Cows Fed Grass Silage-based Diets Research Articles

Effect of a blend of cinnamaldehyde, eugenol and capsicum oleoresin on methane emission and lactation performance of Nordic Red dairy cows fed grass silage-based diets

The objective of this study was to investigate the effect of administering a blend of cinnamaldehyde, eugenol, and capsicum oleoresin (CEC) to lactating dairy cattle for 105 days (i.e., 15 weeks) on enteric methane emission, feed intake, milk yield and composition, and body weight. The experiment utilized 40 Nordic Red lactating dairy cows (97 ± 59 days in milk at the start of the trial; mean ± SD) blocked into pairs based on dry matter intake (DMI), milk yield, parity, and lactation stage. Cows within block were randomly assigned to 1 of 2 dietary treatments; 1) CEC supplemented at 1.2 g/cow/d or 2) a control diet without CEC. Cows were offered ad libitum a basal diet of grass silage and concentrate fed separately in a 55:45 forage to concentrate ratio on a dry matter (DM) basis. A GreenFeed system was used to measure emissions of carbon dioxide (CO2), methane (CH4) and hydrogen (H2). Supplementation with CEC decreased daily CH4 production (g/d; 3.4%) and yield (g/kg DMI; 4.2%) and daily CO2 production and yield (3.3% and 4.0%, respectively) whereas CH4 and CO2 intensities were not affected by treatment. Daily CEC supplementation tended to reduce H2 production and intensity by 21% compared with control. Additionally, feed intake, milk production, milk composition, body weight, and body condition score were not influenced by dietary CEC supplementation. These results indicate that CEC supplementation can reduce CH4 production without affecting performance of lactating dairy cows.

Effect of the nature of energy (lipids vs. carbohydrates) on enteric methane emission and dairy performance in cows fed grass silage-based diets

This work aimed to investigate the effect of energy nature (lipids vs. carbohydrates) on enteric methane emission (eCH4 ) and performance in dairy cows fed grass silage-based diets. Eight multiparous Holstein cows were used in a 4 × 4 Latin square design, with 4 experimental periods of 28 days each. Cows were fed with 4 iso-energetic diets based on grass silage and supplemented with different levels of rapeseed oil (RO) (0, 1.5, 3.0, 4.5% of dietary dry matter (DM), Control, RO-low, RO-medium, RO-high diets, respectively) in substitution of starch from concentrate. Dairy performance, total-tract digestibility, and rumen parameters were measured when animals were in individual respiration chambers for quantifying eCH4. Intake of DM decreased with RO-high compared to other diets. Methane emissions were lowered similarly with all diets containing RO compared to Control (on average, -19% in g/d, −13% in g/kg DMI, −21% in g/kg milk). Ruminal propionate proportion was higher, whereas that of butyrate was lower with RO-high compared to the other diets. Milk yield was higher with RO-low and RO-medium, and was lower for RO-high compared to Control. Milk C16:0 concentration was lower, and C18:1c9, C18:1t11, and other rumen biohydrogenation intermediate concentrations were higher with diets containing RO compared to Control. The shift from the C18:1t11 to C18:1t10 biohydrogenation pathway is in agreement with the milk fat depression observed with RO-medium and RO-high. The inclusion of RO at 1.5% was the best compromise between eCH4, feed efficiency, and milk nutritional quality in cows fed grass silage-based diets.

O21 The effects of grain legume and rapeseed meal supplementation on amino acid metabolism of dairy cows fed grass silage-based diets

O21 The effects of grain legume and rapeseed meal supplementation on amino acid metabolism of dairy cows fed grass silage-based diets

Effects of faba bean, blue lupin and rapeseed meal supplementation on amino acid metabolism of dairy cows fed grass silage-based diets.

Information about the amino acid (AA) supply of locally produced protein supplements to dairy cow metabolism is needed to design sustainable diets for milk production. In this dairy cow experiment, grass silage and cereal-based diets supplemented with isonitrogenous amounts of rapeseed meal (RSM), faba beans (FB) and blue lupin seeds (BL) were compared with a control diet (CON) without protein supplementation. The diets were arranged as a 4×4 Latin Square using periods of 21days, and four rumen-cannulated Nordic Red dairy cows were used in the experiment. The intake of all AAs increased in response to protein supplementation and was for many individual AAs higher when RSM rather than the grain legumes FB and BL were fed. The total AA flow at the omasal canal was 3026, 3371, 3373 and 3045g/day for cows fed CON, RSM, FB and BL, respectively, but only RSM resulted in higher milk protein output. This may be explained by the higher provision of essential AA for milk protein synthesis when RSM was fed. The cows fed FB showed some positive features such as a tendency for greater omasal flow of branched-chain AA compared with BL. Overall, low plasma methionine and/or glucose concentrations in all treatments suggest that their supply was possibly limiting further production responses under the dietary conditions of the current study. It seems that the benefits of grain legume supplementation are limited when high-quality grass silage and cereal-based diets are used as the basal diet, but higher responses in amino acid supply and subsequent production responses can be expected when RSM is used.

Effects of replacement of barley with oats on milk fatty acid composition in dairy cows fed grass silage-based diets

This study consists of milk fatty acid (FA) data collected during 2 in vivo experiments. For this study, 8 cows from each experiment were included in a replicated 4 × 4 Latin square design. At the start of experiment 1 (Exp1) cows were at (mean ± standard deviation) 87 ± 34.6 d in milk, 625 ± 85.0 kg of body weight, and 32.1 ± 4.17 kg/d milk yield and at the start of experiment 2 (Exp2) cows were at 74 ± 18.2 d in milk, 629 ± 87.0 kg of body weight, and 37.0 ± 3.2 kg/d milk yield. In Exp1, we examined the effects of gradual replacement of barley with hulled oats (oats with hulls) on milk FA composition. The basal diet was grass silage and rapeseed meal (58 and 10% of diet DM, respectively), and the 4 grain supplements were formulated so that barley was gradually replaced by hulled oats at levels of 0, 33, 67, and 100% on dry matter basis. In Exp2, we examined (1) the effects of replacing barley with both hulled and dehulled oats (oats without hulls) and (2) the effects of gradual replacement of hulled oats with dehulled oats on milk FA composition. The basal diet was grass silage and rapeseed meal (60 and 10% of diet DM, respectively), and the 4 pelleted experimental concentrates were barley, hulled oats, a 50:50 mixture of hulled and dehulled oats, and dehulled oats on dry matter basis. In Exp1, gradual replacement of barley with hulled oats decreased relative proportions of 14:0, 16:0, and total saturated FA (SFA) in milk fat linearly, whereas proportions of 18:0, 18:1, total monounsaturated FA, and total cis unsaturated FA increased linearly. Transfer efficiency of total C18 decreased linearly when barley was replaced by hulled oats in Exp1. In Exp2, relative proportions of 14:0, 16:0, and total SFA were lower, whereas proportions of 18:0, 18:1, monounsaturated FA, and cis unsaturated FA were higher in milk from cows fed the oat diets than in milk from cows fed the barley diet. Moreover, in Exp2, gradual replacement of hulled oats with dehulled oats slightly decreased the relative proportion of 14:0 in milk fat but did not affect the proportions of 16:0, 18:0, 18:1, total SFA, monounsaturated FA, trans FA, or polyunsaturated FA. In Exp2, transfer efficiency of total C18 was lower when cows were fed the oat diets than when fed the barley diet and decreased linearly when hulled oats were replaced with dehulled oats. Predictions of daily CH4 emissions (g/d) using the on-farm available variables energy-corrected milk yield and body weight were not markedly improved by including milk concentrations of individual milk FA in prediction equations. In conclusion, replacement of barley with oats as a concentrate supplement for dairy cows fed a grass silage-based diet could offer a practical strategy to change the FA composition of milk to be more in accordance with international dietary guidelines regarding consumption of SFA.

Effects of faba bean, blue lupin and rapeseed meal supplementation on nitrogen digestion and utilization of dairy cows fed grass silage-based diets

There is increasing interest in using locally produced protein supplements in dairy cow feeding. The objective of this experiment was to compare rapeseed meal (RSM), faba beans (FBs) and blue lupin seeds (BL) at isonitrogenous amounts as supplements of grass silage and cereal based diets. A control diet (CON) without protein supplement was included in the experiment. Four lactating Nordic Red cows were used in a 4 × 4 Latin Square design with four 21 d periods. The milk production increased with protein supplementation but when expressed as energy corrected milk, the response disappeared due to substantially higher milk fat concentration with CON compared to protein supplemented diets. Milk protein output increased by 8.5, 4.4 and 2.7% when RSM, FB and BL were compared to CON. The main changes in rumen fermentation were the higher propionate and lower butyrate proportion of total rumen volatile fatty acids when the protein supplemented diets were compared to CON. Protein supplementation also clearly increased the ruminal ammonia N concentration. Protein supplementation improved diet organic matter and NDF digestibility but efficiency of microbial protein synthesis per kg organic matter truly digested was not affected. Flow of microbial N was greater when FB compared to BL was fed. All protein supplements decreased the efficiency of nitrogen use in milk production. The marginal efficiency (amount of additional feed protein captured in milk protein) was 0.110, 0.062 and 0.045 for RSM, FB and BL, respectively. The current study supports the evidence that RSM is a good protein supplement for dairy cows, and this effect was at least partly mediated by the lower rumen degradability of RSM protein compared to FB and BL. The relatively small production responses to protein supplementation with simultaneous decrease in nitrogen use efficiency in milk production suggest that economic and environmental consequences of protein feeding need to be carefully considered.

Postpartum responses of dairy cows supplemented with cereal grain or fibrous by-product concentrate

The present study examined the effect of replacing cereal grain with a fibrous by-product concentrate on nutrient intake, milk production traits and fatty acid composition, diet digestibility, feed conversion efficiency (FCE), CH4 and CO2 emissions, and plasma blood parameters of dairy cows in early lactation. Twenty-two Nordic Red cows were randomly assigned to one of two dietary treatments immediately after calving until 18 weeks in lactation. The cereal grain treatment contained 593 g/kg of grass silage, 317 g/kg of cereal grain mixture (barley, oat, and wheat), 79 g/kg of heat-treated rapeseed meal, and 11 g/kg of a mineral mix on a DM basis. A mixture of unmolassed beet pulp, wheat middlings, barley fibre, and wheat bran replaced cereal grains in the by-product treatment. The diets were isocaloric and isonitrogenous and were fed ad libitum as total mixed rations. The by-product diet had a higher fibre content, while starch content was reduced compared with the cereal grain diet. Despite the 12 %-unit difference in dietary starch content, no differences in DMI were observed. Similarly, no differences in body weight and body condition score (BCS) were observed between treatments. Cows fed the fibrous by-product diet had lower apparent total-tract digestibility of DM (683 g/kg), organic matter (700 g/kg), and crude protein (665 g/kg) compared to those fed cereal grain diet (735, 749, and 699 g/kg, respectively), but milk yield and composition, as well as FCE were not affected by treatment. The edible feed conversion ratio in the by-product group was on average 3.7- folds higher than the cereal grain group. Total CH4 emission (g/d) and CH4 yield (g/kg DMI) reduced by 10.3% on average when by-product replaced cereal grains, but CH4 intensity (g CH4/kg ECM) was not significantly influenced by diet. Although the feeding of by-product had no effect on milk fat content, it changed its fatty acid profile by increasing the proportion of some unsaturated fatty acids (ƩC18:1 trans, C18:3 cis-9 cis-12 cis-15, omega-3) in milk fat. Replacing cereal grain with fibrous by-product in the diets of early lactation dairy cows had no effect on their risk of developing metabolic disorders. These findings suggest that cows fed grass silage-based diets can be supplemented with fibrous by-product concentrates without affecting feed efficiency or energy balance status, thereby supporting sustainable food production. However, future works should evaluate the economic aspects of feeding by-product concentrates to determine their practical application for feed manufacturers and farmers.

Effects of replacing wheat starch with glycerol on methane emissions, milk production, and feed efficiency in dairy cows fed grass silage-based diets

To lower the effect of climate change from cattle production, we should aim at decreasing their enteric methane emissions per kilogram of milk or meat. Glycerol may be absorbed through the rumen epithelium and would consequently be less available to microbes in the rumen. Glycerol could thus supply dairy cows with energy for milk production without contributing much to methane production. This study evaluated the effect of replacing wheat starch with glycerol on milk production, feed intake, and methane emissions. Twenty-two Swedish Red cows in mid lactation were used in a switch-back, change-over experiment with 3 periods of 21 d. The 2 dietary treatments consisted of a total mixed ration based on (g/kg of dry matter) grass silage (605), rapeseed meal (120), and barley (70) and either wheat starch or refined glycerol (200) fed ad libitum. The glycerol diet resulted in higher dry matter intake (21.6 vs. 20.1 kg/d) and methane emissions (482 vs. 423 g/d) compared with the diet containing wheat starch, whereas no difference was found in energy-corrected milk yield (28.4 vs. 29.7 kg/d). These results indicate that when glycerol is mixed with the feed, it is available to rumen microbes to a larger extent than initially assumed. Compared with wheat starch, adding refined glycerol (200 g/kg of dry matter) to the feed of dairy cows does not seem to have the potential to decrease enteric methane emissions.

Plant oil supplements reduce methane emissions and improve milk fatty acid composition in dairy cows fed grass silage-based diets without affecting milk yield

Four lipid supplements varying in chain length or degree of unsaturation were examined for their effects on milk yield and composition, ruminal CH4 emissions, rumen fermentation, nutrient utilization, and microbial ecology in lactating dairy cows. Five Nordic Red cows fitted with rumen cannulas were used in a 5 × 5 Latin square with five 28-d periods. Treatments comprised total mixed rations based on grass silage with a forage-to-concentrate ratio of 60:40 supplemented with no lipid (CO) or 50 g/kg of diet dry matter (DM) of myristic acid (MA), rapeseed oil (RO), safflower oil (SO), or linseed oil (LO). Feeding MA resulted in the lowest DM intake, and feeding RO reduced DM intake compared with CO. Feeding MA reduced the yields of milk, milk constituents, and energy-corrected milk. Plant oils did not influence yields of milk and milk constituents, but reduced milk protein content compared with CO. Treatments had no effect on rumen fermentation characteristics, other than an increase in ammonia-N concentration due to feeding MA, RO, and SO compared with CO. Lipid supplements reduced daily ruminal CH4 emission; however, the response was to some extent a result of lower feed intake. Lipids modified microbial community structure without affecting total counts of bacteria, archaea, and ciliate protozoa. Dietary treatments had no effect on the apparent total tract digestibility of organic matter, fiber, and gross energy. Treatments did not affect either energy secreted in milk as a proportion of energy intake or efficiency of dietary N utilization. All lipids lowered de novo fatty acid synthesis in the mammary gland. Plant oils increased proportions of milk fat 18:0, cis 18:1, trans and monounsaturated fatty acids, and decreased saturated fatty acids compared with CO and MA. Both SO and LO increased the proportion of total polyunsaturated fatty acids, total conjugated linolenic acid, and cis-9,trans-11 conjugated linoleic acid. Feeding MA clearly increased the Δ9 desaturation of fatty acids. Our results provide compelling evidence that plant oils supplemented to a grass silage-based diet reduce ruminal CH4 emission and milk saturated fatty acids, and increase the proportion of unsaturated fatty acids and total conjugated linoleic acid while not interfering with digestibility, rumen fermentation, rumen microbial quantities, or milk production.

The effects of legume seeds on the lactation performance of dairy cows fed grass silage-based diets

The aim was to study if locally produced organic legume seeds as protein supplement could improve the performance of dairy cows. The experiment was a cyclic change over design were the control diet consisted of grass silage and barley (60:40) on a dry matter (DM) basis. Barley was replaced with rapeseed expeller (RSE), or isonitrogenous supplements of peas, untreated field beans (UFB), heat-treated FB (TFB) or a lower level of TFB (TFB-low) that provided the same dietary metabolizable protein concentrations as of UFB. None of the legume protein supplementations had effect on DM intake (DMI) neither on energy corrected milk yield compared to control. The RSE treatment increased milk (24.8 vs. 23.6 kg d-1) and protein yield (913 vs. 863 g d-1) compared to other protein supplements. Heat-treated FB had no effect on DMI, milk or protein yield compared to UFB. Only RSE resulted in improvements in dairy cows performance in relation to the control diet.

Effects of soybean meal or canola meal on milk production and methane emissions in lactating dairy cows fed grass silage-based diets

This study evaluated the effects of soybean meal (SBM) and heat-moisture-treated canola meal (TCM) on milk production and methane emissions in dairy cows fed grass silage-based diets. Twenty-eight Swedish Red cows were used in a cyclic change-over experiment with 4 periods of 21 d and with treatments in 2×4 factorial arrangement (however, the control diet without supplementary protein was not fed in replicate). The diets were fed ad libitum as a total mixed ration containing 600g/kg of grass silage and 400g/kg of concentrates on a dry matter (DM) basis. The concentrate without supplementary protein consisted of crimped barley and premix (312 and 88g/kg of DM), providing 130g of dietary crude protein (CP)/kg of DM. The other 6 concentrates were formulated to provide 170, 210, or 250g of CP/kg of DM by replacing crimped barley with incremental amounts of SBM (50, 100, or 150g/kg of diet DM) or TCM (70, 140, or 210g/kg of diet DM). Feed intake was not influenced by dietary CP concentration, but tended to be greater in cows fed TCM diets compared with SBM diets. Milk and milk protein yield increased linearly with dietary CP concentration, with greater responses in cows fed TCM diets compared with SBM diets. Apparent N efficiency (milk N/N intake) decreased linearly with increasing dietary CP concentration and was lower for cows fed SBM diets than cows fed TCM diets. Milk urea concentration increased linearly with increased dietary CP concentration, with greater effects in cows fed SBM diets than in cows fed TCM diets. Plasma concentrations of total AA and essential AA increased with increasing dietary CP concentration, but no differences were observed between the 2 protein sources. Plasma concentrations of Lys, Met, and His were similar for both dietary protein sources. Total methane emissions were not influenced by diet, but emissions per kilogram of DM intake decreased quadratically, with the lowest value observed in cows fed intermediate levels of protein supplementation. Methane emissions per kilogram of energy-corrected milk decreased more when dietary CP concentration increased in TCM diets compared with SBM diets. Overall, replacing SBM with TCM in total mixed rations based on grass silage had beneficial effects on milk production, N efficiency, and methane emissions across a wide range of dietary CP concentrations.

Dietary fish oil supplements depress milk fat yield and alter milk fatty acid composition in lactating cows fed grass silage-based diets

The potential of dietary fish oil (FO) supplements to increase milk 20:5n-3 and 22:6n-3 concentrations and the associated effects on milk fatty acid (FA) composition, intake, and milk production were examined. Four multiparous lactating cows offered a grass silage-based diet (forage:concentrate ratio 58:42, on a dry matter basis) supplemented with 0, 75, 150, or 300g of FO/d (FO0, FO75, FO150, and FO300, respectively) were used in a 4×4 Latin square with 28-d experimental periods. Milk FA composition was analyzed by complementary silver-ion thin-layer chromatography, gas chromatography-mass spectrometry, and silver-ion HPLC. Supplements of FO decreased linearly dry matter intake, yields of energy-corrected milk, milk fat and protein, and milk fat content. Compared with FO0, milk fat content and yield were decreased by 30.1 and 40.6%, respectively, on the FO300 treatment. Supplements of FO linearly increased milk 20:5n-3 and 22:6n-3 concentrations from 0.07 to 0.18 and 0.03 to 0.10g/100g of FA, respectively. Enrichment of 20:5n-3 and 22:6n-3 was accompanied by decreases in 4- to 18-carbon saturated FA and increases in total conjugated linoleic acid (CLA), trans FA, and polyunsaturated FA concentrations. Fish oil elevated milk fat cis-9,trans-11 CLA content in a quadratic manner, reaching a maximum on FO150 (from 0.61 to 2.15g/100g of FA), whereas further amounts of FO increased trans-10 18:1 with no change in trans-11 18:1 concentration. Supplements of FO also resulted in a dose-dependent appearance of 37 unique 20- and 22-carbon intermediates in milk fat. Concentrations of 16-, 18-, 20-, and 22-carbon trans FA were all increased by FO, with enrichment of trans 18:1 and trans 18:2 being quantitatively the most important. Decreases in milk fat yield to FO were not related to changes in milk trans-10,cis-12 CLA concentration or estimated milk fat melting point. Partial least square regression analysis indicated that FO-induced milk fat depression was associated with changes in the concentrations of multiple FA in milk. Even though a direct cause and effect could not be established, a decrease in 18:0 supply in combination with increased mammary uptake of cis-11 18:1, trans-10 18:1, and trans 20- and 22-carbon FA may contribute. In conclusion, dietary FO supplements enrich 20:5n-3 and 22:6n-3 in milk, but also elevate mono- and polyenoic trans FA concentrations, and in high amounts alter the distribution of individual trans FA isomers.

Effect of camelina oil or live yeasts (Saccharomyces cerevisiae) on ruminal methane production, rumen fermentation, and milk fatty acid composition in lactating cows fed grass silage diets

The potential of dietary supplements of 2 live yeast strains (Saccharomyces cerevisiae) or camelina oil to lower ruminal methane (CH4) and carbon dioxide (CO2) production and the associated effects on animal performance, rumen fermentation, rumen microbial populations, nutrient metabolism, and milk fatty acid (FA) composition of cows fed grass silage-based diets were examined. Four Finnish Ayrshire cows (53±7 d in milk) fitted with rumen cannula were used in a 4×4 Latin square with four 42-d periods. Cows received a basal total mixed ration (control treatment) with a 50:50 forage-to-concentrate ratio [on a dry matter (DM) basis] containing grass silage, the same basal total mixed ration supplemented with 1 of 2 live yeasts, A or B, administered directly in the rumen at 1010 cfu/d (treatments A and B), or supplements of 60g of camelina oil/kg of diet DM that replaced concentrate ingredients in the basal total mixed ration (treatment CO). Relative to the control, treatments A and B had no effects on DM intake, rumen fermentation, ruminal gas production, or apparent total-tract nutrient digestibility. In contrast, treatment CO lowered DM intake and ruminal CH4 and CO2 production, responses associated with numerical nonsignificant decreases in total-tract organic matter digestibility, but no alterations in rumen fermentation characteristics or changes in the total numbers of rumen bacteria, methanogens, protozoa, and fungi. Compared with the control, treatment CO decreased the yields of milk, milk fat, lactose, and protein. Relative to treatment B, treatment CO improved nitrogen utilization due to a lower crude protein intake. Treatment A had no influence on milk FA composition, whereas treatment B increased cis-9 10:1 and decreased 11-cyclohexyl 11:0 and 24:0 concentrations. Treatment CO decreased milk fat 8:0 to 16:0 and total saturated FA, and increased 18:0, 18:1, 18:2, conjugated linoleic acid, 18:3n-3, and trans FA concentrations. Decreases in ruminal CH4 production to treatment CO were related, at least in part to lowered DM intake, whereas treatments had no effect on ruminal CH4 emission intensity (g/kg of digestible organic matter intake or milk yield). Results indicated that live yeasts A and B had no influence on animal performance, ruminal gas production, rumen fermentation, or nutrient utilization in cows fed grass silage-based diets. Dietary supplements of camelina oil decreased ruminal CH4 and CO2 production, but also lowered the yields of milk and milk constituents due to an adverse effect on intake.

Identification and Ruminal Outflow of Long‐Chain Fatty Acid Biohydrogenation Intermediates in Cows Fed Diets Containing Fish Oil

The abundance of 20- to 24-carbon fatty acids in omasal digesta of cows fed grass silage-based diets supplemented with 0 (Control) and 250 g/day of fish oil (FO) was examined to investigate the fate of long-chain unsaturated fatty acids in the rumen. Complimentary argentation thin-layer chromatography and gas-chromatography mass-spectrometry analysis of fatty acid methyl esters and corresponding 4,4-dimethyloxazoline derivatives prepared from fish oil and omasal digesta enabled the structure of novel 20- to 22-carbon fatty acids to be elucidated. Compared with the Control, the FO treatment resulted in the formation and accumulation of 27 novel 20- and 22-carbon biohydrogenation intermediates containing at least one trans double bond and the appearance of cis-14 20:1, 20:2n-3, 21:4n-3 and 22:3n-6 not contained in fish oil. No conjugated ≥ 20-carbon fatty acids were detected in Control or FO digesta. In conclusion, fish oil in the diet results in the formation of numerous long-chain biohydrogenation intermediates in the rumen of lactating cows. Comparison of the intake and flow of 20-, 21- and 22-carbon fatty acids at the omasum in cows fed the Control and FO treatments suggests that the first committed steps of 20:5n-3, 21:5n-3 and 22:6n-3 hydrogenation in the rumen involve the reduction and/or isomerisation of double bonds closest to the carboxyl group.

Estimation of rumen outflow in dairy cows fed grass silage-based diets by use of reticular sampling as an alternative to sampling from the omasal canal

A study was conducted to compare nutrient flows determined by a reticular sampling technique with those made by sampling digesta from the omasal canal. Six lactating dairy cows fitted with ruminal cannulas were used in a design with a 3 × 2 factorial arrangement of treatments and 4 periods. Treatments were 3 grass silages differing mainly in neutral detergent fiber (NDF) concentrations: 412, 530, or 639 g/kg of dry matter, each combined with 1 of 2 levels of concentrate feed. Digesta was collected from the reticulum and the omasal canal to represent a 24-h feeding cycle. Nutrient flow was calculated using the reconstitution system based on 3 markers (Co, Yb, and indigestible NDF) and using 15N as a microbial marker. Large and small particles and the fluid phase were recovered from digesta collected at both sampling sites. Bacterial samples from the reticulum and the omasum were separated into liquid- and particle-associated bacteria. Reticular samples were sieved through a 1-mm sieve before isolation of digesta phases and bacteria. Composition of the large particle phase differed mainly in fiber content of the digesta obtained from the 2 sampling sites. Sampling site did not affect marker concentration in any of the phases with which the markers were primarily associated. The 15N enrichment of bacterial samples did not differ between sampling sites. The reticular and omasal canal sampling techniques gave similar estimates of marker concentrations in reconstituted digesta, estimates of ruminal flow, and ruminal digestibility values for dry matter, organic matter, starch, and N. Sampling site × diet interactions were also not significant. Concentration of NDF was 2.2% higher in reconstituted omasal digesta than in reconstituted reticular digesta. Ruminal NDF digestibility was 2.7% higher when estimated by sampling the reticulum than by sampling the omasal canal. The higher estimate of ruminal NDF digestibility with the reticular sampling technique was due to differences in NDF concentration of reconstituted digesta. This study shows that nutrient and microbial protein outflow from the rumen can be measured using a reticular sampling technique. The reticular sampling technique provides a promising alternative to sampling from the omasal canal because there is less interference with the animal and it does not require advanced sampling equipment.

A meta-analysis of feed digestion in dairy cows. 2. The effects of feeding level and diet composition on digestibility

A meta-analysis based on published experiments with lactating dairy cows fed mainly grass silage-based diets was conducted to study the effects of intake, diet composition, and digestibility at a maintenance level of feeding on the apparent total diet digestibility. A data set that included a total of 497 dietary treatment means from 92 studies was collected and analyzed using mixed model regression analysis with a random study effect. Diet organic matter digestibility (OMD) in dairy cows at a production level (OMDp) was positively associated with OMD at maintenance (OMDm), but the slope was less than 1 (0.69). Diet OMDp decreased as feed intake increased, and diets with high OMDm exhibited greater depressions in digestibility with increased intake than did diets with low OMDm. Digestibility of organic matter and neutral detergent fiber (NDF) increased as dietary crude protein concentration increased, whereas increased concentrate fat decreased digestibility. Replacement of grass silage with whole-crop cereal silage was associated with a quadratic decrease in diet digestibility. Metabolic fecal output, defined as fecal organic matter minus NDF, averaged 95.8 (SE=0.65) g/kg of dry matter intake, and it was not influenced by intake or diet composition. Variation in OMDp in cows fed grass silage-based diets was therefore attributable to variation in dietary NDF concentration and NDF digestibility. Depression in digestibility of organic matter with increased intake was less than predicted by the National Research Council and Cornell Net Carbohydrate and Protein systems. The following 2-parameter model indicates that the difference between OMD estimated in sheep fed at maintenance compared with dairy cows at production level is related both to dry matter intake and digestibility at maintenance level: OMDp=257 (±43) + 0.685 (±0.054) × OMDm (g/kg of dry matter) – 2.6 (±0.44) × dry matter intake (kg/d); adjusted residual mean square error=8.4g/kg. It was concluded that diet digestibility in dairy cows can be predicted accurately and precisely from digestibility estimated at maintenance intake in sheep by using regression models including animal and dietary factors.

Utilization and Partition of Dietary Nitrogen in Dairy Cows Fed Grass Silage-Based Diets

Data from 207 production trials (998 treatment means) were used to study the effects of animal and dietary characteristics on the efficiency of N utilization for milk protein production, and on fecal N, urinary N, and total manure N output. The average efficiency of transferring dietary N to milk N (MNE; milk N/N intake) was 277 (SD=36.0) g/kg. Nitrogen efficiency was poorly related to milk yield. Dietary concentrations of crude protein (CP) and protein balance in the rumen (PBV) were the best single predictors of MNE. Dietary CP concentration explained variation in MNE better than did N intake. Bivariate models with PBV or metabolizable protein (MP) explained the variation better than CP alone. The effects of protein feeding parameters on MNE were consistent among data subsets from studies investigating the effects of the amount and protein concentration of concentrate supplement, silage digestibility, silage fermentation quality, or substitution of grass silage with legume silage. The model with total dry matter and N intakes as independent variables explained fecal, urinary, and total manure N output more precisely than N intake alone. The model of fecal N output suggested that the true digestibility of dietary N was 0.91, and that metabolic and endogenous N was the major component in fecal N. The proportion of urine N in manure N was strongly related to dietary CP concentration. Including the concentration of dietary carbohydrates only slightly improved the models, indicating that the most effective strategy to improve MNE and to decrease N losses in manure, especially in urine, is to avoid feeding diets with excessively high CP concentration and especially excess ruminally degradable CP.

Evaluation of the effects of dietary particle fractions on fermentation profile and concentration of microbiota in the rumen of dairy cows fed grass silage-based diets

The study evaluated the effects of three different theoretical particle lengths (TPL) of grass silage on the distribution of particle fractions of the diet and the resulting effects on fermentation profile and concentrations of protozoa and mixed bacterial mass in the rumen of three lactating Holstein cows fed total mixed rations (45% grass silage, 5% grass hay and 50% concentrate) ad libitum. Decreasing TPL of grass silage (long, medium, short) reduced particles retained on the 19-mm sieve of the Penn State Particle Separator, while particle fractions from 8 mm to 19 mm and smaller than 8 mm were increased. Different TPL did not affect pH and the concentration of volatile fatty acids in the rumen. However, lowering the TPL from long to medium increased significantly the bicarbonate concentration, acetate proportion and protozoal number in the rumen, whereas the proportion of bacterial protein in ruminal digesta and its amino acid concentration were significantly increased by the short TPL. For the current feeding conditions, it can be concluded that increasing the fraction of particles between 8 and 19 mm and probably even the fraction below 8 mm by decreasing TPL of grass silage do not adversely affect rumen conditions and can be beneficial in terms of optimising concentration and activity of ruminal microbiota in high-yielding dairy cows.

Effects of Various Glucogenic Sources on Production and Metabolic Responses of Dairy Cows Fed Grass Silage-Based Diets

Four rumen cannulated Finnish Ayrshire cows in midlactation were used in an experiment designed as a 4×5 incomplete Latin square with 2-wk periods to compare effects of glucogenic substrates on grass silage-based diets. The five treatments were continuous infusions of 1) water (control), 2) casein 300g/d, 3) glucose 300g/d, 4) propionic acid 247g/d, and 5) barley starch 270g/d. Substrates were infused either into the rumen (propionic acid) or into the abomasum (other substrates). As a basal diet, cows were fed a formic acid treated grass silage ad libitum (digestible organic matter 690g/kg dry matter [DM], crude protein [CP] 131g/kg DM) and a barley-rapeseed concentrate (CP 141g/kg DM) at a rate of 7kg/d. Production responses to glucogenic substrates other than casein were negligible, suggesting that glucose supply of the cows did not primarily limit milk production. However, with casein cows produced significantly more milk, milk protein, and lactose than with other glucogenic substrates. Casein increased urea and essential amino acid (EAA), and decreased nonessential AA (NEAA) in arterial plasma compared with other substrates, suggesting that casein provided precursors both in terms of NEAA for gluconeogenesis and EAA for milk protein synthesis. This puts forward that providing the AA needs of the mammary gland for milk protein synthesis are met, glucose supply may become the next limiting factor for milk protein synthesis in cows fed diets based on restrictively fermented grass silage. The limited supply of AA from the basal diet, and possibly the low production levels of cows partly invalidated the hypothesis of monitoring differing glucogenic substrates for grass silage-based diets.

Effects of increasing concentrate energy supply on the performance of loose-housed dairy cows fed grass silage-based diets

The effects of increased concentrate level on milk production was assessed during two consecutive indoor feeding seasons according to a continuous randomised block design using 44 (season 1) and 47 (season 2) Finnish Ayrshire cows. Treatments allocated according to a 2×2 factorial design consisted of two concentrate levels and two protein feeding systems. Low and high concentrate feeding regimens were applied to multiparous cows as 9 and 14 kg/day during days 1–150 of lactation and 8 and 11.5 kg for days 151–224, respectively. Primiparous cows received proportionately 0.80 of that fed to multiparous cows. In order to identify the effects of concentrate energy alone, concentrates were formulated so that increases in concentrate feeding resulted in either a constant supply of concentrate crude protein (CP) (mean 1.4 kg/day) or constant intake of rapeseed meal (RSM) (mean 1.7 kg DM/day). Consequently, concentrate CP content decreased with the increasing level of concentrate. Concentrate was offered through computerised self-feeders and silage was fed ad libitum. Increasing energy intake at a constant CP level seemed to have a more negative effect on silage dry matter (DM) intake compared with feeding a constant supply of RSM. Increases in concentrate DM intake resulted in mean substitution rates of 0.48 and 0.25 for CP and RSM diets, respectively. However, the positive effect of concentrate supplementation on milk yield was independent of protein feeding strategies. Milk production increased ( P<0.05) from 24.4 to 26.4 kg energy corrected milk (ECM) when energy level was increased, and on average 0.58 kg milk per kg increase in concentrate DM intake. The response to increased concentrate energy corresponded well with the responses reported earlier with a fixed concentrate composition. It is concluded that it was not possible to compensate a high amount of concentrate with low CP content with low amounts of concentrate with high CP content. However, feed utilization (ECM kg/kg DM) was more efficient for diets containing low amounts of concentrate. The ratio of milk nitrogen/feed nitrogen was highest when a high amount of concentrate with low CP content was used.