Papers by Alejandro Jiménez Jiménez
Se determinó el efecto de la suplementación sobre la actividad ovárica y tasa de gestación en nov... more Se determinó el efecto de la suplementación sobre la actividad ovárica y tasa de gestación en novillas Bosindicus (n=41) nulíparas de dos a tres años, divididas aleatoriamente en dos grupos: el suplementado (GS n=21) con un concentrado comercial (13,5% PC, 2,850 Mcal ED/kg MS) a razón del 1% del peso; con un periodo de 15 días de adaptación más 30 de suplementación y el testigo (GNS n=20). Ambos pastando Estrella Africana (Cynodonplestostachium), Ratana (Ischaemumindicum) y Tanzania (Panicummaximum); agua y sales minerales ad libitum). Las hembras se sincronizaron con Crestar® y servidas con dos toros de fertilidad probada. El diseño experimental fue al azar utilizando el programa estadístico JMP 10® de SAS Institute Inc. para el análisis. La condición corporal (CC) y grasa dorsal (GD) no son diferentes (P>0.05) así como los porcentajes entre grupos para actividad ovárica (ciclicidad y estructuras ováricas), tasa de preñez, los eventos de ciclicidad y gestación a lo largo del tiempo (P>0.05). La estimación de ocurrencia de la gestación en función del suplemento y la ciclicidad, según el modelo: Gest = f(GEST, CYC, TRAT) no mostró efecto del tratamiento (P>0.05) pero si significancia en los momentos de detección de la gestación (día 33 y día 45 respectivamente) entre grupos (P< 0.0001). En conclusión, el método de suplementación ensayado no tuvo mayor efecto sobre las variables estudiadas.
To compare the fertility results and to assess the cost-effectiveness of several synchronization ... more To compare the fertility results and to assess the cost-effectiveness of several synchronization protocols applied under the conditions of beef cattle enterprises in Colombia, 1658 multiparous zebu crossbred cows mostly Brahman and Nelore ranging between 2-6 parities were used. Five protocols of pharmacological treatments varying in hormones used, dosage and the time of application were tested. All cows were inseminated at 52 h by appointment. Pregnancy diagnosis was undertaken over 45 d after insemination by rectal palpation. The total cost per cow and the total cost per gestation, for each protocol, were calculated. Taking a herd of one-hundred cows as baseline for calculations, it was estimated the cost of the total amount of pregnancies possibly obtained in each protocol; then, the excess between the costs of a pregnant cow and the cost of a treated cow was estimated. Additionally, the costs due to cows empty after four services were calculated. A total of 874 pregnancies were registered (52.7%), with pregnancies per protocol varying between 46.9% and 66.2% (p < 005). The cost per treated cow, varied between $64.08 and $97.47 and the cost per gestation from $126.01 to $177.26, without association between the cost of the treatment and the pregnancy rate. Protocol A was the best cost-effective with the lowest additional costs, the lowest amount of open days (2107.7 to 2231.7 d) and IA straws (average = 134), with an additional costs of $6940.00. Synchronization of estrus using pharmacological products seems to have a place in the management of cattle; however, caution should be called upon a careful assessment both from the part of the farm and the professional in charge of the enterprise to avoid using the technique indis-criminatively thus propitiating the use of a method that might not be cost efficient.
The intensity and duration of sexual behavior in Bos indicus was assessed through the continuous ... more The intensity and duration of sexual behavior in Bos indicus was assessed through the continuous observation of sexual receptivity. Two groups of cows were formed: only synchronized (n = 50) and other group further superovulated (n = 20). An intravaginal implant that released progesterone over 9 d was used. After removing the implant, 25 mg of PGF2α was administered. In the superovulated group, the administration of 280 mg (Follicle stimulant hormone) FSH-P1 per cow with a decreasing dosage over 4 d was utilized. In both groups, behavioral observations began at the moment of implant removal. Sexual behavior was analyzed using a Kruskal-Wallis test to compare the mean of hours in estrus, effective mountings and number of mounts/hour during estrus. A nonparametric survival analysis was performed using the time in two ways: i) when an event happened it was placed in a 24 h time- frame and, ii) the time of observation in continuous form (96 h) assessing the difference between curves by the log rank test Chi-square. The only significant difference was the number of mounts/h during receptivity (p<0.05). In the superovulated group three periods of sexual activity during the day were identified, with these events being of greater frequency and duration than the synchronized group (p = 0.02); besides, the superovulated group began estrus before the synchronized group (p = 0.0035) when using the total period. In a simulation study, when the number of observations went from two (06:00-18:00) to three periods (06:00, 12:00 and 18:00) cows detected accurately (<6 h after the onset) increased more than 20%. The results show that superovulated cows presented greater intensity and duration of sexual activity in contrast with only synchronized animals. (Key Words : Sexual Behavior, Bos indicus, Superovulation, Synchronization, Estrus)
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Papers by Alejandro Jiménez Jiménez