Calves' sex ratio in naturally and artificially bred cattle in central Ethiopia

Effects of Developmental Programming Caused by Maternal Nutrient Intake on Postnatal Performance of Beef Heifers and Their Calves

In this study, we evaluated the effects of maternal subnutrition in early pregnancy on the growth and reproductive performance of female offspring during their rearing, first gestation, and lactation. We inseminated 21 Parda and 15 Pirenaica multiparous cows and assigned them to a CONTROL (100% of nutrition requirements) or SUBNUT (65%) diet until day 82 of gestation. Cows were fed 100% requirements afterward. During the rearing of female offspring, growth, physiological profiles and ovarian follicular dynamic were studied. At 16 months old, heifers were inseminated. After first calving, dam-calf weights were recorded during lactation. Heifers born from CONTROL cows were heavier at weaning (four months old) than heifers born from SUBNUT cows, but this difference disappeared at the end of rearing and during the first gestation and lactation periods. All heifers reached puberty at a similar age and live weight. During rearing, SUBNUT heifers had higher concentrations of non-esterified fatty acids, urea, and cholesterol and a lower antral follicle count than CONTROL, but no difference was found in their fertility rate. After heifer first calving, dam-calf weights were similar among groups. In conclusion, maternal undernutrition reduced offspring postnatal gains at weaning, compromising metabolic status and follicle population during rearing but did not impair performance in the first gestation and lactation periods of beef heifers.

The Importance of the Periconception Period: Immediate Effects in Cattle Breeding and in Assisted Reproduction Such as Artificial Insemination and Embryo Transfer

In livestock breeding, the successful outcome is largely depending on the "periconception environment" which, in a narrow sense, refers to the genital tract, where gametogenesis and embryogenesis occur. During these early stages of development, gametes and embryos are known to be particularly sensitive to alterations in their microenvironment. However, as the microenvironment somehow reflects what is going on in the external world, we must widen our definition of "periconception environment" and refer to all events taking place around the time of conception, including metabolic state and health and nutrition of the dam. In modern dairy cows that have to manage an optimal reproductive performance with continued growth and high milk yield, the periconception period is particularly challenging. The metabolic priority for growth and lactation is known to generate adverse conditions hampering optimal ovarian function, oocyte maturation, and development of embryo/fetus. In addition, by using artificial reproductive technologies (ARTs), gametes and/or embryos of livestock are exposed to unnatural conditions outside the male and female genital tract. Artificial insemination, the most widely used technique, is currently yielding pregnancy rates similar to natural mating, and calves produced by AI are equally viable after natural mating. In contrast, other ART, such as multiple ovulation and embryo transfer, have been reported to induce changes in gene expression and DNA methylation patterns with potential consequences for development.Finally, the "periconceptional" environment has been shown to not only influence the successful establishment of pregnancy but also the long-term health and productivity of the offspring. Hence, the optimization of management around the time of conception might open doors to improve animal production and product quality.