Reproductive seasonality in creole hair sheep in the tropic

Abstract

The objective of the present study was to evaluate the annual ovulatory activity of hair sheep at 15° N. Nineteen Creole ewes with body weight of 40.8 ± 0.3 kg were used. The ovulatory activity was monitored for a year by quantifying progesterone concentrations in blood samples obtained from all the ewes every 7 days. The differences in monthly proportions of ewes with ovulatory activity were analyzed by the chi-square test. Ovulatory activity decreased from May to July and in September, and 42% of ewes ovulated year round. It is concluded that at 15° N, a high proportion of ewes is capable of ovulating throughout the year in the tropical southeastern region of Mexico.

Genes con efecto mayor sobre la fertilidad de ovejas. Revisión

“…In Mexico, Arroyo (77) has extensively documented the absence or low seasonality of hair ewes, mainly Pelibuey, characteristic surely to be associated with genetic factors, but so far they have not been studied at molecular level, to confirm if the involved genes and their frequencies correspond to the ones found by other authors (78,79) and other latitudes (80) . valina), donde las cabras con genotipo FG tuvieron 0.76 más cabritos, comparada con las FF, lo cual sugiere que el gene PRLR también tiene un efecto mayor sobre la prolificidad en cabras (72) .…”

“…The Merino breed and its predecessors (Rambouillet and Dorset) show a relative long seasonal period (76) and respond particularly to the introduction of the ram (male effect) for stimulating ovulation and oestrus (77) . The European prolific breeds, such as Finish Landrace and Romanov show lesser seasonality with good behaviour in summer, in comparison with British breeds, such as Down, which show short breeding season and less response to male effect (75) .…”

“…En la raza Merino y sus antecesores (Rambouillet y Dorset) muestran una relativa estacionalidad larga (76) y responden particularmente a la introducción del carnero (efecto macho) para estimular la ovulación y el estro (77) . Razas europeas prolíficas tales como la Finish Landrace y Romanov muestran menor estacionalidad con buen comportamiento en verano, en contraste con razas Británicas como la Down, que muestran época corta de empadre y menor respuesta al efecto macho (75) .…”

“…En México, Arroyo (77) ha documentado extensamente la ausencia o baja estacionalidad de las ovejas de pelo principalmente Pelibuey, característica que seguramente está asociada a factores genéticos, pero que hasta el momento no se han estudiado a nivel molecular, para confirmar si los genes involucrados y sus frecuencias corresponden a las encontradas por otros autores (78,79) y en otras latitudes (80) .…”

Effects of summer heat stress on physiological variables, ovulation and progesterone secretion in Pelibuey ewes under natural outdoor conditions in an arid region

“…Pelibuey sheep is a tropical hair breed widely distributed in Mexico, Central America and the Caribbean. Consequently, its reproductive activity has been extensively characterized under tropical and subtropical environmental conditions (Arroyo 2011). However, nowadays Pelibuey sheep are also distributed in arid and semiarid regions due to their rusticity and high adaptability to environmental conditions of heat stress (HS) (Macías-Cruz et al 2010), but available information on their reproductive and productive ability under these natural environmental conditions is scarce.…”