F. Forabosco

Genetic variability in three Italian beef cattle breeds derived from pedigree information

Abstract The aim of the present work was to estimate genetic variability in Chianina (CH), Marchigiana (MC) and Romagnola (RO) breeds using pedigree information. Different approaches based on probability of identity-by-descent (effective population size through an increase in inbreeding Ne) or probability of gene origin (total number of founders f, effective number of founders fe, ancestors fa and founder genomes fg) were used. Reference populations were defined using female animals born between 1996 and 2000 where both parents are known. Generation intervals were 5.35, 4.93 and 5.15 years for CH, MC and RO, respectively. The total number of founders were 7092, 11947, 3928, for CH, MC and RO, respectively. Complete generation equivalent showed the relative high quality of pedigree information: 5.66 for CH, 4.54 for MC and 4.95 for RO. For CH, MC and RO, respectively, a fe value of 152.1, 70.9 and 89.8, a fa value of 73.6, 48.0 and 59.5 and a fg value of 39.5, 25.0 and 38.5, were calculated. When inbreeding was used effective population sizes were 138, 122 and 124 for CH, MC and RO, respectively. Parameters derived from the probabilities of gene origin were variable among the investigated breeds and the results for MC demonstrate the need to pay specific attention to breeding strategies.

Parâmetros genéticos e fenotípicos do desempenho reprodutivo de fêmeas Chianina

ABSTRACT This study aimed to evaluate the reproductive performance of Chianina cows born from 1977 to 2002. Data was used to calculate age at first calving (AFC), first calving interval (CI1) and average calving intervals (avgCIs) for the whole lifetime of cows. After editing data, the number of records used for AFC, CI1 and avgCIs analyses were respectively 31,023; 23,998 and 94,497 respectively. Statistical analyses were done using the SAS program (Statistical Analysis System) and variance components were estimated by REML using the software MTDFREML fitting animal models. Means for AFC, CI1 and avgCIs were 1,037.69 ± 186.37, 457.93 ± 12.22 and 436,26 ± 12,17 days, respectively. Heritability estimates for AFC, CI1 and avgCIs were respectively 0.36 ± 0.014; 0.13 ± 0.014 e 0.05±0.004 and the repeatability for avgCIs was 0.075 ± 0.004. The use of AFC and CI1 in genetic improvement programs may lead to an increase in precocity and potential longevity. Changes in management of females may decrease avgCIs, leading to higher and faster improvement in reproductive efficiency.

Genetic selection strategies to improve longevity in Chianina beef cattle

Abstract Longevity in beef cattle is an important economic trait. Including this trait in a breeding scheme increases profit and has a positive impact on the well-being and welfare of the animals. The aim of the present study was to evaluate the consequences of alternative selection strategies to include longevity in different breeding schemes using deterministic simulation. Different schemes were compared and economic (EcW) and empirical weights (EmW) were used to evaluate the responses. The empirical weights of average daily gain (ADG) and muscularity (MU) were identical because both traits have an identical importance for the breeders. Economic weights have been derived from profit equations. Traits used in the Base scenarios were: average daily gain pre-performance test (ADG1), average daily gain during the performance test (ADG2) and muscularity (MU); longevity (L) was included in the alternative schemes. When longevity was included both in the breeding index and in the breeding goal (scenario A-2), the total longevity response using EmW and EcW was +2.97 d/yr and +4.92 d/yr, respectively. The total economic response for scenario A-2 using EmW and EcW were 3.020 €/yr and 3.342 €/yr, respectively, and the total response in units of Bull Selection Index were +0.699 and +0.678, respectively. Longevity decreased when it was not included in either the breeding goal or in the breeding index (scenario Base), and economic response was the lowest found. The results of the current study indicate that the highest total response using either economic weights or empirical weights was found when information on longevity was included both in the breeding index and in the breeding goal (scenario A-2).