F. Graf

Hormonal changes during lactation in cows of three different breeds

Abstract Changes of somatotropin (bST), insulin-like growth factor I (IGF-I), insulin (INS) and free fatty acids (NEFA), and milk yield were measured ante partum and during an entire lactation period in groups of dual-purpose cows of the German Fleckvieh (FV) and German Brown Swiss (BS) breeds and of German Black and White (BW) dairy type cows. In total, 26 cows were studied located on two farms. Blood was collected weekly (8 weeks ante partum (ap) until 40 weeks post partum (pp)) and more frequently (10 h, 30 min intervals) at 6 and 2 weeks ap and Weeks 2, 4, 8, 12, 20 and 30 pp. Episodic secretion pattern was recorded only for bST. bST, NEFA and milk showed a clear increase after parturition in all three breeds. NEFA started to rise 2 weeks ante partum. In contrast, INS and IGF-I fell immediately post partum to significantly lower concentrations. As lactation progressed, all of the investigated plasma parameters returned to values seen in pregnancy. The three groups studied of FV, BS and BW cows exhibited significantly different values for bST, INS, IGF-I and milk yield during the first 8 weeks of lactation. NEFA concentrations were significantly higher in BW vs. FV and BS cows. The relation between bST and milk yield was positive and significant in BS cows ( r = 0.58). The elevation of bST pp is due to an increase of episodic secretion pattern (baseline, peak frequency, peak amplitudes and rise of suprabasal peak secretion).

Claw measurements of young bulls at performance testing stations in Bavaria

Abstract The aim of the investigation was to test the suitability of morphological claw parameters as auxiliary traits for selection. At three Bavarian performance testing stations, claw measurements and descriptive traits of claws and legs were recorded. The material consists of 235 Simmental bulls descending from 41 sires. The bulls were measured at the ages of 6, 9 and 12 months. The posture of the limbs and the conformation of the claws was scored. The following characters were measured: length of the dorsal border, length of the heel, hardness of the dorsal wall (Shore D), angle of the dorsal border, area of the ground surface and circumference of the ground surface. From the measurements taken, the following quotients were computed: length of the dorsal border divided by length of the heel and body weight divided by the area of the ground surface (pressure on the ground surface/cm 2 ). The influence of position (front/hind, inner/outer claw), performance testing station, posture of the limbs and fetlock, season, body weight and age were estimated with an LSQ model. Position, season and body weight had a significant influence on the results of the measurements and scores. Interactions between sire and age group, as well as sire and performance testing stations do not allow an unbiased estimation of heritability. Repeatability estimates are used to estimate the individual influences and the upper limit of the additive genetic variance of the traits. Repeatability estimates range between 0.1 and 0.7. The differences between the same measurements taken on medial and lateral claws are small. The parameters: length of the dorsal border, angle of the dorsal border and area of the ground surface seem to be well suited to describe the genetically caused morphological differences between claws. Their relationship to the frequency of claw diseases to be expected in later life has to be investigated in a further analysis.