The aim of this study was to evaluate the influence of body weight on the efficiency of dairy cows. Data were derived from 161 commercial Austrian dairy farms. An optimum body weight range for efficiency does exist as the relationship of milk yield and body weight is nonlinear. Specialized dairy breeds seem to respond more intensively to body weight range than dual-purpose breeds. Cows with medium weights are the most efficient. A further increase in dairy cows’ body weights should be avoided.

The lactation curve and lactation survival are important in dairy cattle breeding. Their simultaneous improvement results in economic benefits. The genetic relationship between the lactation survival and the lactation curve shape traits of milk yield and fat and protein percentages using information from of 25 981 primiparous Tunisian Holsteins was investigated. Cows that had higher persistencies for fat and protein percentages were more likely not to survive.

The aims of the study were to estimate allele and genotype frequencies at g.-274C > G locus in the promoter region of the SIRT1 gene and to investigate, for the first time, the relationship among different genotypes and milk and reproduction traits in the Agerolese cattle breed. The investigated population was found to be polymorphic at the investigated locus. Concerning milk production performance, significant differences between genotypes were found.

Improved milk yield in dairy cows results in worsening health and reproduction. Some linear traits are genetically associated with health and reproduction and can be used to assist selection programs. The National Breeding Centre for Dairy and Forage of Indonesia has not included linear traits in the breeding program. This study estimates genetic parameters of linear traits. The traits under study were found to be heritable and can be included in the breeding program along with milk yield.

The objective of this study was to predict dairy cows' body weight from body size measurements. Body weight is an important trait for both management and breeding. Data were derived from 167 commercial Austrian dairy farms. To ensure high prediction accuracy, the use of a combination of both heart girth and belly girth is recommended if the use of scales is impossible. The large and heterogeneous data set supported a valid prediction.