Producción de semen de toros en Colombia durante los años de 1953 a 1956

Sección de inseminación Artificial. — Centro Nacional de Investigaciones Agropecuarias, Tibaitatá.

 Muchos estudios se han hecho sobre la producción de semen en toros nacidos o aclimatados en países estacionales, pero pocos o ninguno han informado sobre los efectos en la producción de semen en animales importados y aclimatados a 2.550 metros de altura en países sin estaciones definidas en el trópico.

RESUMEN

Durante los cuatro años de 1953 a 1956, se recolectaron un total de 4.945 eyaculados de 19 toros, de cuatro razas de leche y dos de carne.

El mayor número de eyaculados se recolectó de toros - Holstein (2.250), que

corresponde más o menos al 50 por ciento del total de eyaculados. Se hicieron 1.515 recolecciones en toros Pardo Suizos. Estas dos razas dieron aproximadamente el 80 por ciento de todos los eyaculados.

En las seis razas se encontró un volumen promedio de producción de semen de 5.4 centímetros cúbicos. En razas de leche el promedio fue de 5.6, con variaciones de 4.3 a 6.8 centímetros cúbicos y en razas de carne varió de 4.0 a 6.2 en promedio. El menor volumen promedio lo produjo el toro Angus Rojo (4.0), y el más alto (6.8), toros Normandos.

El volumen promedio de semen tendió a aumentar con la edad. Los toros mas viejos con peso corporal mayor, produjeron un mayor volumen que los toros jóvenes y de poco desarrollo.

Hubo un aumento en el número de eyaculados desde abril, que fue bajo hasta septiembre, y una disminución desde septiembre, que fue alto hasta abril. Igual mente, hubo aumento en el volumen promedio, de mayo hasta agosto; ligera disminución de agosto a septiembre y volumen casi constante desde septiembre a mayo.

El mayor volumen promedio por eyaculado correspondió a épocas de lluvia y de sequía en Colombia, que corresponden a los meses de primavera y verano de los países estacionales de clima suave.

El volumen promedio más alto se obtuvo durante los meses de más alta temperatura diaria, mayor luminosidad y baja humedad.

SUMMARY

This study was conducted in the National Agricultural Research Center of Tibaitata located in the Sabana of Bogota at an altitude of 2.550 meters above sea level. Tibaitata is situated geographically between 4 o 42” north latitude and meridian 74. Due to its location in the tropics, true seasonal influences are not felt; however, two wet periods called winters and two dry periods called summers are normally obtained each year. The temperature fluctuates between 4 and 20 degrees centigrades, with an average of 14 degrees.

During the four years of 1953 through 1956, a total of 4.945 ejaculates were collected from nineteen bulls of four dairy and two beef breeds. Only quantitative data of the semen samples are presented in this paper.

The greatest number of semen samples were collected from the seven Holstein bulls (2.250). This corresponded to almost 50 per cent of the total number of collections studied. A total of 1.515 collections were made from the Brown Swiss bulls. These two breeds accounted for almost 80 per cent of all the collections made. The number of collections made from bulls of the Red Polled and Normando breeds were low when compared with the number of collections made from the Holstein and Brown Swiss bulls.

A total of 172 ejaculates were collected from the Santa Gertrudis bull, and 290 ejaculates were collected from the Red Angus bull. The total number of ejaculates collected from the bulls of these two beef beeds was equal to or greater than the number collected from the bulls of the Red Polled breed, but greatly inferior to the number collected from any of the other three dairy breeds.

Average semen volumen per ejaculate was found to be 5.4 cubic centimeter from bulls of all breeds, while average semen volumen for bulls of the dairy breeds was 5.6 and ranged from 4.3 to 6.8 cubic centimeters. Average volume in bulls of the beef breeds ranged from 4.0 to 6.2 cubic centimeters.

Lowest volumen per ejaculate was produced by the Red Angus bull (4.0), slighthy inferior to the Red Polled bulls (4.3), while the highest average volume per ejaculate (6.8) was produced by the Normando bulls.

Average semen volumen per ejaculate tended to increase progressively with an increase in age up to maturity, and sperm concentration tended to decrease with an increase in age after naturity. In general, older mature bulls of a heavier body weight, produced a largcr ejaculate volume than younger.

Dilution rates ranged from 7.2 to 13.2 and the average dilution rate was 10.4 during the four years of this study. Dilution rate was low, sperm concentraron per cubic centimcter of diluted semen was high. In all cases, more than 12 million spermatozoa were contained peri cubic centimeter of diluted semen.

In an attempt to correlate the number of ejaculates collected and average volume per ejaculate with season of the year, it was found that there are essentially two distinct periods of semen production. There was a gradual increase in the number of ejaculates collected from the low of April to the high of September, and a gradual decrease from the high of September to the low of April. There was also found to be a gradual increase in average volumen per ejaculate from May to August, a sharp decline from August to September, and an almost con stant volumen from September to May, following almost the same seasonal pattern as for the total number of ejaculates collected.

A direct relationship was found to exist between the number of ejaculates collected, average volumen per ejaculate and season of the year. The period of the highest average volumen per ejaculate corresponds to a wet followed by a dry season in Colombia, and in Countries with definite seasons and temperate climates to the Spring and summer months.

It would appear that the highest average volumen per ejaculates are produced during the months with the highest daily temperatures, lowest humidity, and most number of'hours of sunlight.