Asunto(s)
Cabras/genética , Polimorfismo Genético , Secuencias Repetitivas de Ácidos Nucleicos , Alelos , Animales , Secuencia de Bases , Cartilla de ADN/genética , ADN Satélite/genética , Femenino , Frecuencia de los Genes , Marcadores Genéticos , Masculino , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos/genética , Rumiantes/genéticaAsunto(s)
Cabras/genética , Polimorfismo Genético , Secuencias Repetitivas de Ácidos Nucleicos , Alelos , Animales , Secuencia de Bases , Cartilla de ADN/genética , ADN Satélite/genética , Femenino , Frecuencia de los Genes , Marcadores Genéticos , Masculino , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos/genética , Rumiantes/genéticaRESUMEN
Concepts used to derive a deterministic model for evaluating embryo transfer for commercial steer production taking into consideration genetic merit for growth and mature size, herd feed supply, and recipient maternal environment are discussed. Genetic potential of an embryo is used to derive optimal growth rates that can be sustained by available herd feed per animal per day. Equations are provided for various measures of performance as functions of the feed, genotype of the embryo, and recipient maternal contribution. To assess the value of a particular line of embryos, interactions between genotype and nutrient environment are quantified, so that the benefits of embryos of high genetic merit are evaluated objectively. Product quality and weight are predicted from the model to provide a framework that will allow commercial beef producers to determine marketing strategies likely to result in optimal return.
Asunto(s)
Bovinos/fisiología , Transferencia de Embrión/veterinaria , Modelos Biológicos , Modelos Econométricos , Alimentación Animal , Fenómenos Fisiológicos Nutricionales de los Animales , Animales , Peso al Nacer , Bovinos/genética , Bovinos/crecimiento & desarrollo , Enfermedades de los Bovinos/epidemiología , Distocia/epidemiología , Distocia/veterinaria , Transferencia de Embrión/economía , Metabolismo Energético , Femenino , Genotipo , Masculino , Embarazo , Prevalencia , Probabilidad , Reproducción , Aumento de Peso/genética , Aumento de Peso/fisiologíaRESUMEN
A bioeconomic model was developed and used to evaluate economic implications of embryo transfer for steer production. Sensitivity analysis indicated that the net returns were strongly influenced by pregnancy and growth rates. Matching of recipient and embryo sizes reduced dystocia prevalence and resulted in as much as a $98 saving per transfer in costs associated with dystocia. Optimal weight and age and net returns at slaughter were found to be a function of mature size and growth rate. Varying growth rates resulted in optimal slaughter weight and net present value (NPV) ranging from 403 to 494 kg and $156 to $273, respectively, for medium-sized steer genotypes characterized by a mature size of 600 kg. The optimal slaughter weight ranged from 456 to 607 kg and NPV from $182 to $344 for large-sized steer genotypes characterized by a mature size of 750 kg. The results showed that high pregnancy rates and embryos with high growth rates generated the greatest profitability from investment in embryo transfer. The model has a wide potential application in formulating optimal biological and economic strategies for matching embryo genetic resources to physical and economic environments for commercial beef production.
Asunto(s)
Bovinos/fisiología , Transferencia de Embrión/economía , Modelos Biológicos , Modelos Econométricos , Factores de Edad , Animales , Peso al Nacer , Peso Corporal , Bovinos/crecimiento & desarrollo , Enfermedades de los Bovinos/prevención & control , Distocia/prevención & control , Distocia/veterinaria , Estudios de Evaluación como Asunto , Femenino , Masculino , EmbarazoRESUMEN
A model was developed for the economic evaluation of embryos for producing bull lines for use in commercial beef production. The fundamental concept underlying the model is that a cloned and sexed embryo of known genetic characteristics for beef traits is used to produce a bull. After reaching physiological maturity, the bull is used in natural matings. Equations relating feed energy requirements and growth rates based on NRC requirements and costs and returns discounted to present value allow investigation of expected economic merits of progeny from different embryo bull lines. The model has the flexibility to determine optimal embryo characteristics for different production environments. Model sensitivity to variation in progeny sex ratios, growth rates, yield and quality grades, and herd fertility characteristics was examined. Net present values (NPV) per embryo transferred were determined at the optimal marketing age of progeny produced from mating the bull to 30 cows per year for 5 yr. Relative to the lowest NPV of $18,209 for progeny with an expected quality grade of Select and yield grade of 4 at 400 d, increments in NPV ranged from $329 to $22,708 depending on differences in expected progeny carcass grade characteristics. The difference between NPV for 100% male and 40% male sex ratios was $7,518. The NPV differences between progeny growth rates of 1.6 and .9 kg/d holding herd conception rate constant at .9 and .5 were $8,311 and $4,611, respectively. The model evaluates relative economic values of embryo lines for producing bulls, accommodating interactions among progeny characteristics, and environments.
Asunto(s)
Bovinos/fisiología , Transferencia de Embrión/veterinaria , Modelos Biológicos , Animales , Bovinos/embriología , Bovinos/genética , Células Clonales , Transferencia de Embrión/economía , Estudios de Evaluación como Asunto , Femenino , Fertilización , Genotipo , Vigor Híbrido , Masculino , Carne/normas , Razón de MasculinidadRESUMEN
The anthelmintic activity of thiabendazole (TBZ) at 88 mg kg-1 and ivermectin at 0.2 mg kg-1 was examined in goats with naturally-acquired nematode infections. In one experiment, a herd of 450 does was treated with TBZ or ivermectin at 4-week intervals for 9 months and efficacy was measured by reduction in faecal egg counts after each treatment. In a second experiment, 100 kids were treated with ivermectin and effectiveness measured at 2 and 4 weeks after treatment by comparison of their egg counts with those of nontreated controls. In a third experiment, efficacy of treatment with TBZ and ivermectin was determined by recovery of parasites at necropsy in a controlled test with 15 kids. The results indicated that TBZ generally did not reduce egg counts and only removed 19% of Haemonchus contortus in the controlled test. The efficacy of ivermectin approached 100% for reduction in egg counts and elimination of H. contortus. Species of Ostertagia, Trichostrongylus, Nematodirus and Oesophagostomum also were present in some subjects, but not in sufficient numbers to evaluate effectiveness of treatment.
Asunto(s)
Cabras/parasitología , Ivermectina/uso terapéutico , Infecciones por Nematodos/veterinaria , Tiabendazol/uso terapéutico , Animales , Femenino , Kenia , Infecciones por Nematodos/tratamiento farmacológico , Distribución AleatoriaRESUMEN
Breed additive, maternal, and heterozygotic effects on 11 monthly postpartum body weights, average size, weight gain, age at first calving, and days open were estimated by linear regression analyses from records of 680 purebred and crossbred animals. Calving year, age, and milk yield were significant environmental effects. Positive regressions of age on body weights indicated late calving cows were heaviest postpartum and had most days open. Negative regressions of milk yield on weight gain and postpartum weight showed greatest losses of weight associated with highest yields. There were breed differences in growth; purebreds highest to lowest were Brown Swiss, Holstein, Red Dane, Jersey, and Ayrshire and for weight gain, Brown Swiss, Ayrshire, and for weight gain, Brown Swiss, Ayrshire, Jersey, Holsteins, and Red Dane. Crosses were superior to purebreds in these traits. Additive effects of Holstein were greater than Ayrshire, Jersey, and Red Dane for postpartum body weights and average size. All constants for heterozygotic effect combinations were significant for postpartum weights and average size. Heterozygosity effects increased in magnitude with advancing lactation. Generally, age at first calving and postpartum interval to conception reflected little heterozygotic or maternal effects. There was some indication of breed differences in mean and additive effects for age at first calving.
Asunto(s)
Bovinos/crecimiento & desarrollo , Cruzamientos Genéticos , Lactancia , Animales , Bovinos/genética , Femenino , Heterocigoto , EmbarazoRESUMEN
Effects of year, season, parity, age, their two-way interactions, lactation length and calving interval on milk yield were investigated utilizing 9,086 lactation records collected from 1930 to 1975 from six breed groups kept in one herd at Karnal, India. The breed groups involved three native breeds (Sahiwal, Red Sindhi and Tharpakar) and three crossbreds with Brown Swiss (F1 crosses between Brown Swiss and three native breeds, inter se crosses, and 3/4 Brown Swiss). Breed, year, season, parity, age and all of the two-way interactions with the exception of breed X season and parity X season were important. Tharpakar produced more milk than Sahiwal and Red Sindhi by 232 and 204 kg. The milk production difference between Sahiwal and Red Sindhi was only 28 kg. The three crossbreds outproduced the purebreds by an average of 766 kg; however, differences in management could have favored crossbreds. Among the crossbreds, F1 crosses were superior. The linear and quadratic regressions on lactation length accounted for 28% of the variation in milk yield after year, season, parity, age and their interactions were absorbed. Calving interval and lactation length together accounted for 29%. Estimates of heritability, from paternal half-sib analyses, and repeatability of milk yield for Red Sindhi, Sahiwal and Tharpakar ranged from .10 to .30. Differences among heritability estimates from different parities were small when more than 500 records were involved.
Asunto(s)
Bovinos/genética , Cruzamientos Genéticos , Ambiente , Leche/metabolismo , Factores de Edad , Animales , Bovinos/fisiología , Femenino , Variación Genética , India , Lactancia , Masculino , Modelos Genéticos , Paridad , Embarazo , Estaciones del AñoRESUMEN
This study was to determine if breed groups ranked differently in warm (May to August) and cool (November to February) seasons of calving and to determine if heterosis was more important in the warm season. A total of 719 records of cows in first lactation in four herds in the southeastern United States were used. Breeds were Holsteins, Brown Swiss, and Jerseys and the crosses among them. Milk and milk fat yields were greater in the cool season than in the warm season. Holsteins exceeded other breeds for milk and milk fat yield in both seasons, but their superiority was less among cows calving from May through August. Days open were longer for Holsteins, particularly in the warm season. In the cool season only the 3/4 Holstein X 1/4 Swiss group exceeded Holsteins for milk, but two groups--1/2 Holsteins X 1/2 Swiss and 5/8 Holstein X 1/4 Swiss-1/8 Jersey--were higher in the warm season. In the cool season three crossbred groups--1) 1/2 Holstein X 1/2 Swiss (Holstein sires), 2) 3/4 Holstein X 1/4 Swiss, and 3) 1/2 Holstein X 1/4 Swiss-1/4 Jersey--had greater milk fat yields than Holsteins, and a fourth--1/2 Holstein X 1/2 Jersey--yielded an equal amount. In the warm season six of the eight crossbred groups had greater milk fat yields than Holsteins. More crossbreds exceeded Holsteins in the warm than in the cool season, suggesting interactions for yields. There was slightly more heterosis in warm than in cool seasons for all traits.
Asunto(s)
Bovinos/genética , Trabajo de Parto , Leche/metabolismo , Reproducción , Animales , Bovinos/fisiología , Frío , Cruzamientos Genéticos , Femenino , Calor , Vigor Híbrido , Lactancia , Masculino , Modelos Genéticos , Embarazo , Estaciones del AñoRESUMEN
Actual milk and milk fat yields of 328 crossbred cows in first lactation in four experimental herds and Predicted Differences for the same traits on their 165 sires were the basic data used. Predicted Differences (PD) for milk and fat on a 1974 base were the measures of transmitting value. They were computed from all straightbred progeny of these bulls in milk recorded herds in the United States. Standard deviations of PD for the 95 Holstein and 70 Brown Swiss bulls were similar to those of all bulls of their breeds in use in artificial insemination at the same time. Regressions of milk yields of crossbred progeny on PD for milk were .77 +/- .44 for Holstein-sired crosses and 1.42 +/- .58 for crosses sired by Brown Swiss bulls. Corresponding values for milk fat were .55 +/- .41 and 1.25 +/- .60. The four regression coefficients averaged 1.00. Correlations corresponding to the four regressions were .22, .35, .17 and .31, respectively. These averaged .26, slightly higher than their expected value based on heritabilities of .25 for milk and fat yields. Regressions based on 405 straightbred Holstein and Brown Swiss progeny in the same four experimental herds averaged .99, while respective correlations averaged .21. These results suggest that selection of dairy bulls based on their progeny tests from straightbred progeny would be effective in improving lactation yields of crossbred progeny.