AGRIP End of Project Reports: Recent submissions
Now showing items 41-60 of 168
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Shortening the interval to resumption of ovarian cycles in postpartum beef cows.• In beef cows the interval from calving to first ovulation, or postpartum interval, is affected by nutrition and by the suckling effect of the calf. • The suckling effect is the biggest determinant of this interval, comprising: (i) physical contact and (ii) maternal bonding between cow and calf. Restricted suckling and calf isolation induce a rapid resumption of oestrous cycles. • Prepartum nutrition is the next most important determinant of the postpartum interval. Cows that calve in poor body condition have a longer interval than cows that calve in good body condition. • Increasing the level of nutrition in the postpartum period has only a limited effect in shortening the postpartum interval. • In most cows the first postpartum ovulation is silent and is succeeded by a short oestrous cycle of approximately 8-10 days. The first observed oestrus occurs prior to the second ovulation. • When used in combination with calf isolation and restricted suckling, progesterone pre-treatment for 6 days induces oestrus in the majority of cows and eliminates the short oestrous cycle. • The prolonged postpartum interval in beef cows is not due to failure of ovarian follicle development but to failure of successive dominant follicles to ovulate due to the inadequate frequency of LH pulses.
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Maximising grazed grass in the diet of the ewe for mid-season lamb production.A trial was conducted at the Knockbeg Sheep Unit, Co. Carlow over the years 1998/99 and 1999/00 with objectives centred on maximising the role of grazed grass in the diet of the ewe by accumulating autumn pasture and carrying it forward for winter grazing. Using a farmlet system approach, two systems of mid season lamb production, intensive and extensive, were compared for ewe productivity, lamb performance, carcass output per ha and associated management inputs. The stocking rates chosen for the two systems were: (1) 13 ewes per ha including silage conservation and housing for a 100-day winter and, (2) 10 ewes per ha with extended grazing in winter.
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Biodegradable Microparticles as Non-Live Viral Vectors for Respiratory Tract Vaccination.The potential of a microparticulate vaccine delivery system in eliciting a specific humoral response in the upper respiratory tract of calves was evaluated. Microparticles composed of poly(lactideco- glycolide) containing ovalbumin, a model immunogen, were prepared by a solvent evaporation technique. The microparticles were under 10μm in diameter as determined by fluorescence activated cell sorter (FACS) analysis. Following immunisation, the microparticles induced production of specific secretory IgA (sIgA) in nasal samples.The sIgA was detected after only one week and persisted throughout the length of the study. Additionally, the effects of microencapsulated synthetic peptides (F peptide (0.5mg) and G peptide (0.5mg), representing known protective epitopes against bovine respiratory syncytial virus (BRSV), on the cellular and humoral immune responses of calves were investigated. ∗ No significant change in the cellular immune response was detected. * The secretory IgA response was significantly more prolonged following administration of the SF (F111-148) peptide when compared with the SG (G174-187) peptide. * It is concluded that microparticles incorporating antigens show potential in the quest for generating complete protection in the young bovine against respiratory tract pathogens. * Vaccination of calves with the SF (F111-148) and SG (G174-187) peptide resulted in a significant reduction in the requirement to treat with antibiotics for respiratory disease in the post-vaccination period.
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Concentrate Supplementation of Pasture for Beef Production* Unsupplemented cattle offered a high grass allowance (18 kg (DM)/head/day), achieved 0.97 of the DM intake of a positive control offered concentrates ad-libitium. At a low grass allowance (6 kg/DM/head/day), there was no effect of supplementary concentrates on grass intake. At a medium (12 kg/DM/head/day), and high grass allowance, supplementary concentrates reduced grass intake by 0.43 and 0.81 kg/DM respectively per kg/DM concentrate offered. * Supplementary concentrates increased complete diet digestibility even though offering supplementary concentrates also increased total DM intake. Complete diet digestibility was higher than the additive values of the grass and concentrates. This would imply that the supplementary concentrates increased the grass DM digestibility. * Increasing the grass allowance increased plasma urea concentration; supplementary concentrates increased total dietary nitrogen intake and reduced plasma urea concentration. These findings suggest that the concentrate supplement enabled greater utilisation by rumen micro-organisms of the degradable nitrogen supplied by the grass. * Supplementing with concentrates increased carcass growth by 116 g/kg concentrate DM eaten whereas increasing the grass allowance increased carcass growth by 38 g/kg/DM grass eaten. The carcass weight response to concentrates of grazing animals was twice that of animals offered concentrates ad-libitum which gained 57 g carcass per kg concentrate DM eaten. * The relationship between carcass gain (Y) (kg/day) and supplementary concentrates (X) (kg/day) was quadratic (P< 0.001) and was best described by the equation: Y = -0.0099X2 + 0.1364X + 0.2459 (R2 = 0.60). The relationship between carcass gain (Y) (kg day-1) and grass intake (X) was also quadratic (P< 0.01) and was best described by the equation: Y = -43X2 + 275X + 133 (R2 = 0.48). Although there was a much larger (double) carcass growth response to supplementary concentrates than to additional grass DM eaten, increasing grass intake significantly increased carcass fat scores whereas offering supplementary concentrates did not. This would imply that relative to concentrates, autumn grass led to a change in the partitioning of energy from muscle towards subcutaneous fat. * As a strategy for increasing the performance of cattle grazing the type of autumn grass used in this study, offering supplementary concentrates offers more scope to improve animal performance than altering grass allowance. * The carbohydrate source of the three concentrates formulated to differ in rate of degradability did not alter rumen fluid pH, volatile fatty acid (VFA) concentration or the rate of grass DM or N degradation when grass supply was considered to be limiting or liberal. The autumn grass was apparently capable of buffering the effects of concentrate DM degradation rate which varied by up to two fold. * The rumen fluid parameters were more influenced by the pat-tern of grass intake than type of concentrate offered. Hence, there was no effect of concentrate type on animal performance.
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Weaning Mart SurveyThe weanling survey was carried out for the period January 1998 to December 1999. * There were 123,259 weanling surveyed. * The distance travelled to the mart ranged from 1.4 to 216 km. * All weanlings travelled < 4 h to the mart. * The majority of weanlings travelled < 50 km to and from the mart. * The distance travelled from the mart ranged from 2.1 to 364km. * Only 32 weanlings travelled > 500 km on the combined jour neys to and from the mart. * The longest distance travelled on the combined journey to and from the mart was 579 km. * The number of weanlings that remained within the county where the marts were located ranged from 23.5% to 99.5%. * No animals travelled for > 8 h. * There are no welfare issues involved in the selling of weanlings through Irish marts.
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Characterisation of feedstuffs for ruminants.A wide variety of feed ingredients are used in the manufacture of compound feeds in Ireland. Unprocessed feedstuffs vary from batch to batch due to differences caused by variety, soils, weather, etc. By -product feeds may also vary due to the processes from which they were produced. Accurate information on the nutritive value of feeds is essential for accurate ration formulation. A series of experiments was carried out to determine various nutritional characteristics of concentrate ingredients either locally produced or imported into Ireland. From these experiments it was concluded that : * The digestibility values of concentrate ingredients derived in maintenance-fed sheep are applicable to maintenance-fed cattle. * Feed is not utilised as efficiently when the level of feeding is increased from maintenance to 2 x maintenance. * The improved feed conversion efficiency in steers offered a restricted allowance of concentrates cannot be attributed to a difference in digestibility but can be attributed in part to a lower rate of fat deposition compared to steers offered ad libitum concentrates. * The residue after oil extraction from Camelina sativa could replace some imported protein-rich feedstuffs in ruminant rations but to fully achieve this potential, the residual oil content must be decreased. * For measurement of ruminal degradability of concentrate ingredients a wide range of forage to concentrate ratios and feeding levels can be used. * It is important to consider the actual outflow rate of nutrients from the rumen when measuring the feed value of individual concentrate ingredients as this can have an impact on the effective degradability and the relative nutritive values assigned to such ingredients. * Large variations in ruminal degradation occur within and among feeds. The ruminal degradability of different samples of any one feed should be measured to determine their true nutritive value for feeding ruminants. * Within most concentrate ingredients examined, the variation in small intestinal digestibility (SID) due to source indicates a range in the quantity of amino acids supplied to the animal for productive purposes. The more rapid and cost effective in vitro technique can be used to screen the SID of concentrate ingredients. * Target volatile fatty acid (VFA) concentrations and proportions may be produced by varying the proportions of the individual ingredients in a concentrate ration. * An in vitro procedure allowed VFA production to be measured across a large range of feeds under standardised conditions. * On average, 75% of gas produced during ruminal fermentation consists of carbon dioxide. The variation in methane production among individual concentrate ingredients provides an opportunity to formulate rations to minimize environmental pollution with methane.
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Increasing the use of AI in suckler herds.Reproductive efficiency is a major factor affecting production and economic efficiency of beef herds. For herds using artificial insemination (AI) heat detection rate and calving rate are the two major determinants of compactness of calving and ultimately the calving-to-calving interval. Heat detection is a time consuming repetitive chore that must be carried out up to 5-times each day for as long as AI is used. Heat detection rate, usually measured as submission rate, is hugely variable from herd-toherd but for most herds only between 40% and 70% of cows that exhibit heat are actually detected by the stockman. Despite an increased understanding of the endocrine control of the oestrous cycle the goal of fixed-time insemination is not yet consistently achievable in either cows or heifers treated at different stages of the oestrous cycle and in different physiological states. The overall objective of the this project was to develop an improved cost effective hormonal method to control the time of ovulation to allow beef cows be bred by AI without the need for heat detection. A total of 3 studies were carried out and the results are summarised in this report.
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Optimisation of Nutrient Supply for Beef Cattle Fed Grass or Silage.Since forage forms a large part of growing ruminant rations in Ireland, the trust of this project was to examine the effect of ensilage on ruminal digestion of grass and to examine ruminal microbial protein and intestinally absorbable protein supplied by grass and/or clover. A range of in vitro and in vivo techniques were employed and strategies used by commercial beef producers to optimise cattle growth (and nutrient supply) were also documented. To accomplish the aims of this project, a range of methodology developments/ modifications in vitro and in vivo was carried out. From in vitro methodology development it was concluded that : (i) Compared with fresh silage, drying per se may give artifically higher rates of dry matter (DM) digestion. (ii) Greater experimental precision can be obtained by ensuring a greater substrate surface area to reaction volume ratio in each reaction vessel. (iii) For studies where the rate of digestion is of greatest importance, pre-incubation of frozen inoculum in a nutrient medium best simulated the cellulolytic activity of unfrozen inoculum. In studies that require large volumes of inoculum for extended work, freezing directly is justified. (iv) Neutral detergent extraction altered in vitro digestion characteristics of silage. The residue after washing with water at 70°C has a high residual fibre concentration and is more representative of the structural components of silage ingested by ruminants. (v) A semi-continuous culture system developed at Grange Research Centre can successfully model in vitro ruminal digestion of fibre and starch-based diets in a controlled environment. From in vivo methodology development it was concluded that : (i) Oven drying at 60°C and correction for loss of volatiles gives a good estimation of DM concentration of ruminal particulate digesta. This procedure has the added advantage that drying at 60°C allows the residual materials to be analysed for fibre fractions without concern for heat damage which can occur at a higher drying temperature. (ii) A naso-ruminal sampling device can be used to measure the relative patterns of fermentation of contrasting diet types when in situ for up to 7 days. (ii) Application of a vacuum to withdraw samples had no negative effect on ruminal fluid variables. From in vitro studies on grass digestion, it was concluded that : (i) Ensiling of grass decreased the apparent extent of digestion of cell walls when in the presence of the whole plant and that this largely reflected an increase in the lag time before digestion commenced. (ii) Ensiling of grass did not negatively affect the digestion of isolated cell walls. (iii) There is a negative impact of ensiling on microbial protein production from the water soluble carbohydrate fraction of grass. (iv) Supplementation with the water soluble fraction of grass significantly improved the apparent extent of digestion for ensiled forages when compared with the supplementation of the post-ensiling fraction in a batch culture system. (v) There is a negative impact of maturity on the pattern of cell wall fermentation and that this impact can be decreased by ensiling method. From studies on herbage digestion in vivo it was concluded that : (i) Grass silage type had a greater effect than the rate of concentrate fermentation on ruminal microbal protein synthesis. (ii) Harvesting time had a bigger impact on nutrient supply from herbage than sward type (grass or grass/clover). (iii) Increasing clover content in the herbage decreased the biological value (g nitrogen retained/kg absorbed) of dietary protein. Diverse stratgies were used on commercial beef farms to optimise nutrient supply and animal growth. Average animal performance on individual farms was not better than would be typically recorded in a research environment. There was scope on many of the farms to improve technical performance and to decrease the costs of production.
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Viability of in vitro produced cattle embryos.Embryo transfer is being increasingly used in the cattle industry. As well as direct embryo transfers, many embryo-based biotechnologies have the potential to improve cattle production efficiency through enhanced breeding strategies, by facilitating the introduction of desirable traits such as disease resistance and through the production of desirable medical or pharmaceutical products in the milk. These biotechnologies are, however, dependent on a supply of viable in vitro produced (IVP) embryos. While the in vitro fertilization rate is high (80%) in cattle, only about 30 transferable embryos, or blastocysts, are produced from every 100 fertilized oocytes. A major factor affecting the viability of IVP embryos is their failure, in a high proportion of cases, to undergo normal development to the blastocyst stage in the manner of in vivo embryos. The major problem relates to a failure of the cells of IVP embryos to form a compact cell mass when they are 5 - 6 days old. This ultimately leads to developmental problems and compromised viability. Cell compaction is recognized as a critical event in early embryo development and has been associated with marked changes in protein synthesis and phosphorylation in the embryos of some species. This report is the first, to our knowledge, to describe the rate and pattern of protein synthesis and phosphorylation before, during and after compaction in both in vivo and in IVP cattle embryos. The main results are summarised below.
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Maximising Annual Intake of Grazed Grass for Beef Production.Grass is by far the most important crop grown in Ireland.Well-managed grassland supports high levels of animal performance, and the production of high quality produce. Grazed grass is a relatively cheap feed source for beef production (O'Kiely, 1994). Grazed grass does not always match feed requirements in efficient beef production systems. Supply tends to exceed demand in the late spring and summer whereas deficiencies in feed supply occur in late autumn and during the winter and early spring. The objective of the present series of experiments was to examine the potential to increase the utilization of grazed grass in beef production systems.There are two aspects to this: one relates to the utilization of grass in situ; the second relates to the strategic approach to grass utilization, i.e. matching feed requirements with supply of grazed grass and silage conservation during the year. The first two experiments presented in this report examine the utilization of grass in situ. The effects of pre-grazing pasture mass and nitrogen (N) fertilization on the production and subsequently the utilization and digestibility of the grass under grazing by cattle were examined. A third experiment and examines the effect of pre-grazing pasture mass on performance of beef cattle during a grazing season. The fourth experiment investigates the role of perennial ryegrass cultivars in supplying grass for grazing during the spring, and for the production of high nutritive value first cut silage.
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Studies on Housing of Pregnant Sows in Groups and IndividuallyIntensive methods of sow housing and their effects on health and welfare have become a topic of intense debate. In the EU the use of tethers for pregnant sows must be phased out by 2006. At pre s e n t there are no plans to ban stalls for pregnant sows. In 1997 the EU released a report on sow housing which was critical of stalls but did not recommend a ban (SVC, 1997). Some member countries have introduced more stringent legislation. The UK government has banned the use of both stalls and tethers for pregnant sows fro m January 1, 1999. Sweden has also imposed a ban on both stalls and tethers, and the Netherlands and De n m a rk have announced restrictions on when individual penning may be used. • This study included a comparison of pregnant gilts in loose housing (groups of 4) and in individual stalls from early pregnancy. Behaviour and skin lesions were monitored both during pregnancy and in the farrowing house. Stalled gilts tended to have higher skin lesion scores. Salivary cortisol levels in stalled gilts showed evidence of a chronic stress response. Loose gilts showed more distress when confined in the farrowing crate pre - f a r rowing than did gilts which had been housed in stalls in pregnancy. • Comparison of two group housing systems namely, groups of four with 3.0m2 per sow and groups of eight with 2.2m2 per sow showed a higher level of aggression in the larger group. Both treatments had free-access stalls with full length partitions but the groups of eight had a smaller communal lying area and they spent a greater proportion of their time in the stalls.
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Cattle Embryo Growth Development and Viabilty.A major problem for the cattle breeding industry is the high rate of early embryo loss which compromises reproductive efficiency and genetic improvement, resulting in serious financial loss to farmers. An important part of the Teagasc research programme in this area is the investigation of basic parameters of cattle embryo growth, development and viability during the critical period when most of the embryo loss occurs. We have now characterised this period of embryo development and to our knowledge, this is the first report describing the morphology, growth rate, protein content and metabolic activity of cattle embryos during this period. The main results are summarised here and detailed results have been published in the papers listed at the end of this report. Embryo growth rate and protein content increased exponentially between days 8 and 13 after fertilisation. Furthermore, there was a high rate of protein synthetic activity, energy and amino acid metabolism and signal transduction activity, all reaching a peak between days 8 and 13 after fertilisation. Because of the high rate of metabolic activity evident during this time it is likely that the embryos are very susceptible to environmental changes that have the potential to interfere with normal developmental mechanisms. The results arising from this project suggest that the critical period of early embryo loss in cattle may now be narrowed to a time window of day 8 to 13 rather than day 8 to 16 as presumed up to now. The main results are summarised.
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Copper, Iodine and Selenium Status in Irish Cattle.At 9 abattoirs throughout the state, samples of blood, liver and kidney were collected from the three cattle categories (cull dairy cows, cull beef cows and finished steers) at slaughter. In all, 2612 cattle were sampled for the following assays: copper (Cu), haemoglobin (Hb) and glutathione peroxidase (GPx, a selenoenzyme) on whole blood, inorganic iodine (I) in plasma, and Cu in liver and Selenium (Se) in a subset of liver and kidneys. The survey documented the overall status of Cu, I and Se in Irish cattle at slaughter and compared the trace element status of three categories of cattle. It also examined the effects of housing / season (late spring versus late autumn). I deficiency was the most prevalent mineral deficiency in all three bovine categories. Overall, in spite of whatever supplementation was being used preslaughter, 69% of samples had low (<50 µg/L) plasma inorganic I status (51% at the end of spring, 84% at the end of autumn). Overall, in spite of whatever supplementation was being used preslaughter, liver Cu status was low (<20 mg/kg DM) in 19% of samples (11% at the end of spring, 26% at the end of autumn). Liver Cu reflects Cu status more accurately than blood Cu. However, the relationships between Cu levels in liver and blood were poor in these data; it was not possible to predict a blood Cu level accurately from a given liver Cu level. Also, relative to liver levels, blood levels underestimated the extent of low Cu status by a factor of >2, with a wide range of error (0.9-2.6 times). However, as liver biopsy seldom is a practical option in commercial herds, blood tests usually are used for routine assessment of mineral status in live cattle. GPx levels in whole blood closely reflect blood Se status. In spite of whatever supplementation was being used preslaughter, blood GPx status was low (<40 iu/g Hb) in 11% of samples (4% at the end of spring, 16% at the end of autumn). In a subset of the data, blood GPx and Se levels in bovine kidney and liver had positive linear relationships but predictability was poor. A similar conclusion applies to levels of Se in liver and kidney. Also, liver Se correlated better with blood GPx (R2 = 0.443) than with kidney Se (R2 = 0.264). Cattle slaughtered off grass in late autumn had lower Cu, I and Se status than those slaughtered out of sheds in late spring. Finished beef steers and cull suckler cows had lower Cu and Se status than cull dairy cows. Liver and kidney had few high Cu or Se levels, indicating that current inputs of minerals do not pose a threat of toxicity to cattle, or to the human food chain. Mean PII levels in dairy cows were too low to pose a threat of excessive milk I levels for human consumption. Other research at Grange shows that trace element supplementation and trace element status in bovine blood, especially from dairy cows, improved nationally in recent years. However, this survey shows clearly that current national inputs of Cu, I and Se are inadequate to maintain normal trace element status in finished steers and cull (especially beef) cows at slaughter. This report concludes that current national inputs of Cu, I and Se are inadequate to maintain normal trace element status in finished steers and cull (especially beef) cows at slaughter, and from current inputs, the risk of Cu or Se toxicity to cattle, or to the human food chain, is minimal.
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Effect of Grazing System and Anthelmentic Treatment of Ewes on Parasitic Challenge and Lamb Growth.The adverse effect of parasites on lamb growth rate has been well documented. The combination of concerns about worm resistance to anthelmintics and consumer demand for products without chemical residues has increased the need to re-evaluate current control methods. In order to be effective and sustainable, control measures should include grazing management systems that exploit parasite life cycles. This will facilitate the rational use of anthelmintics. The work undertaken, over three grazing seasons, was designed to evaluate the effect of a “safe” grazing system on the gastrointestinal parasite (roundworms) levels in ewes and lambs, on the number of infective larvae on herbage and on lamb growth. The study comprised 6 similar sized paddocks; 2 paddocks of permanently grazed sheep pasture (“contaminated”) and 4 paddocks of which 2 were rested from lambs in alternate years to render them safe for lambs (“safe”). Ewes and lambs were set stocked on 2 “safe” and 2 “contaminated” paddocks each year. The first year was treated as an establishment year for the study. The main results confirm the merits of not grazing ewes and their lambs on the same pasture from lambing to weaning in successive years in achieving lower numbers of infective Nematodirus larvae on pasture, which ultimately translates as “safer” levels in lambs. There was a low level of residual over-wintered infection of “other trichostrongyles” on pasture in spring and this most likely could be attributed to the dosing regime used in the study which served to reduce contamination on pastures in late summer / autumn period.
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Protein Nutrition and Fertility in Cattle.The objectives of the project were to determine the effects of dietary crude protein intake, on blood concentrations of ammonia and urea and on fertility, and on the possible biological mechanisms involved. Heifers were used in all experiments in order to avoid any confounding effects of lactation and, or, negative energy balance. The results are summarised as follows. • • • • 5 Blood urea and ammonia increased linearly with increases in dietary urea. Fermentable carbohydrate, in the form of molassed sugar beet pulp (MSBP), was more effective than barley in reducing blood urea concentration. Plasma ammonia concentrations were more variable but MSBP was again more effective than barley in reducing these. Embryo survival rate was not affected by either dietary crude protein (CP) or fermentable energy intake irrespective of whether animals were fed a silage diet supplemented with feed grade urea or were grazing pasture with a high crude protein content. Despite generating systemic urea concentrations of up to 25 mmol/L and systemic ammonia concentrations of up to 242 μmol/L no significant relationship between these parameters and embryo survival rate was established. Consistent with these results on embryo survival, elevated blood urea or ammonia had little effect on the biochemical composition of oviduct fluid, the environment of the early developing embryo. It can be concluded that elevations in systemic concentrations of ammonia or urea per se, particularly of the magnitude observed under normal feeding conditions, are unlikely to impair embryo survival in cattle as a consequence of disruptions to the oviductal environment.
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Fluctuations in Energy Intake and Fertility in Cattle.Reproductive failure in dairy cows results in fewer calves born, lower milk sales, slower genetic progress and consequently, significant financial loss to the industry. Dairy cattle breed improvement programmes have, at least until very recently, focused primarily on increasing the yields of milk or milk solids. The resulting genetic improvement has led to significant increases in milk yield per cow but this increase is now associated with a significant decline in cow reproductive wastage. An important part of the Teagasc research programme in this area is to determine the time at which embryo loss occurs and also to determine whether the extent of the embryo loss is affected by the energy nutrition of the cow and to devise strategies to reduce its extent. This project has focused on the relationship between changes in dietary energy intake near the time of insemination and the extent and pattern of embryo survival. The main results are summarised in this report and detailed results of the several experiments involved have been published in the papers listed at the end of this report. • • 4 The objectives of this project were to determine the effect of changes in energy intake near the time of insemination on embryo loss rate, on the timing of embryo loss and on the possible biological mechanisms involved. Cross bred heifers were provided with either high or low energy intakes that were based on pasture allowances calculated to provide either 0.8 or 2.0 times their maintenance requirements. These energy intakes were allocated for two weeks before and about five weeks after insemination. The effect of the changes in energy intake on embryo loss and on the time at which embryo loss occurred, relative to the time of insemination, was established. Possible associations between embryo loss and blood concentrations of progesterone, NEFAs, insulin and glucose were examined. A sudden reduction from a high to a low energy intake imposed for two weeks from the day of insemination reduced the subsequent embryo survival rate by 30 percentage points to a survival rate of 38%. When energy intake over this same period was either maintained or increased, embryo survival rate remained high (overall mean, 69%), within a range of 65-71%. The time at which embryo loss occurred was established. Embryo survival or pregnancy rates measured on days 14 and 30 after insemination and at full term were 68%, 76% and 72%, respectively. These results provide new information indicating that most embryo loss, at least in heifers, had occurred on or before day 14 after insemination. There was no evidence of any association between the shortterm changes in energy intake either before or after AI and blood progesterone concentration. Neither was there any evidence that the detrimental effect of the sudden reduction in energy intake on embryo survival was mediated through changes in the systemic concentrations of non-esterified fatty acids (NEFAs) or insulin. There was a suggestion, however, that the detrimental effect of the reduced energy intake may operate through a reduction in systemic glucose concentrations.
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Biotechnology in Cattle Reproduction.Over the next decade the Irish agri-food industry will have to compete in a rapidly changing world environment arising from increased competitiveness, decreased world market prices and increased consumer demands for higher quality, healthier and safer food. To become competitive in this environment the scale and efficiency of production at both farm and factory level will have to increase significantly and this must be achieved with due regard for the protection of the environment and the welfare of animals. New technologies will be needed to achieve this. Biotechnology will be central to the development of these new technologies. This project has been concerned with the identification and evaluation of biotechnology developments that have the potential to increase reproductive efficiency in cattle. This includes a range of technologies relating to the in vitro production, manipulation, cryopreservation and transfer of cattle embryos. The potential of other emerging technologies such as embryo and sperm sexing, cloning and biopharming or the production of commercially desirable proteins in cows milk are also addressed in this report.
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Factors Affecting the Cleanliness of Cattle Housed in Buildings wiith Concrete Slatted Floors.From a series of experiments at Grange Research Centre, cattle were cleanest at housing in the autumn, however, within 3 to 4 weeks of housing on concrete slats and fed with a diet of grass silage, cattle were dirtiest, with the majority of the cattle in category 4 or 5. Cattle tended to be cleaner in the late March, early April period as they shed their winter hair coat. Cattle fed concentrates plus straw were significantly cleaner at slaughter compared to similar cattle offered grass silage plus concentrates. Cattle housed indoor on slats during the summer were cleaner than cattle on similar diet and accommodation during the winter. High dry matter silage produced cleaner cattle than did low dry matter silages. Back and tail clipping of cattle at the commencement of the winter finishing period did not have any positive effect on cleanliness score or liveweight gain when the cattle were accommodated in well ventilated slatted floor houses. A survey of 19 farms specialising in finishing cattle failed to show any correlation between stocking density, solid floor area or level of concentrate feeding on the cleanliness of finishing cattle. A survey of 36 finishing units, designated as producers of "clean" or "dirty" cattle at slaughter, found that units with clean cattle had houses which were in general well ventilated, had A-type roofs with an open ridge outlet and in general the grass silage offered was a higher dry matter. In contrast, finishing units with dirty cattle tended to be poorly ventilated and the grass silage offered had a lower dry matter. Overall in the survey cattle cleanliness score was not affected by stocking density (2.0m 2 3.8m 2) or the proportion of solid floor area in the pen. Cattle accommodated on gang slats were dirtier than those accommodated on single slats.
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Electronic Animal Identification.The technology for electronic identification (ID) of bovines is currently available with the advent of passive electronic transponders. At issue is the most appropriate method to attach the electronic ID to the animals. The options include an electronic button tag in the ear, an implantable electronic chip in the ear base or an electronic bolus placed in the rumen/reticular via the oesophageal route. • Aseries of experiments which compared different implantation sites for electronic chips found that the most suitable site for implantation was under the scutellar cartridge of the ear.This site gave very good retention values and was also a secure site, however, it was not possible to palpate the transponder. • The recovery of injectable transponders post slaughter was problematic and as a result due to potential risk of implantable transponder entering the food chain it was not possible to recommend the injectable (implantable route). • Electronic rumen boluses with a specific density less than 2 were rapidly expelled from the rumen, with 100% expulsion by day 56 following placement in the reticulo-rumen. • Rumen boluses with a specific density of 2.75 and greater had an annual non reading rate of less than 1%, however, the loss rate in adult beef cows was greater than in growing and finishing cattle.The reason for this difference was unclear and may be diet related. • Recovery of boluses at slaughter was undertaken in the offal hall and generally the bolus was present in the reticulum and was easily detected by palpating the reticulum. One hundred percent recovery was not achieved in practice, various unforseen events including accidental dislodgment and cutting techniques prevented recovery. • Abolus dispenser with a long connection will facilitate delivery of the bolus directly to the calf’s reticulum. • Electronic failure of transponders in the reticulo-rumen was not a problem and read-failure rate was associated with boluses expelled from the reticulo-rumen. • There was no differences in read-failure rate (or loss rate) between two commercial boluses which were compared in different catgories of cattle. • Electronic button tags from two commercial companies were compared and it was found that any difference between the electronic button ear tags was associated with a defective applicator taggers. • Overall, the animal loss rate for electronic button tags was somewhat higher than that reported for electronic rumen boluses.
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Development of an Intensive Dairy Calf-to-Beef System and Associated Grassland Management.Over the years, beef production systems have been intensified and de-intensified in response to national and European Union policy changes. In the mid 1990s, a millennium target was set to produce 1000kg of beef carcass per ha in a dairy calf-to-beef system. This was in anticipation of possible future decoupling of premia from animals and the evolution of a production environment favourable to intensification. Results from a dairy calf-to-beef system for the years 1994 to 1997 are included in an earlier report (Keane and O’Riordan, 1998). This report presents the results of three production cycles of a two-year-old system (1996- 1998, 1997-1999 and 1998-2000) together with the findings from a comparison of three systems of grazing management. In cycle 1, Standard and Improved management options were compared. The differences between the two were that under Improved management, the yearlings were put to pasture about 3 weeks earlier than normal and they grazed the silage area until Standard turnout time, there were double the number of grazing paddocks in the rotation, and the animals remained at pasture later in autumn. Stocking rate was 2.76 animal units (yearling + calf) per ha. In cycles 2 and 3, stocking rate was 3.0 animal units per ha. Spring-born Charolais x Friesian steers were used in all cycles. Improved management increased liveweight gain of yearlings particularly in the early part of the grazing season but the Standard management animals exhibited compensatory growth subsequently which continued throughout finishing so that by slaughter there were no differences between the two management systems. In cycles 1, 2 and 3, total fertiliser N inputs were 217, 230 and 264 kg/ha, total silage yields conserved were 1.8, 1.6 and 1.7 t dry matter per animal unit, total lifetime concentrate inputs were 1057, 1042 and 1118 kg per animal and total number of days from arrival to slaughter were 736, 738 and 769, respectively. For cycles 1, 2 and 3, mean slaughter weights were 665, 660 and 644 kg, mean carcass weights were 360, 356 and 346 kg, mean carcass conformation scores were 2.77, 2.75 and 2.75 and mean carcass fat scores were 4.16, 4.19 and 4.15, respectively. Slaughter weight and carcass weight outputs per ha were 1833, 1980 and 1932 kg, and 992, 1068 and 1038 kg for cycles 1, 2 and 3, respectively, indicating achievement of the millennium target of 1000 kg/ha carcass output. Three systems of grazing management namely leader/follower, calves and yearlings mixed, and calves and yearlings grazed separately, were compared. Mean liveweight gains for the grazing season as a whole for the treatments as listed were 891, 948 and 1076 (s.e.d. 35.5) g/day for the yearlings, and 744, 702 and 671 (s.e.d 13.5) g/day for the calves. Leader/follower calves were 39 and 51 kg, respectively heavier than the mixed and separate calves at housing as weanlings. The corresponding values at turnout the following spring and at housing as yearlings were 42 and 52 kg, and 22 and 39 kg, respectively. There was no evidence of compensatory growth during the winter but some compensation did occur during the following grazing season. Having calves graze ahead of yearlings in the leader/follower system reduced housing weight of the latter by 18 and 34 kg compared with the mixed and separate treatments, respectively. There was no compensation during the following (finishing) winter at the end of which the corresponding slaughter weight differences were 19 and 36 kg resulting carcass weight differences of 12 and 21 kg. In the current policy environment where the optimum economic stocking rate is well below that which is technically possible and where it is no longer necessary to simultaneously optimise output per animal and output per ha, the challenge is to devise grazing strategies which maximise the performance of both calves and yearlings during the grazing season.