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In this study, it was aimed to investigate polymorphisms in seven genes (GH, PRL, STAT5A, OPN, PIT-1, LEP and FGF2) related to reproductive traits in dairy heifers. Frequency distributions of the genotypes between fertile and repeat breeder heifers groups were investigated. Allele effects on fertility were also analyzed. Blood samples were taken from a total of 160 Holstein-Friesian heifers and they were divided into two groups according to their artificial insemination numbers (AI). The heifers becoming pregnant after the first AI were used as the fertile heifers (FH, n= 80) and the heifers with 3 or more equal AIs were accepted as the repeat breeder heifers (RBH, n= 80). All the animals were genotyped by the PCR-RFLP method for seven genes and the association works were performed for 145 animals (RBH, n= 79; FH n= 66). For all loci investigated, two alleles and three genotypes were found for overall population with the exception that PRL locus had two alleles and two genotypes. The chi-square test (.2) revealed that the whole population and the two groups separately were at Hardy-Weinberg equilibrium. The genotype distributions of PIT-1 and STAT5A conspicuously differed between the FH and the RBH groups; however, these differences were not found significant. Association of GH-AB genotype was found significant on AI number for the first pregnancy. Mixed effect logistic regression model was used to investigate the allele effects on fertility. No linkage disequilibrium was detected between the investigated loci.

Subclinical endometritis contributes to repeat breeder syndrome in dairy cows. This study evaluated the effect of intrauterine cephapirin benzathine administration aft er timed artificial insemination (TAI) on the conception rate (CR) in repeat breeder dairy cows. To determine the antibiotic effects, all cows (n = 335) that had more than 3 services with no clinical abnormalities of the reproductive tract received the same combined synchronisation protocol: an ear implant containing progestagen using the Ovsynch protocol and a third gonadotropin-releasing hormone (GnRH) administration 7 days aft er TAI. Cows in the treatment group (TRT; n = 160) received intrauterine cephapirin 12 h aft er TAI, and cows in the control group (CON; n = 175) did not receive intrauterine antibiotics. The percentage of cows that responded to the first (67.5% in TRT, 70.9% in CON) and second (98.8% in TRT, 97.1% in CON) GnRH of Ovsynch was similar between the groups. In addition, the response to the third GnRH administration aft er TAI (88.1% in TRT, 83.9% in CON) did not differ between the groups. However, there was no effect of the cephapirin administration on CR on days 31 and 62 in the repeat breeder cows (43.8% in TRT and 44.0% in CON; 39.4% in TRT and 40.6% in CON, respectively). Thus, post-TAI intrauterine cephapirin administration was not found to be useful for the treatment of potential subclinical endometritis in repeat breeder dairy cows.

This study aimed to develop a timed artificial insemination (TAI) protocol using PGF(2 alpha) and GnRH with acceptable pregnancy rate in dairy heifers. Dairy heifers (n=290), aged between 13 and 26 months (mean 16.1 months), were used in this study. Heifers were synchronized with two PGF(2 alpha) administrations by 14 d intervals. After the second PGF(2 alpha), heifers were randomly assigned into two groups. In Group 1 (n=155), GnRH was given at 56h following 2nd PGF(2 alpha) and TAI was performed at 16-18h after the GnRH. In Group 2 (n=135), GnRH was administered at 72h after 2nd PGF(2 alpha), at the time of TAI. Ultrasonography was performed at both PGF(2 alpha) administrations to determine cyclicity, at the time of TAI to measure ovulatory follicle size, 7 d after TAI to determine ovulation, 31 and 62 d post-AI to determine pregnancy. Ovulatory follicle size at the time of TAI was not significantly different between groups (12.8 +/- 1.6 mm and 13.2 +/- 1.8 mm in group 1 and 2, respectively). Synchronization rate was similar in group 1 (85.2%;132/155) and in group 2 (91.1%;123/135). Conception rate (CR) at 31 d was not different in group 1(59.8%;79/132) and in group 2 (55.3%;68/123). Embryonic loss (7.6%; 6/79 and 7.4%; 5/68 in group 1 and 2 respectively) was not different. Gender ratio of the calves was found different between groups. Proportion of the female calves born were higher (P=0.03) in group 1 (63.3%; 38/60) than in group 2 (42.0%; 21/50). In conclusion, both protocols can be used in order to eliminate estrous detection in large dairy herds. Although GnRH administration at the time of TAI was found to be useful to reduce handling of heifers, GnRH can be applied 16-18 h before Alto achive higher female calves ratio in large dairy farms.