Demographic structure and population dynamics of Maremmana cattle local breed after 35 years of traditional selection

Thirty-five years of pedigree data has been studied to investigate the role of the Herd Book in maintaining the genetic diversity and control the inbreeding while applying a selection scheme in local cattle breeds. More than 64,000 genealogical records of Maremmana beef cattle born from 1951 to 2019 were used to investigate demographic and genealogical structure of Maremmana breed in a time frame 1980–2015. Along these 35 years, the number of herds in the Herd Book increased 2.5-fold, and the number of pure animals raised from 4,849 to 10,984. The Effective Population Size (Ne) based on inbreeding coefficient (F) rate was 123.5 on average, with large periods under 100 (since 1990 to 2007) or even under 50 (since 2000 to 2005). With the support of the Herd Book, Maremmana recovered from a very critical Ne only in the last timeframe explored attaining a Ne of 380 in 2009, however still critical. The average generation interval for the whole population was 6.31 years, characterized by a larger interval in dams respect to sire (7.16 vs 5.36 years respectively). In 2015, the pedigree completeness index (PCI) over the 6 generation was 94.6% as valuable effect of the raised awareness about data recordings promoted by the Herd Book. In spite of the low population size, the smooth selection pressure (1 out of 10 in sire and 1 out of 2 in dams lines respectively) contributed to keep the inbreeding rate under control, (inbreeding raised from 0% of 1980 to 2.78% in 2015 with an average rate of 0.0725% per year) still improving the genetic make-up of the breed. However, in the last years both the average additive genetic relationships (AGR) and the inbreeding accelerate alarmingly (3.65% in 2017), calling for urgent safeguard measures. Our data support the Herd Book as an effective infrastructure to manage, improve and conserve local genetic resources: contributing to maintain pure animals, stimulate the record of reproductive information, keep inbreeding under observation, increase the effective population size and support the overall economic sustainability of the herds, ultimate in situ conservation sites. A step further into the genomics, likely guided by the Herd Book data, will boost the sustainable conservation of Maremmana genetic diversity, enabling the application of genomic breeding plan and models based on the optimal contribution approach.