Abstract The effect of climatic factors on ovarian activity and reproductive behavior (RB) was evaluated in 46 Bos indicus cows kept under grazing conditions. Temperature-humidity index (THI) was used as an indicator of stress and divided in alert, damage and emergency levels. Fat thickness (FAT) was taken during the last trimester of gestation (LTG) to approximately 90d postpartum (PP). At 30d PP animals received a progesterone (P4)-releasing device (CIDR) which was withdrawn 9d later. Ovarian activity was assessed by blood progesterone on days 21, 24, 27, 30, 49, 51, and 54 PP. Animals were divided into three groups, higher, and moderate RB and non-behavior. Sixty percent presented a THI >74 increasing dramatically from June to September up to >78. During LTG, animals lost 27% of their body reserves contrasting to PP where an increase of 2.6% (P=0.002) was observed. The percentages of cyclic and non-cyclic animals were 57 and 43%, respectively (P> 0.05). Seventy-two percent displayed RB and 28% were non-behavior (P<0.05). A negative correlation (r = -0.307; P = 0.038) between THI and RB, and a positive correlation (r = 0.427; P = 0.003) between the onset of ovarian activity and RB were observed. Differences in THI during the LTG (P<0.01) were observed between cyclic and non-cyclic animals. Non-behavior cows in the LTG had a higher THI (P <0.05). High levels of THI have a negative effect on the resumption of ovarian activity and RB in Bos indicus especially if high THI occurs during the last trimester of gestation.

El objetivo del presente estudio fue evaluar la fertilidad obtenida en un hato, según dos tiempos de Inseminación Artificial (IA) a tiempo fijo: 48 y 72 horas, posterior a un programa de sincronización de celos, tomando en cuenta las manifestaciones y la intensidad del estro. Se utilizaron 114 hembras Bos indicus, sincronizadas con 2mg de benzoato de estradiol más un implante intravaginal de progesterona (CIDR), que permaneció in situ por 9 días. Al retiro del CIDR, los animales fueron divididos en 2 grupos: 61 y 53 hembras, que fueron inseminadas 48 horas y 72 horas postratamiento, respectivamente. Todas fueron observadas continuamente durante 90 horas, con el fin de detectar el comportamiento sexual y clasificarlas, de acuerdo a la intensidad del celo, en dos categorías: alta y baja. Se utilizó la prueba de Ji-cuadrado para la comparación de proporciones. El porcentaje de hembras con manifestación estral fue de 68,4%, sin diferencia entre las categorías alta y baja intensidad (37,7 y 30,7%, respectivamente). El 85,4% de los animales con signos de estro ovuló, diferente de las hembras sin manifestación estral, con 63,8% (P<0,05). El porcentaje global de preñez fue 25,4%; el 86,2% de estas gestaciones corresponde al grupo de hembras que manifestaron conducta estral. De acuerdo al momento de IA y la intensidad del estro, los porcentajes de gestaciones para IA a 48 horas fueron 1) alta: 91,6%, 2) baja: 84,6% (P<0,05) y 3) sin celo: 25%, por su parte, en las hembras inseminadas a las 72 horas los porcentajes fueron: 1) alta: 8,4%, 2) baja: 15,4% y 3) sin celo: 75% (P<0,05). Se concluye que las hembras con expresión estral tienen mayor oportunidad de preñarse tras la IA a 48 horas postratamiento hormonal, mientras que en los animales sin manifestación de estros, los mayores porcentajes de gestaciones son a las 72 horas.

The aim of this study was to evaluate the fertility obtained in a herd, according to two times of fixed time AI: 48 and 72 hours, following an estrus synchronization program, taking into consideration the manifestations and the intensity of estrus. One hundred and fourteen Bos indicus females were used; synchronized with 2mg of estradiol benzoate and a progesterone-releasing intravaginal device (PRID), which remained in situ for 9 days. After the removal of the PRID, the animals were divided into two groups: 61 and 53 females that were inseminated, respectively, 48 and 72 hours posttreatment. All were continuously observed for 90 hours, with the objective of detecting sexual behavior and classifying them according to heat intensity into two categories: high and low. Chi-square test was used for the comparison of proportions. The percentage of females with estrus manifestation was 68.4%, without difference between high and low intensity categories (37.7 and 30.7%, respectively). Of the animals with signs of estrus, 85.4% ovulated; different from the females without estrus manifestation, with 63.8% (P<0.05). Global pregnancy rate was 25.4%; 86.2% of these gestations correspond to the group of females that manifested estral behavior. According to the moment of AI and the intensity of the estrus, the percentages of pregnancy for AI at 48 hours were 1) high: 91.6%, 2) low: 84.6% (P<0.05) and 3) without estrus: 25%, on the other hand, in females inseminated at 72 hours, the percentages were: 1) high: 8.4%, 2) low: 15.4% and 3) without estrus: 75% (P<0.05). It is concluded that females with estral manifestation are more likely to get pregnant after AI at 48 hours following hormonal treatment, while for animals without estral manifestation, the higher pregnancy percentages are at 72 hours.

El objetivo del presente estudio fue evaluar el modelo NRC (1996) nivel I para la predicción de la ganancia diaria de peso en novillas suplementadas bajo condiciones tropicales. Para tal fin, se realizaron dos experimentos. En el experimento 1 se evaluaron 30 novillas divididas en dos grupos de 15 animales cada uno, el grupo suplementado (GS) presentó un peso inicial de 365,27 ± 24,40 kg, recibió concentrado a razón de 1% del peso vivo (5,5% PC, 2,85 Mcal ED) y el no suplementado (GNS) con un peso inicial de 367,47 ± 31,65 kg. En el experimento 2 se utilizaron 45 novillas divididas en dos grupos, el GSb con 22 animales, teniendo un peso inicial de 342,23 ± 36,04 kg se les proporcionó alimento a razón del 1% del peso vivo (13% PC; 3,15 Mcal ED) y el GNSb se constituyó por 23 animales teniendo un peso inicial promedio de 326,30 ± 31,53 kg. En ambos experimentos los animales fueron suplementados a lo largo de 45 días, y estuvieron pastoreando praderas de Estrella Africana (Cynodon nlemfuensis), Candelario (Pennisteum purpureum) y Ratana (Ischaemum indicum). En ambos experimentos no se observaron diferencias (P > 0,05) para los cambios de peso. El GS obtuvo ganancias diarias de peso (GDP) de 0,27 kg/d, mientras que el GNS mostró pérdidas de -0,05 kg/d; en el experimento 2 el GSb presentó GDP de 0,90 kg/d y el GNSb de 0,60 kg/d. La GDP predicha en el experimento 1 fue similar a la ganancia observada para el grupo suplementado (P > 0,05) en contraste con la presentada en el grupo no suplementado en el que la ganancia de peso fue sobrestimada (P < 0,05). En el segundo experimento, la predicción de la GDP tanto para el grupo suplementado como el no suplementado fue subestimada (P < 0,05). El nivel 1 del modelo de simulación NRC no fue apropiado para la predicción de los cambios de peso en novillas bajo condiciones tropicales

The aim of this study was to evaluate the model NRC level 1 to predict the daily weight gain in heifers supplemented under tropical conditions. For this purpose, two experiments were done, in the first experiment 30 heifers were divided into two groups of fifteen animals each, the supplemented group (GS) showed an initial weight of 365.27 ± 24.40 kg, received commercial concentrate to the ratio of 1% of live weight (5.5% PC 2.85 Mcal ED) and the control group which was not supplemented (GNS) with an initial weight of 367.47 ± 31.65 kg. In the second study 45 heifers were divided in two groups, the GSb with 22 animals having an initial weight of 342.23 ± 36.4 kg and given concentrate to the rate of 1% of live weight (13% PC 3.5 Mcal ED) and the GNSb were made up of 23 animals having an initial average weight of 326.0 ± 31.3 kg. In both trials the animals were supplemented throughout for forty-five days and let them grazed on African Star grass (Cynodon nlemfuensis), Candelario grass (Pennisteum purpureum) and Ratana grass (Ischaemum indicum). In both experiments no differences were observed (P > 0.05) in weight change .The GS had daily weight gains (GDP) of 0.27 kg/d while the GNS showed losses of -0.05 kg/d. In the second trial the GSb showed a GDP of 0.90 kg/d and the GNSb of 0.60 kg/d. The predicted GDP of the first experiment was similar in comparison with the observed value for the supplemented group (P > 0.05), in contrast with that presented in the GNS group in which the daily weight gain was over estimated (P < 0.05). In the second trial the GDP predicted for both groups was under estimated (P < 0.05). The level 1 of the NRC simulation model does not seem to be appropriate for predicting changes in weight in heifers under tropical conditions

Foi administrada dexametasona para indução de degeneração testicular experimental em touros de uma raça taurina pura (Aberdeen Angus) e de sua sintética derivada (Brangus-Ibagé). O objetivo deste estudo foi o de averiguar a diferença de sensibilidade na função gametogênica em frente à degeneração experimental. Para tal, foram avaliados os aspectos físicos e morfológicos do sêmen. Os dados obtidos foram analisados considerando o dia de coleta e genótipo. Os resultados revelaram que os dois grupos raciais comportaram-se semelhantemente ao longo das coletas. A despeito do número de animais empregados, o uso da degeneração testicular experimental possibilitou evidenciar que não há diferença entre as duas raças quanto à intensidade da degeneração e tempo necessário para o restabelecimento do quadro espermático normal.

Testicular degeneration was induced by dexamethasone injection in bulls from a European breed Aberdeen Angus and a derived synthetic crossbreed (Brangus-Ibagé). Aiming to investigate differential sensibility on gametogenic function in these genotypes, physical and morphological semen characteristics were evaluated. The data analysed considered the day of the semen samples and the breed. Our results reveal that both breeds behave similarly during the experimental period. Even considering the number of bulls used in this experiment, the employed methodology gives no evidence of any difference between breeds, intensity of degeneration or time required to the reestablishment of normal sperm frequencies after experimental induction of testicular degeneration.