Caracterización reproductiva de la raza caprina blanca andaluzapapel de la condición corporal, peso vivo y fotoperiodo

Abstract

Nowadays, the Blanca Andaluza goat breed is an endangered local breed with a small number of breeders as well as an almost total lack of reproductive data. Therefore, the main objective of this work was to determine the reproductive characteristics of the Blanca Andaluza goat breed. To achieve these objectives, we have done five experiments. In the first experiment, the objective was to know the effect of body condition score (BCS), independently of bodyweight (BW), on the onset of puberty in Blanca Andaluza female kids born in Autumn. The results of the present work indicate that, Blanca Andaluza female kids reach puberty in their first natural breeding period after birth, and that BCS is a determining factor in the onset of puberty. The second experiment was designed to determine whether the response and the events that follow the synchronisation by intravaginal progestagen sponge treatment (follicular development, the timing of oestrus, the preovulatory LH surge and ovulation) are modified by the moment of application and by the body condition score (BCS) in adult female Blanca Andaluza goats. These results demonstrate that the season at the time of synchronisation was the most important factor affecting the outcome of synchronisation treatment. However, other than increasing the basal LH concentration in the does synchronised during seasonal anoestrus, and the number of follicles >1 cm before ovulation, BCS would appear to have no direct effect on the studied variables. The aim of the third experiment was to describe the seasonal pattern of Blanca Andaluza goats and the influence of BCS and BW as modulators of reproductive activity, and to determine whether there is any additive or compensatory interaction between these variables. These results demonstrate that Blanca Andaluza goats show a marked reproductive seasonality with a breeding season between August and April and an anoestrus period between May and June. This reproductive activity during the year is clearly and independently modulated by BCS and BW. The females that had ovulations during the whole experiment (including the seasonal anoestrus) were in the group with, at least, a BCS of 2.75. In the fourth experiment, the objective was to determine the seasonal reproductive pattern of Blanca Andaluza bucks, and whether this affects the quality of their semen and its freezability over the year. In conclusion, the results reveal that Blanca Andaluza bucks show seasonal reproductive activity in terms of their plasma testosterone concentration, but no clear change in their sexual behaviour was observed. In relation to results of the values of fresh sperm variables, these reached their lowest values during winter. However, after freezing-thawing, winter-collected sperm is the best quality semen. The last experiment was designed to compare the effects of exposure to exogenous melatonin treatment (MEL), short days (SD, 8h of light: 16h of darkness), and long days (LD, 16h of light: 8h of darkness), on reproductive activity, sperm motility and other reproductive variables as well as semen freezability of Blanca Andaluza bucks. In conclusion, the results of the present experiment showed that, in Blanca Andaluza bucks, two months of SD treatment provide semen of a quality equal to that achieved with two months of exogenous MEL treatment. About reproductive activity, testosterone concentrations was associated with the treatment to which the animals were subjected, with high testosterone concentrations recorded during the MEL and SD treatments and low concentrations during the LD treatment. Finally, the MEL treatment improved the fresh semen motility variables, but this did not improve the motility of frozen-thawed sperm over that recorded for either SD or LD treatment.