The influence of ordinal number and stage of lactation on milkability traits in Holstein cows

Muzna svojstva goveda imaju sve veću važnost u suvremenoj govedarskoj proizvodnji mlijeka, iako su sekundarno selekcijsko obilježje. Strojna mužnja krava ukazala je da ne postoji potpuna usklađenost između muznog uređaja i životinje, što dovodi do produžene mužnje ili narušavanja zdravlja vimena. Zato je cilj rada bio istražiti utjecaj stadija i redoslijeda laktacije na sljedeće muzne parametre: ukupna količina mlijeka po mužnji (KMM), maksimalni protok mlijeka (MPM), prosječni protok mlijeka glavne faze mužnje (PPM), vrijeme trajanja startnog protoka (tS500), trajanje uzlazne faze mužnje (tUFM), trajanje plato faze mužnje (tPFM), trajanje silazne faze mužnje (tSFM) i trajanje glavne faze mužnje (tGFM), te iste preporučiti za selekcijski rad. Istraživanje je uključilo 322 krave holstein pasmine od prve do treće laktacije, raspoređene u tri stadija (prvi od 50. do 90. dana, drugi od 91. do 135. dana i treći od 136. do 180. dana laktacije). Rezultati istraživanja pokazali su kako je redoslijed laktacije značajno (P<0,01) utjecao na KMM i MPM, te na PPM i tGFM (P<0,05). U drugoj laktaciji značajan utjecaj (P<0,05) stadija uočen je za MPM, tS500 i tUFM. Značajan utjecaj stadija laktacije na KMM zabilježen je u prvoj i drugoj laktaciji (P<0,05) odnosno u trećoj laktaciji (P<0,01). Utvrđen je značajan pozitivan utjecaj KMM (P<0,05) na MPM, tPFM, tSFM i tGFM (r = od 0,22 do 0,52). Utvrđena je negativna korelacija MPM (P<0,05) s pojedinim dijelovima vremenskog trajanja faza mužnji (r = od -0,14 do -0,47). Dobiveni rezultati ukazuju na činjenicu da postoji mogućnosti za selekcijski rad na poboljšanju muznosti krava, što se može pozitivno odraziti na ekonomičnost utroška vremena prilikom mužnje, te indirektno popraviti zdravlje vimena.Milkability traits have an increasing importance in modern cattle production, although they are the secondary selective trait. The machine milking of cows has indicated that there is no complete alignment between the machine and the animals, what lead to increasing duration of milking and disturbances in health of udder. Because of that, the aim of this study was to investigate the influence of the ordinal number of lactation and stage of lactation on milkability traits (amount of milk per milking (KMM), maximum milk flow rate (MPM), average milk flow rate (PPM), duration of the start of milk flow (tS500), duration of the ascending phase of milking (tUFM), duration of the plateau phase of milking (tPFM), duration of the descending phase of milking (tSFM), duration of the main phase of milking (tGFM)), and recommend the same for the selection work. The study was done on 322 Holstein cows in the period from the first to third lactation, arranged in three stages of lactation (the first of the 50-90 day, the second stage of the 91-135 day and a third of 136-180 day of lactation). The results showed that the ordinal number of lactation had a highly statistically significant influence (P<0.01) on KMM and MPM, and on the PPM and tGFM (P<0.05). Statistically significant influence of the stage of lactation on the KMM was recorded in the first and second lactation (P<0.05) respectively in the third lactation (P<0.01). Was recorded a significant positive influence of KMM (P<0.05) on the MPM, tPFM, tSFM and tGFM (r = from 0.22 to 0.52). The negative correlation of the MPM (P