Medycyna Wet. 64 (9), 1136-1140, 2008
| Miciński J., Pogorzelska J., Barański W. |
| Relationships Between the Performance Traits of Primiparous Cows and the Genetic Variants of Selected Milk Proteins |
| The study was conducted during the years 2005 - 2007. The experimental materials comprised 48 Holstein-Friesian primiparous cows purchased from Germany. The objective of the study was to determine relationships between the genetic variants of selected milk proteins and the yield and composition of milk produced over the first 305-day lactation and full lactation, and the reproductive traits of cows in their first reproduction cycle. Milk performance parameters were analyzed on day 30, 60, 100, 200, 300 and 400 of lactation. Milk urea concentration (MUC) and somatic cell count (SCC) were also estimated. The genetic variants of milk protein fractions were determined by starch gel electrophoresis. In the tested population of HF primiparas, the LGB AB genotype was more frequent than LGB BB, while the CSN3 AA genotype dominated over CSN3 AB. The highest milk yield in a 305-day lactation cycle was reported for LGB AA (7387 kg) and CSN3 AA (7453 kg) homozygous cows. Milk fat and protein yield were higher in cows with the LGB BB genotype (523 kg) than in those with the LGB AA (511 kg) and LGB AB (505 kg) genotypes, as well as in cows with the CSN3 AA genotype (520 kg) than in those with the CSN3 AB genotype (509 kg). Milk fat and protein content were slightly higher in cows with the LGB AB and CSN3 AB genotypes. The highest milk urea concentration and the highest somatic cell count were recorded in cows with the LGB BB and CSN3 AA genotypes. The daily yield of milk, converted into value-corrected milk (VCM), increased until day 100 of lactation. The highest VCM yield (31 kg) was observed in the LGB AA genotype. The highest increase in daily yield was noted between day 60 and 100 of lactation. On day 100 of lactation (± 2 days), the highest VCM production was reported for cows with the LGB AA and CSN 3 AA genotypes (31 kg and 30 kg respectively), while the lowest – for cows with the LGB AB and CSN3 AB genotypes (29 kg). On day 400 of lactation (± 2 days), the highest daily content of milk fat (4.04%) and milk protein (3.87%) was noted in cows with the LGB AB and LGB BB genotypes, respectively; among CSN3 variants, the highest values reaching 4.26% (fat) and 3.81% (protein) were recorded in the AB genotype. The longest inter-calving intervals were observed in CSN3 AA and LGB BB cows (464 and 446 days respectively). The most heifer calves were born to cows with the following genotypes: LGB AA, LGB AB and CSN3 AB. |
| Key words: cows, primiparas, milk proteins, -lactoglobulin, -casein, genotype. |