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Grange - Research

The Centre is currently engaged in research in a broad range of areas supporting the beef sector.  These include:

 

Genomic Selection

A new method of identifying genetically elite animals was launched by the Irish Cattle Breeding Federation this Spring for dairy cattle. The new method is called “genomic selection” and has the whole breeding world excited by its potential benefits. The current method of genetic evaluation (BLUP) in beef cattle uses information on progeny and other relatives, such as carcass weights from the factory, to estimate the genetic merit of a sire. Because of the necessity to wait for a sire’s progeny to be slaughtered, bulls are usually at least 4 to 5 years of age before they can achieve moderate to high reliability for traits such as carcass weight. Imagine the genetic gain achievable if we could accurately predict an animal’s genetic merit at only a few weeks! This is the basis behind the new technology of genomic selection and animals selected using this method are said to be "genomically selected".

Genomic selection involves analysing the DNA of an animal. DNA is the building blocks of genes and it is the genes that determine whether an animal will grow fast or be a difficult calver etc. DNA is present in all cells and remains the same throughout an animal’s life; in other words the DNA of a calf taken at one day of age is the same as that animal’s DNA several years later. Apart from identical twins, each animal has a different “DNA signature”. The same principles hold for humans and this is what forensic scientists use to catch criminals; however, we can use this principle for animal breeding. We can get DNA from blood, hair or tissue samples.

In practice, genomic selection involves taking a biological sample, such as a hair sample, from an animal and sending to a laboratory to determine the animal’s “DNA signature”. The technology is currently available to look at variations at 54,001 locations across an animal’s DNA but this number is likely to increase considerably in the coming years. These tiny changes in the DNA sequence of an animal are commonly called SNPs (pronounced "snips") and the platform used to determine the DNA signature of an animal is referred to as a SNPchip (pronounced "snip-chip"). If we know the good DNA signature for carcass weight or conformation, or for any other trait evaluated by the ICBF, then we can determine if the DNA signature of our sampled calf is good, or in other words will it make a good sire? The same principles can be applied to a heifer calf; will the DNA of the heifer calf translate to a good cow? The cost at the moment to determine the DNA signature of an animal is approximately €210 per animal although research will soon start on developing methodology to hopefully reduce the cost substantially without a large decrease in accuracy - more information
(Donagh Berry)

 

Genetics and Breeds

In the beef genetics and breeds programme a study was undertaken  to validate the Irish beef production sub-index (BPSI). The preliminary data showed that energy intake, average daily gain, slaughter weight, carcass weight and conformation score increased with BPSI, although none of the effects were significantly different from zero.  Liveweight at slaughter and carcass weight increased significantly with increased PTACwt. An increase in carcass weight of 1.31 kg per unit PTACWT was slightly greater than the expectation of 1 kg.  Sire PTACwt was significantly associated with heavier animals at slaughter.
( M. McGee)

The relationship of live animal body scores and measurements on carcass attributes was further studied and it was concluded that ultrasound scanned muscle and fat measurements and visual muscular scores showed good correlations with carcass traits and could be useful in predicting carcass meat yield and carcass value. However, correlations between visual skeletal scores and carcass traits were not significant. A one unit (scale 1 to 15) increase in carcass conformation increased carcass meat proportion by 11.9 g/kg and value by 5.9 c/kg.  A one unit increase in carcass fat score decreased carcass meat proportion by 11.1 g/kg and decreased value by 5.2 c/kg. The study further concluded that carcass conformation and fat scores obtained with mechanical grading were good predictors of meat and bone yield and carcass value but were modest predictors of carcass fat. Although carcass conformation and fat scores were poor predictors of the proportion of high value cuts these showed a high significant positive relationship with live conformation score and were negatively associated with fat score. When these relationships were applied to caracsses of progeny from the suckler and Holstein/Friesian herds it was found that with almost similar carcass fat and conformation scores, difference in meat yield of almost 10% in favour of the former was observed.
(M. McGee)

The growth and carcass differentiation between progeny of sires with average (A) and high (H) expected progeny difference (EPD) for carcass conformation was studied. The average EPD for growth (kg carcass), conformation and fat score (scale 1-5) was 25.6, 1.48, -0.35, and 30.9, 1.95 and -0.73 for A  and H sires, respectively. The results revealed there was no effect of sire EPD for carcass conformation on live or carcass weight or their gains but kill-out proportion was significantly higher for progeny of H sires.  Muscular scores at weaning and slaughter were significantly higher for bulls from H than A sires but not in heifers, which did not differ.  Compared to A sires, muscle depth was significantly greater for H sires in both bulls and heifers.  Carcass conformation score was higher and fat score lower for H than A sires in bulls, but heifers did not differ.  There was a higher proportion of hindquarter, meat and high-value cuts and, a lower proportion of fat and bone in bulls from H than A sires but there was no effect  of sire on heifers for these variables.   Overall it is concluded that bull progeny from sires with high EPDs for carcass conformation had a higher muscular score, kill-out proportion, carcass conformation score, proportion of meat and high-value cuts and a lower fat score, carcass fat and bone proportion.  Sire differences were smaller or absent in heifer progeny.
(M. McGee)

 

Beef Systems 

A beef systems study examined the options of pasture or concentrate finishing of Holstein-Friesian (HF), Aberdeen Angus x Holstein-Friesian(AA) and Belgian Blue x Holstein-Friesian(BB) steers for beef production and evaluated different finishing strategies at the end of the second grazing season, and compared the response to concentrates in autumn and winter. Animals were either grazed or supplemented at pasture before sale in the autumn  or housed  for a conventional winter for finishing. For the finishing period as a whole, live weight gains differed significantly for the three finishing strategies, being lowest for pasture finishing and highest for early concentrate finishing and estimated carcass gains differed significantly for the three finishing strategies also.  They were lowest for pasture finishing and highest for early concentrate finishing.  Carcass weight per day of age did not differ significantly for the two concentrate finishing strategies but was significantly lower for the pasture finishing strategy. Compared with the animals at pasture, the animals finished early on concentrates gained 63 kg more live weight and 45 kg more carcass weight, for a concentrate input of 867 kg DM.  Thus, the conversion rates of concentrates DM to live and carcass gains above those obtained at pasture were 13.7 and 19.2 kg, respectively.  Based on concentrate costs and live and carcass weight prices, the early concentrate finishing strategy was uneconomic unless other factors such as improved carcass grades were considered. Live and carcass weight gains during late concentrate finishing were 130 and 85 kg for a concentrate input of 941 kg DM, giving conversion rates of concentrates to live and carcass weight gains of 7.2 and 11.1, respectively.  Based on these values, the late concentrate finishing strategy would be economic at current concentrate costs and live animal and carcass prices.  The reason for the large difference in estimated conversion rates between the two concentrate finishing strategies is that in the early finishing strategy only the increment of performance above that obtained at pasture is considered, whereas in late finishing that increment is assumed to be zero.  This is because grass growth had ceased and all available herbage had been utilised at the time the late concentrate finished group was housed. While the late concentrate finishing strategy may be acceptable economically, it can not be considered as early finishing or finishing without housing. Overall there were few differences between the breed types in life time live weights and live weight gains. 

Another systems study was undertaken to compare young bulls from Holstein-Friesian (HF), Norwegian Red (NR), Norwegian Red x Holstein-Friesian (NX) and Jersey (JX) for feed intake, growth and carcass traits. The relative slaughter weights for HF, NR, NX and JX were 100, 102, 101 and 95, respectively.  Overall it is concluded that silage and concentrate intakes scaled for carcass weight were similar for HF, NR and NX, but JX had significantly higher values.  Growth, slaughter and carcass traits were similar for HF, NR and NX, but JX grew more slowly although the difference, while significant, was relatively small.  JX also had a lower kill-out proportion and a lower carcass weight.  Carcass fat score was similar for all the breed types.  JX had a higher proportion of perinephric plus retroperitoneal fat than the other breeds and their carcass fat was more yellow in colour.  All measures of carcass compactness were poorer for JX than for the other breed types.

Grassland

In grassland research a study was undertaken to examine the initial productivity of 4-species grass/legume mixtures compared with monocultures in terms of total dry matter (DM) yield and suppression of weeds in the first year after sowing. Preliminary analysis of the data indicates there was no effect of overall seeding rate on total yield (at three sites) throughout the country.  However, the mean total yield of the mixtures was greater than the mean total yield of the monocultures by 2-3 t DM/ha/year, which was consistent across the three sites and two levels of nitrogen fertiliser.  Although the species-specific effects on the total yields of the monocultures were different across the sites and N treatments, the magnitude of the difference in total yield was the same.  Conversely, the mean yield of weeds from the monocultures was consistently greater than that from the mixtures.  Therefore, there were advantages of the 4-species grass/legume mixtures over the monocultures in terms of both total yield and suppression of weeds in the first year after sowing.
(Edward O' Riordan)

Another grassland study examined the early growth and development of seedlings of contrasting pasture species after autumn sowing. There were six cultivars of red clover, either more suited to cutting or grazing, and two cultivars each of Caucasian clover, white clover  and perennial ryegrass. These results suggest that the growth and development of individual pasture species need to be considered when making decisions on time of sowing and composition of pasture seed mixtures.  All the red clover cultivars had high rates of leaf area expansion and could, therefore, be sown in autumn with perennial ryegrass.  In contrast, spring sowing of Caucasian clover in seed mixtures that do not include perennial ryegrass or red clover should be recommended, to minimise the interval in days to axillary leaf development and to reduce competition for light from other pastures species.
(Edward O' Riordan)

The vast majority of spring-born calves are housed for their first winter, returned to pasture in spring and in late autumn, housed for their second winter for finishing.  This may not always be cost effective due to the high costs involved in spending two winters inside, even though feed costs have been kept low.  A system in which young cattle graze pasture through their first winter or not spend a winter inside would eliminate bedding, feeding and possibly reduce costs.  In addition, an ability to maintain a proportion of the herd exclusively on pasture may contribute to the development of a high value grass-fed beef brand.  A grazing study has commenced to measure growth and intake of weanling heifers managed on pasture or indoors on grass silage during winter is being undertaken.
(Edward O' Riordan)

A further grassland study examined the growth of steers grazing perennial ryegrass cultivars bred for normal or elevated concentrations of water soluble carbohydrates. There were no differences in mean liveweight gain and carcass weight between steers grazing either perennial ryegrass. There was a non-significant  increase in plant WSC across the season. Similar values were also found between the two cultivars for herbage mass, herbage allowance, apparent intake, crude protein, digestibility and sward height post grazing. It is concluded that with the grasses used in this study there was no advantage by steers grazing elevated compared with normal water soluble carbohydrate perennial ryegrasses, which was associated with similar levels of herbage mass and nutritive value between the two cultivars.
(Edward O' Riordan and Padraig O’Kiely)

It could be postulated that increasing the concentration of water soluble carbohydrates (WSC) in grass might better align the kinetics of carbohydrate and nitrogen metabolism in the rumen, leading to potentially improved growth rates and reduced excretion of urinary nitrogen by beef cattle. A further grassland experiment was carried out, where  the sugar concentration of zero-grazed grass was incrementally increased by adding supplementary sucrose, to simulate such a WSC increase, and to quantify the resulting effects on the intake, digestion, N metabolism and growth of growing beef cattle. The data showed that increasing the sucrose content of ingested grass improves synchrony between carbohydrate and nitrogen compounds in the rumen, as evidenced by increased microbial protein production. The mean difference in intake between the unfortified and sucrose-fortified grass was equal to the mean intake of added sucrose, indicating that the mean intake of grass dry matter, per se, was unchanged. The mean numerical response in growth rate was higher than predicted solely from the incremental intake of energy from added sucrose, suggesting that increasing the sugar content of grass can improve the growth of grazing beef cattle if the increase is sufficiently large to adequately ameliorate asynchrony in the rumen. Also, increasing grass sugar content partitions nitrogen excretion from urine to faeces, which is an environmentally beneficial change.
(Padraig O’Kiely)

 

Forage Conservation

However, in a forage conservation study it  is concluded that unwilted grass silage offered to growing steers fortifying with sucrose did not alter any of the intake, digestion, growth or feed efficiency variables examined, nor did it interact with concentrate supplementation.
(Padraig O’Kiely)

As silages are inherently unstable once exposed to air, the mixing of concentrates with silage increases exposure to air and may increase the supply of fungal inoculum and/or respirable substrate, an  experiment was carrier out to determined the aerobic stability of grass silages and quantified the impacts of mixing with concentrates at time of feeding. It is concluded that mixing dry concentrates with silage at feed-out did not make silage aerobically less stable. However, once aerobic deterioration commenced, having mixed silage with dry concentrates increased the overall extent of deterioration.
(Padraig O’Kiely)

Although the content and stage of development of grain in forage maize has a major impact on the nutritive value of the harvested whole crop, stover yield and quality also make an important contribution. Stover chemical composition at sequential harvest times could be influenced by factors modulating the physiological stage of crop development. Thus an experiment was conducted to evaluated the effects of cultivar, plastic mulch and harvest date on stover composition and contribution to crop yield. In general, delaying harvest date from early September to November reduced the proportion of stover in the crop  and its digestibility (DMD) but increased dry matter (DM) content  and neurtal detergent fibre (NDF) contents. Stover DM content increased sharply in early November after air frost damage increased senescence.  In general, delaying harvesting  increased the proportion of cob in the crop and cob DM and starch contents but reduced  NDF , ADF (acid detergent fibre), ash and crude protein contents. In general, forage maize cobs continued to mature from early September through to early November, with the rate of change declining as time progressed. By early September both the earlier cultivar and the use of plastic mulch had additively progressed crop maturity. However, between early September and November both the late cultivar and maize grown with no plastic mulch underwent the most extensive physiological development. Nevertheless, the earlier cultivar and the use of plastic mulch still resulted in cobs of more advanced maturity in early November.
(Padraig O’Kiely)

In a survey to establish the incidence of fungal growth on baled grass silage in Ireland, 90% of bales examined had visible fungal growth present.  Penicillium roqueforti and Penicillium paneum, two fungi known to be mycotoxin producers, represented 52% and 4.5%, respectively, of all fungal isolates detected.  The study characterised the secondary metabolite profiles of P. roqueforti and P. paneum isolated from silage bales and concluded that Penicillium spp. commonly found in baled silage produce a variety of toxic compounds that may pose a risk to livestock and human health.
(Padraig O’Kiely)



Nutrition

In a nutrition study the effects of method (total mixed rations (TMR) or ingredients offered separately)  and level of feeding on muscle chemical composition in steers was measures (animal production data presented in previous years). It is concluded that as there was no effect of concentrate feeding method on carcass weight, no effect would be expected on measures of carcass fatness or muscle chemical composition.  The increase in carcass weight with increasing concentrate level was associated with increases in measures of carcass fatness but the highly significant quadratic component of the response was unexpected.  There is no obvious explanation for why all measures of carcass fatness increased up to the medium concentrate feeding level but not beyond.  There were no significant method of feeding effect or method of feeding x concentrate level interaction for carcass traits or muscle chemical composition.  Carcass weight and measures of carcass fatness increased quadratically with increasing concentrate level.  Muscle moisture concentration decreased and lipid concentration increased with increasing concentrate feeding level.  Carcass weight and measures of carcass fatness were poorly related to muscle chemical composition.

A further nutrition  experiment quantified the response of finishing steers to supplementation of grass silage with concentrate feedstuffs offered as a TMR constituted at ensiling or at feeding. Previous work indicated that similar animal productivity occurred when finishing beef cattle were offered grass silage and concentrates separately or as a TMR produced at feeding time. An alternative option to the established TMR system is to co-ensile the concentrates with the grass and subsequently feed this TMR directly from the silo. This could reduce mechanisation costs, reduce labour input at feeding, reduce effluent production and potentially enhance silage fermentation. Potential risks include losses due to unsatisfactory silage fermentation, excess effluent flow or severe aerobic deterioration.  In addition to ad libitum diets of grass silage or concentrates, total mixed rations  constituted at ensiling or at feeding time in approximate dry matter ratios of grass silage: concentrates of 75:25, 50:50 and 25:75, respectively, were fed. Increasing concentrate content in the diet resulted in both linear and quadratic increases in total DM intake, and live weight and carcass gains. There was a significant effect of method of feeding for total DM intake, live weight gain and carcass gain  in favour of the feeding time mixing. Fat score increased linearly and quadratically  with increasing concentrate level. Method of feeding had no significant effect on fat score. It is concluded that increasing concentrate proportion in the ration improved animal performance and carcass traits and that offering steers a TMR constituted at feeding resulted in greater intakes and better animal performance than when the diet was constituted at ensiling. 
(Padraig O’Kiely)

A further nutrition study was conducted to examine the effects of increasing grass regrowth interval (RI) on intake, rumen fermentation, in situ degradability, rumen digesta kinetics and nutrient flow to the omasum in beef cattle. The results indicate that increasing the RI of a perennial ryegrass-based sward by 10 days (28 vs. 38 )  had no adverse effect on feed intake, rumen fermentation or digestion, but reduced ammonia N levels in the rumen, potentially reducing nitrogen excretion to the environment.
(Mark McGee)

In a further nutrition study rumen fermentation and plasma metabolites in steers offered concentrates differing in energy source either as a supplement to grass silage or ad libitum  concluded that concentrate energy source had no effect on rumen pH or fermentation parameters when offered as a supplement to grass silage but significantly altered the end products of rumen fermentation when offered ad libitum.  A further study was conducted to determine, the intake, rumen fermentation pattern, microbial protein synthesis and nutrient flows to the omasum in beef cattle offered grass silage, maize silage, fermented whole-crop wheat and urea-treated unprocessed whole crop wheat, each supplemented with 3 kg of concentrate. Relative to grass silage, it is concluded that, non-grass conserved forages can significantly increase feed dry matter intake, alter the site of digestion and the capture of N in the rumen in beef cattle.
(Mark McGee)

In nutrition of the suckler cow studies the performance of beef cows  selected as low or high residual feed intake (RFI) capacity on grass-based systems was  measured and the data showed that cows of low RFI had a lower  grass silage intakes,  but there was no effect  on cow liveweight, body condition score or changes, calving difficulty, calf birth or weaning weights.  These results indicate that beef suckler cows with lower RFI are more energy efficient. 
(Mark McGee)

 

Meat Quality

In meat quality research some studies have focused on the differentiation of beef according to the pre-slaughter diet using the stable isotope ratios of carbon and nitrogen. The δ13C value distinguished between beef from concentrate/wheat silage, grass silage, grazed grass and grazed grass/clover-fed cattle, but not between beef from alkalage and wheat silage-fed cattle or between beef from alkalage and concentrate-fed cattle.    It is concluded that differences in the carbon and nitrogen stable isotope composition of the feeds examined were reflected in the muscle of cattle, thereby, allowing this approach to be used as a component, at least, of a scheme to authenticate the dietary history of beef cattle consuming these feeds. A further component of this work is examining whether the isotopic composition of light elements (δ13C, δ15N, δ D, δ18O and δ34S) can be used as an intrinsic, biochemical marker for tracing and authenticating beef.  The specific objectives are  to determine the temporal variability in the stable isotope composition of C (δ13C) in feed materials over one growing season, and  to determine the speed at which changes in the isotopic composition of beef muscle tissue occur following a change in diet. The data to date concludes that  while δ13C showed little temporal variation in concentrate and silage feed materials, it was more variable in fresh grass over one growing season, and that bulk muscle tissue reflected small isotopic differences between dietary components after about 100 days.
(Aidan Moloney)

This programme is also examining new approaches to tracking dietary change in animals. Stable isotope analysis of incremental tissues such as hair and teeth are powerful tools used to track dietary changes and movement in animals. Spatially separated samples record the isotopic composition of the tissue at the time it was deposited. A study is underway to determine whether sequential analysis of tissues such as hooves or hair can be used to reconstruct the dietary history of cattle. The initial experimental results have demonstrate for the first time that hooves are a suitable incremental tissue for high-resolution isotopic reconstruction of the dietary and life history of bovine animals.  Thus, stable isotopes measured in continually growing keratinised tissues like hair or hoof are proving to be a useful tool for reconstructing the individual history even at a weekly to daily basis with precision for 1 to 2 years prior to sampling date. 
(Aidan Moloney)

In other meat quality studies the effects of supplementation beef animal with a source of long chain ω-3 rumen protected-PUFA on the colour stability of minced beef was carried out and it could be  hypothesised that such supplementation would decrease the colour stability of beef under simulated retail display conditions. However, it is concluded that supplementing  did not have a deleterious effect on colour stability of minced beef stored for 1 week in high O2 packs relative to control animals. A related study was conducted  to investigate the effect of high c9,t11-CLA beef (produced by supplementing grazing cattle with sunflower oil and fishoil) on risk factors associated with the metabolic syndrome and to determine its efficacy relative to the synthetic form of the fatty acid. The preliminary results suggest that beef enriched with CLA may have beneficial effects on glucose metabolism, insulin sensitivity and mediators of inflammation, all of which are important health factors.
(Aidan Moloney)

 

Animal Welfare

In animal welfare and health research a study was conducted to examine the expression of candidate neutrophil genes of young cattle subjected to transportation stress.  The genes selected for profiling were sensitive to glucocorticoids. Given the prominence of neutrophils as a target of stress and in innate immune responses during bacterial infections, it is conceivable that measurements of altered neutrophil gene expression during stress may be effective indicators of altered immune status and thus susceptibility to infectious diseases.  Thus, a broader investigation of the neutrophil transcriptome during transportation stress was performed in order to elucidate possible functional themes and a signature of changes that may illuminate future biomarkers of disease susceptibility. As expected, transportation elicited a classic stress response as evidenced by an acute and pronounced increase in plasma cortisol  and in circulating neutrophil counts. Genes involved in immune response, apoptosis, and wound healing were confirmed as differentially expressed in this study, and mRNA abundance changes occurred at the same times that elevated plasma cortisol and circulating neutrophil counts were observed.    The expression of 88 genes was significantly changed by transportation stress, as highlighted by differences in mRNA abundance.  Seventeen of these genes were differentially expressed at more than one time point.  The ontological clusters and number of genes (in brackets) included in each are were, signal transduction (16), immune response (15), protein trafficking (7), apoptosis (6), transcriptional regulation (6), ribosomal (6), wound healing (5), mitochondrial (3), metabolic enzymes (2), translational regulation (2), ubiquitin pathways (2), protein activation (1), RNA processing (1), steroid (1), and cell structure (1).  The identification and/or function of 14 affected genes was not available in the databases searched and were thus grouped in a cluster called “unknown.”

A further study addressed  concerns about long distance transport of animals by sea and its effects on animal welfare. The study involved a sea journey of approximately 12 days from Ireland to the Lebanon. Fifteen hundred Holstein-Friesian bulls accommodated on  5 decks of a shipping vessel were transported from Ireland to the Lebanon in October 2005.  Physiological and haematological measurements  showed that the blood paramaters of transported animals returned to pre-transport levels by day 3 of sailing while the physiological variables (neutrophil and lymphocyte numbers, non-esterified fatty acid concentrations) remained altered  compared with baseline. Transport of bulls for 12 days by sea did not impact negatively on animal welfare.

In a finishing beef cattle housing study where the effects of placing mats or wood-chips on concrete slatted floors on production, behavioural, physiological and immunological responses were measured, it is concluded that under the conditions of the study, there was no evidence to suggest that housing animals on slats alone was detrimental to their performance or welfare, based on the performance measurements and welfare indices  that were evaluated. Placing mats or wood-chips over the concrete slats did not alter either animal production or welfare.

 

Environment

In the environmental programme the effect of low-rate intermittent aeration on nutrient concentration and homogeneity of beef cattle slurry is being examined. The Nitrates Regulations establish that animal slurry must be considered as a valuable source of nutrients which must be taken into account when calculating crop nutrient requirements. It is, therefore, desirable that landspread slurry is homogeneous to ensure that even distribution of nutrients is achieved. During storage, slurry stratifies into different layers. Conventional slurry management includes agitation, whereby stored stratified slurry must be mixed in situ prior to landspreading. The effect of low-rate intermittent aeration on beef cattle slurry has been investigated to establish whether there is any difference in a) slurry stratification between conventionally managed slurry and aerated slurry during the slurry storage period, and b) nutrient concentration between conventionally managed agitated slurry and aerated slurry.  

A beef cattle shed divided into twelve slatted floor pens underlain by six underfloor slurry tanks was selected for the experiment. Each slurry tank was overlain by two cattle pens. A low-rate intermittent aeration system was installed in three of the six slatted tanks. Fourteen animals were housed in each pen and fed the same diet (grass silage ad libitum plus 3 kg concentrates). The experiment commenced on 22 December 2005 lasted for 99 days. On the advice of the aeration system manufacturer, water was added to each of the six tanks early in the animal housing period (day 47). The cattle were removed and slurry samples taken at various depths and distances from the feed face within each tank. The samples were analysed for dry matter concentration (DM), pH and electroconductivity (EC) as it was considered that these parameters were good indicators of slurry homogeneity. Aerated slurry was then pumped to a reception tank and slurry samples collected from the pump outlet at varying times during the pumping period. Test pumping of conventionally managed slurry was carried out and it was concluded that agitation was required. Water was added to two of the non-aerated tanks during agitation to aid the mixing (14% and 31% of slurry volume, respectively). The agitated diluted slurry was pumped to a reception tank and slurry samples collected as for aerated slurry. The slurry samples from each treatment were composited and analysed for EC, pH and DM. Differences between treatments were tested by a two-sample paired t-test. Samples of pumped agitated slurry and pumped aerated slurry were collected and their nutrient composition analysed.

Standard deviation values of pH for both treatments showed small dispersion about the mean. However, standard deviations of EC and DM values were greater for conventionally managed slurry than for aerated slurry which indicates that slurry samples taken from conventionally managed tanks were more variable than those sampled from the aerated slurry tanks. It is reasonable to suggest that beef cattle slurry which has undergone low-rate intermittent aeration is in a more homogeneous state than conventionally managed slurry. During the pumping phase, it was possible to pump the aerated slurry directly to the reception tank without requiring agitation or further water addition, whereas, both agitation and water addition were required for the conventionally managed slurry. 

This experiment indicates that low-rate intermittent slurry aeration reduces stratification of beef cattle slurry during storage. Furthermore, low-rate intermittent aeration does not appear to have an effect on nutrient concentration of stored beef cattle slurry. 
(Padraig O’Kiely)

Methane emissions account for c. 16% of total greenhouse gas (GHG) emissions in Ireland. Given that Ireland currently produces substantially more GHG than its Kyoto target, all sectors of the economy including agriculture will face pressure to reduce emissions. There is an urgent need for a better understanding of the process of methane formation in the rumen so that the details of the application of mitigation practices can be optimised and new strategies can be proposed for testing. Research currently being undertaken in Grange will expand the national research effort considerably, and broaden it to include a strong dimension focusing on rumen microbiology. The overall objectives of the work area are to provide new information on how mitigation strategies work, and in this context, to further investigate some strategies that have been shown to have potential. An artificial rumen system has been established, and this and an in vitro gas production technique will be used to screen a large number of potential strategies for their effect on methane emissions and rumen fermentation. Finally, the impact of forage quality and additives to the diet on methane emissions will be intensively examined in a series of in vitro and rumen fermentation experiments.

Crops grown specifically for renewable energy production and other novel uses offer opportunities for sustainable agricultural systems. Where this involves marginal land or grassland use, new economic potential could be realised. A 4 year project in Grange, in collaboration with researchers in University College Cork and The Questor Centre Queens University Belfast, will investigate the potential utilisation of grass for the production of biobased products and biofuel
(Joseph McEniry)

 

Systems Modelling

In beef systems modelling a mathematical model (The Grange Beef Model) of Irish spring-calving suckler beef production has been developed. The aim of the Grange Beef Model is to specify a detailed and integrated set of management alternatives within the feeding and livestock specifications of Irish beef production systems and to identify optimal systems based on these alternatives and farm resources available. The model is deterministic, largely empirical and employs a single year steady-state design. The equations are specified in a Microsoft Excel spreadsheet and solved using the ‘add-in’ optimisation software “What’s Best!”. Budgets are formulated for each activity using the most recently available Irish data. These budgets assign a cost or revenue to each activity and based on these the model identifies the optimal beef production system. The objective function of the model maximises farm gross margin.

The model is constructed around a typical suckler beef cow herd based on spring-calving Limousin x (Limousin x Friesian) cows with animal groups based on the average animal within that group. Animal feed requirements and forage characteristics are based on well established biological functions. Animal performance and forage yield estimates are taken from experiments conducted at Grange Beef Research Centre. Diets for animal groups are based on a combination of grazing, grass silage, concentrate and maize silage, if available. All feeding activities are specified on a monthly basis to incorporate the seasonal variation in animal diets during the year. The model is now being used to investigate development options for Irish beef farms.
(Paul Crosson)

 

Cattle Reproduction

In cattle reproduction research, tissue concentrations of ω-3 PUFA can be manipulated through dietary supplementation and blood plasma concentration may be a useful predictor of concentrations of PUFA in some key reproductive tissues. Dietary ω-3 PUFA supplementation alters uterine expression to promote the production of prostaglandin E which is known to be embryotrophic.  Dietary ω-3 PUFA supplementation inhibits gene expression of D-9 desaturase in the muscle of beef cattle. Fifty days of supplementation was sufficient to down regulate D-9 desaturase gene expression. These findings have important implications for the development of dietary strategies to augment the concentrations of both CLA and ω-3 PUFA in beef.
(Sinead Waters and Dermot Morris, Athenry)

Other studies in reproduction found that cows in severe negative energy balance in early lactation  show elevated expression of key genes involved in the inflammatory response  and reduced  expression of genes involved in cellular proliferation  which is likely to compromise adaptation  and recovery from negative energy balance.
(Sinead Waters and Michael Diskin, Athnery)

Blood concentrations of insulin-like growth factor-I during early oestrus cycle are strongly associated with subsequent conception rate and may potentially be a good marker for cow fertility. 
(Michael Diskin, Athenry)