The climatic conditions in Croatia are deteriorating which significantly increases the frequency of heat stress. This creates a need for an adequate dairy farming strategy. The impact of heat stress can be reduced in many ways, but the best long-term solution includes the genetic evaluation and selection for heat stress resistance. In order to create the basis for genetic evaluation, this research determined the variation in daily milk yield (DMY) and somatic cell count (SCC) as well as the differences in resistance to heat stress due to production level (high, low) and breed (Holstein, Simmental) of dairy cattle breed in Croatia. For statistical analysis, 1,070,554 test-day records from 70,135 Holsteins reared on 5679 farms and 1,300,683 test-day records from 86,013 Simmentals reared on 8827 farms in Croatia provided by the Croatian Agricultural Agency were used. The results of this research indicate that the high-producing cows are much more susceptible to heat stress than low-producing especially Holsteins. Also, the results of this research indicate that Simmental breed, in terms of daily milk production and somatic cell count, could be more resistant to heat stress than Holstein. The following research should determine whether Simmentals are genetically more appropriate for the challenges that are in store for the future milk production in this region. Furthermore, could an adequate production level be achieved with Simmentals by maintaining the heat resistance?

Considering the rapid climate changes worldwide, with the purpose to reduce financial losses for dairy farmers and enable a more sustainable farming as well, there is an increasing necessity to implement breeding values for heat resistance in breeding strategies. The estimation of breeding values requires a determination of temperature-humidity index (THI) threshold value. Therefore, the objective of this study was to determine the temperature-humidity index (THI) threshold values for daily milk yield, daily fat and protein content of milk produced by Holsteins and dairy Simmentals in Croatian farms. With that purpose, 1.070,554 test-day records from 70.135 Holsteins reared on 5.679 farms and 1.300,683 test-day records from 86.013 Simmentals reared on 8.827 farms in Croatia were compared to records of ambient temperature and relative humidity collected in the barn, during regular milking recordings from January 2005 to December 2012. Accordingly the following conclusions could be drawn: threshold values for daily milk yield were highly dependant on the parity and breed (Holsteins: 68, 69 and 72 for 1 st , 2 nd , 3+ parity; Simmentals: 77 for 1 st ); daily fat and protein contents showed a highly significant decrease due to heat stress condition (THI in 66-80) in both, Holstein and Simmental cows, and in all parity classes; multiparous cows were more resistant to heat stress than primiparous; Simmental cows were more resistant to heat stress than Holsteins.

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Original scientific paperIzvorni znanstveni članak seed quality and plantlets development. The highest average values for germination and seedling root and shoot lengths were obtained after the storage at -80°C, and the lowest after storage at room temperature. The highest average values for emergence, plantlet height and roots and shoots fresh weights were obtained after the storage at -20°C, while the root length was greatest after the storage at -80°C. Tetraploid cultivar Calibra had significantly greater average values than diploid Bartwingo for all the investigated traits except for germination and primary shoot length. SUMMARY The aim of this research was to investigate the seed quality of perennial ryegrass after 5-year storage treatments at various temperatures. The seeds of two cultivars of perennial ryegrass (diploid Bartwingo and tetraploid Calibra) were used, and the storage treatment temperatures were: room temperature (about 21°C), 10°C, -20°C and -80°C. Seed quality traits (germination and seedlings' root and shoot lengths) were determined before and after the storage treatments. Additionally, early development traits in mini-pots during the first two months of development (emergence, plantlet height, plantlet root length, fresh weight of roots and shoots) were tested. The research has shown significant effects of storage temperatures to all the investigated traits of

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The objective of this research was to determine the effect of addition of n-3 unsaturated fatty acids (α-linoleic, eicosapentaenoic and docosahexaenoic) in dairy goats’ ration on milk composition (fat and protein content). Also, the persistence of the effect after supplementation was analysed. The research was conducted on dairy goats (Alpine and Saanen) bred at an indoor farm. Regarding the experimental period, the milk sampling at milking (morning and evening) was performed in the period before supplementation (BS), during supplementation (S), and after supplementation (AS). According to the added supplement, animals were randomly allocated into a group (G-4) with no added supplement and three test groups (G-1; G-2; G-3) where a supplement containing n-3 unsaturated fatty acid was added over a period of five days. The results of this research indicate that the addition of PUFA in goats’ ration changes the milk composition. The supplementation of α-linoleic resulted in increase of both milk fat and protein content. Furthermore, the addition of eicosapentaenoic and docosahexaenoic resulted in decrease of fat but increase of protein content in milk. The observed trends also persisted after the supplementation period.

Field rodents can cause considerable economic losses in perennial crops, especially lucerne. Predatory birds can provide biological control of field rodent populations. However, modern arable landscape usually provides few or no natural standpoints for predatory birds to wait for their prey. According to the old farmers in eastern Croatia, T-standpoints installed into lucerne were traditional implements assisting the bird predation over field rodents. Aim of this study was to check whether the T-standpoints really are appropriate installations for the predatory birds to wait for their prey on the ground or not. The research has confirmed that predatory birds (Buteo buteo and Falco tinnunculus) descended on the installed T-standpoints (in average 1.35 arrivals per day of observation), waited (average period of stay was 17 minutes in the morning and 34 minutes in the afternoon) and landed on the ground, most probably to catch the prey (in average 13 % of arrivals to T-standpoints ended with landing to the ground, likely for the prey attack). Small forest restoration in arable landscapes and less chemical rodent control would probably improve the predatory bird populations, thus enhancing the biological control of field rodents. There remains the need for further investigation of efficiency of field rodent control by predatory birds

Seeds of two perennial ryegrass (Lolium perenne L.) cultivars (diploid ‘Bartwingo’ and tetraploid ‘Calibra’) were stored in hermetically sealed glass jars at four different temperatures (-80, -20, 10 and 20°C) for five years. After the storage period the seeds were sowed in containers filled with commercial substrate. Initial growth and development occurred under natural sunlight and manual watering to maintain optimum substrate moisture. After 60 days of vegetation plants were taken from the substrate, developed plants were counted, their roots were washed and whole plants were measured for shoot and root dry-weight and total biomass.Stems and leaves per plant were counted too. The research has revealed significant effects (p<0.01) of storage temperature, cultivar and their interaction to all of the investigated traits. When averaged over cultivars the highest values were observed upon storage temperature of -20°C for all the traits except root dry-weight which did not differ between -20 and -80°C. The lowest values of all investigated traits were observed upon storage at 20°C. When averaged over storage temperatures, diploid cultivar had greater number of stems and leaves and the tetraploid one had greater root dry-weight, shoot dry-weight and total biomass.