Onset of puberty in Maremmana heifers

The Maremmana breed is characterised by rusticity, resistance to harsh environments and good growth ability and it could be considered as one of the most suited breeds for extensive rearing in Italy. Moreover, Maremmana presents high fertility and good fostering ability but, on the other hand, the age at first calving appears quite high. This could probably be due to reduced feed availability to which animals are frequently subjected. The aim of this paper was to determine the age at puberty in Maremmana heifers, the repeatability of the reproductive cycles along the seasons and to verify the possibility to anticipate the age at first service. Haematic levels of progesterone and 17-β-estradiol were determined weekly in 6 heifers raised in pens and fed with 0.70 Milk FU/kg DM and 121 g of gross protein/kg d.m, starting from 9 up to 25 months of age. Metabolic profile was determined monthly to highlight possible metabolic unbalances that could affect reproductive activity. Plasma was submitted to RIA analysis in order to measure steroidal hormones. Puberty was considered reached when two subsequent measures of progesterone resulted higher than 1 ng/ml of plasma. This happened in 5 out of 6 heifers at an average age of 17 months. The fluctuation of the hormonal levels throughout the year seems to exclude the seasonality of the oestrous cycle. The results showed that the level of the most important metabolites is within the normal range and it does not seem to interfere with the choice to anticipate the first service by one year. Possible periods of anoestrus noticed in some herds could be linked to the reduced availability of pastures in a few months of the year.