Monthly variation of fertility and oestrus frequency in crossbred dual-purpose cows in three agroecological areas of the South American tropics |
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Authors: | F Perea G E Soto B H Hernández F D González V R Palomares N A De Ondiz S C González S |
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Institution: | (1) Departamento de Ciencias Agrarias, Universidad de los Andes, Trujillo, Venezuela;(2) Facultad de Ciencias Veterinarias y Facultad de Agronomía, Universidad del Zulia, Maracaibo, Venezuela;(3) Miembros del Grupo de Investigadores de la Reproducción Animal en la Región Zuliana (GIRARZ), Venezuela |
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Abstract: | The aim of this study was to examine the monthly variation of the first service conception (FSC) and oestrus frequency (OF)
from 8308 artificial inseminations (AI) of 2960 crossbred dual-purpose cows on three commercial farms with improved management
located in the Maracaibo Lake Basin, Venezuela. The effects of month of the year, agroecological area (from dry tropical forest
to sub-humid tropical forest on the three farms), predominant breed (BT, Bos taurus; BI, Bos indicus), and season (December–April}; May–August; and September–November) were considered. Data were analysed using logistic regression
(FSC) and GLM (OF) from SAS. The mean FSC was 55.4% overall and 48.7%, 57.0% and 58.3% for farms A, B and C, respectively
(p < 0.01). Within the three agroecological areas (farms A, B and C), the FSC was highest during the cooler and drier months
of the year (season 1), while the lowest FSC was obtained during the months of highest rainfall and humidity (season 3) (53.3%
vs 37.4%; 58.5% vs 49.0% and 63.0% vs 52.3% on farms A, B, C, respectively; p < 0.01). In the three studied farms, OF was
higher during the first 4 months of the year; with a diminishing trend towards the end of the year (p % 0.05). In general,
BI cows had a higher FSC than BT cows, especially during the second half of the year, when environmental conditions were characterized
by higher rainfall and humidity with lower wind velocity (58.8%a 55.5%b and 46.4%c in season 1, 2 and 3 respectively; a, b, c p < 0.01). |
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Keywords: | First service conception Oestrus frequency Crossbred cows Postpartum Tropic |
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