The effect of supplemental concentrate fed during the dry period on morphological and functional aspects of rumen adaptation in dairy cattle during the dry period and early lactation.

Ten rumen-cannulated Holstein-Friesian cows were used to examine the effect of feeding supplemental concentrate during the dry period on rumen papillae morphology and fractional absorption rate (ka) of volatile fatty acids (VFA) during the dry period and subsequent lactation. Treatment consisted of supplemental concentrate [3.0kg of dry matter (DM)/d] from 28d antepartum (ap) until the day of calving, whereas control did not receive supplemental concentrate. Cows were fed for ad libitum intake and had free access to the dry period ration (27% grass silage, 28% corn silage, 35% wheat straw, and 11% soybean meal on a DM basis) and, from calving onward, to a basal lactation ration (42% grass silage, 42% corn silage, and 16% soybean meal on a DM basis). From 1 to 3d postpartum (pp), all cows were fed 0.9kg DM/d of concentrate, which increased linearly thereafter to 8.9kg of DM/d on d 11 pp. At 28, 18, and 8d ap, and 3, 17, 31, and 45d pp, rumen papillae were collected and kaVFA was measured in all cows. On average, 13.8 (standard deviation: 3.8) papillae were collected each from the ventral, caudodorsal, and caudoventral rumen sacs per cow per day. The kaVFA was measured by incubating a standardized buffer fluid (45 L), containing 120mM VFA (60% acetic, 25% propionic, and 15% butyric acid) and Co-EDTA as fluid passage marker, in the evacuated and washed rumen. Treatment did not affect ap or pp DM and energy intakes or milk yield and composition. Treatment increased papillae surface area, which was 19 and 29% larger at 18 and 8d ap compared with 28d ap, respectively. Surface area increased, mainly due to an increase in papillae width. However, treatment did not increase kaVFA at 18 and 8d ap compared with 28d ap. In the control group, no changes in papillae surface area or kaVFA were observed during the dry period. In the treatment group, papillae surface area decreased between 8d ap and 3d pp, whereas no decrease was observed for control. From 3 to 45d pp, papillae surface area and kaVFA increased for all cows by approximately 50%, but the ap concentrate treatment did not affect kaVFA pp. In conclusion, the efficacy of supplemental concentrate during the dry period to increase papillae surface area and kaVFA in preparation for subsequent lactation is not supported by the present study. Current observations underline the importance of functional measurements in lieu of morphological measurements to assess changes in the adapting rumen wall.

Enteric methane production in lactating dairy cows with continuous feeding of essential oils or rotational feeding of essential oils and lauric acid.

Rumen microbes can adapt to feed additives, which may make the decrease in enteric CH4 production upon feeding an additive a transient response only. This study investigated alternate feeding of 2 CH4 mitigating feed additives with a different mode of action on persistency of lowering CH4 production compared with feeding a single additive over a period of 10 wk. Four pairs of cows were selected, and within pairs, cows were randomly assigned to either the control (AR-AR) or the alternating (AR-LA) concentrate treatment. The AR concentrate contained a blend of essential oils (Agolin Ruminant, Agolin SA, Bière, Switzerland; 0.17 g/kg of dry matter) and the LA concentrate contained lauric acid (C12:0; 65 g/kg of dry matter). A basal concentrate without Agolin Ruminant and lauric acid was fed during the pretreatment period (2 wk). Thereafter, the cows assigned to the AR-AR treatment received the AR concentrate during all 10 treatment weeks (5 periods of 2 wk each), whereas cows assigned to the AR-LA treatment received AR and LA concentrates rotated on a weekly basis. Methane emission was measured in climate respiration chambers during periods 1, 3, and 5. From period 3 onward, dry matter intake and milk protein concentration were reduced with the AR-LA treatment. Milk fat concentration was not affected, but the proportion of C12:0 in milk fat increased upon feeding C12:0. Molar proportions of acetate and propionate in rumen fluid were lower and higher, respectively, with the AR-LA than with the AR-AR treatment. Methane yield (g/kg of dry matter intake) and intensity (g/kg of fat- and protein-corrected milk yield) were not affected by treatment. Methane yield and intensity were significantly lower (12 and 11%, respectively) in period 1 compared with the pretreatment period, but no significant difference relative to pretreatment period was observed in period 3 (numerically 9 and 7% lower, respectively) and in period 5 (numerically 8 and 4% lower, respectively). Results indicate a transient decrease in CH4 yield and intensity in time, but no improvement in extent or persistency of the decline in CH4 due to rotational feeding of essential oils and C12:0 in lactating dairy cows.

Feeding nitrate and docosahexaenoic acid affects enteric methane production and milk fatty acid composition in lactating dairy cows.

An experiment was conducted to study potential interaction between the effects of feeding nitrate and docosahexaenoic acid (DHA; C22:6 n-3) on enteric CH4 production and performance of lactating dairy cows. Twenty-eight lactating Holstein dairy cows were grouped into 7 blocks of 4 cows. Within blocks, cows were randomly assigned to 1 of 4 treatments: control (CON; urea as alternative nonprotein N source to nitrate), NO3 [21 g of nitrate/kg of dry matter (DM)], DHA (3 g of DHA/kg of DM and urea as alternative nonprotein N source to nitrate), or NO3 + DHA (21 g of nitrate/kg of DM and 3 g of DHA/kg of DM, respectively). Cows were fed a total mixed ration consisting of 21% grass silage, 49% corn silage, and 30% concentrates on a DM basis. Feed additives were included in the concentrates. Cows assigned to a treatment including nitrate were gradually adapted to the treatment dose of nitrate over a period of 21 d during which no DHA was fed. The experimental period lasted 17 d, and CH4 production was measured during the last 5d in climate respiration chambers. Cows produced on average 363, 263, 369, and 298 g of CH4/d on CON, NO3, DHA, and NO3 + DHA treatments, respectively, and a tendency for a nitrate × DHA interaction effect was found where the CH4-mitigating effect of nitrate decreased when combined with DHA. This tendency was not obtained for CH4 production relative to dry matter intake (DMI) or to fat- and protein corrected milk (FPCM). The NO3 treatment decreased CH4 production irrespective of the unit in which it was expressed, whereas DHA did not affect CH4 production per kilogram of DMI, but resulted in a higher CH4 production per kilogram of fat- and protein-corrected milk (FPCM) production. The FPCM production (27.9, 24.7, 24.2, and 23. 8 kg/d for CON, NO3, DHA, and NO3 + DHA, respectively) was lower for DHA-fed cows because of decreased milk fat concentration. The proportion of saturated fatty acids in milk fat was decreased by DHA, and the proportion of polyunsaturated fatty acids was increased by both nitrate and DHA. Milk protein concentration was lower for nitrate-fed cows. In conclusion, nitrate but not DHA decreased enteric CH4 production and no interaction effects were found on CH4 production per kilogram of DMI or per kilogram of FPCM.

Short communication: Using diurnal patterns of (13)C enrichment of CO2 to evaluate the effects of nitrate and docosahexaenoic acid on fiber degradation in the rumen of lactating dairy cows.

Nitrate decreases enteric CH4 production in ruminants, but may also negatively affect fiber degradation. In this experiment, 28 lactating Holstein dairy cows were grouped into 7 blocks. Within blocks, cows were randomly assigned to 1 of 4 isonitrogenous treatments in a 2×2 factorial arrangement: control (CON); NO3 [21g of nitrate/kg of dry matter (DM)]; DHA [3g of docosahexaenoic acid (DHA)/kg of DM]; or NO3+DHA (21g of nitrate/kg of DM and 3g of DHA/kg of DM). Cows were fed a total mixed ration consisting of 21% grass silage, 49% corn silage, and 30% concentrates on a DM basis. Based on the difference in natural (13)C enrichment and neutral detergent fiber and starch content between grass silage and corn silage, we investigated whether a negative effect on rumen fiber degradation could be detected by evaluating diurnal patterns of (13)C enrichment of exhaled carbon dioxide. A significant nitrate × DHA interaction was found for neutral detergent fiber digestibility, which was reduced on the NO3 treatment to an average of 55%, as compared with 61, 64, and 65% on treatments CON, DHA, and NO3+DHA, respectively. Feeding nitrate, but not DHA, resulted in a pronounced increase in (13)C enrichment of CO2 in the first 3 to 4 h after feeding only. Results support the hypothesis that effects of a feed additive on the rate of fiber degradation in the rumen can be detected by evaluating diurnal patterns of (13)C enrichment of CO2. To be able to detect this, the main ration components have to differ considerably in fiber and nonfiber carbohydrate content as well as in natural (13)C enrichment.

Effects of lactic acid bacteria silage inoculation on methane emission and productivity of Holstein Friesian dairy cattle.

Inoculants of lactic acid bacteria (LAB) are used to improve silage quality and prevent spoilage via increased production of lactic acid and other organic acids and a rapid decline in silage pH. The addition of LAB inoculants to silage has been associated with increases in silage digestibility, dry matter intake (DMI), and milk yield. Given the potential change in silage and rumen fermentation conditions accompanying these silage additives, the aim of this study was to investigate the effect of LAB silage inoculants on DMI, digestibility, milk yield, milk composition, and methane (CH4) production from dairy cows in vivo. Eight mid-lactation Holstein-Friesian dairy cows were grouped into 2 blocks of 4 cows (multiparous and primiparous) and used in a 4×4 double Latin square design with 21-d periods. Methane emissions were measured by indirect calorimetry. Treatments were grass silage (mainly ryegrass) with no inoculant (GS), with a long-term inoculant (applied at harvest; GS+L), with a short-term inoculant (applied 16h before feeding; GS+S), or with both long and short-term inoculants (GS+L+S). All diets consisted of grass silage and concentrate (75:25 on a dry matter basis). The long-term inoculant consisted of a 10:20:70 mixture of Lactobacillus plantarum, Lactococcus lactis, and Lactobacillus buchneri, and the short-term inoculant was a preparation of Lc. lactis. Dry matter intake was not affected by long-term or short-term silage inoculation, nor was dietary neutral detergent fiber or fat digestibility, or N or energy balance. Milk composition (except milk urea) and fat and protein-corrected milk yield were not affected by long- or short-term silage inoculation, nor was milk microbial count. However, milk yield tended to be greater with long-term silage inoculation. Methane expressed in units of grams per day, grams per kilogram of DMI, grams per kilogram of milk, or grams per kilogram of fat and protein-corrected milk yield was not affected by long- or short-term silage inoculation. However, CH4 expressed in units of kilojoules per kilogram of metabolic body weight per day tended to be greater with long-term silage inoculation. Results of this study indicate minimal responses in animal performance to both long- and short-term inoculation of grass silage with LAB. Strain and dose differences as well as different basal silages and ensiling conditions are likely responsible for the lack of significant effects observed here, although positive effects have been observed in other studies.

Effect of nitrogen fertilization rate and regrowth interval of grass herbage on methane emission of zero-grazing lactating dairy cows.

Dairy cattle farming in temperate regions often relies on grass herbage (GH)-based diets but the effect of several grass management options on enteric CH4 emission has not been fully investigated yet. We investigated the combined effect of N fertilization rate and length of regrowth period of GH (predominantly ryegrass) on CH4 emission from lactating dairy cows. In a randomized block design, 28 lactating Holstein-Friesian dairy cows received a basal diet of GH and compound feed [85:15; dry matter (DM) basis]. Treatments consisted of GH cut after 3 or 5 weeks of regrowth, after receiving either a low (20kg of N/ha) or a high (90kg of N/ha) fertilization rate after initial cut. Feed intake, digestibility, milk production and composition, N and energy balance, and CH4 emission were measured during a 5-d period in climate respiration chambers after an adaptation to the diet for 12d. Cows were restricted-fed during measurements and mean DM intake was 15.0±0.16kg/d. Herbage crude protein content varied between 76 and 161g/kg of DM, and sugar content between 186 and 303g/kg of DM. Fat- and protein-corrected milk (FPCM) and feed digestibility increased with increased N fertilization rates and a shorter regrowth interval. Increasing the N fertilization rate increased daily CH4 emission per cow (+10%) and per unit of DM intake (+9%), tended to increase the fraction of gross energy intake emitted as CH4 (+7%), and (partly because of the low crude protein content for the low fertilized GH) only numerically reduced CH4 per unit of FPCM. The longer regrowth interval increased CH4 emission per unit of FPCM (+14%) compared with the shorter regrowth interval, but did not affect CH4 emission expressed in any other unit. With increasing N fertilization CH4 emission decreased per unit of digestible neutral detergent fiber intake (-13%) but not per unit of digestible organic matter intake. There was no interaction of the effect of N fertilization rate and regrowth interval on CH4 emission, but effects of N fertilization were generally most distinct with GH of 5 wk regrowth. The present results suggest that altering grass quality through an increase of N fertilization and a shorter regrowth interval can reduce CH4 emission in zero-grazing dairy cows, depending on the unit in which it is expressed. The larger amount of CH4 produced per day and cow with the more intensively managed GH is compensated by a higher feed digestibility and FPCM yield.

Enteric methane production, rumen volatile fatty acid concentrations, and milk fatty acid composition in lactating Holstein-Friesian cows fed grass silage- or corn silage-based diets.

The objective of this study was to determine the effects of replacing grass silage (GS) with corn silage (CS) in dairy cow diets on enteric methane (CH4) production, rumen volatile fatty acid concentrations, and milk fatty acid (FA) composition. A completely randomized block design experiment was conducted with 32 multiparous lactating Holstein-Friesian cows. Four dietary treatments were used, all having a roughage-to-concentrate ratio of 80:20 based on dry matter (DM). The roughage consisted of either 100% GS, 67% GS and 33% CS, 33% GS and 67% CS, or 100% CS (all DM basis). Feed intake was restricted (95% of ad libitum DM intake) to avoid confounding effects of DM intake on CH4 production. Nutrient intake, apparent digestibility, milk production and composition, nitrogen (N) and energy balance, and CH4 production were measured during a 5-d period in climate respiration chambers after adaptation to the diet for 12 d. Increasing CS proportion linearly decreased neutral detergent fiber and crude protein intake and linearly increased starch intake. Milk production and milk fat content (on average 23.4 kg/d and 4.68%, respectively) were not affected by increasing CS inclusion, whereas milk protein content increased quadratically. Rumen variables were unaffected by increasing CS inclusion, except the molar proportion of butyrate, which increased linearly. Methane production (expressed as grams per day, grams per kilogram of fat- and protein-corrected milk, and as a percent of gross energy intake) decreased quadratically with increasing CS inclusion, and decreased linearly when expressed as grams of CH4 per kilogram of DM intake. In comparison with 100% GS, CH4 production was 11 and 8% reduced for the 100% CS diet when expressed per unit of DM intake and per unit fat- and protein-corrected milk, respectively. Nitrogen efficiency increased linearly with increased inclusion of CS. The concentration of trans C18:1 FA, C18:1 cis-12, and total CLA increased quadratically, and iso C16:0, C18:1 cis-13, and C18:2n-6 increased linearly, whereas the concentration of C15:0, iso C15:0, C17:0, and C18:3n-3 decreased linearly with increasing inclusion of CS. No differences were found in short- and medium-straight, even-chain FA concentrations, with the exception of C4:0 which increased linearly with increased inclusion of CS. Replacing GS with CS in a common forage-based diet for dairy cattle offers an effective strategy to decrease enteric CH4 production without negatively affecting dairy cow performance, although a critical level of starch in the diet seems to be needed.

Meta-analysis of factors that affect the utilization efficiency of phosphorus in lactating dairy cows.

A meta-analysis investigation based on literature data was conducted to estimate the effect size of nutritional and animal factors on phosphorus (P) excretion in feces and concentrations of P in milk. Two data sets were created for statistical analysis: One to derive prediction equations for P in feces (25 studies; 130 treatments) and another for P in milk (19 studies; 94 treatments). Prediction equations were derived using mixed model regression analysis with a random effect for study, and equations were evaluated based on values for Bayesian information criterion (BIC), root mean square prediction error (RMSPE), and concordance correlation coefficient (CCC) statistics. In terms of RMSPE and CCC values, fecal P excretion was best predicted by P intake, where P in feces (g/d)=-3.8(±3.45) + 0.64(±0.038) × P intake (g/d) (RMSPE: 18.3%, CCC: 0.869). However, significant effects of crude protein [g/kg of dry matter (DM)], neutral detergent fiber (g/kg of DM), and milk yield (kg/d) on fecal P excretion were also found. Despite a lack of improvement in terms of RMSPE and CCC values, these parameters may still explain part of the variation in fecal P excretion. For milk P, expressed as a fraction of P intake, the following equation had the highest CCC and the lowest RMSPE value: P in milk as a fraction of P intake (g/g)=0.42(±0.065) + 0.23(±0.018) × feed efficiency (i.e., fat- and protein-corrected milk yield/dry matter intake) - 0.11(±0.0199) × P in feed (g/kg of DM) (RMSPE: 19.7%; CCC: 0.761). Equations derived to predict fecal P as a fraction of P intake (g/g) or milk P content (g/kg) could not adequately explain the observed variation and did not perform well in terms of RMSPE and CCC values. Examination of the residuals showed that P balance was a seemingly confounding factor in some of the models. The results presented here can be used to estimate P in feces and milk based on commonly measured dietary and milk variables, but could also be used to guide development of mechanistic models on P metabolism in lactating dairy cattle. Factors to consider in future research and modeling efforts regarding efficiency of P use include the effects of dietary neutral detergent fiber, crude protein, starch, variation in P content of milk, and effects of P resorption from bone and body tissues during early lactation.

Changes in in vitro gas and methane production from rumen fluid from dairy cows during adaptation to feed additives in vivo.

The adaptation of dairy cows to methane (CH4)-mitigating feed additives was evaluated using the in vitro gas production (GP) technique. Nine rumen-fistulated lactating Holstein cows were grouped into three blocks and within blocks randomly assigned to one of three experimental diets: Control (CON; no feed additive), Agolin Ruminant® (AR; 0.05 g/kg dry matter (DM)) or lauric acid (LA; 30 g/kg DM). Total mixed rations composed of maize silage, grass silage and concentrate were fed in a 40 : 30 : 30 ratio on DM basis. Rumen fluid was collected from each cow at days -4, 1, 4, 8, 15 and 22 relative to the introduction of the additives in the diets. On each of these days, a 48-h GP experiment was performed in which rumen fluid from each individual donor cow was incubated with each of the three substrates that reflected the treatment diets offered to the cows. DM intake was on average 19.8, 20.1 and 16.2 kg/day with an average fat- and protein-corrected milk production of 30.7, 31.7 and 26.2 kg/day with diet CON, AR and LA, respectively. In general, feed additives in the donor cow diet had a larger effect on gas and CH4 production than the same additives in the incubation substrate. Incubation substrate affected asymptotic GP, half-time of asymptotic CH4 production, total volatile fatty acid (VFA) concentration, molar proportions of propionate and butyrate and degradation of organic matter (OMD), but did not affect CH4 production. No substrate×day interactions were observed. A significant diet×day interaction was observed for in vitro gas and CH4 production, total VFA concentration, molar proportions of VFA and OMD. From day 4 onwards, the LA diet persistently reduced gas and CH4 production, total VFA concentration, acetate molar proportion and OMD, and increased propionate molar proportion. In vitro CH4 production was reduced by the AR diet on day 8, but not on days 15 and 22. In line with these findings, the molar proportion of propionate in fermentation fluid was greater, and that of acetate smaller, for the AR diet than for the CON diet on day 8, but not on days 15 and 22. Overall, the data indicate a short-term effect of AR on CH4 production, whereas the CH4-mitigating effect of LA persisted.

Effects of nitrogen fertilisation rate and maturity of grass silage on methane emission by lactating dairy cows.

Grass silage is typically fed to dairy cows in temperate regions. However, in vivo information on methane (CH(4)) emission from grass silage of varying quality is limited. We evaluated the effect of two rates of nitrogen (N) fertilisation of grassland (low fertilisation (LF), 65 kg of N/ha; and high fertilisation (HF), 150 kg of N/ha) and of three stages of maturity of grass at cutting: early maturity (EM; 28 days of regrowth), mid maturity (MM; 41 days of regrowth) and late maturity (LM; 62 days of regrowth) on CH(4) production by lactating dairy cows. In a randomised block design, 54 lactating Holstein-Friesian dairy cows (168±11 days in milk; mean±standard error of mean) received grass silage (mainly ryegrass) and compound feed at 80 : 20 on dry matter basis. Cows were adapted to the diet for 12 days and CH(4) production was measured in climate respiration chambers for 5 days. Dry matter intake (DMI; 14.9±0.56 kg/day) decreased with increasing N fertilisation and grass maturity. Production of fat- and protein-corrected milk (FPCM; 24.0±1.57 kg/day) decreased with advancing grass maturity but was not affected by N fertilisation. Apparent total-tract feed digestibility decreased with advancing grass maturity but was unaffected by N fertilisation except for an increase and decrease in N and fat digestibility with increasing N fertilisation, respectively. Total CH(4) production per cow (347±13.6 g/day) decreased with increasing N fertilisation by 4% and grass maturity by 6%. The smaller CH(4) production with advancing grass maturity was offset by a smaller FPCM and lower feed digestibility. As a result, with advancing grass maturity CH(4) emission intensity increased per units of FPCM (15.0±1.00 g CH(4)/kg) by 31% and digestible organic matter intake (33.1±0.78 g CH(4)/kg) by 15%. In addition, emission intensity increased per units of DMI (23.5±0.43 g CH(4)/kg) by 7% and gross energy intake (7.0±0.14% CH(4)) by 9%, implying an increased loss of dietary energy with advancing grass maturity. Rate of N fertilisation had no effect on CH(4) emissions per units of FPCM, DMI and gross energy intake. These results suggest that despite a lower absolute daily CH(4) production with a higher N fertilisation rate, CH(4) emission intensity remains unchanged. A significant reduction of CH(4) emission intensity can be achieved by feeding dairy cows silage of grass harvested at an earlier stage of maturity.