Now showing items 21-40 of 168

    • Genetic and non-genetic factors affecting lamb growth and carcass quality.

      Hanrahan, James P (Teagasc, 1999-05-01)
      The work undertaken under this project concerned the effects of genetic and non-genetic factors on lamb growth, both pre and post-weaning, and carcass traits. The principal objective of the genetic studies was to estimate the performance effects of selecting terminal sires on the basis of the lean meat index (LMI) which is produced for pedigree lambs in flocks that participate in the national Breed Improvement Programme operated by the Department of Agriculture and Food. The merits of the Beltex breed, recently introduced to this country, were also evaluated on comparisons with Texel and Suffolk sires. Estimates of within-breed genetic variation for growth and carcass traits were obtained.
    • Effect of cattle enterprise type on the rate of disclosure of TB reactors and the geographical distribution of the Irish cattle population.

      Fallon, Richard J.; Hammond, R.F. (Teagasc, 1999-05-01)
      The prevalence of tuberculin reactors in the Irish cattle population has remained constant over the past 20 years. During each year some 30,000 reactors have been identified annually. • A study of the national cattle herd, over a 6-year period (1988-1993), was undertaken to determine the association between enterprise type and the prevalence of tuberculin reactors adjusted for herd size and geographical region. • The data were examined on a herd (n=165,000) basis according to the following enterprise types: Dairy - herds with a milk ring test result and no cows eligible for beef cow premia in 1993; Suckler - herds eligible for beef cow premia; Drystock - herds without cows but with other cattle. Other - herds with cows but not categorised as dairy or beef. • Herd size (no. of cattle) was categorised as: Small (<30), Medium (30 to 59), Large (60 to 99) and Very large (>100). Regional categorisation was: West (Donegal, Sligo, Leitrim, Mayo, Roscommon, Galway and Clare), South West (Limerick, Kerry, Cork, Waterford and South Tipperary), East (Louth, Meath, Dublin, Kildare, Wicklow and Wexford) and Midland (Cavan, Monaghan, Longford, Westmeath, Offaly, Laois, Kilkenny, Carlow and North Tipperary). • Enterprise type had no effect on the prevalence of tuberculin reactors for any herd size. The number of tuberculin reactors annually per 1000 animals was greatest in the Midland (7.3) and lowest in the South West (3.8). • It is concluded that the incidence of tuberculin reactors was independent of enterprise type within each of the four regions.
    • An Evaluation of High Genetic Merit Cows Using Forage and Pasture-based Systems.

      Dillon, Pat; Buckley, Frank (Teagasc, 1999-09-01)
      The rate of genetic improvement in Ireland up until the mid-80’s was low (approx. 0.5% per year) compared to North America where genetic merit for milk production was increasing by 1.5% per year (Funk, 1993). Since 1985 the rate of genetic improvement increased markedly to about 1.5% per year in 1992 (Coffey, 1992). This high rate of genetic progress has mostly been achieved through the importation of North American and European genetics. The relative merit of these sires has been obtained from the performance of their progeny in systems of milk production which differ greatly from those operated in Ireland. The term “high genetic index” (HGI) is used to describe a cow, which as a result of selection, is generally predisposed to produce significantly more milk than a cow of lower merit status. Studies from New Zealand have shown that cows of high “genetic index” at pasture, produce more milk (20 to 40%), consume more herbage (5 to 20%), were more efficient convertors of food into milk (10 to 15%) than lower merit cows (Holmes, 1988). However, these “high” genetic index cows would be considered “low” when compared to present-day genetics. Recent results from Langhill (Veerkamp et al., 1994) have shown that increasing genetic index results in major increases in feed efficiency, reflecting increases in milk yield with cows fed indoors on silage/concentrate diets. There is little information available on the performance of present-day HGI dairy cows, on seasonal calving, grass-based systems of milk production
    • Evaluation of mix specification and PFA as a cement replacer in concretes used in silage storage structures.

      Lenehan, J.J.; O'Kiely, Padraig (Teagasc, 1999-09-01)
      At present, concrete for silage storage structures is specified by the Irish Farm Development Service (DAFF, 1992) in terms of a characteristic 28 day crushing strength of 40 N/mm2 and a minimum cement content of 350 kg/m3. In addition, the maximum aggregate size used must not exceed 20 mm and the slump of the unplasticised concrete must not exceed 75 mm. There is no stipulation on the maximum water to cement ratio to be used. This specification represents a high strength concrete for agricultural use and has been upgraded to this level in an attempt to improve the material’s resistance to corrosion by silage effluent. A cement content of 350 kg/m3 is regarded as a relatively high cement content and may promote thermal cracking in the structures (Blackledge, 1990). This would result in a concrete which would be more susceptible to attack by corrosive effluent. A system of carrying out accelerated durability tests on concrete specimens under controlled conditions has been developed by Teagasc and University College Dublin (O’Donnell, C., 1993). Trials carried out by O’Donnell, indicated that cement content had little influence on the durability of concretes exposed to silage effluent for the ranges of mixes examined, but the use of excess water resulted in marked increases in deterioration. The present study aims to further examine the effect of (i) cement content and (ii) the use of PFA as a cement replacer.
    • Alternative Enterprises: Economic Performance and Viability.

      Connolly, Liam (Teagasc, 1999-11-01)
      The economic environment for Irish farming has changed dramatically over the last two decades. The reform of the Common Agricultural Policy with the introduction of quotas on the main farm enterprises in the 1980’s, forced farmers to consider diversifying into new or “alternative” uses for their land, buildings and other resources. The main objectives of this study were to identify the factors affecting the profitability and expansion in the main alternative livestock enterprises and also in rural tourism. Investment costs, returns on investment and market prospects for these new enterprises were investigated. The main livestock enterprises considered were deer, sport horses, dairy goats and free range poultry.
    • Measurement of Grassland Management Practice on Commercial Dairy Farms

      O'Donovan, Michael; Dillon, Pat (Teagasc, 1999-12-01)
      Visual assessment (>4 cm) was found to be the preferred method of pasture mass estimation. Grass budgeting with the use of grass cover measurement, was found to be the most effective aid to good grazing management. Closing farm grass cover in late November/early December should be 350 to 450 kg DM/ha with a range in covers of 200 to 900. Target farm grass covers of 550 to 600 kg DM/ha at turnout at stocking rate of 2.75 cow/ha. Pre-grazing yields at turnout should not be less than 1000 kg DM/ha, giving daily grass allowance of not less than 5 kg DM/cow. The available grass supply in Spring should be budgeted so as to finish the first grazing rotation between the 10th-20th April (grass supply equal grass demand). During the main grazing season (May to August), grazing grass cover should be maintained at 900 to 1000 kg DM/ha or 200 to 240 kg DM/cow. Pre-grazing yield should be maintained at 1800 to 2000 kg DM/ha, with post-grazing residuals at 150 to 200 kg DM/ha (5.5 to 6.5 cm post-grazing height). Stocking rates of greater than 4.5 cow/ha on the grazing area in May/June mostly resulted in inadequate grass supply at some periods over that time. Rotation length can be increased from 21 days in mid/late August to 35 days in late September, allowing grass cover to increase to 1100 to 1300 kg DM/ha. Last rotation should be 25 to 35 days, with first paddocks rested from the 10th to 15th October. Greater use of grass measurements at farm level will allow dairy farmers to obtain a greater proportion of the dairy herd’s feed demand from grazed grass, and higher cow performance.
    • Effect of Transport and Mart Experience on Production, Health, Immune and Physiological Parametres of 2 to 4 Week Old Calves.

      Finnerty, Martina; Prendiville, Daniel J.; Earley, Bernadette; Fallon, Richard J. (Teagasc, 1999-11-01)
      This study examined the effects of transporting dairy calves (less than four weeks of age), on a journey of 170-mile-route to and from a mart in Spring 1996 and 1997, Calf performance, immunological and physiological variables were examined prior to and subsequent to transport. There was no effect of treatment on liveweight or intakes at any time throughout the experiment. Interferon  production was reduced in all treatment groups on days 1, 2 and 5, compared to Day 0 in experiment 1, indicating that even the procedures imposed on the control (C) calves had been sufficient to cause suppression of this component of the immune response. Calves in all treatment groups in Experiment 1, had increased (P<0.05) cortisol concentrations at Day 0.5 (post-transport on Day 0) and experienced physiological changes related to food restriction, e.g., increased (P<0.05) plasma non-esterified fatty acids (NEFA) on Day 0.5. Cortisol levels remained low on days 1, 2 and 5 after the journey and there was no obvious response in the levels of either plasma glucose or haematological parameters indicating that the calves did not show a stress response following transportation and/or mart experience. Transportation of 2 to 4 week old calves had no effect on plasma haptoglobin (acute phase response) levels indicating that the calves did not experience a stress response which would affect cell mediated immunity. The acute phase response is the reaction of the animal to disturbances in its homeostasis caused by infection, tissue injury, stress or immunological disorders. The absence of significant stressful responses in young dairy calves following transportation and mart experience could be interpreted as indicating that transport did not pose significant welfare problems.
    • Calf Health and Immunity.

      Earley, Bernadette; Fallon, Richard J. (Teagasc, 1999-11-01)
      Suckled calves had significantly higher serum IgG 1 concentrations than mart purchased dairy calves. The marked differences in immunoglobulin levels between suckled calves and dairy calves suggest that these calves received either insufficient quality or quantity of colostral immunoglobulins. Factors affecting calf serum Ig concentrations are, Ig concentration in colostrum, colostrum intake, Ig mass, calf age at first feeding, nutrition of the dam, method of ingestion, presence of the dam, age of the dam and the calf. When suckled calves were fed a similar volume of colostrum relative to birth weight (40 ml/kg) and at the same time interval post birth, there was no significant difference across the three suckler herd progeny for IgG1, IgA and IgM and total Ig serum levels at 28 and 56 days of age. However, serum IgG2 levels were significantly lower in the Limousin x beef breed when compared with the Charolais x beef breed suckled calves at 28 days of age. Healthy calves had higher serum immunoglobulins (IgG1) than calves treated for respiratory disease, enteric disease or for both respiratory disease and enteric disease. It is well recognised that immunoglobulins are absorbed from the intestine for only a short period post birth and that efficiency of absorption is dependent on ensuring that the calf receives adequate colostrum in the immediate post-partum period. Low serum IgG1 concentrations are attributable to failures to obtain adequate colostral immunoglobulins in the period immediately following birth. The mean IgA and IgM serum levels of suckled calves in the present study were only slightly higher than dairy calves while IgG1 serum levels were almost approximately twice as high. Feeding colostrum high in Ig results in higher calf serum Ig concentrations at 48h. The low serum Ig levels reported in the present study suggest that dairy calves failed to obtain adequate transfer of colostral immunoglobulins. Calves with a lower immune status are more susceptible to neonatal infection and thus the importance of colostrum in the immediate post partum period cannot be overemphasised. Thus, the identification of calves with low levels of immunity might stimulate calf producers to ensure that calves receive adequate levels of colostral immunoglobulins. The implications of the present findings are that compared with suckled calves, dairy calves are not receiving 1). adequate quantity of colostrum 2). adequate quality of colostrum. 3). Colostrum soon enough post birth 4). or a combination of all of the previous factors. Rearing calves outdoors using calf jackets had no beneficial effect on calf performance. The incidence of respiratory disease was higher in calves reared indoor when compared with calves reared outdoor with and without jackets. There was an increased incidence of diarrhoea in calves reared outdoors irrespective of calf jacket. Lymphocytes from calves with respiratory disease manifest an impaired capability to blast in vitro. Chromium (Cr) supplementation (250 mg/kg dry matter intake) enhanced the blastogenic response in healthy calves, while, calves with respiratory had impaired blastogenic responses. Supplementation with organic Cr (250 mg/kg dry matter intake) for 63 days had no major effect on physiological parameters and had select effects on haematological parameters, namely, the % monocytes. The % monocytes were significantly higher in the standard commercial milk replacer (CMR) (Skim) Cr supplemented calves when compared with the whey based (CMR) + Soya Brand B or whey based CMR + Soya Brand C or whey based enzyme processed soya Brand C + Cr treatment groups.
    • Optimising sward structure and herbage yield for the performance of dairy cows at pasture.

      Casey, Imelda A.; Brereton, A. J. (Teagasc, 1999-12-01)
      The basic unit of intake is the bite. The total daily intake of grazed grass is determined by the number of bites taken and the weight of the average bite. In this project the focus was on sward structure (architecture) and its effects on bite volume and weight. There were two objectives. The first was to determine the plant growth mechanism responsible for variations in sward structure. The investigation was carried out at The Queen’s University in Belfast and involved microscopic study of leaves from plants grown under controlled conditions. The second objective, to determine how bite volume and mass was affected by differences in sward structure was a field study using fistulated cows and was done at Moorepark.
    • Increasing intake by the development of optimal grazing management in relation to animal behaviour at pasture.

      Linnane, M.; Brereton, A. J.; Giller, P.S. (Teagasc, 1999-12-01)
      In each month from July to December, grazing activity for each of 12 animals was recorded over a number of days continuously using vibrarecorders. The work was done at Killarney National Park and the animals were heifers of the Kerry breed living under semi-natural conditions with abundant pasture available. In July (16 hour day-length) - all animals began grazing at dawn and grazed for about 2.5 hours. This first bout was followed at intervals of about 2 hours by shorter bouts each about one hour in duration. In late afternoon another bout commenced which continued for 4 to 5 hours through until after dusk. During darkness, about midnight, there was a short bout of grazing. All of the animals behaved thus and the pattern was repeated each day. Total grazing time was near 11 hours each day. By October day-length had decreased. There was still a bout at dawn and a bout at sunset. As in July there were three smaller bouts but all occurred during darkness. The total grazing time was close to 11 hours as before. The pattern of grazing was consistent between animals and days. In August-September-October and November there were always two major bouts of grazing related to dawn and dusk. Grazing total time was always near 11 hours. As day-length decreased the smaller daylight bouts were progressively replaced by bouts during darkness. Similar patterns were also found in studies of grazing Holstein/Friesian heifers and of housed non-lactating cows at Moorepark. The primary feature of the grazing pattern is the bout. The bout implies that there is a control that determines when grazing commences and ends. Rumen capacity plays a part but does not explain why minor bouts are only one hour and major bouts are more than 4 hours. The rigid association of the two major bouts with dawn and dusk implies that light also plays a part. That the total grazing time is constant suggests that yet another control is operating that is related to the state of the animal relative to a target state. And this control relates to a 24-hour period. Domestic bovines do not display any patterns of behaviour related to seasonal or lunar cycles. The patterns appear to be circadian and in that case it would not be surprising to find that the suggested light cue was present as a means of measuring the day.
    • Iodine Supplementation of Cattle.

      Rogers, Philip (Teagasc, 1999-12-01)
      Plasma total iodine (I) and thyroxine are of no practical value to assess I status of cattle. When interpreted carefully, plasma inorganic iodine (PII), is a sensitive index of current dietary I status. PII can confirm suspicions of deficiency or excess of dietary I. Between 1988 and 1999, 32- 62% of commercial herds had low or very low I status and the I status of the national herd has fallen since 1995. 2. I deficiency is the most important trace-element deficiency in Irish cattle and sheep. Our ruminants, especially those at pasture, and at critical times of their annual physiological cycle, need routine I supplementation. The most critical times for cows are from 1 month prepartum to 4 months postpartum, except in herds with unexplained abortions, when supplementation throughout pregnancy may be needed. Also, calves, lambs and growing stock may need regular I supplements if unknown factors compromise their performance or immune status. 3 Even in the absence of goitrogens, Irish forages supply <33% of the minimum I needed by cattle and 97% of our forages are deficient in I. 4. Irish mineral mixes supplied circa 32-44 mg I/cow/d in 1989. In the past few years they supply close to 60 mg I/cow/d. Increased use of iodised minerals would greatly improve the I status of the national herd. 5. Oral supplements of 30-60 mg I/cow/d via feed or drinking water maintained normal PII levels. Weekly skin application of 9 ml of 5% tincture of I to the flank-fold pocket was also effective, as was Ionox, a new slow-release bolus. A mean oral supplement (mg I/100 kg LW) of 11.8 is suggested for dairy cows, 4.7 for beef calves, heifers and cows and 6.4 for steers. These are higher inputs than are recommended or used in some countries. However, they are <45% of the inputs defined as safe by EU Feed Legislation, which allows a total intake of 11 mg I/kg feed DM, or 165 mg I/cow/d at an assumed DMI of 15 kg/cow/d. 6. Though Lipiodol injection increased PII for 42-90d, it is not registered on the therapeutic veterinary product list and oral I supplements can maintain normal PII levels for a fraction of its price. Because other methods are effective, faster acting and cheaper, and there is little evidence to support its use as an effective preventative of stillbirth in I deficient herds, Lipiodol is not recommended as an I-supplement for cows. 7. Milk I levels give no cause for concern as regards the risk of human thyrotoxicosis. However, there is a case for monitoring larger numbers of bulk-tank samples and, especially, samples of milk at retail outlets, on grounds of herd health and human health.
    • Breed compostition of the Irish cattle herd.

      Drennan, Michael J (Teagasc, 1999-12-01)
      Information was collected on cow and sire breeds in both dairy and suckler herds in the National Farm Survey (NFS) in autumn 1998. The number of farms included in the analysis was 1030 with farms containing less than 2 economic size units (equivalent to 3 to 4 dairy cows) excluded from the sample. The main findings of the survey were as follows: • Ninety-eight percent of dairy cows and 96% of dairy herd replacements were Friesian/Holstein • The suckler cow herd contained 46% early-maturing breed crosses (Hereford 31%, Aberdeen Angus 12% and Shorthorn 3%) 2% Friesians, 48% of the three main continental breed crosses (Charolais 17%, Simmental 16%, Limousin 15%) and 4% other (mainly continental crosses). Compared to the adult cows herd replacements had less early-maturing breed crosses and Friesians (total 42%) and more (55%) of the three main continental breed crosses (Charolais 20%, Simmental 15%, Limousin 20%). • Overall, in 1998, it was estimated that the national cow herd consisted of 52% Friesian/Holstein, 23% early maturing breed crosses and 26% late maturing breed crosses. • Forty-seven percent of dairy cows were bred to Friesian/Holstein sires, 26% were bred to early maturing sire breeds and 27% were bred to continental sire breeds. The corresponding figure for dairy herd replacements were 40%, 46% and 13%. • Seventeen percent of suckler cows were bred to early maturing sire breeds, 46% were bred to Charolais, 16% were bred to Simmental, 17% were bred to Limousin and the remaining 6% were bred to mainly other continental breed sires. The sires used on suckler herd replacements were 43% early maturing breeds, 16% Charolais, 10% Simmental, 25% Limousin and 5% other. • Based on the sire breeds used in 1998, the breed composition of the 1999 calf crop was estimated to be 24% Friesian/Holstein, 24% early maturing breeds, 24% Charolais cross, 10% Simmental cross, 12% Limousin cross and 6% other (mainly other continental crosses). • Although the proportion of continental breed crosses in the calf crop continues to increase (48% in 1993 to 52% in 1999), the use of continental sire breeds is declining in the dairy herd (from 33% in 1992 to 27% in 1998), particularly where AI is the method of breeding. However, this trend may be at an end as the 1999 AI figures to date (September 30) show substantial decreases in Hereford and Aberdeen Angus inseminations with increases in Belgian Blue, Limousin and Friesian/Holstein. • The dairy herd is a relatively unimportant source of the better quality animals accounting for only 25% of total continental breed crosses which have a lower proportion of continental breed genes than those from the suckler herd. • It was estimated that the 1999 calf crop from the suckler herd consisted of 18% early maturing breeds, 29% of half to threequarters continental breed genes and 53% containing at least three-quarters continental breed genes. • A total of 48,200 herds used bulls. The proportion of bulls of each breed used were 9% Frieisan/Holstein, 17% Hereford, 11% Aberdeen Angus, 1% Shorthorn, 29% Charolais, 12% Simmental, 16% Limousin and 5% other. Continental breeds accounted for 38% and 84% of bulls on dairy and suckler farm, respectively. • In the present study the number of animals (cows plus replacements) bred to continental sire breeds was 1.22 million of which 40% were by AI. • National AI figures show that the total number of inseminations (excluding DIY) have declined from 1.03 million in 1992 to 0.79 million in 1998. • Assuming that the suckler cow should be at least half continental breeding and that Belgian Blue crosses are unsuitable if increases in calving problems are to be avoided then the dair y herd may provide as little as 25% of suitable suckler herd replacements. Thus, the main source of replacements would be from within the suckler herd. Factors to be considered include hybrid vigour which involves crossbreeding, milk production potential of the cow and the fact that the most widely used terminal sire is Charolais. In these circumstances one suitable crossbred cow would be obtained from alternate crossing with Limousin and Simmental sires. • Heat synchronisation was used on 3% of herds. The figures for dairy and suckler herds was 6.8% and 0.5%, respectively. • Vaccination for leptospirosis was used on 29% of dairy farms and 4% of suckler farms.
    • A preliminary study of Dystocia in Belgain Blue x Friesian heifers and other cross breeds.

      Drennan, Michael J (Teagasc, 1999-12-01)
      Calving data were collected on 17 Belgian Blue x Friesian (BBF), 10 Limousin x Friesian (LF), 8 Simmental x Limousin x Friesians (SLF) and 4 Charolais (C) heifers. The animals were bred by artificial insemination (AI) to one Limousin bull to calve at 2 years of age. The BBF and LF were bucket reared while the SLF and C were single-suckled to 7-8 months of age. Subsequently, all animals were treated similarly. Because of the small number of C involved, information on these was excluded in breed comparisons but was included for correlations between various traits. The main findings were: • The mean liveweights at calving were 524, 521 and 583 kg for BBF, LF and SLF animals, respectively. • Measurements taken during late pregnancy showed that SLF had significantly greater wither height, pelvic height, pelvic width, cannon bone length and hind-quarter roundness than the BBF and LF which were the same. These differences tended to reflect the liveweight differences recorded. • Chest width of both the SLF and BBF was greater than for LF indicating, that despite having similar liveweights, the BBF had a wider chest than the LF. • Gestation length was longer for the SLF (294 days) than for the other two breed types (290 days). • There was no significant effect of heifer breed type on calf birth weight but when expressed as a proportion of dam liveweight, birth weights of the BBF were greater than SLF with no significant difference between the LF and the other two breed types. • Calving difficulty score was significantly higher for BBF than for SLF with LF intermediate. The incidence of caesareans was 29%, 10% and 0% for the BBF, LF and SLF, respectively. Cow internal pelvic height was greater for the SLF than for the other two breed types but there was no effect of breed type on pelvic width. Pelvic areas were 272 cm2 for BBF, 279 cm2 for LF and 285 cm2 for SLF. Those were not significantly different. • There was no significant relationship between cow liveweight or external skeletal measurements and calf birth weight. • Calf birth weight was positively related to cow internal pelvic width and pelvic area. • There was a close relationship between the birth weight of calves and calf chest girth, hind-quarter roundness and calf head circumference. • Calving difficulty score increased with increasing birth weight and particularly as birth weights expressed as a proportion of cow weight increased. • Increased hind-quarter roundness and increased chest girth of the calf were associated with increased calving difficulties. • Calving difficulty score decreased as cow size increased. All correlations between calving difficulty score and external skeletal measurements were negative but only those with withers height and pelvic height were significant.
    • Nutrition and Oestrus and Ovarian Cycles in Cattle

      Diskin, Michael G.; Stagg, K.; Mackey, D.R.; Roche, J.F.; Sreenan, J.M. (Teagasc, 1999-12-01)
      The overall objective of this project was to establish the effects of both long- and short-term changes in nutrition on ovarian follicle dynamics and on the systemic concentrations of metabolic and reproductive hormones. In order to avoid the confounding effects of lactation, suckling and maternal–calf bonding, beef heifers were used in a series of three studies.
    • Quality Meat Production from Beef Cattle During Winter Finishing.

      Moloney, Aidan P (Teagasc, 2000-12-01)
      A series of experiments were carried out to examine the performance of the UK metabolisable energy (ME)/metabolisable protein (MP) system in an Irish context, and to determine the response in lean tissue growth to changes in the form of nutrients available for absorption from the intestine. In Experiment 1, the response of finishing continental heifers to an increase in MP supply was examined. It was demonstrated that this type of animal responded positively to an increase in MP supply in excess of requirements as presently estimated by the UK ME/MP system. Such an anomaly requires clarification. In Experiment 2, growth, digestibility and nitrogen retention in finishing continental steers offered ad libitum, concentrates based on barley and soyabean or on a mixture of industrial by-products were examined. The observed higher nitrogen retention in animals offered the by-product based ration suggested that there is opportunity to increase carcass protein content by judicious choice of feed ingredients. This suggestion was explored in Experiment 3. In Experiment 3, nitrogen retention and carcass composition were measured in sheep offered rations which resulted in different patterns of volatile fatty acid supply from the rumen. Nitrogen retention and the growth of carcass lean tissue were increased by the inclusion of sodium propionate in a starch-based ration but not in a fibre-based ration. The apparently contradictory effects of an increase in propionate supply by dietary means (starch vs fibrebased rations) or by addition of a salt of propionic acid suggests that the pattern, as well as the total supply of propionate is physiologically important in the growing ruminant. The endocrine mechanism of changes in carcass composition was also explored in this experiment. Differences in plasma concentrations of hormones which play a major role in the partition of absorbed nutrients towards muscle or adipose tissue suggests a role for the endocrine system in the regulation of growth, independent of energy intake. In Experiment 4, the effect of starch form and concentration (a dietary means of increasing propionate supply) in high concentrate rations on growth, efficiency and estimated lean content was examined in Friesian bulls. Supporting mechanistic measurements were made in Friesian steers fed the corresponding experimental rations. For optimum growth, ground starch should not exceed 210 g/kg of the ration. When included at approximately 300 g/kg, ground rather than rolled starch had a negative impact on growth. Coarse rations containing 300g or 480g starch/kg resulted in similar growth and efficiency. An increase in ground but not rolled starch concentration decreased the insulin response to a glucose challenge.
    • Extending the season for prime lamb production from grass

      Grennan, Eamonn J. (Teagasc, 2001-01-01)
      In recent years there has been some interest shown by exporters in acquiring younger lambs than those remaining from the normal springlambing flocks involved in mid-season or store lamb production systems, to supply niche markets in the November to February period. Lambing ewes later in the year, i.e. April to June, offers an opportunity to supply such niche markets with younger lamb. Two farmlet systems were each operated over two years with 59 to 69 ewes on 4.5 ha of pasture in an all-grass production system. The objectives were: to assess the overall performance of flocks in late-lambing systems, to monitor lamb growth rates and drafting pattern, to monitor carcass quality in terms of weight, conformation and fatscore, and to identify any difficulties that may be associated with late lambing systems.
    • Effect of Genetic Merit for Milk Production, Dairy Cow Breed and Pre-Calving Feeding on Reproductive Physiology and Performance.

      Mee, John F; Snijders, Sylvia M. E.; Dillon, Pat (Teagasc, 2000-10-01)
      The overall objective of this project was to determine, following four experiments, the effects of genetic merit for milk production, dairy cow breed and prepartum feeding on reproductive physiology and performance. In the present experiments, the high proportion of Holstein- Friesian genes played a more important role in reducing reproductive performance than milk production. Significant breed differences in reproductive performance were detected.
    • Evaluation of Milking Systems in Terms of Mastitis Risk, Teat Tissue Reactions & Milking Performance.

      O'Callaghan, Edmond J; Gleeson, David E (Teagasc, 2000-11-01)
      Measurements of milking vacuum recorded on a flow simulator can provide guidelines for optimum design of milking units. • Increasing the bore of the short milk tube above the recommended diameter or claw volume above 150ml does not improve milking efficiency. • Increasing the long milk-tube bore from 13.5mm to 16mm increased the level of milking vacuum. • The milking vacuum was highest with wide-bore tapered liners and simultaneous pulsation. • The minimum vacuum was increased with narrow-bore liners and alternate pulsation. • The milk yield with wide-bore tapered liners in heavy 3-kg clusters and using simultaneous pulsation was 5% higher than with light clusters (1.65 kg) with alternate pulsation. • The milk yield depressions obtained with light clusters were similar in short and long term experiments and increased with the magnitude of the milk yield per milking. • The teat condition scores were not affected by the magnitude of vacuum fluctuations.
    • Population and Virulence Factor Analysis of Staphylococcus aureus from Bovine Mastitis.

      Fitzgerald, J.R.; Meaney, William J; Hartigan, Patrick J.; Smyth, Cyril James (2000-11-01)
      Staphylococcus aureus is a major cause of bovine mastitis and the disease is responsible for substantial economic losses in the dairy industry world-wide. A large number of commonly accepted virulence factors are associated with S. aureus but it is yet to be elucidated which of these are important for infection of the bovine udder. A rational and effective strategy for the control of intramammary infections may need to be directed against clones of S. aureus that commonly cause disease. The objective of this study was to characterise the genetic variance of S. aureus isolate populations from infected udders in Ireland using RAPD-PCR, ribotyping and multilocus enzyme electrophoresis (MLEE). Similar S. aureus isolates collected in the USA were also typed in order to compare strain differences in staphylococcal populations in a different environment. Phenotypic diversity based on a number of presumed virulence factors together with antibiotic sensitivity was examined and correlations between phenotype and genotype were identified, if present. In addition, a pathogenicity island encoding multiple superantigens was completely sequenced and characterised. Knockout mutants of these superantigens were also constructed and in vitro functional analysis performed. Laboratory animal experiments (mice and rabbits) were used to study the relative pathogenicity of individual staphylococcal strains (mice) and also to measure the immunological responses after prolonged exposure to the predominant strains (rabbits).
    • AI For Sheep Using Frozen-thawed Semen.

      Donovan, A.; Hanrahan, James P; Lally, T.; Boland, Maurice; Byrne, G.P.; Duffy, P.; Lonergan, P.; O'Neill, D.J. (Teagasc, 2001-01-01)
      International experience has been that cervical insemination of sheep with frozen-thawed semen usually yields unacceptably low pregnancy rates (10 to 30%). An exceptional case has been Norway where non-return rates in on-farm usage are around 60%. The objective of the work described in this report was to develop an AI procedure for Irish conditions, based initially on Norwegian protocols, using semen from individual rams. Such a procedure would greatly facilitate and enhance genetic improvement programmes for sheep. The work undertaken had two separate aspects:- (i) studies on semen, including processing and freezing methods, laboratory evaluation of semen quality post thawing and the relationship of in vitro evaluation to fertilisation rate in vivo (ii) studies on pregnancy rate following AI in relation to issues such as ram breed effects, effects of synchronisation, operator differences and the role of ewe breed inducing the timing of ovulation and various physical and physiological assessments of the cervix at AI. The main results in relation to semen studies were that, while a range of differential staining procedures could be used to objectively evaluate semen with respect to proportion of live speramatozoa and the integrity of sperm cells after thawing, these results were not useful as indicators of fertilisation capacity in vivo. The in vitro fertilisation (IVF) of sheep oocytes recovered from abattoir material gave promising results as a method for evaluating the fertilisation capacity of frozen-thawed semen. The technique requires further validation.