ABSTRACT
The aim of this research was to compare two artificial insemination protocols (AIP): hormonal synchronization with fixed time artificial insemination (SC-FTAI) and the use of a table based on visual observation of estrus signs (VO) in order to identify cows in natural or spontaneous estrus being assigned to AI (NSE-IA). Two groups were formed: in the first group 109 cows were assigned to SC-FTAI, in which a commercial protocol is used; the second one included 108 randomly chosen cows, which were assigned to NSE-AI and in this group a modified table was used. Response variable was first service fertility rate (FSF), which was coded 1 for pregnant and 0 for empty. Predictor variables were AIP, postpartum anestrus, daily milk yield, body condition score at AI and calving number. Statistical analyses included association chi-square tests and logistic regression. Results showed an overall 41.94% FSF and a significant association was detected (P < 0.05) between FSF and daily milk yield; pregnancy rates were 42.20% and 41.67% for the SC-FTAI and NSE-IA groups, respectively (P > 0.05). The odds ratio for the effect of AIP was only 1.050, suggesting no differences in FSF between groups. The NSE-AI protocol can enhance both the technique of VO and reproductive efficiency. Further validation of the table is required.
ABSTRACT
En la ganadería mestiza de doble propósito (DP), las relaciones entre factores asociados al primer celo posparto (PCP), la fertilidad y los días vacíos han sido poco estudiados. En una finca ubicada en una zona de bosque húmedo tropical de la cuenca del Lago de Maracaibo, estado Zulia, Venezuela, se estudió un rebaño de 300 vacas mestizas Brahmán Rojo, GIR (Bos indicus) y Holstein Rojo (Bos taurus), ordeñadas manualmente dos veces al día en dos grupos posparto, <100dpp y >100 dpp, (GPP) con apoyo del becerro, pastoreando en potreros de pasto Alemán (Echinocloa polyistachia) y otras gramíneas. Estaban acompañadas de toros receladores en una proporción 25:1, observadas cuatro veces al día en corrales y potreros. Mediante la prueba de Ji- cuadrado se estudió la relación de la fertilidad (FER) con las variables: color de la mucosa de la vulva (CMV), tipo de moco cervical (TMC ) al celo, volumen celular aglomerado (VCA), el tipo de monta (TMON), el lugar de detección (LUGCE) del celo y el GPP. Mediante un análisis de varianza-covarianza, se estudió el efecto de tales variables sobre los días vacíos (DV), considerándose como covariables el número de partos (NP), su condición corporal (CC) y producción de leche/día (PLD) al PCP. Los resultados muestran que 30 por ciento de los celos fueron detectados en los potreros, un VCA >28 por ciento se relacionó significativamente (P<0,05) la fertilidad con un 67 por ciento de preñez, El CMV y TMC mostraron ventaja favorable a la mayor fertilidad con las vacas con mucosa roja y moco transparente y fluido. La media de los DV fue de 127 ± 44 d, con favorable tendencia (P<0,08) para moco transparente y fluido. La observación del celo en potreros y el registro de los factores asociados pueden mejorar la fertilidad.
In crossbreed dual purpose cattle (DPC), the relationship between the factors associated with the first postpartum estrus (FPE), fertility and open days has rarely been studied. For this purpose, on a farm located in the humid tropical forest in the Lake Maracaibo basin Zulia State, Venezuela, a group of 300 crossbred cows was studied: Red Brahman, Gyr (Bos indicus) and Red Holstein (Bos taurus). These cows were manually milked twice a day in two groups, <100ppd and >100ppd (PPG), with calf support; they grazed on fields of German grass (Echinocloa polystachia) and other grasses. In order the estrus detection, the cows were accompanied by teaser bulls in a 25:1 ratio and watched four times a day at cement pens and pasture area. Using the chi-square test, variables such as vulva mucus color (VMC), the type of cervical mucus (TCM), the value of packed cell volume (PCV), the type of mount (TMOU), the place of detection (PLADET) of the estrus and the PPG and their relation with the fertility were studied. Using a variance-covariance analysis, it was studied the effect of these variables on the open days (OD). The parity (P), body condition (BC)and daily milk production (DMP) at the FPE was considered as co variables. The results show a 30% of estrus detected at the pasture area, the PCV >28% had a significant relationship (P<0.05) with fertility, with pregnancy at 67%; the VMC and TCM showed a favorable advantage for cows with red mucus and transparent and flowing mucus. The OD were 127 ± 44 d, with favorable tendency (P<0.08) for fluid and transparent mucus. The observation of estrus at the pasture area and the register of associated factors can improve fertility.
