Grass Silage Diets Research Articles

Assessing the dry matter intake and enteric methane emissions of pre-partum dairy cows offered grass clover or grass-only silage from two different silage systems

Over the winter period, the low grass growth and availability in pasture-based dairy systems results in animals being housed and predominantly fed a diet of grass silage. There is limited availability of methane (CH4) data evaluating the impact of forage type on dairy cows over the pre-partum period. The objective of the current experiment was to evaluate the impact of feeding grass clover (GC) silage and grass-only (GO) silage on the dry matter intake (DMI) and enteric CH4 emissions of dairy cows pre-partum. A complete randomised block design was utilised for the 6-week experiment over two winter periods: from December 2020 to January 2021 and from December 2021 to January 2022. In each year, 30 non-lactating pregnant dairy cows were randomly allocated to two treatments (n = 15). In both years, cows in the GC treatment were offered grass clover bale silage, while cows in the GO treatment were offered grass-only pit silage. The DMI and gaseous emissions of individual animals were monitored daily using Hokofarm RIC (roughage intake control) feed stations and the GreenFeed technology. GC silage consistently had greater (p< 0.05) organic matter (OM) digestibility and lower (p< 0.05) neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents when compared with GO silage. Cows in the GC treatment had significantly greater (p< 0.05) total DMI (TDMI) compared with cows in the GO treatment. The daily CH4 emissions (in grams per day) were not affected by treatment; however, cows in the GC treatment had reduced (p< 0.05) CH4 yield (in grams per kilogram TDMI). Offering dairy cows GC silage over the pre-partum period resulted in greater DMI with reduced CH4 yield when compared with cows offered GO silage.

Substituting imported soybean meal with locally produced novel yeast protein in concentrates for Norwegian Red dairy cows: implications for rumen microbiota and fatty acid composition.

This research paper addresses the hypothesis that substituting soybean meal with locally produced yeast protein from Cyberlindnera jadinii in barley-based concentrates for Norwegian Red (NR) dairy cows does not have adverse effects on milk fatty acid (FA) composition, rumen microbiota and sensory quality of milk. As soybeans also represent valuable protein sources for human consumption, alternative protein sources need to be investigated for animal feed. A total of 48 NR dairy cows were allocated into three feeding treatments, with the same basal diet of grass silage, but different concentrates. The concentrates were all based on barley, but 7% of the barley in the barley-concentrate (BAR; negative control) was replaced by either soybean meal (SBM; conventional control) or yeast microbial protein (YEA). The experiment lasted for a total of 10 weeks, including 2 weeks of adaptation with the soybean meal concentrate. Analysis of the feed revealed some differences in the FA composition of the YEA concentrate compared to the SBM and BAR concentrates. In milk, only two FAs (C17:1n-8cis9 and an unidentified isomer of C18:3) were significantly different between the YEA- and SBM-group, while six FAs differed between the BAR- and SBM-group. However, the amount of these FAs was low compared to the entire FA profile (<0.7 g/100 g). The experimental diets did not affect rumen microbiota nor the milk sensory quality. This study shows that C. jadinii can replace soybean meal as a protein source in concentrates (7% inclusion) for NR dairy cows fed a diet composed of grass silage and concentrates without any effects on rumen microbiota, and without compromising the FA composition or sensory quality of milk.

Development and validation of a model for early prediction of residual feed intake in beef cattle using plasma biomarkers

Identification of plasma biomarkers for feed efficiency in growing beef cattle offers a promising opportunity for developing prediction models to improve precision feeding strategies. However, these models must accurately predict feed efficiency at early stages of fattening. Our study aimed to evaluate the reliability of candidate biomarkers previously identified in late-fattening cattle when analyzed during early fattening stages and to develop diet-specific prediction equations for residual feed intake (RFI). From a total of 364 Charolais bulls across 7 cohorts, we selected 64 animals with extreme RFI values. The animals were fed either a corn‑ or grass-silage diets. These animals were chosen from 4 out of available 7 cohorts. Animals from three cohorts (24 high-RFI and 24 low-RFI, having a mean RFI difference of 1.48 kg/d) were used for biomarker confirmation and prediction model training. Animals from a fourth cohort (8 high-RFI and 8 low-RFI, having a mean RFI difference of 0.98 kg/d) were used for model external validation. Blood samples were collected at the beginning of the feed efficiency test (333±20 days), and plasma underwent targeted metabolomic for 630 metabolites, natural abundance of 15N (δ15N), insulin, and IGF-1 analysis. Seven previously identified plasma biomarkers for RFI in late-fattening beef cattle still kept their capability for discriminating low and high RFI animals when analyzed during early fattening stages (P < 0.05). Among these confirmed biomarkers, five were common for both grass- and corn-fed animals (creatinine, β-alanine, triglyceride TG18:0_34:2, symmetric dimethyl-arginine and phosphatidylcholine PC aa C30:2) while two were diet-specific (insulin-like growth factor 1 for grass silage-based diet, and isoleucine for corn silage-based diet. No new plasma biomarkers of RFI were identified at early-fattening stages (false discovery rate, FDR>0.05). Prediction models were developed based on seven confirmed RFI biomarkers analyzed during early-fattening. Two logistic regression models incorporating creatinine and either IGF-1 (for grass silage-based diet) or PC aa C30:2 (for corn silage-based diet) effectively distinguished between high and low-RFI animals with high sensitivity and specificity (area under the curve, AUC > 0.80). The biomarkers used in the models showed moderate to high repeatability between early and late fattening stages (45 < r <65). The models were successfully externally validated, with more than 85% of animals from the fourth cohort correctly classified. Once validated in larger cohorts and utilizing cost-effective and rapid analytical methods, these models could support precision feeding and breeding programs, aiming to reduce the cost of raising beef cattle.

Effects of protein and forage source on performance, and splanchnic and mammary net fluxes of nutrients in lactating dairy cows

This study was conducted to determine if the decreased MP supply predicted by the NRC (2001) when canola meal (CM) substitutes soybean meal (SBM) was supported by direct measurement of net portal absorption of AA or energy-yielding nutrients, plus the impact of the type of forage in CM-based rations. Nine Holstein cows with indwelling catheters in splanchnic blood vessels, 8 also with a ruminal cannula were used to examine the effects of protein source in corn silage-based diets, comparing SBM versus CM, and forage source in CM-based diets, comparing corn versus grass silage. The cows were allocated to a triple 3 × 3 Latin square design with 21-d periods. The 3 experimental diets, formulated to be isoenergetic and isonitrogenous, were based on: 1) SBM and corn silage (SoyCorn); 2) CM and corn silage (CanCorn) and 3) CM and cool-season grass silage (CanGrass). Averages of intake, milk yield and milk composition of the last 3 d of each period were used for statistical analyses. On d 21 of each period, 6 sets of arterial, portal, hepatic and mammary blood samples and 2 ruminal fluid samples were collected. On d 12 of period 2, the protein sources were incubated in nylon bags to determine 16h-ruminal disappearance of DM and N and to obtain 16-h residues. Finally, 5 d after the completion of the Latin square design, the mobile bag technique was used to determine DM and N intestinal disappearance of the 16-h residues of SBM and CM. Pre-planned contrasts were used to compare the effect of the protein source in cows fed corn silage, i.e., SoyCorn versus CanCorn, and the effect of forage in cows fed CM, i.e., CanCorn versus CanGrass. Data of the cow without a rumen canula could not be used because of health problem. In corn silage-based diets, substitution of SBM by CM tended to increase milk (6%) and milk fat (7%) yields. The 8% higher ruminal N disappearance and the 19% decreased MP supply from RUP predicted by NRC (2001) were not supported by the 25% decrease in ruminal ammonia concentration, similar net portal absorption of AA (except 22% higher for Met), and the 14% decrease in urea hepatic removal when CM substituted SBM. Ruminal incubation of CM in nylon bags does not appear suitable for adequate determination of the rumen by-pass of a protein source like CM. Inclusion of grass silage rather than corn silage in CM-based diets tended to increase milk (6%) and increased milk lactose (8%) yields. Neither protein nor forage source resulted in variations of metabolism of energy-yielding nutrients that could explain observed increments in cow performance. The present study indicates no decreased AA availability when CM substitutes SBM. Therefore, substitution of SBM by CM in diets based on corn silage and CM in corn- or grass silage-diets can be used successfully in high producing dairy cows.

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.

Enhancing Milk Quality and Antioxidant Status in Lactating Dairy Goats through the Dietary Incorporation of Purple Napier Grass Silage.

Oxidative stress resulting from an imbalance between oxidants and antioxidants can cause damage to certain cellular components. Purple Napier grass, a semi-dwarf variety, is characterized by its purple leaves and contains anthocyanins, which provide it with antioxidant properties. This study examined the effects of feeding purple Napier grass ("Prince") silage to lactating dairy goats on blood antioxidant activity, milk yield, and milk quality. Eighteen female Saanen crossbred goats, weighing 52.34 ± 2.86 kg and producing milk for 14 ± 2 days, were systematically divided into three groups based on their lactation period in the previous cycle as follows: early, mid, and late lactation. In a randomized complete block design (RCBD), treatments were randomly allocated to six animals in each block. The dairy goats were fed a total mixed ration (TMR) consisting of the three following treatments: control (100% Napier Pakchong 1 grass silage), 50% (a 50% replacement of the control with purple Napier grass silage), and 100% (100% purple Napier grass silage). The results show that goats who were fed a diet including 100% purple Napier grass silage showed higher levels of certain milk contents, especially with regard to lactose, when compared to those who were fed a control diet, as well as a diet with a 50% replacement of purple Napier grass silage. The somatic cell count (SCC) of these goats was reduced. In terms of antioxidant activity, dairy goats who were fed 100% purple Napier grass silage showed higher levels of enzymes in both plasma and milk, including glutathione s-transferase, total antioxidant capacity, superoxide dismutase, and 2,2-diphenyl-1-picrylhydrazyl radical, compared to the control group and the 50% replacement group. The plasma and milk of these goats showed lower levels of malondialdehyde. The dairy goats who were fed a 100% purple Napier grass silage diet showed higher concentrations of anthocyanins, including C3G, P3G, Peo3G, M3G, Cya, Pel, and total anthocyanins in milk, when compared to the control group and the 50% replacement group. The increased replacement of purple Napier grass silage led to significant differences in lactose levels, somatic cell count, glutathione S-transferase, total antioxidant capacity, superoxide dismutase, 2,2-diphenyl-1-picrylhydrazyl radical, and the composition of anthocyanins. This study provides evidence to support the use of purple Napier grass silage as a beneficial source of roughage for lactating dairy goats.

Common and diet-specific metabolic pathways underlying residual feed intake in fattening Charolais yearling bulls

Residual feed intake (RFI) is one of the preferred traits for feed efficiency animal breeding. However, RFI measurement is expensive and time-consuming and animal ranking may depend on the nature of the diets. We aimed to explore RFI plasma biomarkers and to unravel the underlying metabolic pathways in yearling bulls fed either a corn-silage diet rich in starch (corn diet) or a grass-silage diet rich in fiber (grass diet). Forty-eight extreme RFI animals (Low-RFI, n = 24, versus High-RFI, n = 24, balanced per diet) were selected from a population of 364 Charolais bulls and their plasma was subjected to a targeted LC-MS metabolomic approach together with classical metabolite and hormonal plasma analyses. Greater lean body mass and nitrogen use efficiency, and lower protein turnover were identified as common mechanisms underlying RFI irrespective of the diet. On the other hand, greater adiposity and plasma concentrations of branched-chain amino acids (BCAA) together with lower insulin sensitivity in High-RFI animals were only observed with corn diet. Conversely, greater plasma concentrations of BCAA and total triglycerides, but similar insulin concentrations were noted in efficient RFI cattle with grass diet. Our data suggest that there are diet-specific mechanisms explaining RFI differences in fattening Charolais yearling bulls.

Effect of Dietary Seaweed Supplementation in Cows on Milk Macrominerals, Trace Elements and Heavy Metal Concentrations.

This study investigated the effect of seaweed supplementation in dairy cow diets on milk yield, basic composition, and mineral concentrations. Thirty-seven Icelandic cows were split into three diet treatments: control (CON, no seaweed), low seaweed (LSW, 0.75% concentrate dry matter (DM), 13–40 g/cow/day), and high seaweed (HSW, 1.5% concentrate DM, 26–158 g/cow/day). Cows were fed the same basal diet of grass silage and concentrate for a week, and then were introduced to the assigned experimental diets for 6 weeks. The seaweed mix of 91% Ascophyllum nodosum: 9% Laminaria digitata (DM basis), feed, and milk samples were collected weekly. Data were analyzed using a linear mixed effects model, with diet, week, and their interaction as fixed factors, cow ID as random factor, and the pre-treatment week data as a covariate. When compared with CON milk, LSW and HSW milk had, respectively, less Se (−1.4 and −3.1 μg/kg milk) and more I (+744 and +1649 μg/kg milk), while HSW milk also had less Cu (−11.6 μg/kg milk) and more As (+0.17 μg/kg milk) than CON milk. The minimal changes or concentrations in milk for Se, Cu, and As cannot be associated with any effects on consumer nutrition, but care should be taken when I-rich seaweed is fed to cows to avoid excessive animal I supply and milk I concentrations.

Enteric and Fecal Methane Emissions from Dairy Cows Fed Grass or Corn Silage Diets Supplemented with Rapeseed Oil.

Simple SummaryIn this study, we evaluated methane emissions from dairy cows fed grass or corn silage diets supplemented with rapeseed oil. Enteric methane emissions decreased on adding rapeseed oil to the diet, but methane emissions from feces of dairy cows fed diets supplemented with rapeseed oil did not differ. Thus, no trade-offs were observed between enteric and fecal methane emissions due to forage type or addition of rapeseed oil to diets fed to Swedish dairy cows.This study evaluated potential trade-offs between enteric methane (CH4) emissions and CH4 emissions from feces of dairy cows fed grass silage or partial replacement of grass silage with corn silage, both with and without supplementation of rapeseed oil. Measured data for eight dairy cows (two blocks) included in a production trial were analyzed. Dietary treatments were grass silage (GS), GS supplemented with rapeseed oil (GS-RSO), GS plus corn silage (GSCS), and GSCS supplemented with rapeseed oil (GSCS-RSO). Feces samples were collected after each period and incubated for nine weeks to estimate fecal CH4 emissions. Including RSO (0.5 kg/d) in the diet decreased dry matter intake (DMI) by 1.75 kg/d. Enteric CH4 emissions were reduced by inclusion of RSO in the diet (on average 473 vs. 607 L/d). In 9-week incubations, there was a trend for lower CH4 emissions from feces of cows fed diets supplemented with RSO (on average 3.45 L/kg DM) than cows with diets not supplemented with RSO (3.84 L/kg DM). Total CH4 emissions (enteric + feces, L/d) were significantly lower for the cows fed diets supplemented with RSO. Total fecal CH4 emissions were similar between treatments, indicating no trade-offs between enteric and fecal CH4 emissions.

Feeding concentrates with different protein sources to high-yielding, mid-lactation Norwegian Red cows: Effect on cheese ripening

Soybean meal is one of the most important protein sources in concentrate feeds for dairy cows. The objective of the present study was to provide knowledge on the effects of using a novel yeast microbial protein source (Candida utilis) in concentrate feed for dairy cows on the production and quality of a Gouda-type cheese. Forty-eight Norwegian Red dairy cows in early to mid lactation were fed a basal diet of grass silage, which was supplemented with 3 different concentrate feeds. The protein source of the concentrates was based on conventional soybean meal (SBM), novel yeast (C. utilis; YEA), or barley (BAR; used as negative control because barley has a lower protein content). The experiment was carried out for a period of 10 wk, with the first 2 wk as an adaptation period where all dairy cows were fed grass silage and the SBM concentrate. The cows were then randomly allocated to 1 of the 3 different compound feeds: SBM, yeast, or barley. Cheeses were made during wk 8 and 9 of the experiment, with 4 batches of cheese made from milk from each of the 3 groups. The cheeses made from milk from cows fed SBM concentrate (SBM cheese) had a higher content of dl-pyroglutamic acid and free amino acids than the other cheeses, indicating a faster ripening in the SBM cheeses. Despite these differences, the sensory properties, the microbiota, and the Lactococcus population at 15 wk of ripening were not significantly different between the cheeses. This experiment showed that although the raw materials used in the concentrate feed clearly influenced the ripening of the cheeses, this did not affect cheese quality. Yeast (C. utilis) as a protein source in concentrate feed for dairy cows can be used as a replacement for soybean meal without compromising the quality of Norwegian Gouda-type cheeses.

Effect of weaning and sex on meat fatty acid profile of grazing lambs

Article Details: Received: 2020-10-20 | Accepted: 2020-11-27 | Available online: 2021-01-31 https://doi.org/10.15414/afz.2021.24.mi-prap.25-28 Twenty Tsigai and Suffolk crossbreed lambs in grazing conditions were used to investigate the effect of weaning status (weaned vs. unweaned) and sex on fatty acid composition of meat. Six males and four females were included in both groups, the weaned lambs group (WL) and the unweaned lambs group (UL). The fatty acid profile of Musculus longissimus lumborum et thoracis intramuscular fat (IMF) were determined by gas chromatography and analysed by analysis of variance. WL displayed higher proportion of t 11-C18:1 (P < 0.001), n-6 polyunsaturated fatty acid (PUFA) C18:2 (P < 0.01) and C20:4 (P < 0.05), n-3 PUFA C18:3 (P < 0.05), C20:5 (P < 0.01), C22:5 (P < 0.05), C22:6 (P < 0.05) and the total PUFA (P < 0.01) in IMF than UL. On the contrary, IMF of UL had higher proportion of the medium-chain saturated fatty acids (SFA) such as C12:0 (P < 0.01), C14:0 (P < 0.01) and C16:0 (P < 0.01), the total SFA (P < 0.05) and the total monounsaturated fatty acids (MUFA) (P < 0.05). The weaning status had no significant effect on n-6/n-3 ratio, however the ratio was satisfactory low in both groups. The sex had no effect on a profile of essential and health beneficial fatty acids in meat of lamb. In conclusion, meat of weaned lambs in grazing system might be considered to obtain a higher proportion of healthy n-3 fatty acids compared to unweaned lambs. Keywords: fatty acids, intramuscular fat, lamb meat, weaned lambs, unweaned lambs References Belanche, A. et al. (2019). Amulti-kingdom study reveals the plasticity of the rumen microbiota in response to a shift from non-grazing to grazing diets in sheep. Frontiers in Microbiology , 10, 1-17. Doi: https://doi.org/10.3389/fmicb.2019.00122 Caneque, V. et al. (2001). Effect of weaning age and slaughter weight on carcass and meat quality of Talaverana breed lambs raised at pasture. Animal Science , 73, 85-95. Cividini, A. et al. (2014). Fatty acid composition of lamb meat from the autochthonous Jezersko-Solcava breed reared in different production systems. Meat Science , 97(4), 480-485. Doi: https://doi.org/10.1016/j.meatsci.2013.12.012 Cividini, A. et al. (2008). Fatty acid composition of lamb meat as affected by production system, weaning and sex. Acta Agriculturae Slovenica , Suplement 2, 47-52. De Brito, G. F. et al. (2017). TheEfect of Extensive Feeding Systems on Growth Rate, Carcass Traits, and Meat Quality of Finishing Lambs. Comprehensive Reviews. Food Science and Food Safety . 16(1), 23-38. Doi: https://doi.org/10.1111/1541-4337.12230 Enser, M. et al. (1998). Fatty acid content and composition of UK beef and lamb muscle in relation to production systemand implications for human nutrition. Meat Science ., 49, 329–341. French, P. et al. (2000). Fatty acid composition, including conjugated linoleic acid, of intramuscular fat from steers offered grazed grass, grass silage, or concentrate-based diets. Journal of Animal Science , 78, 2849-2855. Howes, N. L. (2015). Opportunities and Implications of Pasture-Based Lamb Fattening to Enhance the Long-Chain Fatty Acid Composition in Meat. Comprehensive Reviews in Food Science and Food Safety , 14(1), 22-36. Doi: https://doi.org/10.1111/1541-4337.12118 Jacques, J. et al. (2016). Meat quality, organoleptic characteristics, and fatty acid composition of Dorset lambs fed different forage to concentrate ratios or fresh grass. Canadian Journal of Animal Science , 97, 290-301.Doi: https://doi.org/10.1139/cjas-2016-0104 Kosulwat, S. et al. (2003). Lipid composition of Australian retail lamb cuts with differing carcass classification characteristics. Meat Science , 65, 1413-1420. Margetin, M. et al. (2018). Fatty acids in intramuscular fat of Ile de France lambs in two different production Systems. Archives Animal Breeding , 61 (4), 395-403. Doi: https://doi.org/10.5194/aab-61-395-2018 Velasco, S et al. (2004). Effect of different feeds on meat quality and fatty acid composition of lambs fattened at pasture. Meat Science , 66(2), 457-465. Doi: https://doi.org/10.1016/S0309-1740(03)00134-7 Velasco, S. et al. (2001) Fatty acid composition of adipose depots of suckling lambs raised under different production systems. Meat Science , 59(3), 325-333. Velasco, S. et al. (2000). Carcass and meat quality of Talaverana breed sucking lambs in relation to gender and slaughter weight . Animal Science , 70, 253-263. Woods, V. B., &Fearon, A. M. (2009). Dietary sources of unsaturated fatty acids for animals and their transfer into meat, milk and eggs: A review. Livestock Science , 126, 1-20.

PSIV-23 Variations in chewing behavior and rumino-reticular pH in dairy cows during gradual adaptation to a high-grain diet

Abstract Physical effective fiber in the diet promotes chewing, contributing to the regulation of ruminal pH through saliva production, which leads to rumen health. However, lower dietary fiber content in high-grain diets may reduce rumination time and compromise ruminal pH regulation. The objective of this experiment was to evaluate rumination behavior and rumino-reticular pH variations during an 8-day adaptation to a 65% concentrate diet. For this study nine ruminally cannulated non-lactating Holstein cows were used. Prior to the initiation of the adaptation, cows were transitioned from a forage-only grass silage diet to a 65% DM concentrate diet over eight days. Rumination was monitored using RumiWatch halters (RumiWacthSystem ITIN+HOCH). Rumino-reticular pH was measured using eCow indwelling pH systems in five of nine cows recording data every 15 minutes. Data were analysed with SAS, the statistical model included day as fixed effect and cow was considered as random effect. Adaptation days had an effect (P &amp;lt; 0.01) on rumination time, number of rumination chews per minute, and mean daily (rumino-reticular) pH. Especially, rumination time decreased from 439 to 327±62.8 minutes per day from day 1 to 8, respectively. Concomitantly, rumination chews per minute decreased from 68.8 to 65.6±2.06, and mean daily pH decreased from 6.54 and 6.26±0.07, respectively. Nevertheless, daily dry matter intake (P = 0.23) and eating time (P = 0.37) were not affected during the adaptation period. In conclusion, adaptation to a high-grain diet and the associated decrease in physically effective fiber gradually reduced chewing activity and ruminal/reticular pH. However, compared to the forage-only diet, significant reduction in rumination time was only noted at the 65% concentrate level.

Natural 15N abundance in specific amino acids indicates associations between transamination rates and residual feed intake in beef cattle.

Improving the ability of animals to convert feed resources into food for humans is needed for more sustainable livestock systems. Genetic selection for animals eating less while maintaining their performance (i.e., low residual feed intake [RFI]) appears a smart strategy but its effectiveness relies on high-throughput animal phenotyping. Here, we explored plasma nitrogen (N) isotope ratios in an attempt to identify easily superior young bulls in terms of RFI. For this, 48 Charolais young bulls fed two contrasting diets (corn vs. grass silage diets) were selected from a larger population as extreme RFI animals (24 low-RFI vs. 24 high-RFI) and their plasma analyzed for natural 15N abundance (δ15N) in the whole protein (bulk protein) and in the individual protein-bound amino acids (PbAA). For the first time, we showed that the δ 15N in plasma bulk protein differed (P = 0.007) between efficient (low-RFI) and inefficient (high-RFI) cattle regardless of diet. Furthermore, most analyzed PbAA followed the same trend as the bulk protein, with lower (P < 0.05) δ 15N values in more efficient (low-RFI) compared with less efficient (high-RFI) cattle, again regardless of diet. The only three exceptions were Phe, Met, and Lys (P > 0.05) for which the first metabolic reaction before being catabolized does not involve transamination, a pathway known naturally to enrich AAs in 15N. The contrasted isotopic signatures across RFI groups only in those PbAA undergoing transamination are interpreted as differences in transamination rates and N-use efficiency between low- and high-RFI phenotypes. Natural isotopic N signatures in bulk proteins and specific PbAA can be proposed as biomarkers of RFI in growing beef cattle fed different diets. However, the current study cannot delineate whether this effect only occurs post-absorption or to some extent also in the rumen. Our data support the conclusion that most efficient cattle in terms of RFI upregulate N conservation mechanisms compared with less efficient cattle and justify future research on this topic.

Metabolisable energy of grass and red clover silages fed to sheep at maintenance level

This study investigated the effect of forage type (grass or red clover) and harvesting time (primary growth or regrowth) of silage on energy and N utilisation by sheep fed at maintenance level. Specifically, the assumption of constant loss of energy of digestible organic matter from energy losses in urine and CH4 applied in evaluation of silage metabolisable energy (ME) was investigated. Urinary excretion of high-energy phenolic compounds related to solubilisation of lignin was assumed to affect urinary energy (UE) losses from sheep fed highly digestible grass silage (GS). A total of 25 primary growth and regrowth silages of timothy (Phleum pratense) and meadow fescue (Festuca pratensis) grass mixtures and red clover (Trifolium pratense) samples collected in digestibility trials with sheep, including faecal and urine samples, were used for energy and N determinations. Urinary concentration of monophenolic compounds and CH4 emissions in vitro were also analysed. Daily faecal N output, CH4 yield (MJ/kg DM intake), proportion of CH4 energy in digestible energy (DE) and proportion of UE in DE were greater (P ≤ 0.03) in sheep fed red clover silage (RCS) than GS. Furthermore, less (P = 0.01) energy was lost as UE of DE in sheep fed primary growth GS compared with the other treatments. The relationship between UE and silage N intake or urinary N output for both silage types (i.e. grass v. red clover) was strong, but the fit of the regressions was better for GS than RCS. The CH4/DE ratio decreased (P < 0.05) and the UE/DE ratio increased (P < 0.05) with increasing organic matter digestibility in RCS. These relationships were not significant (P < 0.05) for the GS diets. The regression coefficient was higher (P < 0.05) for GS than RCS when regressing ME concentration on digestible organic matter. The results of this study imply that ME/DE ratio is not constant across first-cut GS of different maturities. The ME production response may be smaller from highly digestible first-cut GS but could not be clearly related to urinary excretion of monophenols derived from solubilisation of lignin. Furthermore, energy lost in urine was not clearly defined for RCS and was much more predictable for GS from silage N concentration.

Digestibility and protein utilization in wethers fed whole-crop barley or grass silages harvested at different maturity stages, with or without protein supplementation1.

Effects of whole-crop barley and grass silages harvested at different maturity stages, with or without protein supplementation, on intake, in vivo digestibility, feces characteristics, and protein utilization in wethers were evaluated. Whole-crop barley silage harvested at heading stage (BH) and at medium milk stage (BM), grass silage (GE) taken at the flag leaf-early heading stage, and grass silage (GL) taken at medium-late heading stage were fed to eight wethers in two 4 × 4 Latin squares. Wethers in one square were fed supplementary rapeseed meal. Experimental periods lasted for 4 wk and wethers were fed ad libitum during the first 3 wk, with intake recorded during the third week. During the fourth week, wethers were fed 80% of ad libitum, and feces and urine were collected during the last 4 d. The GE and BH diets had greater (P < 0.05) in vivo apparent digestibility of DM and its nutrients, lower proportion of fecal particle DM (PDM) with a greater proportion of small particles compared with GL and BM diets, respectively. The GE diet had greater (P < 0.001) in vitro OM digestibility and in vivo digestibility of OM and fibre, resulting in a smaller (P < 0.001) proportion of PDM with a greater (P < 0.001) proportion of small particles compared with the other diets. In vivo NDF digestibility was negatively related to fecal PDM across forage types (R2 = 0.91, RMSE = 2.55). The GE silage had greater CP concentration, and animals fed the GE diet had greater intake of CP (P < 0.001) and sum of the degradable CP fractions A, B1, and B2 (P < 0.01), resulting in greater (P < 0.05) urinary nitrogen (N) excretion than when fed any of the other diets and a lower (P < 0.05) N retention compared with BH and BM diets. Microbial N supply tended to increase when animals were fed the BH diet (P = 0.10) and when rapeseed meal was added to the forages (P = 0.08). Increased N intake (P = 0.008) by rapeseed meal supplementation increased urinary N excretion in gram per day (P = 0.05). The strong relationship between in vivo NDF digestibility and fecal PDM indicates potentials for using PDM as a cheap method to predict NDF digestibility. Early harvest of the forages improved in vivo digestibility of nutrients, resulting in less fecal PDM with a greater proportion of small particles compared with late harvest within forage type. However, wethers fed the GE diet had greater urinary N losses compared with wethers fed the GL diet but this effect of maturity was absent when fed whole-crop barley silage.

Milk fatty acid profile and nitrogen utilization of dairy cows fed ryegrass-red clover silage containing plantain (Plantago lanceolata L.)

The effect of plantain (Plantago lanceolata L.) ensiled with ryegrass and red clover (GCP) on the milk fatty acid (FA) profile and nitrogen utilization of dairy cows was tested. Diet GCP was compared to diets based on ryegrass (G), ryegrass and red-clover silage (GC) and total mixed rations (TMR) composed of maize silage, soybean meal and hay (760, 150 and 90 g/kg dry matter (DM), respectively). Cows fed grass-silage diets were supplemented with 3 kg/day of wheat resulting in forage-to-concentrate ratios (DM basis) of 79:21, 85:15 and 86:14 for G, GC and GCP diets, respectively. On average per kg DM, diet G was composed of 790 g ryegrass, diet GC of 577 g ryegrass, 12.3 g blue grass, 218 g red clover, 37.4 g white clover and 5.54 g other species. Diet GCP contained 352 g ryegrass, 127 g red clover, 22.8 g white clover, 7.31 g dandelion and 351 g plantain per kg DM. In a completely randomized design, 24 multiparous dairy cows were fed one of the experimental diets during 13 days of adaptation and 7 days of sampling. The yields of energy-corrected milk (ECM) (27.1 kg/day) and milk protein (910 g/day) of cows fed diet GCP were higher than those of cows fed diet G (20.2 kg ECM/day, 680 g milk protein/day), but did not differ from those of cows fed diet GC or TMR. Urinary nitrogen (N) excretion relative to N intake and relative to total manure N did not differ between treatments. Utilization of dietary N for milk N formation (g/kg) was lowest for diets GCP (251) and GC (257), highest for diet G (357) and intermediate for diet TMR (313). The proportion of polyunsaturated FA in milk fat was highest for cows fed GCP followed by GC, G and TMR. The ratio of n-6 to n-3 FA was lower for diet GCP (1.5:1) compared to G (2.5:1) and TMR (5.7:1). Compared to G, GC and TMR, the cows fed GCP had a higher secretion of 18:1 trans-11 and 18:2 cis-9, trans-11 in the milk relative to dietary 18:3 n-3 + 18:2 n-6 consumed. In conclusion, increasing botanical diversity in the diet by adding plant species from another functional group, as done when switching from diet G to GC to GCP, did not improve N utilization but did lead to distinctly different milk FA profiles, especially when compared to a maize-silage based diet.

Methane prediction based on individual or groups of milk fatty acids for dairy cows fed rations with or without linseed

Milk fatty acids (MFA) are a proxy for the prediction of CH4 emission from cows, and prediction differs with diet. Our objectives were (1) to compare the effect of diets on the relation between MFA profile and measured CH4 production, (2) to predict CH4 production based on 6 data sets differing in the number and type of MFA, and (3) to test whether additional inclusion of energy-corrected milk (ECM) yield or dry matter intake (DMI) as explanatory variables improves predictions. Twenty dairy cows were used. Four diets were used based on corn silage (CS) or grass silage (GS) without (L0) or with linseed (LS) supplementation. Ten cows were fed CS-L0 and CS-LS and the other 10 cows were fed GS-L0 and GS-LS in random order. In feeding wk 5 of each diet, CH4 production (L/d) was measured in respiration chambers for 48 h and milk was analyzed for MFA concentrations by gas chromatography. Specific CH4 prediction equations were obtained for L0-, LS-, GS-, and CS-based diets and for all 4 diets collectively and validated by an internal cross-validation. Models were developed containing either 43 identified MFA or a reduced set of 7 groups of biochemically related MFA plus C16:0 and C18:0. The CS and LS diets reduced CH4 production compared with GS and L0 diets, respectively. Methane yield (L/kg of DMI) reduction by LS was higher with CS than GS diets. The concentrations of C18:1 trans and n-3 MFA differed among GS and CS diets. The LS diets resulted in a higher proportion of unsaturated MFA at the expense of saturated MFA. When using the data set of 43 individual MFA to predict CH4 production (L/d), the cross-validation coefficient of determination (R2CV) ranged from 0.47 to 0.92. When using groups of MFA variables, the R2CV ranged from 0.31 to 0.84. The fit parameters of the latter models were improved by inclusion of ECM or DMI, but not when added to the data set of 43 MFA for all diets pooled. Models based on GS diets always had a lower prediction potential (R2CV = 0.31 to 0.71) compared with data from CS diets (R2CV = 0.56 to 0.92). Models based on LS diets produced lower prediction with data sets with reduced MFA variables (R2CV = 0.62 to 0.68) compared with L0 diets (R2CV = 0.67 to 0.80). The MFA C18:1 cis-9 and C24:0 and the monounsaturated FA occurred most often in models. In conclusion, models with a reduced number of MFA variables and ECM or DMI are suitable for CH4 prediction, and CH4 prediction equations based on diets containing linseed resulted in lower prediction accuracy.

The effect of silage type on animal performance, energy utilisation and enteric methane emission in lactating dairy cows

The present study aimed to investigate the effect of silage type on dry matter (DM) intake, nutrient digestibility, energy utilisation and methane (CH4) emission. Six late lactating Holstein dairy cows were used in a replicated 3 × 3 Latin square design study with three treatments (grass silage (GS), maize silage (MS) and whole-crop wheat silage (WCWS)) and three periods (3 weeks/period). All animals were offered forage ad libitum and 5.55 kg/day of a concentrate supplement, which contained (DM basis) 66.0% rapeseed meal, 28.3% soyabean meal and 5.7% a mineral/vitamin supplement. During each period, animals were subject to digestibility, CH4 and heat production measurements during the final 6 days using calorimeter chambers. The results demonstrated that total DM intake for MS and WCWS diets were higher (P &amp;lt; 0.001) than for the GS diet. Faecal energy and heat production loss for the GS diet were lower (P &amp;lt; 0.01) than for MS and WCWS diets. In contrast, cows fed the GS diet had higher (P &amp;lt; 0.05) urine energy loss compared with MS and WCWS diets. In comparison with the GS and MS diets, WCWS diet produced a lower CH4 loss per kg DM and organic matter intake (P &amp;lt; 0.01), and CH4 energy output as a proportion of gross energy and metabolisable energy intake (P &amp;lt; 0.05). The present study demonstrates that choice of forage types affects energy utilisation and CH4 emission in dairy cows.

Yield gap analysis of feed-crop livestock systems: The case of grass-based beef production in France

Sustainable intensification is a strategy contributing to global food security. The scope for sustainable intensification in crop sciences can be assessed through yield gap analysis, using crop growth models based on concepts of production ecology. Recently, an analogous cattle production model named LiGAPS-Beef (Livestock simulator for Generic analysis of Animal Production Systems – Beef cattle) was developed, which allows yield gap analysis in beef production systems. This paper is the first to assess yield gaps of integrated feed-crop livestock systems, to analyse underlying causes of yield gaps, and to identify feasible improvement options. We used grass-based beef production in the Charolais area of France as a case study. To this end, we combined LiGAPS-Beef with crop growth models that simulate grass production (fresh grass under grazing, grass silage, hay) and wheat production (concentrate). Feed crop and cattle production were integrated to simulate potential and resource-limited live weight (LW) production per hectare. Potential production is defined as the theoretical maximum LW production per ha, in the absence of resource or management limitations. Resource-limited production is determined by availability of one or several resources: water and nutrients for crops, and feed quality and quantity for animals. Potential production of a cattle herd with an ad libitum diet of grass silage was 2380kgLWha−1year−1 and resource-limited production was 664kgLWha−1year−1. Actual LW production (354kgLWha−1year−1) was 15% of the potential production, implying a relative yield gap of 85%, and 53% of the resource-limited production, implying a relative yield gap of 47%. Applying yield gap analysis disentangled the major biophysical causes of these yield gaps: feeding diets other than the ad libitum grass silage diet, water-limitation in feed crops, and sub-optimal management. These yield gaps suggest scope to intensify beef production. We demonstrate, however, that yield gap mitigation decreased the operational profit per kg LW under the European regulations for bovine and grassland premiums operational in 2014. Hence, as expected, the premiums aiming to support farmers' income and to promote sustainable agriculture and rural development were not conducive to narrow yield gaps at the same time. The current common agricultural policy (CAP, 2015–2020) provides more scope for intensification, such as increasing stocking density via better grassland management.

Effect of dietary supplementation with heat-treated canola meal on ruminal nutrient metabolism in lactating dairy cows

An experiment was conducted to quantify the effects of incremental levels of heat-moisture-treated canola meal (TCM) fed to dairy cows on the relationship between ruminal nutrient digestion and milk production. Experimental diets were fed to 4 multiparous rumen-cannulated Nordic Red cows, averaging (mean ± standard deviation) 681 ± 54.8 kg of body weight, 111 ± 16 d in milk, and 29.1 ± 9.1 kg of milk/d at the start of the study, in a Latin square design with four 21-d periods. The 4 experimental dietary treatments consisted of a basal diet of grass silage and crimped barley, and 3 diets in which the crimped barley was replaced with TCM, giving 3 incremental levels of protein supplementation. Nutrient flow was quantified by the omasal sampling technique using 3 markers (Cr, Yb, and indigestible neutral detergent fiber). Continuous infusion of 15N was used to label bacterial crude protein. Additionally, ruminal sampling and evacuations and measurements of total-tract digestibility were conducted. The experimental diets provided 132, 148, 164, and 180 g of crude protein/kg of dry matter. The increased level of TCM linearly increased dry matter intake from 15.1 to 16.6 kg/d and energy-corrected milk yield from 21.0 to 25.6 kg/d. The increased proportion of TCM when substituting barley with TCM was associated with greater total-tract digestibility of neutral detergent fiber and potentially digestible neutral detergent fiber, which could be explained by increased digestion rate of potentially digestible neutral detergent fiber. Omasal flow of nonammonia N naturally increased with greater dietary TCM inclusion, but the increased intestinal supply of rumen-undegradable protein was partly offset by diminished microbial protein synthesis when feeding more TCM. This was also reflected in a decreased proportion of milk protein from ruminal bacterial protein when TCM supplementation increased.