This study aimed to elucidate the phenotypic patterns and genetic architecture of fertility traits in Ningxia Holstein cattle, providing a theoretical basis for establishing a balanced breeding program in the region. We compiled 216 787 fertility records from 92 152 Holstein cattle across 15 farms in Ningxia during 2005—2024. Genetic parameter were estimated for 4 heifer traits and 9 cow traits (first, second, and third parities) using the AI-REML algorithm in DMU. Single-trait animal models were fitted to estimate heritability within parity, whereas bivariate models were used to get genetic and phenotypic correlations. Heifer heritabilities ranged from 0.097 0±0.008 to 0.500 9±0.012 9, with AFS the highest and CR_h the lowest. Heritability estimates for fertility traits in cows across the first, second, and third parities ranged from 0.007 6 (0.002 5) to 0.150 8 (0.011 6), 0.010 1 (0.003 4) to 0.149 9 (0.010 2), and 0.003 9 (0.005 2) to 0.137 6 (0.013 3), respectively; differences for the same trait between parities were small and consistently lower than those observed in heifers. Genetic and phenotypic correlations among heifer fertility traits ranged from -0.845 8 to 0.835 1 and from -0.550 7 to 0.908 4, respectively; the strongest negative genetic correlation (-0.845 8) was observed between CR_h and IFL_h. Within any parity, genetic and phenotypic correlations among cow fertility traits showed consistent trends, with phenotypic correlations consistently lower than genetic correlations. As parity increased, genetic correlations strengthened among DO, IFL_c, and CI, whereas BW, CS, CE and GL exhibited weak genetic correlations with other fertility traits and can be selected independently. The same fertility trait measured in adjacent parities showed high genetic correlations, indicating that it is largely controlled by the same gene, whereas the phenotypic correlations remained low, suggesting that the trait is strongly influenced by environmental factors. Fertility traits show low-to-moderate heritability in Ningxia Holstein cattle, with greater genetic variation in heifers. CR_h and IFL_h are strongly and negatively correlated and should be treated as core traits in a heifer fertility index. DO, IFL_c, and CI can be selected jointly, and multi-parity records for cow fertility traits can be combined to increase selection accuracy. This study provides scientific basis for developing a balanced breeding programs for Holstein cattle in Ningxia and facilitates the simultaneous improvement of fertility and productive performance.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |