Genetic polymorphims in the growth hormone (GH) gene were studied in 410 Holstein dairy cows. Genotyping was carried out using PCR-RFLP. Data were analyzed by the MIXED procedure to reveal the effect of GH genotypes on reproductive traits. GH-AluI had a favorable effect on exanimate traits except for the age at the first calving. The homozygous LL genotype seemed to be advantageous for calving interval and days open. A significant effect of different GH-AluI–MspI combined genotypes was found.

This study aims to investigate the screening of leptin genetic polymorphism and its effect on lameness prevalence. Prevalence of lameness was evaluated and results showed that genotypes and other factors included in the logistic regression model significantly affect the prevalence of lameness in Holstein cows (P < 0.01). The probability of lameness incidence varied between 37 % and 99 % with parity. This recorded incidence is greater in winter and autumn than in the summer and spring.

This study aimed at screening genetic diversity and differentiation in four horse breeds raised in Tunisia: the Barb (BA), Arab-Barb (AB), Arabian (AR), and English Thoroughbred (TS) breeds. A total of 200 blood samples were collected and genomic DNA was extracted. The average number of alleles per locus was 7.52 (0.49), 7.35 (0.54), 6.3 (0.44), and 6 (0.38) for the AB, BA, AR, and TS, respectively. Results showed that the important amount of genetic variation was within population.

Genetic parameters for 11 456 Tunisian Holstein cows were estimated for the following five reproductive traits: calving interval (CI), calving to first service interval, calving to conception interval (CCI), first service to conception interval and number of services per conception. Low heritabilities were estimated for these traits, and genetic correlation estimates between them were moderately high. The CCI–CI genetic correlation was 0.85, indicating that they are the same trait genetically.