Alejandro Alzina-López

Risk factors for Aujeszky’s disease in pig herds and detection of field virus antibodies in fattening pigs in the state of Yucatan, Mexico

Two epidemiological studies were conducted from August 1997 to May 1998: a case-control study to identify herd level risk factors for antibodies to Aujeszkys disease virus (ADV) in sows in the state of Yucatan, Mexico and a cross-sectional study to determine the prevalence of antibodies against ADV in fattening pigs. In the case-control study, data on herd management and biosecurity were obtained from all the 27 ADV known field-virus-seropositive farms (cases) and 62 randomly selected seronegative farms (controls) by questionnaire. Breeding animals of these seropositive farms had received a gE-deletion vaccine. In the cross-sectional study, 26 farrow-to-finish farms of the 27 seropositive farms were used and blood samples taken from 60 fattening pigs per herd (15 pigs for each stage of production). Serum samples were analyzed by the screening-ELISA and gE-ELISA tests. In the case-control study, three of the 15 risk factors were significant. Odds ratios for distance to the nearest farm (< or = 2.5km), not sampling for the detection of ADV and herds with origin of breeding animals within the state were 9.5, 18.1 and 8.7. In the cross-sectional study, 11 (42.3%) of the 26 sampled farms were seropositive to vaccine antibodies. None of the piglets were positive to antibodies against field virus risk--suggesting that the strategy of vaccinating only the breeding animals reduced the ADV infection of the piglets.

Risk Factors Associated with the Occurrence of the Second-Litter Syndrome in Sows in Southeastern Mexico

The objective was to estimate the incidence of and to determine the effect of some risk factors on the decrease of litter size at parity 2 of sows in three commercial farms in Yucatan, Mexico. Data on 8,592 farrowing records of 4,296 sows were analyzed using a binomial logistic regression procedure. The model included the fixed effect of farm (1, 2, and 3), year of farrowing (2003–2011), season of farrowing (dry, rainy, and windy), number of pigs born alive at first parity (<9, 9-10, 11-12, and >12 piglets), lactation length (<18, 18–24, and >24 days), and weaning to conception intervals (<4, 4–11, and >11 days). Fifty-five point eight percent of all sows presented a reduced or similar litter size at parity 2. The odds of decrease in the second litter size were 1.56 and 2.01 for farms 2 and 3, respectively. Higher odds were found for sows farrowing during the rainy and dry seasons (1.20 and 1.24, resp.) and for sows with large litters at parity 1 (>12 piglets, odds = 33.2). Sows with weaning to conception intervals <4 days and between 4 and 11 days had higher odds of a decrease in the second litter (1.78 and 2.74 pigs, resp.).

Effect of reduced or increased number of pigs born alive at second farrowing on lifetime productivity of sows in southeastern Mexico

El objetivo de este estudio fue determinar el efecto del cambio en el tamano de la camada entre el parto uno y dos (DNBA) y por la suma del numero de cerdos nacidos vivos en el parto uno y dos (SNBA) sobre la vida productiva de las cerdas en cuatro granjas porcinas en el tropico de Mexico. Se utilizaron los datos de 6.046 cerdas, con informacion sobre los lechones nacidos vivos por vida productiva (LBA), la duracion de la vida productiva (LPL), numero de partos a la eliminacion (NP) y lechones nacidos vivos por ano (PBY). Las cerdas fueron clasificadas en 11 grupos DNBA: ≤ -5, -4, -3, -2, -1, 0, 1, 2, 3, 4 y ≥ 5 lechones, y 5 del grupo SNBA: ≤ 17, de 18 a 20, 21 a 22, 23 a 25 y ≥ 26 lechones. Se observo una tendencia lineal positiva de LBA, LPL y PBY para cerdas que disminuyeron en ≤ 5 lechones a cerdas que aumentaron en ≥ 5 lechones. Las cerdas con mayor SNBA permanecen mas tiempo en la granja y produjeron mas lechones durante su vida productiva. Las cerdas que aumentaron el tamano de camada al segundo parto y las que tuvieron mas lechones en sus dos primeros partos fueron mas productivas

Factores ambientales que afectan algunas características postdestete de las cerdas en el trópico de México

El objetivo de este estudio fue determinar el efecto de algunos factores ambientales sobre el intervalo destete-primer servicio (IDS), intervalo destete-concepcion (IDC), intervalo parto-primer servicio (IPS) e intervalo entre partos (IEP) y estimar sus repetibilidades bajo condiciones del tropico subhumedo de Mexico. Se utilizaron mas de 33.000 observaciones de aproximadamente 8.500 cerdas. El modelo estadistico que describio las variables de respuesta incluyo los efectos de granja (1, 2, 3, 4), ano de parto (2007-2012), epoca de parto (sequia, lluviosa y nortes), numero de partos (1 a > 8), sus interacciones simples, los efectos aleatorios de cerda y el error. Las covariables usadas fueron duracion de la lactacion y tamano de la camada. Las medias para IDS, IDC, IPS, e IEP fueron 6,84, 9,8, 29,1 y 146 dias, respectivamente. Todos los factores y la interaccion ano y epoca fueron significativas (P < 0,05), con excepcion de la epoca sobre IDS e IPS. La duracion de la lactancia tuvo efecto cuadratico sobre todas las variables. Las repetibilidades estimadas para IDS, IDC, IPS, e IEP fueron 0,067, 0,055, 0,067, y 0,05, respectivamente. En conclusion, en los programas de manejo y alimentacion deben ser considerados el numero de parto y la duracion de la lactacion para mejorar el comportamiento reproductivo de las cerdas. Las repetibilidades para las caracteristicas estudiadas fueron bajas.