corn silage on the milk yield potential of dairy cows.

The neutral detergent fibre (NDF) degradability of corn silage samples, measured in vitro (ivNDFd) by a filter bag system, was used to examine (i) the relationship between the ivNDFd and that calculated from acid detergent lignin (L) content (NDFd) and (ii) the impact of ivNDFd variations on the predicted milk yield (MY) of dairy cows fed corn silage based diets. A total of 173 samples of corn silage were collected during a period of three years (2001-03) in different dairy farms of the Po Valley (Northern Italy). Each sample was analysed for chemical composition and was also tested in triplicate for the ivNDFd using the DaisyII incubator (Ankom, Tech. Co., Fairport, NY, USA) with incubation time of 48hs. Moreover, the NDFd of samples was calculated from the L contents, while the measured ivNDFd values were used to estimate the NEl, the potential dry matter intakes (DMI) and to predict the MY of cows. Corn silage samples of the three years were similar for NDF and starch contents (44.2 and 30.7% DM, on average, respectively) while samples from 2003, in comparison with 2001 and 2002, had lower crude protein (6.9 vs 8.3-8.4% DM, P<0.01) and L contents (3.3 vs 3.6-3.9% DM, P<0.01) and higher ivNDFd values (53.3 vs 45.6-47.8%, P<0.01). The relationship between ivNDFd and NDFd was weak (R2=0.09, not significant). The MY predicted from the NEl content and DMI of corn silage (5.5 MJ/kg DM and 8.9 kg/d) minus the maintenance energy costs, was 11.5 kg/d on average (coefficient of variation 20%). Our simulations indicate that a variation of ivNDFd by +1.0% changes the NEl of corn silage to have an expected variation in milk yield of +0.15 kg/d. If the ivNDFd is also used to predict the corn silage DMI then a +1.0% variation in ivNDFd of corn silage produces an overall +0.23 kg/d MY variation. The present results indicate that ivNDFd is highly variable in corn silage populations and differences in this nutritional parameter have an appreciable impact on the predicted milk yield from dairy cows

the use of quantitative real time polymerase chain reaction to quantify some rumen bacterial strains in an in vitro rumen system

The aim of this work was to quantify four rumen bacterial strains (Butyrivibrio fibrisolvens, Ruminococcus albus, Streptococcus bovis, Megasphaera elsdenii) in an in vitro batch rumen fermentative system by quantitative real time polymerase chain reaction (qPCR). The experiment was a 2×2 factorial arrangement with two types of liquid rumen, collected from dairy cows (DC) and fattening bulls (FB) and two types of fermentation substrate (forage:concentrate ratios, 75:25 and 25:75) and was replicated in two fermentation runs. Fermentation fluids from FB compared to those from DC had lower pH, higher total VFA concentrations (averages of 0 and 24 h samplings, 6.70 vs 7.04 and 72.6 vs 42.7 mmol/l P<0.001) and contained less acetic (P=0.014) and more propionic (P<0.01) and butyric (P=0.029) acids. The two types of substrates incubated produced very small differences in the end fermentation products. B. fibrosolvens concentrations were higher (P<0.001) in the DC fermentation fluids compared to that from bulls (averages of 0 and 24 h sampling times, 3.47 vs 1.38 x109 copies /mL), while M. elsdenii was detected only in FB fermentation fluids. R. albus and S. bovis concentrations were not different between the two types of rumen liquid. With the only exception for B. fibrosolvens, bacteria strains considered in this study increased their concentrations in the fermentation fluid during the 24 h of in vitro incubation

repeatability and reproducibility of the cornell net carbohydrate and protein system analytical determinations

The increasing use in Italy of the Cornell Net Carbohydrate and Protein System (CNCPS) led researchers of five Italianuniversities to carry out a collaborative study to evaluate the precision of the CNCPS chemical analysis and derivate fractions.Each laboratory conducted in duplicate the chemical analyses according to the Weende (dry matter; crude protein;ether extract; crude fibre; ash), Van Soest (neutral and acid detergent fibre, NDF and ADF; acid detergent lignin; ADL)and CNCPS (soluble proteins, SP; non-protein nitrogen, NPN; neutral and acid detergent insoluble protein, NDIP andADIP; starch, ST) schemes on the same five feeds (barley meal, wheat straw, maize silage, dried lucerne and fieldbeans). Anomalous analytical data were identified and corrected by the “box-plot” graphic tool before the calculation ofthe CNCPS protein (B1, B2 and B3) and carbohydrate (A, B2 and C) fractions. Finally, repeatability (chemical analysis) andreproducibility (chemical analysis and fractions) were calculated and expressed as relative values (repeatability andreproducibility standard deviation as percentage of the corresponding mean, RSDr and RSDR, respectively). Chemicalanalyses of the Weende scheme, together with NDF, ADF and ST analyses, have satisfactory repeatability (0.3-6.2%) andreproducibility (0.3-11.2%) values. On the contrary the ADL, NPN, NDIP and ADIP analyses showed high variability, bothwithin and between laboratories (RSDr and RSDR between 20 and 45%). The SP analysis had an intermediate value ofprecision (RSDr=10.6%; RSDR=16.4%).Finally, since different combinations of several chemical analyses with scarce (ADL, NPN, NDIP, ADIP, SP) or average precision(e.g. NDF and starch) are used to calculate CNCPS fractions (excluding B2 protein fraction), also the reproducibilitiesof these fractions are poor and range from 10 to 20%

effect of dietary inclusion of flaxseed on milk yield and composition of dairy cows

The aim of the experiment was to study the effects of flaxseed inclusion on milk yield (MY), milk fat and protein contents and milk fatty acids (FA) composition in dairy cows diets. Eight Italian Friesian primiparous cows were divided into two homogeneous groups and fed a control diet (based on corn silage, fescue hay and a concentrate) or the same diet having 0.9 Kg DM concentrate replaced by coarsely grounded flaxseed for a 21 d experimental period. The groups were inverted in respect to the dietary treatments in a subsequent experimental period according to a change-over design. The flaxseed inclusion (4-5% DM) had a positive effect on dry matter intake (DMI, 22.2 vs. 21.3Kg/d) and significantly (P<0.01) increased the MY (26.9 vs. 26.1Kg/d) and milk fat corrected yield (FCM, 27.7 vs. 26.7Kg/d). Milk fat and protein percentages (4.18 and 3.46%, respectively on average) were not affected by flaxseed treatment. Results also indicated a significant (P<0.01) reduction of saturated fatty acid/unsaturated fatty acid ratio (SFA/UFA) and an increase of n-3/n-6FA, monounsaturated (MUFA) and polyunsaturated fatty acid (PUFA). Moreover a higher proportion of total C18:1 and conjugated linoleic acid isomers (CLA) was also observed for treated group

In vitro effects of different levels of quebracho and chestnut tannins on rumen methane production, fermentation parameters, and microbiota

Both condensed and hydrolysable tannins (CTs and HTs, respectively) have the ability to reduce enteric CH4 production in ruminants. However, the precise mechanism of action is not fully understood. Among the proposed hypotheses are the reduction of ruminal digestibility, direct control action on protozoa, reduction of archaea, and a hydrogen sink mechanism. In this in vitro study, which simulated rumen fermentation, two additives, one containing CTs (70% based on DM) from quebracho and one with HTs (75% based on DM) from chestnut, at four levels of inclusion (2, 4, 6, 8% on an as-fed basis) were added to the fermentation substrate and tested against a negative control. Both types of tannins significantly reduced total gas (GP) and CH4 (ml/g DM) production during the 48 h of incubation. The lower GP and CH4 production levels were linked to the reduction in dry matter digestibility caused by CTs and HTs. Conversely, no significant differences were observed for the protozoan and archaeal populations, suggesting a low direct effect of tannins on these rumen microorganisms in vitro. However, both types of tannins had negative correlations for the families Bacteroidales_BS11 and F082 and positive correlations for the genera Prevotella and Succinivibrio. Regarding the fermentation parameters, no differences were observed for pH and total volatile fatty acid production, while both CTs and HTs linearly reduced the NH3 content. CTs from quebracho were more effective in reducing CH4 production than HTs from chestnut. However, for both types of tannins, the reduction in CH4 production was always associated with a lower digestibility without any changes in archaea or protozoa. Due to the high variability of tannins, further studies investigating the chemical structure of the compounds and their mechanisms of action are needed to understand the different results reported in the literature