The growth hormone receptor (GHR), insulin-like growth factor-I (IGFI) and tumor necrosis factor-α (TNFA) genes have important effects on reproduction in cows. This study investigated SNP in each gene associated with differences in fertility among cows. Data on inseminations and days to pregnancy until 210 d in milk (DIM) were collected for cows (479 total) at 4 research stations (NY, NH, PA, WV). DNA from blood of each cow was genotyped for SNPs identified in prior studies by PCR-restriction fragment length (PCR-RFLP) methods. Statistical models (SAS GLM and Glimmix procedures) tested the effects of genotypes and linear contrasts among alleles with station and parity (1 or ≥2) as covariates. Results for effects of genotypes on conception rate and DIM to pregnancy are presented in Table 1. Effects of GHR and IGFI SNP were not significant. The SNP in TNFA had significant effects on fertility; BB cows being most disadvantaged. Neither IGFI nor TNFA SNPs had a linear effect on days to pregnancy. However, combining the effects of SNPs in TNFA + IGFI, cows carrying more favorable alleles (AA for each gene) had fewer DIM to pregnancy than cows having BB genotype for both (AAAA = 112 ± 8, BBBB = 126 ± 10; Linear effect P = 0.019). How the effects of these SNPs are manifested by differences in fertility cannot be ascertained from this study. However, as examples, the TNFA gene regulates expression of the inflammatory cytokine TNFA in tissues and increased plasma TNFA levels are known to affect liver function and ovarian follicle development in early lactation. Also, the effects of the GHR-IGFI system in promoting ovarian follicular and luteal function via plasma IGFI levels are well known. Table 1. Conception rate to first AI and days in milk to pregnancy

Gene	Genotype			P-value
AA	AB	BB
GHR
n	189	60	210
CR 1st AI (%)	0.38 ± 0.04	0.37 ± 0.07	0.41 ± 0.04	0.737
Days to pregnancy	106 ± 3	102 ± 6	97 ± 3	0.177
IGFI
n	141	235	74
CR 1st AI (%)	0.42 ± 0.05	0.42 ± 0.04	0.28 ± 0.06	0.116
Days to pregnancy	102 ± 4	105 ± 3	111 ± 6	0.358
TNFA
n	49	225	179
CR 1st AI (%)	0.41 ± 0.07	0.44 ± 0.04	0.33 ± 0.04	0.098
Days to pregnancy	104 ± 6	98 ± 4	113 ± 4	0.007
Contrast: AA + AB vs. BB				0.015