The aim of the study was to explore the heterosis of Simmental and Holstein, excavate its candidate genes associated with heterosis and analyze the genetic mechanisms of heterosis in cattle. 91 individuals including 9 Simmental bulls, 41 Holstein cows and 41 offspring of Simmental×Holstein were selected to conduct a genome-wide selection signal study using the illumina bovine GGP100k high-density chip. The top 1% of Fst value was used as the threshold. The results showed that 859 SNPs（Fst value >0.19) were selected by Fst within threshold of top 1%, and 249 candidate genes were annotated between F₁ offspring and Simmental (paternal). In addition, 860 SNPs（Fst value >0.15) were selected by Fst, and 261 candidate genes were annotated between F₁ offspring and Holstein (maternal). Gene pathway enrichment analysis found that the candidate genes were mainly enriched in the Axon guidance pathway (P<0.01), Focal adhesions and Prolactin signaling pathway (P<0.05) between F₁ and parents, respectively. It was found that 38 genes related to growth and development, milk production, carcass, reproduction and meat quality traits of cattle, such as OXTR, CHKA, PRKN, were positively selected in F₁. These findings will provide a reference for resolving genetic mechanisms of heterosis and guiding heterosis utilization.

The C3 line of local chicken breed Rugao yellow chickens has good laying performance, but the egg and eliminated hens of it are light in weight, so it is necessary to use big cocks from local chicken breed for cross improvement. In the current study, the cocks of C5 line derived from Luyuan chickens was used as sire and crossed with hens of C3 line. Then the body weight, body measurement, laying performance and egg quality of offspring were detected. The results showed that compared with C3, the growing and developing rate of C5 (sire) × C3 (hens) was faster, the laying performance was lower, and the egg quality was higher. In conclusion, C5 (sire) × C3 (hens) can achieve the purpose of cross improvement basically. The laying performance of C5 line should be improved in the late breeding.

Objective This study aimed to evaluate growth performance, slaughter characteristics, and meat quality traits in hybrid offspring from Duroc and Gannan Tibetan pig crossbreeding, while analyzing changes in production efficiency. Method Three Duroc boars were crossbred with three Gannan Tibetan sows, with their offspring divided into groups for rearing. Upon reaching physical maturity, two pigs from each group were randomly selected and slaughtered to determine the various production parameters. Result The results showed that compared with Gannan Tibetan pigs, the body weight of Dugan hybrid offspring was significantly increased (P < 0.05), the slaughter rate and lean meat rate were significantly increased (P < 0.05). There was no significant change in crude protein content in longissimus dorsi muscle (P > 0.05), but the meat color score was significantly reduced(P < 0.05), and the muscle fiber diameter was significantly thicker (P < 0.05). The muscle fiber density decreased significantly (P < 0.05), but the flavor amino acid content decreased significantly (P < 0.05). Conclusion The findings indicate that using Duroc as the sire effectively enhances growth performance in hybrids, yet leads to a noticeable decline in pork quality.

This paper focuses on the breeding and hybrid utilization of local Chinese cattle breeds, and provides a detailed introduction to the types and genetic characteristics of these local cattle breeds in China. Based on the current status of the local Chinese cattle breeds, it elaborates on the breed selection of local cattle breeds, the cultivation of new varieties through utilizing existing hybrid populations, as well as the theoretical and methodological approaches for genetic resource innovation in cattle through breeding and modern biotechnology. Additionally, it expounds on the efficient hybrid utilization theory and technology of Chinese cattle genetic resources, including hybrid superiority and hybrid methods, determination of complementarity, selection of hybrid parents, factors affecting hybrid effects, prediction of hybrid production performance, ways to enhance the utilization effect of hybrid superiority, and issues to be noted during hybridization. These lay an important theoretical foundation and methodological system for the breeding of local Chinese cattle breeds and efficient hybrid utilization, promoting the healthy, green and sustainable development of China's cattle industry.

Objective This crossbreeding test was conducted to evaluate the effects of Red Angus crossbreeding on growth and slaughter performance of Dabieshan cattle and characterize the resulting heterosis, aiming to provide theoretical basis and practical support for germplasm optimization and new beef strain breeding. Method In this study, Red Angus cattle were used as male parent and Dabieshan cattle were used as female parent to carry out progressive hybridization test. Thirty Dabieshan cattle (D), hybrid F1 generation (F1) and hybrid F2 generation (F2) were selected to systematically determine their growth performance and slaughter performance indexes, so as to promote the breeding of new strains for meat. Result The results showed that the body weight and body size of F1 were significantly superior to those of purebred D at all monthly ages (P<0.05). Among them, the body weight, body length, body height, chest girth and cannon circumference of male and female F1 calves at the birth stage were 27.5 kg, 69.1 cm, 70.2 cm, 71.3 cm, 12.8 cm and 24.6 kg, 70.0 cm, 67.4 cm, 70.4 cm, 12.3 cm respectively. All indicators were significantly higher than those of male and female D (P<0.05). The 24-month-old body weight of F1 bulls and cows were 526.7 and 448.4 kg, which were significantly increased by 67.5% and 53.3% compared with D, respectively (P<0.05). Those of F2 bulls and cows reached 564.6 and 462.2 kg, representing increases of 79.6% and 58.1% relative to D (P<0.05). The body length, body height, chest girth and cannon circumference of F2 bulls were 134.7, 124.3, 176.2 and 20.3 cm, respectively, all significantly higher than those of D (P<0.05). For F2 cows, the corresponding values were 128.8, 120.7, 169.2 and 18.9 cm, respectively, which were also significantly greater than those of D (P<0.05). In terms of slaughter performance after fattening, the pre-slaughter live weight and net meat percentage of F2 reached 604.3 kg and 41.66%, which were 105.8 kg and 1.34 percentage points greater than those of purebred D, respectively. The net meat weight of F2 was 251.7 kg, which was significantly greater than that of D and F1 (P<0.05). Conclusion In conclusion, Red Angus cattle had a significant crossbreeding improvement effect on Dabieshan cattle, and F2 exhibited the optimal comprehensive performance.