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In farm animals, associations between individually identified genotypes and the values of performance traits were investigated since more than 30 years. The topic of research was largely determined by the Veterinary Institute of the University of Göttingen. For the experimental analysis of gene loci, for which allelic variants are connected with alterations of trait values, new techniques of DNA diagnostic were of crucial significance. Thereby, two approaches of analysis of quantitative trait loci (QTL) can be distinguished. By considering informative groups of animals, the first approach uses marker loci in order to trace the inheritance of their alleles and thus simultaneously the transfer of specific chromosome sections to individuals of the offspring generation. By this manner, the associations between the marked chromosome regions and trait values are calculated. Results are shown for examples from experiments with milk performance in cattle and with fatting and carcass traits in pigs. In the second approach, genetic effects of trait values are assigned to distinct genes or gene clusters. For this purpose, variants of the gene structure are identified and then analysed for their effects on the formation of specific trait values. As an example of such a functional analysis of single gene positions, the milk protein coding genes in cattle are given. From the data we see that DNA techniques allow a direct access to genotypic information and so far-reaching potential for tracing back effects on trait values to single nucleotide differences. However, such a functional analysis need specific test systems which are able to consider the complex net work between single gene effects and the multifactorially caused values of performance traits. This will be possible by proceedings, which identify the gene effects in vivo and the balancing forces of haplotype combinations in populations. Genetic parameters of such investigations are needed for farm animal populations before variants of genotypes are applied for breeding.

Laryngoscopic examination during sedation was performed on 24 stallions and on their offspring (240 foals and 474 adult horses). Additionally the dams (n = 308) of 35 foals and 216 horses were examined. With the bilateral comparison of the arytaenoid movements the function of the abductory and adductory laryngeal muscles were evaluated and the left abductory dysfunction (idiopathic laryngeal hemiplegia, ILH) was divided into six degrees. The incidence and degree of ILH depended on age and the occurrence of the same dysfunction in the parents. Foals suffered in significantly lower number (24.7 per cent) than adult horses (49.7 per cent). The progeny of unaffected parents suffered significantly less from ILH (8.9 per cent of the foals, 39.6 per cent of the adult offspring) than did comparable progeny of affected parents (41 per cent of the foals, 60.9 per cent of the adult offspring). There was no correlation between the occurrence of ILH and sex. 120 horses were examined laryngoscopically and during work to get an information about the correlation between a visible ILH and the appearance of a typical inspiratory noise. 54.3 per cent of the horses with ILH had a typical inspiratory noise. 80.9 per cent of the horse with a typical inspiratory noise showed ILH.

Lactational performance in high-yielding dairy cows has its limits in metabolic processes. Energy metabolism is maintained by mobilization of body reserves via hormonal regulation, resulting in lipolysis and sometimes ketoacidosis. For characterization of such conditions the intraruminal and intravascular application of glucose and volatile fatty acids was used in ruminant physiology. On the other hand the results of such experiments were correlated to actual and potential milk yield. For this investigation pairs of monozygous Holstein Friesian twins were tested as heifers and as cows by intravenous infusion of glucose, propionate and butyrate after 18 hours of feed withdrawal. Insulin, growth hormone, glucose, free fatty acids and beta-hydroxybutyrate were measured before, during and up to 4 hours after infusion of substrates. Each substrate caused a transient change in plasma concentrations of metabolites and hormones. Differences between heifers and cows are discussed with the time series of the mean concentrations. The reaction profile of each animal was characterized by different parameters. Analysis of these parameters revealed a close relation between hormones and metabolites even under the conditions of the load-test.

For investigation of bovine milk protein genes several methods of recombinant DNA techniques are presented. Possible applications of genome research in animal breeding are given including the characterization of structure and function for single genes, gene mapping as well as screening for gene variants in populations. Hence it follows that scientific and practical developments can be expected and will be an influence on future animal production.

Before and after infusion of propionate and butyrate the concentrations of volatile fatty acids (VFA) in the blood of heifers were determined by gas chromatography, in order to indicate activity and regulation of the carbohydrate metabolism. 14 heifers were loaded after food deprivation with intravenous infusions of propionate and butyrate. Concentrations of acetate, propionate, isobutyrate, butyrate, and valerate were measured in blood samples which were taken later on. The methods used for clearance and extraction as well as for gas chromatographic analysis are described. Retention times and blood concentrations are given for each VFA. Concentrations prior to infusion were for: acetate 10.14 +/- 2.51 microliters/ml; propionate 0.42 +/- 0.35 microliters/ml; iso-butyrate 3.72 +/- 1.37 microliters/ml; butyrate 3.44 +/- 0.68 microliters/ml blood plasma. The concentrations of the infused VFA showed a 100 (butyrate) to 1000 (propionate) fold increase followed by a subsequent decrease to the initial values. These investigations on the profile of VFA elucidated criteria of the energy metabolism.