Effect of supplementation with n-3 polyunsaturated fatty acids and/or β-glucans on performance, feeding behaviour and immune status of Holstein Friesian bull calves during the pre-and post-weaning periods

Background: Previous research in both calves and other species has suggested n-3 polyunsaturated fatty acids(PUFA) and β-glucans may have positive effects on immune function. This experiment measured performance,behaviour, metabolite and immunological responses to pre-weaning supplementation of dairy bull calves with n-3 PUFA in the form of fish oil and β-glucans derived from seaweed extract. 44 Holstein Friesian bull calves, aged 13.7± 2.5 d and weighing 48.0 ± 5.8 kg were artificially reared using an electronic feeding system. Each calf was offered5 L(120 g/L) per day of milk replacer(MR) and assigned to one of four treatments included in the MR,(1) Control(CON);(2) 40 g n-3 PUFA per day(FO);(3) 1 g β-glucans per day(GL) and(4) 40 g n-3 PUFA per day & 1 g/d β-glucans(FOGL) in a 2 × 2 factorial design. Milk replacer and concentrate was offered from d 0–62(pre-weaning),while concentrate provision continued for a further 31 d post-weaning period. Individual daily feed intake and feeding behaviour was recorded throughout, while bodyweight and blood analyte data were collected at regular intervals.Results: Overall mean concentrate DMI from d 0–93 was 1.39, 1.27, 1.00 and 0.72 kg/d for CON, FO, GL and FOGL calves, respectively(SEM = 0.037;P < 0.0001). Calves supplemented with GL were significantly lighter(P < 0.0001) at both weaning(d 62) and turnout to pasture(d 93) than un-supplemented calves, with a similar effect(P < 0.0001)evident for calves receiving FO compared to un-supplemented contemporaries. Supplementation with GL reduced the number of unrewarded visits where milk was not consumed(P < 0.0001) while supplementation with FO increased mean drinking speed(P < 0.0001). Supplementation with GL resulted in greater concentrations of haptoglobin(P = 0.034), greater serum osmolality(P = 0.021) and lower lymphocyte levels(P = 0.027). In addition,cells from GL supplemented calves exhibited a lower response than un-supplemented contemporaries to both Phytohaemagglutinin A stimulated IFN-γ(P = 0.019) and Concanavalin A stimulated IFN-γ(P = 0.012) following in vitro challenges.Conclusions: Pre-weaning supplementation of bull calves with either n-3 PUFA or β-glucan resulted in reduced voluntary feed intake of concentrate and consequently poorer pre-weaning calf performance. There was no evidence for any beneficial effect of either supplementation strategy on calves’ immune responses.

Impacts of Sward Renewal Method with Perennial Ryegrass (Lolium perenne) on Dry Matter Yield, Tiller Density and Nitrate Leaching

The objective of this study was to evaluate alternative methods of grassland renewal (reseeding) with perennial ryegrass and quantify their effects on subsequent DM yield, tiller density and nitrate leaching. Two experiments were carried out;the first focused on quantifying the influence of Autumn reseeding (August cultivation), and the second, on Spring reseeding (May cultivation) on sward establishment and grass DM production. The study incorporated six treatments namely: direct drill (DD), disc plus power harrow (DPH), power harrow (PH), conventional-plough, till and sow (PLO), and the chemical application of diquat to suppress the existing sward followed by direct drilling (DIQ), represented a rejuvenation method as opposed to full renewal (Spring trial only). All treatments were compared against a control (old permanent pasture). Reseeded swards produced more seasonal (P < 0.05) and total (P < 0.01 Autumn only) DM yield than the control sward. All reseeding methods increased the perennial ryegrass tiller density of the sward compared to the old permanent pasture (P < 0.05 Autumn trial, P < 0.001 Spring trial). All sward renewal methods evaluated were equally as effective as the conventional method of grassland reseeding with the DIQ rejuvenation method intermediate as measured in terms of DM yield and PRG tiller density. The results of the study show no significant difference in the level of nitrate lost in leachate following reseeding regardless of method used or indeed any difference between reseeded swards and old permanent pasture.

Application of a simplified ADM1 for full-scale anaerobic co-digestion of cattle slurry and grass silage:assessment of input variability

Mathematical modeling of anaerobic digestion is a powerful tool to predict gas yields and optimize the process.The Anaerobic Digestion Model No.1(ADM1)is a widely implemented model for this purpose.However,modeling full-scale biogas plants is challenging due to the extensive substrate and parameter characterization required.This study describes the modification of the ADM1 through a simplification of individual process phases,characteristic components and required parameters.Consequently,the ability of the simplified model to simulate the co-digestion of grass silage and cattle slurry was evaluated using data from a full-scale biogas plant.The impacts of substrate composition(crude carbohydrate,protein and lipid concentration)and variability of carbohydrate degradability on simulation results were assessed to identify the most influential parameters.Results indicated that the simplified version was able to depict biogas and biomethane production with average model efficiencies,according to the Nash-Sutcliffe efficiency(NSE)coefficient,of 0.70 and 0.67,respectively,and was comparable to the original ADM1(average model efficiencies of 0.71 and 0.63,respectively).The variability of crude carbohydrate,protein and lipid concentration did not significantly impact biogas and biomethane output for the data sets explored.In contrast,carbohydrate degradability seemed to explain much more of the variability in the biogas and methane production.Thus,the application of simplified models provides a reliable basis for the process simulation and optimization of full-scale agricultural biogas plants.

Sensory quality of meat from eight different types of cattle in relation with their biochemical characteristics

The present study compared eight breeds of cattle differing in gender （heifers, buls and steers） to determine associations between muscle characteristics and meat sensory qualities of theLongissimus thoracis muscle. Animal types differed in al the muscle characteristics and sensory qualities. Many correlations among muscle characteristics and among sensory qualities were consistent for most animal types. Isocitrate dehydrogenase （ICDH） activities alowed discrimination of muscles with respect to myosin heavy chain （MyHC）-I proportions for al animal types. Lactate dehydrogenase （LDH） and phos-phofructokinase （PFK） activities were positively correlated for most animal types. Overal liking was correlated with beef lfavour and abnormal lfavour in al animal types and with global tenderness for al animal types except for Charolais cross breed steers. For al animal types except for Angus×Friesian heifers, beef lfavour and abnormal lfavour were negatively correlated. Overal liking was not correlated with juiciness. PFK, ICDH and citrate synthase （CS） activities were strongly associated with tenderness, beef lfavour and overal liking when average values for al animal types were used. However, associations between muscle characteristics and sensory qualities within animal types were weak and inconsistent.

Quantitative analysis of ruminal methanogenic microbial populations in beef cattle divergent in phenotypic residual feed intake(RFI)offered contrasting diets

Background：Methane（CH_4） emissions in cattle are an undesirable end product of rumen methanogenic fermentative activity as they are associated not only with negative environmental impacts but also with reduced host feed efficiency.The aim of this study was to quantify total and specific rumen microbial methanogenic populations in beef cattle divergently selected for residual feed intake（RFI） while offered（i） a low energy high forage（HF） diet followed by（ii） a high energy low forage（LF） diet.Ruminal fluid was collected from 14 high（H）and 14 low（L） RFI animals across both dietary periods.Quantitative real time PCR（qRT-PCR） analysis was conducted to quantify the abundance of total and specific rumen methanogenic microbes.Spearman correlation analysis was used to investigate the association between the relative abundance of methanogens and animal performance,rumen fermentation variables and diet digestibility.Results：Abundance of methanogens,did not differ between RFI phenotypes.However,relative abundance of total and specific methanogen species was affected（P〈 0.05） by diet type,with greater abundance observed while animals were offered the LF compared to the HF diet.Conclusions：These findings suggest that differences in abundance of specific rumen methanogen species may not contribute to variation in CH_4 emissions between efficient and inefficient animals,however dietary manipulation can influence the abundance of total and specific methanogen species.

Process stability and microbial community composition in pig manure and food waste anaerobic co-digesters operated at low HRTs

This study assessed the effects of reducing hydraulic retention times （HRTs） from 21 days to 10.5 days when anaerobically co-digesting pig manure and food waste. Continuously stirred tank reactors of 3.75 L working volume were operated in triplicate at 42℃. Digester HRT was progressively decreased from 21 to 15 days to 10.5 days, with an associated increase in organic loading rate （OLR） from 3.1 kg volatile solids （VS）·m^-3.day^-1 to 5.1 kg VS·m^3.day-1 to 7.25 kg VS.m^-3·day^-1. Reducing HRT from 21 days to 15 days caused a decrease in specific methane yields and VS removal rates. Operation at a HRT of 10.5 days initially resulted in the accumulation of isobutyric acid in each reactor. High throughput 16S rRNA gene sequencing revealed that this increase coincided with a shift in acidogenic bacterial populations, which most likely resulted in the increased isobutyric acid concentrations. This may in turn have caused the increase in relative abundance of Clocamonaceae bacteria, which syntrophically degrade non-acetate volatile fatty acids （VFAs） into H2 and CO2. This, along with the increase in abundance of other syntrophic VFA oxidizers, such as Spiorchatetes, suggests that VFA oxidation plays a role in digester operation at low HRTs. Reducing the HRT to below 21 days compromised the ability of the anaerobic digestion system to reduce enteric indicator organism counts below regulatory limits.

Effect of genotype on duodenal expression of nutrient transporter genes in dairy cows

Background： Studies have shown clear differences between dairy breeds in their feed intake and production efficiencies. The duodenum is critical in the coordination of digestion and absorption of nutrients. This study examined gene transcript abundance of important classes of nutrient transporters in the duodenum of non lactating dairy cows of different feed efficiency potential, namely Holstein-Friesian （HF）, Jersey （JE） and their F1 hybrid. Duodenal epithelial tissue was collected at slaughter and stored at -80℃. Total RNA was extracted from tissue and reverse transcribed to generate cDNA. Gene expression of the following transporters, namely nucleoside amino acid; sugar; mineral; and lipid transporters was measured using quantitative real-time RT-PCR. Data were statistically analysed using mixed models ANOVA in SAS. Orthogonal contrasts were used to test for potential heterotic effects and spearman correlation coefficients calculated to determine potential associations amongst gen, expression values and production efficiency variables. Results： While there were no direct effects of genotype on expression values for any of the genes examined, there was evidence for a heterotic effect （P 〈 0.05） on ABCGS, in the form of increased expression in the F1 genotype compared to either of the two parent breeds. Additionally, a tendency for increased expression of the amino acid transporters, SLC3A1 （P= 0.072）, SLC3A2 （P= 0.081） and SLC6A 14 （P= 0.072） was also evident in the F1 genotype. A negative （P 〈 0.05） association was identified between the expression of the glucose transporter gene SLCSA1 and total lactational milk solids yield, corrected for body weight. Positive correlations （P 〈 0.05） were also observed between the expression values of genes involved in common transporter roles. Conclusion： This study suggests that differences in the expression of sterol and amino acid transporters in the duodenum could contribute towards the documented differences in feed efficiency between HF, JE and their F1 hybrid. Furthermore, positive associations between the expression of genes involved in common transporter roles suggest that these may be co-regulated. The study identifies potential candidates for investigation of genetic variants regulating nutrient transport and absorption in the duodenum in dairy cows, which may be incorporated into future breeding programmes.

Seasonal variations in nutritive and botanical composition properties of multispecies grazing swards over an entire dairy grazing season

Background Recently,there has been increasing interest in the use of multispecies(MS)swards in dairy grazing systems.Methods A plot grazing study was established to investigate the potential contribution of different sward species(perennial ryegrass,legumes and herbs)sown in grazing pastures.Ten sward mixtures were sown,ranging in complexity from a perennial ryegrass(PRG)monoculture to binary mixtures including either forage legumes or herbs to a five-species mixture;four different nitrogen(N)application rates of 0,100,150 and 200 kg N ha−1 were applied to each sward.Results Species abundance for all sward species components was associated with the interaction of time point and sward mixture;species abundance for all sward components,except PRG,was associated with the interaction of N application and sward mixture.The interactions of time point and sward mixture,and time point and N application rate,were associated with all analysed sward chemical components,except for sward digestibility.Conclusions Increased N application rates reduced the level of clover in all sward mixtures.Increased levels of white clover led to increased sward crude protein levels;the inclusion of ribwort plantain led to some seasonal variation in the nutritive value of swards.

Greenhouse gas emissions from different pig manure management techniques： a critical analysis

Manure management is the primary source of greenhouse gas （GHG） emissions from pig farming, which in turn accounts for 18% of the total global GHG emissions from the livestock industry. In this review, GHG emissions （N20 and CH4 emissions in particular） from individual pig manure （PGM） management practices （European practises in particular） are systematically analyzed and discussed. These manure management practices include manure storage, land application, solid/liquid separation, anaerobic digestion, composting and aerobic wastewater treatment. The potential reduction in net GHG emissions by changing and optimising these techniques is assessed. This review also identifies key research gaps in the literature including the effect of straw covering of liquid PGM storages, the effect of solid/liquid separation, and the effect of dry anaerobic digestion on net GHG emissions from PGM management. In addition to identifying these research gaps, several recommendations including the need to standardize units used to report GHG emissions, to account ~br indirect N20 emissions, and to include a broader research scope by conducting detailed life cycle assessment are also discussed. Overall, anaerobic digestion and compositing to liquid and solid fractions are best PGM management practices with respect to their high GHG mitigation potential.

Localization of urea transporter B in the developing bovine rumen

Urea nitrogen secreted from blood to rumen is a crucial factor shaping the symbiotic relationship between host ruminants and their microbial populations.Passage of urea across rumen epithelia is facilitated by urea transporter B(UT-B),but the long-term regulation of these proteins remains unclear.As ruminal function develops over a period of months,the developing rumen is an excellent model with which to investigate this regulation.Using rumen epithelium samples of calves from birth to 96 d of age,this study performed immunolocalization studies to localize and semi-quantify UT-B protein development.As expected,preliminary experiments confirmed that ruminal monocarboxylate transporter 1(MCT1)short chain fatty acid transporter protein abundance increased with age(P<0.01,n=4).Further investigation revealed that ruminal UT-B was present in the first few weeks of life and initially detected in the basolateral membrane of stratum basale cells.Over the next 2 months,UT-B staining spread to other epithelial layers and semi-quantification indicated that UT-B abundance significantly increased with age(P<0.01,n=4 or 6).These changes were in line with the development of rumen function after the advent of solid feed intake and weaning,exhibiting a similar pattern to both MCT1 transporters and papillae growth.This study therefore confirmed age-dependent changes of in situ ruminal UT-B protein,adding to our understanding of the long-term regulation of ruminal urea transporters.

Genomic prediction of seasonal forage yield in perennial ryegrass

Background:Genomic selection has the potential to accelerate genetic gain in perennial ryegrass breeding,provided complex traits such as forage yield can be predicted with sufficient accuracy.Methods:In this study,we compared modelling approaches and feature selection strategies to evaluate the accuracy of genomic prediction models for seasonal forage yield production.Results:Overall,model selection had limited impact on predictive ability when using the full data set.For a baseline genomic best linear unbiased prediction model,the highest mean predictive accuracy was obtained for spring grazing(0.78),summer grazing(0.62)and second cut silage(0.56).In terms of feature selection strategies,using uncorrelated single-nucleotide polymorphisms(SNPs)had no impact on predictive ability,allowing for a potential decrease of the data set dimensions.With a genome-wide association study,we found a significant SNP marker for spring grazing,located in the genic region annotated as coding for an enzyme responsible for fucosylation of xyloglucans—major components of the plant cell wall.We also presented an approach to increase interpretability of genomic prediction models with the use of Gene Ontology enrichment analysis.Conclusions:Approaches for feature selection will be relevant in development of low-cost genotyping platforms in support of routine and cost-effective implementation of genomic selection.