• Cow serum and colostrum immunoglobulin (IgG1) concentration of five suckler cow breed types and subsequent immune status of their calves

      Murphy, B.M.; Drennan, Michael J; O'Mara, Frank P.; Earley, Bernadette; Teagasc Walsh Fellowship Programme (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      The objective of this study was to determine the effect of cow breed type on (a) cow serum and colostrum immunoglobulin (IgG1) concentrations and (b) subsequent calf serum IgG1 concentration and zinc sulphate turbidity (ZST) units. Five cow breed types were examined: LF (Limousin × Friesian), LLF (Limousin × (Limousin × Friesian)), L (Limousin), C (Charolais) and SLF (Simmental × (Limousin × Friesian)). Three blood samples were taken by jugular venipuncture from the cows at approximately 90, 60 and 30 days pre partum, at parturition and at 15 days or more post partum and from the calves at 48 (40 to 56) h post partum. Prior to suckling a 20 ml sample of colostrum was obtained. Milk yield was estimated using the weigh-suckleweigh technique. The decrease in serum IgG1 concentration in cows between 90 days pre partum and parturition was greater (P < 0.01) for LF cows than all other breed types, except SLF. There was no difference between LLF, L, C and SLF cows. There was no effect of cow breed type on colostrum IgG1 concentration. Milk yield was higher (P < 0.001) for LF cows than all other breed types, while that of SLF was higher than the three remaining breed types, which were similar. Calf serum IgG1 concentration and ZST units were higher (P < 0.01) for the progeny of LF cows than all others except SLF. There was no difference between the progeny of LLF, L, C and SLF cows. Calf serum IgG1 was affected by cow breed type and showed a positive relationship with cow serum IgG1 decreases in late pregnancy.
    • Analysis of DRB1 exon 2 genotyping by STR size analysis in Suffolk and Texel sheep breeds

      Sayers, Gearoid; Mitchel, S; Ryan, Marion T; Stear, Michael J.; Hanrahan, James P; Sweeney, Torres; Department of Agriculture, Food and the Marine; Wellcome Trust; RSF16; 061354 (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      Alleles of the DRB1 exon 2 locus of the major histocompatibility complex have recently been associated with genetic resistance to gastrointestinal nematodes in sheep. While sequence-based typing is the standard method for allele discrimination, a rapid, high throughput method for DRB1 exon 2 genotyping is required if such information is to be incorporated into national breeding programmes. Previous studies have highlighted a simple tandem repeat (STR) located within intron 2 of the DRB1 gene, which could potentially be used to accurately assess the allele present within the adjacent exon 2. The aims of this study were firstly to compare two methods of STR analysis, Genescan™ and autoradiography, and secondly to investigate if STR analysis of DRB1 intron 2 could be used to accurately assess the profile of DRB1 exon 2. Six DRB1 exon 2 alleles were identified by sequence-based typing in Suffolk (n = 31) and eight in Texel (n = 60) sheep. The results indicated that Genescan™ was a more accurate method of STR analysis than autoradiography. The expected 1:1 correspondence between STR size, analysed by Genescan™ and DRB1 exon 2 allele, determined by sequence-based typing, was not observed. However, the correspondence was found to be degenerate, whereby some alleles were associated with two STR sizes. Thus, irrespective of the STR size identified, STR analysis by Genescan™ identified the correct allele in all cases within both populations of animals studied. However, the Genescan™ method of allele identification cannot be used for Suffolk × Texel crossbred progeny or in other breeds where the relationship between STR size and DRB1 exon 2 allele is not known.
    • Genetic relationships among linear type traits, milk yield, body weight, fertility and somatic cell count in primiparous dairy cows

      Berry, Donagh P.; Buckley, Frank; Dillon, Pat; Evans, R. D.; Veerkamp, Roel F.; Allied Irish Bank; AI Managers Association; Holstein-Friesian Society of Great Britain and Ireland (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)
      Phenotypic and genetic (co)variances among type traits, milk yield, body weight, fertility and somatic cell count were estimated. The data analysed included 3,058 primiparous spring-calving Holstein-Friesian cows from 80 farms throughout the south of Ireland. Heritability estimates for the type traits varied from 0.11 to 0.43. Genetic correlations among some type traits were very strong and may indicate the possibility of reducing the number of traits assessed on each animal; the genetic correlation between angularity and body condition score was –0.84. Genetic correlations between all type traits (except body condition score, udder depth and teat length) and milk yield were positive and ranged from 0.08 to 0.69. The possibility of selecting for body weight may be achievable within a national progeny-testing programme using type traits within a selection index. Moderate to strong genetic correlations existed between some type traits and the various fertility measures and somatic cell count indicating the opportunity of indirect selection for improved fertility and health of animals using type traits within a selection index; however, the standard errors of some of the genetic correlations were large and should thus be treated with caution. Genetically taller, wider, deeper, more angular cows with tighter, stronger, shallower udders were predisposed to have inferior pregnancy rates to first service and require more services.
    • Temporal trends in reproductive performance in Irish dairy herds and associated risk factors

      Mee, John F (Biomed Central, 2004-03-01)
      Irish dairy herd fertility has been declining since the 1980s. The extent, nature and causes of this decline in fertility and the current status of Irish dairy herd fertility were described. An increase in calving interval of approximately one day per year has been recorded. The principal components of this trend have been an increased incidence of postpartum endocrinopathies, reduced expression of oestrus and a fall in conception rate. Both submission rate and calving-to-service interval have increased slightly over time. Significant risk factors associated with these trends have been strain substitution within the Holstein-Friesian breed and single trait selection for milk production. Critically, these changes have been reflected in loss of body condition. Contributory factors included increased herd size and possibly increased use of DIYAI. The most recent Irish study showed that 48% of cows conceived to first service and 14% of cows were not pregnant at the end of the industry-average 15-week spring breeding season. However, the top quartile of herds achieved a first-service conception rate of 59%, illustrating the wide variation between herds. These phenotypic trends were attributed to both genetic and environmental factors and their interactions. Recent Irish dairy herd fertility performance falls short of the targets set for seasonal compact calving.
    • Prevalence of antibodies to Leptospira interrogans serovar hardjo in bulk tank milk from unvaccinated irish dairy herds

      Leonard, Nola; Mee, John F; Snijders, Sylvia M. E.; Mackie, Dermot (Biomed Central, 2004-04-01)
      Bulk tank milk samples, collected from 347 herds throughout the Republic of Ireland using a sampling frame based on seven milk-recording organisations, were tested by ELISA for antibodies to Leptospira interrogans serovar hardjo. These herds, which had not been vaccinated against leptospirosis within the previous five years, were categorised according to their province, milk-recording organisation and size. Two-hundred-and-seventy-three herds (79%) had a positive ELISA titre. Both the probability of a herd being seropositive and the antibody level in the herd milk sample were affected by the province (P < 0.05 and P < 0.01, respectively) and the herd size category (P < 0.05 and P < 0.01, respectively). Larger herds were significantly more likely to have positive reactions and higher mean concentrations of antibody. It was concluded that a high proportion of unvaccinated Irish dairy herds have been exposed to infection with Leptospira hardjo.
    • Insulin increases 17β-estradiol production by the dominant follicle of the first postpartum follicle wave in dairy cows

      Butler, Stephen T.; Pelton, Susanne H.; Butler, W.R.; US Department of Agriculture; Teagasc Walsh Fellowship Programme; NE-161 (Bioscientifica on behalf of Society for Reproduction and Fertility, 2004-05-01)
      Prolonged anovulation following parturition has a negative impact on fertility in dairy cows. Insulin plays an important role in ovarian function in many species, and is profoundly depressed in dairy cows during early lactation. We hypothesized that hypoinsulinemia during early lactation represents a key indicator of nutritional status, resulting in delayed ovulation. Holstein cows (n = 10) were subjected to either a hyperinsulinemic–euglycemic clamp (INS) or saline infusion (CTL) for 96 h, beginning on day 10 after parturition during the first postpartum follicular wave. Insulin was infused continuously (0.3 μg/kg body weight per h) via a jugular catheter, and euglycemia was maintained by infusion of glucose. Circulating insulin concentrations were elevated 2.6-fold in INS cows compared with CTL cows (0.73 ± 0.026 vs 0.28 ± 0.026 ng/ml; P < 0.001). Insulin treatment did not affect (P > 0.05) luteinizing hormone (LH) pulse frequency, pulse amplitude or mean circulating LH. Circulating estradiol was elevated in INS cows (P < 0.01) and circulating testosterone also tended to be higher. The ratio of testosterone to estradiol was not different between treatments for the initial 30 h of infusion, but was significantly reduced thereafter in response to insulin (P < 0.01), suggesting that hyperinsulinemia increased follicular aromatase activity. Insulin treatment also resulted in reduced circulating nonesterified fatty acids, and increased circulating total and free insulin-like growth factor-I concentrations. Insulin infusion increased estradiol secretion by the dominant follicle of the first postpartum follicular wave in dairy cows, and this effect appears not to be mediated through changes in pulsatile LH release.
    • Cow factors affecting the risk of clinical mastitis

      Berry, Donagh P.; Meaney, William J (Teagasc (Agriculture and Food Development Authority), Ireland, 2005)
      The objective of the present study was to identify cow risk factors associated with development of clinical mastitis (CM) in subsequent stages of lactation. A total of 3,309 lactations from spring-calving Holstein-Friesian cows were included in the analysis; parity number ranged from one to three, inclusive. A generalised estimating equations approach with a logit link function was used to account for the binary nature of the data and the unequal number of repeated records per cow. The dependent variable was the probability of developing CM in the subsequent stage of lactation. Independent variables included in the model were chosen using stepwise selection; herd, year of birth, month of calving, parity, period of lactation and previous CM history significantly affected the probability of CM. Two-way interactions between parity and period of lactation and between parity and incidence of CM in the previous lactation were also included in the model. A greater probability of developing CM is expected in cows that experienced CM in the previous lactation and/or previously within the same lactation. The probability of CM occurring in cows that experienced at least one case of CM in the previous lactation was 0.92 to 3.75 times that of a cow that experienced no CM in the previous lactation. It is possible to predict the probability of an animal developing CM in the subsequent stage of lactation when information is available on the parity and month of calving of the animal and its previous history of CM.
    • Production and carcass traits of high dairy genetic merit Holstein, standard dairy genetic merit Friesian and Charolais × Holstein-Friesian male cattle

      McGee, Mark; Keane, Michael G.; Neilan, R.; Moloney, Aidan P; Caffrey, Patrick J. (Teagasc (Agriculture and Food Development Authority), Ireland, 2005)
      The increased proportion of Holstein genetic material in the dairy herd has consequences for beef production in Ireland. A total of 72 spring-born male calves (24 Holsteins (HO), 24 Friesian (FR) and 24 Charolais × Holstein-Friesians (CH)) were reared from calfhood to slaughter. Calves were artificially reared indoors and spent their first summer at pasture following which they were assigned, on a breed basis, to a factorial combination of two production systems (intensive 19-month bull beef and extensive 25-month steer beef) and two slaughter weights (560 and 650 kg). After slaughter the pistola hind quarter was separated into fat, bone and muscle. Live-weight gain, carcass gain, kill-out proportion, carcass conformation and carcass fat scores were 830, 811 and 859 (s.e. 14.9) g/day, 540, 533, 585 (s.e. 7.7) g/day, 526, 538 and 561 (s.e. 3.0) g/kg, 1.51, 2.18 and 2.96 (s.e. 0.085), and 3.40, 4.25 and 4.06 (s.e. 0.104) for HO, FR and CH, respectively. Corresponding values for pistola weight as a proportion of carcass weight, pistola muscle proportion and pistola fat proportion were 458, 459 and 461 (s.e. 2.6) g/kg, 657, 645 and 667 (s.e. 3.7) g/kg, and 132, 161 and 145 (s.e. 4.1) g/kg. Compared with the intensive system, animals on the extensive system had a lower (P < 0.001) daily live-weight gain, kill-out proportion and a lower muscle proportion in the pistola. Increasing slaughter weight increased (P < 0.001) carcass weight and carcass fat score and reduced the proportion of muscle in the pistola. Allometric regression coefficients for pistola weight on side weight, and total bone, muscle and fat weights on pistola weight were 0.898, 0.755, 0.900 and 1.910 respectively. It is concluded that HO grew at least as fast as FR but had a lower killout proportion. Carcass conformation and fat scores were greater for FR than for HO and muscle proportion in the pistola was lower and total fat proportion was higher. Compared with FR, CH had heavier carcasses, a higher kill-out proportion and less fat and more muscle in the pistola.
    • Post-weaning performance and carcass characteristics of steer progeny from different suckler cow breed types

      Drennan, Michael J; McGee, Mark; Keane, Michael G. (Teagasc (Agriculture and Food Development Authority), Ireland, 2005)
      In two experiments a total of 44 steer progeny of spring-calving Charolais (C) and Hereford × Friesian (HF) suckler cows and C sires were slaughtered at approximately 2 years of age. Following weaning they were offered silage and 1 kg of concentrate per head daily during a 5 month winter after which they spent 7 months at pasture. In Experiment 1, animals were given a silage/concentrate diet during a finishing period of either 95 or 152 days. In Experiment 2, steers were offered either a daily diet of silage plus 6 kg of concentrates or concentrates to appetite plus 5 kg of silage(fresh weight)during the final 140-day finishing period. Following slaughter, an 8-rib pistola from each animal was dissected. For the two experiments combined C and HF progeny had carcass weights of 372 and 385 (s.e. 6.1) kg, proportions of carcass as pistola of 467 and 454 (s.e. 2.8) g/kg and pistola meat proportions of 676 and 642 (s.e. 5.1) g/kg, respectively. All fat traits were lower for the C than HF progeny but there was no difference in carcass conformation score. Increasing slaughter weight increased carcass weight (P < 0.001), kidney plus channel fat weight (P < 0.001), and pistola fat proportion(P < 0.001) and decreased the proportions of carcass as pistola (P < 0.05), pistola meat (P < 0.01), and bone (P < 0.05). In conclusion, breed type had no effect on carcass growth but the C progeny had higher meat yield than the HF. Increasing slaughter weight increased fatness and reduced meat yield.
    • Effects of supplementary concentrate level with grass silage, and separate or total mixed ration feeding, on performance and carcass traits of finishing steers

      Caplis, J.; Keane, Michael G.; Moloney, Aidan P; O'Mara, Frank P.; National Development Plan 2000–2006 (Teagasc (Agriculture and Food Development Authority), Ireland, 2005)
      Concentrates are a major component of feed costs in winter finishing of beef cattle. The objectives of this study were (1) to determine the response to increasing levels of supplementary concentrates with grass silage, and (2) to determine the effects of feeding silage and concentrates separately or as a total mixed ration (TMR). A total of 117 finishing steers (mean initial live weight 538 (s.d. 35.5) kg) were assigned to a pre-experimental slaughter group of 9 animals and to 6 feeding treatments of 18 animals each. The feeding treatments were (1) silage only offered ad libitum (SO), (2) SO plus a low level of concentrates offered separately (LS), (3) SO plus a low level of concentrates offered as a TMR (LM), (4) SO plus a medium level of concentrates offered separately (MS), (5) SO plus a medium level of concentrates offered as a TMR (MM), and (6) concentrates ad libitum plus a restricted silage allowance (AL). Low and medium concentrate target levels were 3 and 6 kg dry matter (DM) per head daily. When silage (210g/kg DM, 758 g/kg in vitro DM digestibility, pH 3.7) and concentrates were fed separately, the daily concentrate allowance was given in one morning feed. The animals were individually fed for a mean period of 132 days. After slaughter, carcasses were weighed and graded and a rib (6th to 10th) joint was dissected into its component tissues. Silage DM intake decreased (P < 0.001) but total DM intake increased (P < 0.001) with increasing concentrate level. Average live-weight gains for SO, LS, LM, MS, MM and AL was 0.34, 0.86, 0.86, 1.02, 1.00 and 1.12 (s.e. 0.064) kg/day, respectively. Corresponding carcass weight gains were 0.25, 0.58, 0.58, 0.71, 0.68 and 0.82 (s.e. 0.028)kg/day. All measures of fatness increased (P < 0.05), bone proportion of the rib joint decreased (P < 0.001), and muscle proportion was not significantly affected by dietary concentrate level. There were no significant interactions between concentrate level and method of feeding. Compared with offering the feeds separately, feeding as a TMR increased silage DM intake by proportionately 0.06 (P < 0.05) and total DM intake by proportionately 0.04 (P < 0.05). Method of feeding had no significant effect on performance, slaughter or carcass traits. It is concluded that silage intake decreased and total intake increased with increasing concentrate level. Live-weight and carcass-weight gains also increased with increasing concentrate level. Feeding a TMR had no effect on animal performance or carcass traits compared with separate feeding.
    • Comparison of sugar-beet pulp and barley with and without soya bean meal as supplements to silage for growing steers

      Keane, Michael G.; National Development Plan 2000–2006 (Teagasc (Agriculture and Food Development Authority), Ireland, 2005)
      The optimum live-weight gain for growing steers in winter depends on the cost of feed and subsequent compensatory growth. The objectives of this experiment were: (1) to determine the response in growing steers to increasing levels of molassed sugar-beet pulp (MSBP) as a supplement to grass silage, (2) to compare MSBP and barley, and (3) to ascertain if there was a response to the inclusion of soya bean meal as a protein source with both MSBP and barley. Weanling steers (n = 154) were assigned to the following treatments: (1) silage only, (2) silage plus a low level of MSBP, (3) silage plus a low level of MSBP plus soya bean meal, (4) silage plus a high level of MSBP, (5) silage plus a high level of MSBP plus soya bean meal, (6) silage plus a high level of barley, and (7) silage plus a high level of barley plus soya bean meal. Low MSBP, high MSBP and barley levels were 1.5 kg, 3.0 kg and 3.0 kg per head daily, respectively. Where soya bean meal was included it replaced 0.2 kg/day (low) or 0.4 kg/day (high) of MSBP or barley. The duration of the treatments was 125 days (winter) after which the animals grazed together for 148 days. Silage intake decreased linearly (P < 0.001) with increasing MSBP level. Addition of soya bean meal had no effect on silage intake with low MSBP or barley but increased (P < 0.05) intake with high MSBP. Live-weight gain increased both linearly (P < 0.001) and quadratically (P < 0.01) with increasing MSBP. There was a significant live-weight response to the addition of soya bean meal which was greater at the high than at the low MSBP level and was greater for MSBP than barley. Across all treatments, growth rate at pasture was inversely related to growth rate in winter. Final live weights for the treatments as listed were 376, 395, 411, 400, 430, 427 and 428 (s.e. 14.2) kg. It is concluded that there was a curvilinear live-weight gain response to increasing MSBP level. There was no end-of-grazingseason live-weight response to the inclusion of soya bean meal with barley but there was with MSBP, particularly at the high level. MSBP with soya bean meal was equivalent to a similar quantity of barley.
    • Empirical algebraic modelling of lactation curves using Irish data

      Quinn, N.; Killen, L.; Buckley, Frank (Teagasc (Agriculture and Food Development Authority), Ireland, 2005)
      The purpose of this study was to find a well-fitting, robust, single-equation model to describe the shape of lactation curves for Irish dairy cows. The suitability of a number of algebraic models that depict lactation curves was examined, using Irish test day data. The analysis was carried out on a total of 14,956 lactation records from commercial and experimental herds and included both autumn and spring calving animals. ‘Goodness of fit’ and adherence of the various models to the assumptions of regression analysis were examined. Multicollinearity posed a severe problem in the application of the best-fit model but omitting one of the variables from the estimation procedure reduced this effect. The modified model, referred to as the Ali-B model, is a single equation model that can be easily updated and incorporated into computer code. This is in contrast with the Standard Lactation Curve (SLAC) method, a method of interpolation, which is currently used by the Irish industry. The effects of seasonal factors on milk production were estimated and added to the Ali-B model to create a production profile for cows calving in specific months. The Ali-B model provided an acceptable level of accuracy in representing the shape of the lactation curve for Irish dairy cows, and can be easily modified for different environmental scenarios.
    • Accuracy of predicting milk yield from alternative milk recording schemes

      Berry, Donagh P.; Olori, V. E.; Cromie, A. R.; Veerkamp, Roel F.; Rath, Myles V; Dillon, Pat; Teagasc Walsh Fellowship Programme (Cambridge University Press, 2005-02)
      The effect of reducing the frequency of official milk recording and the number of recorded samples per test-day on the accuracy of predicting daily yield and cumulative 305-day yield was investigated. A control data set consisting of 58 210 primiparous cows with milk test-day records every 4 weeks was used to investigate the influence of reduced milk recording frequencies. The accuracy of prediction of daily yield with one milk sample per test-day was investigated using 41 874 testday records from 683 cows. Results show that five or more test-day records taken at 8-weekly intervals (A8) predicted 305-day yield with a high level of accuracy. Correlations between 305-day yield predicted from 4-weekly recording intervals (A4) and from 8-weekly intervals were 0.99, 0.98 and 0.98 for milk, fat and protein, respectively. The mean error in estimating 305-day yield from the A8 scheme was 6.8 kg (s.d. 191 kg) for milk yield, 0.3 kg (s.d. 10 kg) for fat yield, and −0.3 kg (s.d. 7 kg) for protein yield, compared with the A4 scheme. Milk yield and composition taken during either morning (AM) or evening (PM) milking predicted 24-h yield with a high degree of accuracy. Alternating between AM and PM sampling every 4 weeks predicted 305-day yield with a higher degree of accuracy than either all AM or all PM sampling. Alternate AM-PM recording every 4 weeks and AM + PM recording every 8 weeks produced very similar accuracies in predicting 305-day yield compared with the official AM + PM recording every 4 weeks.
    • Post-weaning performance and carcass characteristics of steer progency from different suckler cow breed types

      Drennan, Michael J; McGee, Mark; Keane, Michael G. (Teagasc (Agriculture and Food Development Authority), Ireland, 2005-04)
      In two experiments a total of 44 steer progeny of spring-calving Charolais (C) and Hereford × Friesian (HF) suckler cows and C sires were slaughtered at approximately 2 years of age. Following weaning they were offered silage and 1 kg of concentrate per head daily during a 5 month winter after which they spent 7 months at pasture. In Experiment 1, animals were given a silage/concentrate diet during a finishing period of either 95 or 152 days. In Experiment 2, steers were offered either a daily diet of silage plus 6 kg of concentrates or concentrates to appetite plus 5 kg of silage (fresh weight) during the final 140-day finishing period. Following slaughter, an 8-rib pistola from each animal was dissected. For the two experiments combined C and HF progeny had carcass weights of 372 and 385 (s.e. 6.1) kg, proportions of carcass as pistola of 467 and 454 (s.e. 2.8) g/kg and pistola meat proportions of 676 and 642 (s.e. 5.1) g/kg, respectively. All fat traits were lower for the C than HF progeny but there was no difference in carcass conformation score. Increasing slaughter weight increased carcass weight (P < 0.001), kidney plus channel fat weight (P < 0.001), and pistola fat proportion (P < 0.001) and decreased the proportions of carcass as pistola (P < 0.05), pistola meat (P < 0.01), and bone (P < 0.05). In conclusion, breed type had no effect on carcass growth but the C progeny had higher meat yield than the HF. Increasing slaughter weight increased fatness and reduced meat yield.
    • Comparison of growth curves of three strains of female dairy cattle

      Berry, Donagh P.; Horan, Brendan; Dillon, Pat (Cambridge University Press, 2005-04)
      The objective of the present study was to compare growth curves for live weight (LW) and body size of three strains of female dairy cattle reared under common environments in Ireland. One strain (HP) was selected from a predominantly North-American/European Holstein-Friesian genetic pool selected for high milk production. The second strain (HD) represented a predominantly North-American/European Holstein-Friesian genetic pool selected for high milk production but with greater selection emphasis on functional non-production traits. The third strain (NZ) consisted of New Zealand Holstein-Friesian females of high genetic merit for profitability in New Zealand. The data consisted of 99 animals (33 animals in each strain) with records on LW, length, girth and height from birth to a minimum of 594 days of age. The von Bertalanffy growth function was fitted to each animal's records separately and least-squares analyses were used to investigate the effect of strain on birth LW/body size, parameters of the growth function and average daily gains. Average mature live weight of the HD animals (591 kg) was significantly larger than that of the HP (566 kg) or NZ (543 kg) strain; the HD strain matured more slowly. The HD (134 cm) and HP (135 cm) strains were significantly taller than the NZ (128 cm) strain. Although the data set was relatively small there are indications that dairy females of North-American genetic origin were heavier at birth, grew faster, and were heavier and taller at maturity than dairy females of New Zealand origin.
    • Evaluation of the Progeny of Beef Sires Differing in Genetic Merit

      Keane, Michael G.; Diskin, Michael G.; European Union (Teagasc, 2005-11-01)
      The Irish Cattle Breeding Federation (ICBF) publishes breeding values (BVs) for beef bulls. Historically, BVs were expressed in index form relative to the base population. Sometime ago this changed to expression in units of measurement of trait. This change occurred in the course of this project and was accompanied by some re-ranking of bulls. BVs are published for growth, carcass grades and calving traits. Growth BV is expressed as carcass weight but there is no indication if this results from higher live weight gain or from a higher kill-out proportion and there is no indication of any consequences for feed intake or efficiency. • The objectives of the project were (i) to compare progeny of bulls of high and low growth genetic index, for growth, feed intake, slaughter traits and carcass traits, (ii) to partition the extra live weight of progeny of high growth index bulls into carcass and non-carcass parts, and (iii) to partition any extra carcass weight of progeny from high growth index bulls into its component fat, muscle and bone fractions
    • Evaluation of the Progeny of Beef Sires Differing in Genetic Merit

      Keane, Michael G.; Diskin, Michael G. (Teagasc, 2005-11-01)
      The objectives of the project were (i) to compare progeny of bulls of high and low growth genetic index, for growth, feed intake, slaughter traits and carcass traits, (ii) to partition the extra live weight of progeny of high growth index bulls into carcass and non-carcass parts, and (iii) to partition any extra carcass weight of progeny from high growth index bulls into its component fat, muscle and bone fractions.
    • Dairy cattle breeding objectives combining production and non-production traits for pasture based systems in Ireland.

      Berry, Donagh P.; Buckley, Frank; Dillon, Pat; Veerkamp, Roel F. (Teagasc, 2005-11-01)
      The objectives of this study were: 1) to estimate genetic (co) variances among body condition score, body weight, milk production, linear type traits and fertility, and 2) to investigate the presence of genotype by environment interactions for milk production, body condition score, and body weight, in Irish grass based seasonal calving herds. Genetic parameters were estimated from a potential 8928 primiparous and multiparous Holstein-Friesian cows over two years (1999 and 2000). Heritability estimates for body condition score (BCS) and body weight (BW) were found to be moderate to high; estimates ranged from 0.27 to 0.51 for BCS, and from 0.39 to 0.61 for BW. Heritability estimates for BCS change and BW change at different stages of lactation were all less than 0.11. Heritability for the linear type traits varied from 0.11 to 0.43. Phenotypic and genetic correlations between BCS and BW at the same stage of lactation were all close to 0.50 indicating that approximately 25% of the genetic and phenotypic variation in BW may be attributed to differences in BCS. Genetic correlations between BCS and milk yield tended to be negative (-0.14 to –0.51) and genetic correlations between BW and milk yield were close to zero (-0.07 to 0.09). However, the genetic correlations between BW adjusted for differences in BCS were positive (0.15 to 0.39). Genetic correlations between BCS and the fertility traits investigated were all favourable, indicating that cows with a superior genetic merit for BCS are on average likely to be served sooner, receive less services and have higher pregnancy rates. The genetic correlations between linear type traits and milk yield indicate that selection for milk production has resulted in taller, deeper cows that tend to be more angular and have less body condition. Genetically these cows are predisposed to inferior reproductive efficiency. Moderate genetic correlations were found between some of the linear type traits investigated and somatic cell count. A comparison of BCS, as recorded by Teagasc personnel (scale 1-5) and Holstein herd-book classifiers (scale 1-9) indicated consistency between the two sources. Phenotypic and genetic correlations of 0.54 and 0.86, respectively, were observed between the two measurement sources on the same animals. Genotype by environment interactions, were found for milk yield across different silage quality environments, and for BCS across different herd-year milk yield, concentrate, grazing severity and silage quality environments.
    • The effect of abrupt weaning of suckler calves on the plasma concentrations of cortisol, catecholamines, leukocyte, acute-phase proteins and in vitro interferon-gamma production

      Hickey, Mary-Clare; Drennan, Michael J; Earley, Bernadette; European Union (Teagasc, 2005-12-01)
      The objective of this study was to examine the effect of abrupt weaning (inclusive of social group disruption and maternal separation) on the physiological mediators of stress and measures of immune function. Thirty-eight male and 38 female continental calves were habituated to handling for two weeks prior to bleeding. Calves were blocked on sex, weight and breed of dam and randomly assigned, within block, to either a control (cows remain with calves) or abruptly weaned group (calves removed from cows). Animals were separated into the respective treatment groups at weaning (0 h). Calves were bled at – 168 h, 6 h (males only), 24 h, 48 h and 168 h post weaning. At each sampling time an observer scored the behavioural reaction of calves to sampling. Blood samples were analysed for cortisol, catecholamine concentrations (not sampled at –168 h) and in vitro interferon-gamma production, neutrophil :lymphocyte ratio and acute phase protein concentrations. All continuous data were analysed using a split-plot ANOVA, except that collected at 6 h, which was analysed using a single factor ANOVA model. The effects of weaning, calf sex and time and respective interactions were described. Disruption of the established social groups at 0 h, increased (p<0.001) the plasma cortisol concentration and neutrophil: lymphocyte ratio and reduced the leukocyte concentration (p<0.001) and the in vitro interferon-gamma response to the mitogen concanavalin-A (p<0.001) and keyhole limpet haemocyanin (p<0.001) for weaned and control animals, when compared with –168h. Plasma adrenaline and noradrenaline concentrations were not affected by group disruption. There was no effect of weaning or sex on calf behavioural reaction to handling during blood sampling. Plasma cortisol and adrenaline concentrations were not affected by weaning or sex. Plasma noradrenaline concentration was influenced by weaning x sex (p<0.05) and time x sex (p<0.05). The response increased for male calves with weaning and increased with each sampling time post weaning. For heifers the response was not affected by weaning and plasma concentrations decreased at 168 h post weaning. There was no effect of weaning or sex on leukocyte concentration. The neutrophils : lymphocyte ration increased post weaning (p<0.01) and was affected by sex (p<0.05). Weaning decreased (p<0.05) the in vitro interferon-gamma response to the antigen KLH. There was a time x weaning x sex (p<0.05) interaction for fibrinogen concentration but no effect of treatment on haptoglobin concentration. Abrupt weaning increased plasma cortisol and nor-adrenaline concentrations, which was accompanied by attenuation of in vitro interferon gamma production to novel mitogen and antigen complexes up to 7 days post weaning.
    • The effect of abrupt weaning of suckler calves on the plasma concentrations of cortisol, catecholamines, leukocyte, acute-phase proteins and in vitro interferon-gamma production.

      Hickey, Mary-Clare; Drennan, Michael J; Earley, Bernadette; European Union (Teagasc, 2005-12-01)
      The objective of this study was to examine the effect of abrupt weaning (inclusive of social group disruption and maternal separation) on the physiological mediators of stress and measures of immune function. Thirty-eight male and 38 female continental calves were habituated to handling for two weeks prior to bleeding. Calves were blocked on sex, weight and breed of dam and randomly assigned, within block, to either a control (cows remain with calves) or abruptly weaned group (calves removed from cows). Animals were separated into the respective treatment groups at weaning (0 h). Calves were bled at – 168 h, 6 h (males only), 24 h, 48 h and 168 h post weaning. At each sampling time an observer scored the behavioural reaction of calves to sampling. Blood samples were analysed for cortisol, catecholamine concentrations (not sampled at –168 h) and in vitro interferon-gamma production, neutrophil :lymphocyte ratio and acute phase protein concentrations. All continuous data were analysed using a split-plot ANOVA, except that collected at 6 h, which was analysed using a single factor ANOVA model. The effects of weaning, calf sex and time and respective interactions were described. Disruption of the established social groups at 0 h, increased (p<0.001) the plasma cortisol concentration and neutrophil: lymphocyte ratio and reduced the leukocyte concentration (p<0.001) and the in vitro interferon-gamma response to the mitogen concanavalin-A (p<0.001) and keyhole limpet haemocyanin (p<0.001) for weaned and control animals, when compared with –168h. Plasma adrenaline and noradrenaline concentrations were not affected by group disruption. There was no effect of weaning or sex on calf behavioural reaction to handling during blood sampling. Plasma cortisol and adrenaline concentrations were not affected by weaning or sex. Plasma noradrenaline concentration was influenced by weaning x sex (p<0.05) and time x sex (p<0.05). The response increased for male calves with weaning and increased with each sampling time post weaning. For heifers the response was not affected by weaning and plasma concentrations decreased at 168 h post weaning. There was no effect of weaning or sex on leukocyte concentration. The neutrophils : lymphocyte ration increased post weaning (p<0.01) and was affected by sex (p<0.05). Weaning decreased (p<0.05) the in vitro interferon-gamma response to the antigen KLH. There was a time x weaning x sex (p<0.05) interaction for fibrinogen concentration but no effect of treatment on haptoglobin concentration. Abrupt weaning increased plasma cortisol and nor-adrenaline concentrations, which was accompanied by attenuation of in vitro interferon gamma production to novel mitogen and antigen complexes up to 7 days post weaning.