Short communication: Heterosis by environment and genotype by environment interactions for protein yield in Danish Jerseys

Differences between performance of F1 crossbreds and Holsteins at different production levels

Crossbreeding in dairy cattle has recently become of increased interest. However, farmers in Scandinavian countries are reluctant to implement crossbreeding in their herds, and one reason is the common opinion that only herds at a poor level of management can benefit from crossbreeding. The Danish Cattle Database (SEGES, Aarhus, Denmark) provided data on 14 traits regarding milk yield, udder health, fertility traits, stillbirth, and survival. The data were collected from 103,307 pure Holstein cows and 14,832 F₁ crosses (Holstein dam and Nordic Red sire). The cows were born between 2008 and 2014 and originated from 424 herds that contributed data from at least 5 purebreds and 5 crossbreds across the years. We split the animals into 3 production levels: high, average, and low according to the herd's average production (kg) of 305-d fat plus protein in the given birth year of the cow. We estimated least squares means of breed group (purebred and crossbred) performance within each production level. Crossbred performance in 305-d fat yield in first-parity cows was greater than that of Holstein across all herd production levels; the gain was greater in high- (9 kg more than Holstein) and average-producing herds (7 kg more than Holstein) than in low-producing herds (3 kg more than Holstein). Regardless of production level or parity, crossbreds did not outperform Holstein in terms of 305-d protein yield (0 to 8 kg less). Crossbreds had relatively better udder health than Holstein in both first and second parity (up to 15% less mastitis) within any of the production levels. In terms of fertility, stillbirth, and survival, crossbreds performed better than purebreds, and improved performance was independent of herd production level. We conclude that differences in performance between F₁ crossbreds and Holstein are independent of production level.

Two New Insertion/Deletion Variants of the PITX2 Gene and their Effects on Growth Traits in Sheep

In China, Tong sheep (TS) and Lanzhou fat-tailed sheep (LFTS) are two closely relative endanger breeds for low meat production and low fecundity, finding some marker-assisted selected (MAS) is our first priority for improving their growth traits. For this purpose, Hu sheep (HS) and small-tailed Han sheep (STHS) were compared with two endangered breeds (TS and LFTS). Paired-liked homeodomain transcription factor 2 (PITX2) gene was the important member of PITX family, which could adjust animal growth through hypothalamic-pituitary-adrenal axis. During the past years, insertion/deletion (indel) has become increasingly popular in application as MAS. In this study, two novel indel loci were identified, and five significant differences, including chest width, hip width, chest depth, chest circumference, and body height, were found between different breeds. Interestingly, there was no DD genotype and smaller number of ID genotye. All the ID genotypes were significantly greater than II genotype, which was to say the allele of "D" was dominant variation and its frequency was lower, which demonstrated that it has huge space for selection. Briefly, the two indel were potential and useful DNA markers for selecting excellent individuals in relation to growth traits in sheep.