The description of lactation curves by mathematical models could be an effective tool for management decisions in dairy cattle production systems. In this study the comparative fit of three models: negative exponential (í = (â0e-â1x), incomplete gamma (í = â0xâ1e-â2x) and fifth order polynomial (í = â0 + â1x + ... +â5x5) was evaluated both between and within lactations using 8,763 milk yield records from 770 lactations for the first two models, and 7,228 records from 647 lactations for the third model. Milk yield records included the period 1997-2001 and were collected from five dairy farms located in Lima. The models were compared on the basis of the adjusted multiple coefficient of determination (R2 aj), the residual standard errors (EER), the standard errors of the predicted yield on day 305 (EE305), and the residual scatter plots. Additionally, the effect of parity, calvin...

Sixty-five 3-4 years old Corriedale ewes were used from April to August 2002 to evaluate the effect of PGF2µ treatment at days 4 (GP4) and 10 (GP10) of the estrous cycle on (i) the percentage of estrus, (ii) variability within animals in the onset of estrus, (iii) the length of the treatment-estrus interval and, (iv) the rate of pregnancy. The estrous cycle was synchronized inserting intravaginal sponges impregnated with 30 mg of fluorogestone acetate (FGA) during 12 days. After the occurence of estrus (estrus = day 0), 20 ewes at day 4 (GP4) and 22 at day 10 (GP10) were treated with 0.175 mg of an analogue of PGF2µ. The 23 remaining ewes were not treated and kept as control group (GC). Estrus was detected by introducing vasectomized rams to the flock at 6, 12 and 17 h on daily basis. All FGA-synchronizated ewes showed estrus, as well as after the treatment with PGF2µ; however, the on...

A seroprevalence study on 5439 cattle from April to June 2007 was conducted based on a circumstantial diagnosis of two cases of bovine brucellosis in the district of Codo del Pozuzo, en the region of Huanuco. Two animals resulted positive to the Rose Bengal test but negative to the Complement Fixation test. The beta distribution using a simulation model showed a prevalence of 0.02% with a minimum interval of confidence of 0 and maximum of 0.06%.

The aim of the study was to determine the frequency and characterize testicularanatomo-histopathological alterations in alpacas slaughtered in Nuñoa, Puno.Macroscopic examination of the testes was carried out in 177 alpacas, which 102 showedsmaller size and low weight, and also uni or bilateral epididymal cysts. Tissue sampleswere fixed with the Bouin solution during 28 hours and stained with Haematoxylin andEosin, Periodic Acid Schiff and Masson’s Trichromic stain. The frequency of testicularalterations was 13.7%, corresponding to nonspecific lymphocytic infiltration (7.8%),testicular absence (2.9%), testicular degeneration (1.0%), hidrocele (1.0%), and teratoma(1.0%). Besides, there was 32.2% of epididymal cysts, but without statistical associationwith age or breed.

The effect of feed supplementation and temporary weaning in 46 crossbred Bos taurus x Bos indicus cows on the resumption of post partum ovarian activity was evaluated. Animals were distributed in three treatments: T1, Control, cows without supplementation + calf at foot; T2, Feed supplementation + calf at foot and temporary weaning (48 h) at 60 days post partum; and T3, Feed supplementation + calf at foot. Supplement consisted of 3 kg/cow/day from calving till 60 days post partum. Blood samples were collected twice a week since week 3 till week 16 post partum for the determination of progesterone levels as indicator of the resumption of ovarian activity. The interval calving-first ovulation was 70.6, 56.4, and 57.8 days for cows that ovulate within the first 12 weeks after calving in groups T1, T2, and T3 respectively. The 31.3, 73.3, and 66.7% of cows in each treatment group ovulate wit...

En base a un diagnóstico circunstancial de dos casos de brucelosis en un hato bovino del distrito de Codo del Pozuzo, Huánuco, se llevó a cabo un estudio de prevalencia de Brucella sp. en 5439 bovinos entre abril a junio de 2007. Dos bovinos resultaron positivos a la prueba de Rosa de Bengala, pero negativos a la prueba confirmativa de Fijación del Complemento. El modelo de simulaciones estocásticas de distribución beta mostró una prevalencia de 0.02% con intervalo de confianza mínimo de 0 y máximo de 0.06%.

Se determinó la frecuencia y se caracterizó las alteraciones anátomo-histopatológicas testiculares en alpacas beneficiadas en la zona de Nuñoa, Puno. Se hizo el examen macroscópico de los testículos de 177 alpacas, donde 102 presentaron tamaño y peso disminuido, además de quistes epididimarios uni o bilaterales. Muestras de tejido testicular se fijaron con Solución de Bouin por 28 horas, y se tiñeron con Hematoxilina y Eosina, Ácido Periódico de Schiff y Tricrómico de Masson. Se encontró una frecuencia de 13.7% de alteraciones testiculares, correspondiendo a infiltración linfocítica inespecífica (7.8%), ausencia testicular (2.9%), degeneración testicular (1.0%), hidrocele (1.0%) y teratoma testicular (1.0%). Asimismo, se observó una frecuencia de 32.2% de quistes epididimarios, sin que haya asociación estadística entre presencia de quistes con edad o raza de las alp...

Se evaluó el efecto de la suplementación alimenticia y el destete temporal en 46 vacas cruzadas Bos taurus x Bos indicus sobre el reinicio de la actividad ovárica postparto. Los animales fueron distribuidos al parto en tres tratamientos: T1: Control, sin suplementación y con cría al pie; T2: Suplementación + destete temporal (48 h) a los 60 días post parto; y T3: Suplementación + cría al pie. Se suplementó 3 kg de concentrado/vaca/día desde el parto hasta los 60 días post parto. Se colectó muestras de sangre dos veces por semana desde la semana 3 a la 12 postparto para determinar niveles de progesterona como indicador de reinicio de la actividad ovárica postparto. Se encontró un intervalo parto – primera ovulación de 70.6, 56.4 y 57.8 días para las vacas que ovularon dentro de las primeras 12 semanas postparto en los grupos T1, T2 y T3, respectivamente. El 31.3, 73.3 y...

El uso de modelos matemáticos para describir curvas de lactación suministra valiosa información para la toma de decisiones en sistemas de producción de leche. En este estudio se evaluó comparativamente el ajuste de los modelos exponencial negativo (í = â0e-â1x), gamma incompleto (í = â0xâ1e-â2x) y polinomial quinto (í = (â0 + â1x + ... +â5x5) entre y dentro de lactaciones, y se estimó el efecto del número de lactaciones, estación de parto y fenómeno El Niño 1998 (FEN) sobre parámetros básicos y derivados de los modelos. Se usaron 8,763 registros de producción correspondientes a 770 lactaciones, provenientes de 5 establos de Lima, entre los años 1997-2001. La bondad comparativa de ajuste de los modelos se evaluó en base al coeficiente de determinación múltiple ajustado (Rd,al error estándar residual (EER),al error de predicción de la producción en el día 30...

Se utilizaron 65 borregas Corriedale de 3 y 4 años de edad en los meses de abril a agosto del 2002 para evaluar el efecto de la administración de PGF2µ en los días 4 y 10 del ciclo estrual sobre (i) la incidencia del celo, (ii) la variabilidad entre animales en la presentación del celo, (iii) el intervalo tratamiento-celo y (iv) la tasa de preñez postservicio. El ciclo estrual fue sincronizado previamente con la inserción intravaginal por 12 días de esponjas impregnadas con 30 mg de acetato de fluorogestona (FGA). Luego del celo postsincronización (celo = día 0) se administró 0.175 mg de un análogo de PGF2? a 20 animales en el día 4 del ciclo estrual (GP4) y a 22 animales en el día 10 (GP10), en tanto que 23 animales quedaron sin tratamiento como grupo control (GC) para fines comparativos. Se detectó el celo con carneros vasectomizados a las 6, 12 y 17 h de cada día. El 1...

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The aim of this study was to determine the presence of leptin in adults alpacas, in order to quantify leptin values for these animals, and to relate them with body condition. For this purpose, 36 non pregnant and non nursing female adult alpacas were used. They were divided in two groups according to body condition (BC): G1: BC <3.0 and G2: BC>3.0, using the 1 to 5 scale (1: emaciate, 5: obese). Blood samples by jugular venipunction to obtain serum were taken. Serum samples were maintained at -20 ºC until analysis. The leptin determination was carried out by the radioimmunoassay technique (RIA). The mean of leptin concentration was 17.23 ± 0.81 ng/ml. Values for G1 were 18.14 ± 1.12 ng/ ml and for G2. were 16.32 ± 1.15 ng/ml, without statistical differences between groups. The results showed that the leptin hormone is also present in alpacas.

The effect of vital area on productive and reproductive performance was evaluated in 2,325 guinea pigs at IVITA El Mantaro Research Station (300 growing male and female guinea pigs, 750 fattening male and female guinea pigs and 200 female and 25 first mating male guinea pigs). The study was divided in seven assays. Five different vital areas and five different number of animals per well were evaluated in each assay. A total of 25 wells were used for each assay. Different variables (body weight gain, alfalfa intake, feeding convertion index, number of scars due to fights, litter size, mortality and profit/cost index) associated to each productive phase were analyzed. Larger vital areas in assays that involved growing and fattening males resulted in greater body weight gain, lower alfalfa intake, lower feeding convertion index and lower number of scars due to fights. All of these variables...

The study evaluated the effect of four types of drinkers and the addition of Vitamin C in the supplement on the productive performance and economic benefit of guinea pig (Cavia porcellus) reared during the dry season in the Mantaro valley, Junin, Peru. Four hundred weaned males, 14 ± 3 days of age from the experimental farm of the IVITA Research Centre were used in a completely randomized design with 2 x 4 arrangement factorial (with and without addition of vitamin C and four types of drinkers) using five experimental units for treatment and every experimental unit formed by 10 animals. The drinkers were the type of a bowl (POC), continuous recharge (REC), suction (SUC) and nipple (NIP). The quantity of vitamin C supplied was 12 mg/animal/day. REC and NIP drinkers allowed a major consumption of water than POC and SUC (p<0.05), but REC had a greater waste of water. A similar trend was...

The study evaluated the effect of various types of forage feeders on the efficiency offorage usage and on the productive and economic response of guinea pig (Caviaporcellus) breeding. A total of 250 weaned male of 15 days of age at the Mantaro valley,Junín, Peru were used in a completely randomized design with five treatments of foragesupply and five repetitions per treatment. Each repetition corresponded to a cage withten guinea pigs. Four forage feeders were evaluated: cylindrical mesh on the floor (CMP),hanging U shaped mesh (MCU), iron grilled with foot on the floor (PFP) and hopper meshin V shaped (TMV), plus the traditional method with the forage directly on the floor(DSP). The use of feeders improved forage consumption efficiency, total food consumptionand benefit cost ratio (p<0.05). MCU was the most promising feeder in terms of forageconsumption efficiency, body weight gain,...

The effect of glucose, fructose, trehalose, and sucrose, as components of the extender, was evaluated on canine sperm viability during refrigeration at 5 ºC. The spermatic fraction of 16 dog ejaculations were distributed in 5 aliquots containing an extender based on Tris – citric acid – egg yolk, but differing in the presence of one of the sugars, plus a control without sugar. The five treatments were evaluated after 24, 48, 72, and 96 hours of refrigeration in relation to progressive motility and functional integrity of the membrane by the hypoosmotic swelling test (HOS). All groups, with the exception of the control group, the sperm motility maintained within acceptable ranges during the study (90% on day 0 and 60% on day 4). The integrity of the membrane remained slightly superior in groups with sugar (87-90%) in comparison with the control group (83-85%). The glucose and sucrose...

Se evaluó el efecto la glucosa, fructosa, trehalosa y sacarosa, como componentes del diluyente, sobre la viabilidad espermática en semen canino refrigerado a 5 °C. La fracción espermática de 16 eyaculados de perro fue distribuida en cinco alícuotas conteniendo un diluyente a base de Tris - ácido cítrico - yema de huevo, pero con un azúcar distinto, además del control sin azúcar. Los cinco tratamientos se evaluaron a las 24, 48, 72 y 96 horas de refrigeración en base a motilidad progresiva e integridad funcional de membrana mediante la prueba hipoosmótica (HOS). En todos los grupos, a excepción del grupo control, la motilidad espermática se mantuvo dentro de rangos aceptables durante el estudio (90% en el día 0 hasta cerca de 60% en el día 4). Sin embargo, la integridad de membrana se mantuvo ligeramente superior en los grupos con azúcar (87-90%) en comparación con el g...

El presente estudio tuvo como objetivo determinar la presencia de la hormona leptina en alpacas adultas, cuantificar sus valores y relacionarlos con la condición corporal. Se utilizaron 36 alpacas hembras adultas, vacías y sin cría, las cuales fueron divididas en dos grupos, según su condición corporal (CC): G1: CC <3.0 y G2: CC >3.0, de acuerdo a una escala 1 - 5 (1: emaciada, 5: obesa). Se tomaron muestras de sangre por punción de la vena yugular y el suero resultante fue mantenido en congelación a –20 ºC hasta su análisis. La determinación de leptina fue realizada mediante la técnica de radioinmunoensayo (RIA). La media general de la concentración de leptina fue de 17.23 ± 0.81 ng/ml. Los valores encontrados para G1 fueron de 18.14 ± 1.12 ng/ml y para G2: 16.32 ± 1.15 ng/ml, sin diferencias estadísticas entre grupos. Los resultados obtenidos permiten evidenciar...

El efecto del espacio vital sobre los parámetros productivos y reproductivos fue evaluado en 2,325 cuyes de la Estación IVITA El Mantaro (300 machos y hembras de recría, 750 machos y hembras de engorde y 200 hembras y 25 machos de primer empadre). El estudio se dividió en siete ensayos evaluando en cada uno de ellos cinco diferentes espacios vitales con cinco diferentes cantidades de animales por poza, totalizando 25 pozas para cada ensayo. Se analizaron variables asociadas a cada etapa productiva (ganancia de peso, consumo de alfalfa, índice de conversión alimenticia, número de cicatrices debido a peleas, tamaño de camada, mortalidad y la relación beneficio/costo). En los ensayos de recría y engorde de machos los mayores espacios vitales permitieron obtener mayores ganancias de peso, menor consumo de alfalfa, menor índice de conversión alimenticia y menor número de cicatric...

The study evaluated the effect of four types of drinkers and the addition of Vitamin C in the supplement on the productive performance and economic benefit of guinea pig (Cavia porcellus) reared during the dry season in the Mantaro valley, Junin, Peru. Four hundred weaned males, 14 ± 3 days of age from the experimental farm of the IVITA Research Centre were used in a completely randomized design with 2 x 4 arrangement factorial (with and without addition of vitamin C and four types of drinkers) using five experimental units for treatment and every experimental unit formed by 10 animals. The drinkers were the type of a bowl (POC), continuous recharge (REC), suction (SUC) and nipple (NIP). The quantity of vitamin C supplied was 12 mg/animal/day. REC and NIP drinkers allowed a major consumption of water than POC and SUC (p<0.05), but REC had a greater waste of water. A similar trend was...