E.B. Burnside

Genetic relationships between clinical mastitis, somatic cell count, and udder conformation in Danish Holsteins

Abstract Heritabilities and genetic and phenotypic correlations were estimated for linear scored udder traits, clinical mastitis, incidence of other diseases, and somatic cell count (SCC), using first lactation data from the Danish young sire sampling program. Two sets of data were analyzed using a multi-trait REML procedure with an animal model. Heritabilities were low for mastitis (0.025) and other diseases (0.011). Heritability of SCC was 0.18. For type traits, heritability estimates varied between 0.07 and 0.43. The estimate of the genetic correlation between SCC and clinical mastitis was high at 0.97. Genetic correlations between health and type traits were generally low (−0.32 to 0.37) with few exceptions. The genetic correlation between clinical mastitis and other diseases was moderately high at 0.53. All phenotypic correlations between traits were low. In general, the results indicate that selection for improved udder conformation will reduce the increase in SCC and clinical mastitis associated with selection for production. The high genetic correlation between SCC and clinical mastitis makes SCC a feasible indicator for clinical mastitis.

Additive and Nonadditive Genetic Variation for Conformation Traits in Canadian Holsteins

Abstract Additive and dominance genetic variances for nine conformation traits in the Canadian Holstein population were estimated by REML using the derivative-free algorithm. All traits were analyzed under two sire and dam models differing in assumptions on the data structure. Within-herd relationships due to dam were defined first to be nested within sire in order to estimate both genetic variances, assuming unimportant biases on the estimates. The potential impact of some of these biases was estimated as the difference between the two parental variance components under a cross-classified model. Heritabilities were similar to those previously computed for Canadian Holsteins and ranged from .10 to .30. Results from the hierarchical dam-within-sire model suggest dominance genetic variation, as a proportion of the total variation, to be important for final score (.15), capacity (.16), and mammary system (.13). However, estimates of dam components, as a proportion of the total variance, were significantly greater than sire components for final score (.019), general appearance (.020), and feet and legs (.018) under the cross-classified model. Therefore, the significant dominance genetic parameter estimated for final score under the hierarchical model may have been biased upward.

International evaluation of Holstein-Friesian dairy sires from three countries

Abstract Official 1985 genetic evaluations of Holstein-Friesian dairy sires for milk yield, fat yield and fat percentage from Canada and the U.S.A. were pooled with unofficial 1985 genetic evaluations of sires from Italy in order to obtain international evaluations of sires for these three countries. There were 1766 sires from Canada, 9746 from the U.S.A. and 4191 from Italy with at least 20 daughters or 5 effective daughters each. The linear model for describing a sires daughter average, free of all non-genetic fixed effects, included the country of proof, the country of origin and year of birth, sires within country of origin and year of birth and all additive genetic relationships among bulls. Daughter averages were approximated by de-regressing sire proofs and accounting for year of birth within country. Differences in country of proof solutions reflect differences in genetic bases of evaluation; the Italian minus the Canadian and the U.S. solutions were, respectively, 334 and 565 kg for milk yield, 14.4 and 19.6 kg for fat yield, and 0.05 and -0.01% for fat percentage. Between 1955–1959 and 1960–1964, there was very little genetic progress in all countries. Genetic change in sires born between 1965–1969 and 1975–1979 were 121, 198 and 87 kg for milk yield, 4.6, 6.0 and 2.4 kg for fat yield, and 0.01, -0.02 and -0.02% for fat percentage in Canada, the U.S.A. and Italy, respectively. Sires imported to Canada, the U.S.A. and Italy had average evaluations different from those of local sires within countries by 126, -211 and 45 kg for milk yield, 4.2, -6.4 and 2.0 kg for fat yield, and -0.01, 0.02 and 0.01% for fat percentage, respectively. The estimation of international sire breeding values on a routine basis was shown to be feasible, but many problems still remain to be solved. Besides the need for sufficient links between countries, the primary problem is that of accounting for non-random mating of sires within each country.

Immune responses of Holstein and Norwegian Red × Holstein calves on Canadian dairy farms.

The objective of this study was to compare the immune response of Holstein and Norwegian Red x Holstein calves on 13 commercial Canadian dairy farms. Data were collected on 135 calves, 68 Holstein and 67 Norwegian Red x Holstein calves aged between 2 and 6 mo. The calves were immunized with hen egg white lysozyme to induce antibody-mediated immune response. Candida albicans was used as an in vivo indicator of cell-mediated immune response, with delayed-type hypersensitivity used as the indicator. Antibody response to hen egg white lysozyme (IgG, IgG1, and IgG2) was measured by ELISA. Calves of both breed groups produced a significant primary and secondary antibody-mediated immune response, as well as a delayed-type hypersensitivity reaction. The Norwegian Red x Holstein produced a greater primary IgG antibody-mediated immune response (d 14, and d 14 minus d 0) when compared with the Holstein. No differences were observed between the breeds for secondary response or antihen egg white lysozyme isotype (IgG1 or IgG2) production or the ratio of IgG1:IgG2. There was no effect of breed on delayed-type hypersensitivity. Nonetheless, high and low immune responders could be identified in both breed groups, but with no difference in the proportion of high and low responders observed for either antibody-mediated immune response or cell-mediated immune response between breed groups.

Antibody and cell-mediated immune responses and survival between Holstein and Norwegian Red × Holstein Canadian calves

As an extension of a former study, the objectives of this study were to evaluate purebred Holstein (HO; n=140) and crossbred Norwegian Red × Holstein (NRFX; n=142) calves for antibody (AMIR) and cell-mediated immune responses (CMIR) as well as survival. Blood was collected on d 0, 14, and 21, and calves were immunized on d 0 and 14 with type 1 (Candida albicans) and type 2 (hen egg white lysozyme) antigens, which have been shown to induce CMIR and AMIR, respectively. Day 21 background skin-fold measurements of either side of the tail-fold were taken and intradermal injections of test (type 1 antigen) and control (phosphate saline buffer) were administered. Day 23 final skin-fold measurements were taken to assess delayed type hypersensitivity as an indicator of CMIR. Survival data were obtained from CanWest Dairy Herd Improvement. Statistical Analysis System general linear models were used to analyze all immune response and survival data and to determine statistical significance between breeds. Results showed that NRFX had greater primary IgM, IgG, IgG1, and secondary IgG1 antibody response, as well as greater primary IgG1:IgG2 ratio to the type 2 antigen compared with HO. The NRFX also had greater primary IgG1 and IgG2, and secondary IgG2 antibody response as well as greater primary IgG1:IgG2 ratio to the type 1 antigen. The NRFX calves had a tendency toward greater survival from age at immune response testing to calving. No difference was observed between breeds for other secondary antibody response traits or delayed type hypersensitivity. Results indicate NRFX have greater AMIR and therefore may have enhanced defense against extracellular pathogens. This may contribute to increased survival compared with HO. Both breeds, however, likely have similar defense against intracellular pathogens, because no differences in CMIR were observed. In general, these results may suggest that crossbreeding could improve resistance to certain diseases in dairy calves, resulting in decreased input costs to producers for crossbred calves compared with purebred calves. However, more research with larger sample sizes and different breeds should be conducted to confirm these results and obtain a complete picture of the benefits of crossbreeding on immune response traits in calves.

Effects of female reproductive rate and mating design on genetic response and inbreeding in closed nucleus dairy herds

Hierarchical (each dam mated to one sire) and factorial (each dam mated to several sires) designs involving juvenile selection in a closed nucleus breeding programme were compared for rates of genetic response and inbreeding using stochastic simulation. Numbers of sires and dams selected and herd sizes varied. Generations were discrete. Sires and dams were selected at 15 months on the basis of an estimated breeding value (EBV) calculated using selection index which considered information on close relatives. Selection was for total merit index. Matings were carried out assuming use of multiple emulation and embryo transfer (MOET) or in vitro embryo production (1VEP) technologies, over a range of reproductive parameters. Reproductive rates assumed a fixed number of potential offspring per collection with IVEP and MOET. Comparison of mating designs using MOET showed that rates of genetic response and inbreeding with factorial designs voere from 88 to 431% and 36 to 111% of those with the hierarchical design. Generally rates of genetic response were increased and inbreeding decreased by increasing the number of mates per dam due to a reduction of correlations among EBV. Reduced rates of genetic response were occasionally observed in factorial designs involving the mating of dams to large numbers of sires. This increased the generation interval due to the time to carry out the matings. Factorial designs were found to be most efficient for increasing genetic response and or decreasing inbreeding, for breeding programmes involving the selection of equal numbers of sires and dam. For the breeding programmes considered, rates of genetic response with IVEP equalled the best of the MOET designs, achieved at highest MOET rates, at the lowest level of IVEP. But at the equivalent rate of genetic response, rate of inbreeding was increased by 8%. The increased rate of inbreeding was due to the shorter generation interval with IVEP, and the increased probability of selecting related individuals assuming all donors respond to IVEP.

Adaptive immune response, survival, and somatic cell score between postpartum Holstein and Norwegian Red × Holstein first-calf heifers.

The objectives of this study were to evaluate antibody (AMIR) and cell-mediated immune responses (CMIR), survival, and somatic cell score (SCS) between purebred Holstein (HO) and crossbred Norwegian Red × Holstein (NRHO) first-calf heifers postpartum. Additionally, immune response traits observed as calves in a previous study were correlated with their immune response traits as first-calf heifers. Heifers, previously immunized as calves, were bled and reimmunized 6 to 9 d postcalving with known type 1 and type 2 antigens and human serum albumin (HSA). Seven days later, heifers were rebled, and background skinfold measurements of the tail fold were taken. Intradermal injections of PBS and type 1 antigen were administered on either side of the tail fold. On d 9 final skinfold measurements were taken and used to assess delayed-type hypersensitivity (DTH) as an indicator of CMIR. Blood samples were also collected for a final time on d 14 from heifers that received the antigen HSA. Serum was obtained from blood collected on d 0, 7, and 14 and analyzed by ELISA to assess AMIR. Data on survival and somatic cell count, which was converted to SCS, were obtained from CanWest Dairy Herd Improvement (DHI). All SCS, survival, and immune response data were analyzed using general linear models to determine significance between HO and NRHO first-calf heifers. To determine residual correlations between immune response traits observed in calves to their responses as first-calf heifers, residuals were obtained from models, and correlations between traits were determined using PROC CORR in SAS. Results showed NRHO had a greater primary IgG antibody response to HSA and greater tertiary IgG antibody response to the type 2 antigen compared with HO. Crossbreds (NRHO)also had significantly greater DTH response (P < 0.05) and, in general, greater survival from calving to 100 d in milk (dim), 100 to 305 dim, calving to 305 dim, and age at immune response testing as calf to 305 dim. No difference was observed between breeds for SCS. Results also showed most correlations between calf and first-calf heifer immune response traits were found to be positive and significant (P < 0.05). In conclusion, NRHO heifers have greater survival, which likely relates at least in part to increases in aspects of both AMIR and CMIR and could indicate that crossbred heifers have enhanced disease resistance.

Biotechnologies of reproduction applied to dairy cattle production: Embryo transfer and IVF

The objective of this paper is to review the utilization and outcome of reproductive biotechnologies in dairy cattle. Embryo transfer and IVF have their respective limits that influence their impact on a genetic improvement program. Embryo transfer is efficient and profitable in an artificial insemination breeding and selection program and IVF has great potential. Development of markers highly correlated with various economic traits will progressively be added to the present schemes to make them even more powerful. Key words: Reproductive technologies, embryo transfer, IVF, dairy cows, genetic

Beef production from a dairy farm: A linear programming simulation approach

Abstract A commercial dairy farm was modelled and linear programming used to maximize gross margins within the farms limited resources. The model was static, deterministic and over a one-year planning horizon. Cows not required for generating replacements could be mated to either beef or dairy bulls, while calves not used as replacements could be either sold, or fattened for beef and veal. Three beef breeds (Charolais, Limousin and Hereford) were compared with straight Holstein at three replacement rates (20, 25 and 30%) and at low, medium and high beef price. The most important factors affecting gross margins were beef production, beef price, replacement rate and breed. Gross margins increased by 30% when beef was produced instead of selling all the calves at one week of age, by 17% from low to high beef price, by 9% from high to low replacement rate, and by 3% when Charolais and Limousin were used instead of straight Holstein only. Beef production was profitable on a commercial dairy farm with surplus labour, and beef crossing was always more profitable than straight dairy partly because of the invariable sex ratio used in this deterministic model.