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1.
A new somatic cell count index to more accurately predict milk yield losses
Janez Jeretina, Dejan Škorjanc, Drago Babnik, 2017, izvirni znanstveni članek

Opis: Intramammary infection and clinical mastitis in dairy cows leads to considerable economic losses for farmers. The somatic cell concentration in cow's milk has been shown to be an excellent indicator for the prevalence of subclinical mastitis. In this study, a new somatic cell count index (SCCI) was proposed for the accurate prediction of milk yield losses caused by elevated somatic cell count (SCC). In all, 97238 lactations (55207 Holstein cows) from 2328 herds were recorded between 2010 and 2014 under different scenarios (high and low levels of SCC, four lactation stages, different milk yield intensities, and parities (1, 2, and _>3). The standard shape of the curve for SCC was determined using completed standard lactations of healthy cows. The SCCI was defined as the sum of the differences between the measured interpolated values of the natural logarithm of SCC (ln(SCC)) and the values for the standard shape of the curve for SCC for a particular period, divided by the total area enclosed by the standard curve and upper limit of ln(SCC)=10 for SCC. The phenotypic potential of milk yield (305-day milk yield - MY305) was calculated using regression coefficients estimated from the linear regression model for parity and breeding values of cows for milk yield. The extent of daily milk yield loss caused by increased SCC was found to be mainly related to the early stage of lactation. Depending on the possible scenarios, the estimated milk yield loss from MY305 for primiparous cows was at least 0.8 to 0.9 kg day -1 and for multiparous cows it ranged from 1.3 to 4.3 kg day-1. Thus, the SCCI was a suitable indicator for estimating daily milk yield losses associated with increased SCC and might provide farmers reliable information to take appropriate measures for ensuring good health of cows and reducing milk yield losses at the herd level.
Ključne besede: dairy cows, milk production, lactation intervals, milk yield losses, somatic cell count index
Objavljeno v DKUM: 24.10.2017; Ogledov: 1160; Prenosov: 455
.pdf Celotno besedilo (317,33 KB)
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2.
The Influence of various origins of first calving Simmental and Black-White cows on production and content of milk
Marjan Janžekovič, Dejan Škorjanc, Jože Smolinger, 2004, izvirni znanstveni članek

Opis: A total of 1 070 Simmental and Black-White first calving cows and the same number of mother cows were investigated. The first calving cows originally arrived from Slovenia, the Netherlands, Germany and Denmark. No statistically significant differences were established in the milk production and quality of milk between the first calving cows from abroad compared to the first calving Slovenian cows. Statistically significant higher milk production (8 004 ± 981 kg; P ≤0.001) had mother cows of the imported Black-White compared to the Slovene (6 514 ± 1 142 kg) ones. There were no statistically significant differences, in the milk production and quality of milk, between the imported mothers of first calving cows of Simmental breed comparing with Slovenian mothers of first calving cows of the same breed. The milk production between the mothers and their Simmental daughters had a statistically significant correlation (rp = 0.125; P ≤ 0.01). The higher correlation coefficient for this characteristic was established between the Black-White mothers and their daughters (rp = 0.302; P ≤ 0.001). Among the milk production of first calving cows and protein content in milk a statistically negative significant correlation (rp = -0.198; P ≤ 0.001) was established. This result confirmed that the purchase of more expensive animals with better genetic potential is economically unjustified for the breeder who does not reach intensive technology of basic quality voluminous fodder.
Ključne besede: cattle, Simmental, Black-White, milk production, protein, fat
Objavljeno v DKUM: 10.07.2017; Ogledov: 914; Prenosov: 90
.pdf Celotno besedilo (225,07 KB)
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3.
Kefir grains production - An approach for volume optimization of two stage bioreactor system
Andreja Goršek, Marko Tramšek, 2008, izvirni znanstveni članek

Opis: The main objective of the present study was to design a continuous two-stage bioreactor system for kefir grains production. Based on the experimental data of time-depended kefir grain mass increase and average pH profile during kefir grains batch propagation, parameters of predictive growth and exponential pH models were initially estimated. Afterwards, the non-linear programming (NLP) optimization problem for estimating the optimal volumes of two unequal in series connected continuously stirred tank bioreactors (CSTB) has been developed. The NLP problem is based on criterion of minimal total holding time (MTHT), kefir grain mass balances in CSTB and parameters of the growth and pH models. The results showed that novel kefir grains production plant with two-stage continuous operation, at capacity, qm,KG,pr=3 kgh-1 and conversion, Xo,2=0.980, would primarily require investment in two CSTB with V1=5.93 m3 and V2=5.62 m3, respectively. Technological and economical authorization for a two-stage continuous bioreactor system was mainly confirmed with a more than five times lower total bioreactor volume compared to one-stage plant.
Ključne besede: chemical processing, bioprocesses, milk products, kefir grains production, bioreactor design, modeling, optimization
Objavljeno v DKUM: 31.05.2012; Ogledov: 2600; Prenosov: 114
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