Sexting Behavior Among Youths: Nature, Determinants, and Consequences

The advent of digital technology and smartphones with internet access has affected many aspects of youth development, including sexual development. One frequently studied type of digital technology use related to young people’s sexual communication is sexting, which is the exchange of sexually explicit content electronically for sexual or romantic purposes. This theoretical review of research, lists and explains commonly studied characteristics of sexting: nature, determinants, and consequences of sexting behavior. The consensus was critical for nearly all characteristics examined in sexting research. Gaps in existing knowledge and methodology as well as recommendations for future research on youth sexting are discussed

Utjecaj vrijednosti temperaturno-humidnog indeksa na dnevnu proizvodnju mliječnih goveda

The objectives of this study were to determine the microclimatic conditions in stables in three climactic regions (East, Mediterranean, and Central) of Croatia as well as to evaluate the effect of temperature-humidity index (THI) values on the daily production of dairy cattle. With that purpose, 1675686 test-day records collected from January 2005 until April 2010 were extracted from HPA (Croatian Agricultural Agency) database. For estimation of the effect of THI on daily production of dairy cows fixed-effect model that took into account the effects of lactation stage, breed, calving season, measuring season, and THI group (T1 - THI≤72; T2 - THI>72) was used. Model was applied to each class of parity (P1, P2, P3, P4 and P5) and region. During the analysed period, the highest monthly averages of ambient temperature were determined in Mediterranean region, the highest monthly averages of relative humidity were observed in Central region, while the highest monthly mean values of temperature-humidity index (THI) were determined in Mediterranean region. Heat stress conditions indicated with mean daily values of THI>72 were determined during spring and summer season in all analysed regions. Absence of heat stress conditions during autumn and winter season also characterised all three regions. Highly significant (P72). Model je apliciran zasebno po razredima redoslijeda laktacije (P1, P2, P3, P4 i P5) te regije. Tijekom analiziranog razdoblja, najviše prosječne mjesečne vrijednosti ambijentalne temperature utvrđene su u mediteranskoj, najviše prosječne mjesečne vrijednosti relativne vlage utvrđene su u centralnoj, dok su najviše prosječne mjesečne vrijednosti temperaturno-humidnog indeksa (THI) utvrđene u mediteranskoj regiji. Toplinsko stresni uvjeti indicirani prosječnom dnevnom vrijednošću THI>72 utvrđeni su tijekom proljetne i ljetne sezone u svim analiziranim regijama. Odsustvo toplinsko stresnih uvjeta tijekom jesenske i zimske sezone karakteriziralo je sve tri regije. Visoko signifikantan (P<0.01) pad dnevne količine mlijeka te dnevnog sadržaja mliječne masti i bjelančevina uzrokovan povišenom vrijednošću THI utvrđen je u svih grla neovisno o redoslijedu laktacije te u svim klimatskim regijama. Nadalje, najizraženiji negativni utjecaj toplinskog stresa utvrđen je u istočnoj regiji. Tijekom razdoblja toplinskog stresa, s ciljem minimalizacije utjecaja istog, neophodna je prilagodba managementa u stadu mliječnih grla. Uzgajivačima su na raspolaganju različiti alati za borbu protiv toplinskog stresa. Na primjer, hlađenje okoliša omogućuje unos dostatne količine krmiva dok prikladan sastav obroka osigurava dostatan unos hranjiva. Navedeno omogućava održavanje optimalne proizvodnje mlijeka

Utjecaj vrijednosti temperaturno-humidnog indeksa na dnevnu proizvodnju mliječnih goveda

The objectives of this study were to determine the microclimatic conditions in stables in three climactic regions (East, Mediterranean, and Central) of Croatia as well as to evaluate the effect of temperature-humidity index (THI) values on the daily production of dairy cattle. With that purpose, 1675686 test-day records collected from January 2005 until April 2010 were extracted from HPA (Croatian Agricultural Agency) database. For estimation of the effect of THI on daily production of dairy cows fixed-effect model that took into account the effects of lactation stage, breed, calving season, measuring season, and THI group (T1 - THI≤72; T2 - THI>72) was used. Model was applied to each class of parity (P1, P2, P3, P4 and P5) and region. During the analysed period, the highest monthly averages of ambient temperature were determined in Mediterranean region, the highest monthly averages of relative humidity were observed in Central region, while the highest monthly mean values of temperature-humidity index (THI) were determined in Mediterranean region. Heat stress conditions indicated with mean daily values of THI>72 were determined during spring and summer season in all analysed regions. Absence of heat stress conditions during autumn and winter season also characterised all three regions. Highly significant (P72). Model je apliciran zasebno po razredima redoslijeda laktacije (P1, P2, P3, P4 i P5) te regije. Tijekom analiziranog razdoblja, najviše prosječne mjesečne vrijednosti ambijentalne temperature utvrđene su u mediteranskoj, najviše prosječne mjesečne vrijednosti relativne vlage utvrđene su u centralnoj, dok su najviše prosječne mjesečne vrijednosti temperaturno-humidnog indeksa (THI) utvrđene u mediteranskoj regiji. Toplinsko stresni uvjeti indicirani prosječnom dnevnom vrijednošću THI>72 utvrđeni su tijekom proljetne i ljetne sezone u svim analiziranim regijama. Odsustvo toplinsko stresnih uvjeta tijekom jesenske i zimske sezone karakteriziralo je sve tri regije. Visoko signifikantan (P<0.01) pad dnevne količine mlijeka te dnevnog sadržaja mliječne masti i bjelančevina uzrokovan povišenom vrijednošću THI utvrđen je u svih grla neovisno o redoslijedu laktacije te u svim klimatskim regijama. Nadalje, najizraženiji negativni utjecaj toplinskog stresa utvrđen je u istočnoj regiji. Tijekom razdoblja toplinskog stresa, s ciljem minimalizacije utjecaja istog, neophodna je prilagodba managementa u stadu mliječnih grla. Uzgajivačima su na raspolaganju različiti alati za borbu protiv toplinskog stresa. Na primjer, hlađenje okoliša omogućuje unos dostatne količine krmiva dok prikladan sastav obroka osigurava dostatan unos hranjiva. Navedeno omogućava održavanje optimalne proizvodnje mlijeka

Metode za ranu procjenu laktacijskog tijeka u holstein prvotelki

The aim of this research was to define methods for early prediction (based on I. milk control record) of lactation flow in Holstein heifers as well as to choose optimal one in terms of prediction fit and application simplicity. Total of 304,569 daily yield records automatically recorded on a 1,136 first lactation Holstein cows, from March 2003 till August 2008., were included in analysis. According to the test date, calving date, the age at first calving, lactation stage when I. milk control occurred and to the average milk yield in first 25th, T1 (and 25th-45th, T2) lactation days, measuring monthcalving month-age-production-time-period subgroups were formed. The parameters of analysed nonlinear and linear methods were estimated for each defined subgroup. As models evaluation measures, adjusted coefficient of determination, and average and standard deviation of error were used. Considering obtained results, in terms of total variance explanation (R2 adj), the nonlinear Wood’s method showed superiority above the linear ones (Wilmink’s, Ali-Schaeffer’s and Guo-Swalve’s method) in both time-period subgroups (T1 - 97.5 % of explained variability; T2 - 98.1 % of explained variability). Regarding the evaluation measures based on prediction error amount (eavg±eSD), the lowest average error of daily milk yield prediction (less than 0.005 kg/day), as well as of lactation milk yield prediction (less than 50 kg/lactation (T1 time-period subgroup) and less than 30 kg/lactation (T2 time-period subgroup)); were determined when Wood’s nonlinear prediction method were applied. Obtained results indicate that estimated Wood’s regression parameters could be used in routine work for early prediction of Holstein heifer’s lactation flow.Ciljevi su provedenog istraživanja bili definirati metode za ranu procjenu (temeljem podatka utvrđenog pri I. kontroli mliječnosti) laktacijskog tijeka u prvotelki holstein pasmine te izabrati optimalnu s aspekta predikcijske točnosti te aplikacijske jednostavnosti. Analizom je obuhvaćeno ukupno 304.569 zapisa dnevne količine mlijeka izmjerenih na 1136prvotelki holstein pasmine u razdoblju od ožujka 2003. do kolovoza 2008. godine. U ovisnosti o datumu mjerenja, datumu teljenja, dobi pri prvom teljenju, stadiju laktacije pri I. provedenoj kontroli mliječnosti te prosječnoj dnevnoj proizvodnji u prvih 25, T1 (te 25-45, T2) dana laktacije, kreirane su podgrupe mjesec mjerenja - mjesec teljenja - dob - proizvodnost - vremenski period. Parametri analiziranih nelinearnih i linearnih metoda procijenjeni su za svaku definiranu podgrupu. Kao mjere evaluacije korišteni su korigirani koeficijent determinacije te prosjek i standardna devijacija pogreške. Utvrđeni rezultati, s aspekta udjela pojašnjene varijabilnosti (R2 adj), ukazuju na superiornost nelinearne Woodove metode u odnosu na linearne (Wilminkova, Ali-Schaefferova, te Guo-Swalvejeva metoda) u obje podgrupe vremenskog perioda (T1 - 97,5% pojašnjene varijabilnosti; T2 - 98,1% pojašnjene varijabilnosti). Obzirom na iznos predikcijske pogreške (eavg±eSD), najmanja pogreška procjene dnevne (manje od 0,005 kg/dan), te laktacijske količine mlijeka (manje od 50 kg/laktaciji (T1 vremenski - period podgrupa), te manje od 30 kg/laktaciji (T2 vremenski - period podgrupa)); utvrđena je pri aplikaciji Woodove nelinearne metode procjene. Rezultati utvrđeni provedenim istraživanjem ukazuju na mogućnost uporabe procijenjenih Woodovih regresijskih parametara za rutinsku ranu procjenu laktacijskog tijeka u prvotelki holstein pasmine

Metode za ranu procjenu laktacijskog tijeka u holstein prvotelki

The aim of this research was to define methods for early prediction (based on I. milk control record) of lactation flow in Holstein heifers as well as to choose optimal one in terms of prediction fit and application simplicity. Total of 304,569 daily yield records automatically recorded on a 1,136 first lactation Holstein cows, from March 2003 till August 2008., were included in analysis. According to the test date, calving date, the age at first calving, lactation stage when I. milk control occurred and to the average milk yield in first 25th, T1 (and 25th-45th, T2) lactation days, measuring monthcalving month-age-production-time-period subgroups were formed. The parameters of analysed nonlinear and linear methods were estimated for each defined subgroup. As models evaluation measures, adjusted coefficient of determination, and average and standard deviation of error were used. Considering obtained results, in terms of total variance explanation (R2 adj), the nonlinear Wood’s method showed superiority above the linear ones (Wilmink’s, Ali-Schaeffer’s and Guo-Swalve’s method) in both time-period subgroups (T1 - 97.5 % of explained variability; T2 - 98.1 % of explained variability). Regarding the evaluation measures based on prediction error amount (eavg±eSD), the lowest average error of daily milk yield prediction (less than 0.005 kg/day), as well as of lactation milk yield prediction (less than 50 kg/lactation (T1 time-period subgroup) and less than 30 kg/lactation (T2 time-period subgroup)); were determined when Wood’s nonlinear prediction method were applied. Obtained results indicate that estimated Wood’s regression parameters could be used in routine work for early prediction of Holstein heifer’s lactation flow.Ciljevi su provedenog istraživanja bili definirati metode za ranu procjenu (temeljem podatka utvrđenog pri I. kontroli mliječnosti) laktacijskog tijeka u prvotelki holstein pasmine te izabrati optimalnu s aspekta predikcijske točnosti te aplikacijske jednostavnosti. Analizom je obuhvaćeno ukupno 304.569 zapisa dnevne količine mlijeka izmjerenih na 1136prvotelki holstein pasmine u razdoblju od ožujka 2003. do kolovoza 2008. godine. U ovisnosti o datumu mjerenja, datumu teljenja, dobi pri prvom teljenju, stadiju laktacije pri I. provedenoj kontroli mliječnosti te prosječnoj dnevnoj proizvodnji u prvih 25, T1 (te 25-45, T2) dana laktacije, kreirane su podgrupe mjesec mjerenja - mjesec teljenja - dob - proizvodnost - vremenski period. Parametri analiziranih nelinearnih i linearnih metoda procijenjeni su za svaku definiranu podgrupu. Kao mjere evaluacije korišteni su korigirani koeficijent determinacije te prosjek i standardna devijacija pogreške. Utvrđeni rezultati, s aspekta udjela pojašnjene varijabilnosti (R2 adj), ukazuju na superiornost nelinearne Woodove metode u odnosu na linearne (Wilminkova, Ali-Schaefferova, te Guo-Swalvejeva metoda) u obje podgrupe vremenskog perioda (T1 - 97,5% pojašnjene varijabilnosti; T2 - 98,1% pojašnjene varijabilnosti). Obzirom na iznos predikcijske pogreške (eavg±eSD), najmanja pogreška procjene dnevne (manje od 0,005 kg/dan), te laktacijske količine mlijeka (manje od 50 kg/laktaciji (T1 vremenski - period podgrupa), te manje od 30 kg/laktaciji (T2 vremenski - period podgrupa)); utvrđena je pri aplikaciji Woodove nelinearne metode procjene. Rezultati utvrđeni provedenim istraživanjem ukazuju na mogućnost uporabe procijenjenih Woodovih regresijskih parametara za rutinsku ranu procjenu laktacijskog tijeka u prvotelki holstein pasmine

Methods for estimation of daily and lactation milk yields from alternative milk recording scheme in Holstein and Simmental cattle breeds.

The aim of this study was to compare different statistical methods for the estimation of daily and 305-day lactation milk, fat and protein yields of Holstein and Simmental cattle breeds using an alternative milk recording scheme. Data included 6,824 individual test-day milk yield records collected according to the A4 milk recording method on 668 cows reared on 15 family farms. Daily milk, fat and protein yields were estimated using several statistical methods with regard to breed. The 305-day lactation yields were calculated from estimated daily yields using the Test Interval Method. The correlation between estimated and true yields, as well as the mean difference among estimated and true yield were used as the evaluation criteria for estimation methods. The linear regression of daily to partial milk, fat and protein yields while taking into account the interval between successive milkings was shown to be the most accurate model for estimating daily values, either from morning or evening records. The simple doubling of morning or evening records overestimated and underestimated the daily yields, respectively. When 305-day lactation milk, fat and protein yields were compared no difference between evaluated methods were found. Also, a separate estimation of daily and 305-day lactation yields according to breeds did not result in increased estimation accuracy

Razlike u rezistentnosti na toplinski stres ovisno o pasmini mliječnih goveda

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 1st, 2nd, 3+ parity; Simmentals: 77 for 1st); 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.U svjetlu sve izraženijih te bržih klimatskih promjena širom svijeta, te u cilju redukcije financijskih gubitaka mliječnih farmi i osiguravanja održivog poslovanja, nužnost implementacije uzgojnih vrijednosti za rezistentnost na toplinski stres u uzgojne strategije, biva sve izraženija. Procjena uzgojnih vrijednosti podrazumijeva prethodnu determinaciju threshold vrijednosti. Stoga je cilj ovoga rada bio utvrditi threshold vrijednost za dnevnu količinu mlijeka, dnevni sadržaj mliječne masti te bjelančevina za holstein i simentalsku pasminu na mliječnim farmama u Hrvatskoj. S tim je ciljem analizirano 1.070.554 testday zapisa 70.135 holstein krava uzgajanih na 5679 farmi te 1.300.683 test-day zapisa 86.013 krava simentalske pasmine uzgajanih na 8827 farmi u Hrvatskoj zajedno s podacima o ambijentalnoj temperaturi te relativnoj vlazi na farmi prikupljenih tijekom redovne kontrole mliječnosti u razdoblju od siječnja 2005. do prosinca 2012. Temeljem provedene analize mogu se donijeti slijedeći zaključci: threshold vrijednost za dnevnu količinu mlijeka uvelike ovisi o redoslijedu laktacije te pasmini (holstein: 68, 69 te 72 za 1., 2., te 3+ laktaciju; simentalska: 77 za 1); dnevni sadržaj mliječne masti te bjelančevina statistički visoko signifikantno opada uslijed toplinskog stresa (THI jednak 66-80) u obje pasmine te u svim laktacijama; višetelke su rezistentnije na toplinski stres u odnosu na prvotelke; krave simentalske pasmine su rezistentnije na toplinski stres u odnosu na holstein

USPOREDBA STATISTIČKIH MODELA ZA PROCJENU EMISIJE METANA MLIJEČNIH SIMENTALSKIH KRAVA TEMELJEM PODATAKA KONTROLE PROIZVODNOSTI

In the last decades we have witnessed increasingly pronounced climate change worldwide resulting in environment transformation in various regions by making it not convenient for agricultural and livestock production. The global livestock sector contributes to anthropogenic greenhouse gas emission, but on the other hand, it can also deliver a significant share of the necessary mitigation effort. One of the most significant greenhouse gas is methane. Mitigation methods for the methane emissions in cattle can be classified as short and long term. Short-term methods imply increase of production per animal, reduction of number of animals and feeding optimization, while long-term methods imply genetic evaluation and selection based on methane emission variation. Prerequisite for genetic evaluation is selection of optimal indicators and models with high accuracy and easy applicability in routine Animal Recording. Therefore, the objective of this study was to evaluate different models for methane emission estimation in dairy cows based on Animal Recording data. The results obtained indicate that data from regular Animal Recording could be used in estimation of methane emission of dairy Simmental cows enabling the population analysis and genetic evaluation of dairy cattle for methane emission. Given the very high variability determined in estimated methane emission values regarding the used statistical models and aiming high accuracy of genetic evaluation it is recommended to define estimation models for body weight, dry matter intake and methane emission based on parameters (type traits and test-day records) of particular dairy cattle population. The stated will enable genetic evaluation of dairy cattle for methane emission as well as selection of cows with lower methane emission intensity. Finally, this will lead to environmentally sustainable milk production.Posljednjih desetljeća svjedočimo sve izraženijim klimatskim promjenama diljem svijeta, koje su rezultirale preobrazbom okoliša u različitim regijama čineći ga nepogodnim za poljoprivrednu, a osobito za stočarsku proizvodnju. Globalni stočarski sektor značajno doprinosi antropogenoj emisiji stakleničkih plinova, no, s druge strane, također može značajno doprinijeti mjerama ublažavanja. Jedan od najznačajnijih stakleničkih plinova je metan. Metode ublažavanja emisija metana u goveda mogu se klasificirati kao kratkoročne i dugoročne. Kratkoročne metode podrazumijevaju povećanje proizvodnje po životinji, smanjenje broja životinja i optimizaciju hranidbe, dok dugoročne metode podrazumijevaju genetsku evaluaciju i selekciju na temelju varijacija u emisiji metana. Preduvjet za genetsku evaluaciju je izbor optimalnih indikatora i modela koji su vrlo točni i lako primjenjivi u rutinskoj kontroli proizvodnosti. Cilj ovoga istraživanja bio je procijeniti različite modele za procjenu emisije metana u mliječnih krava na temelju podataka kontrole proizvodnosti. Dobiveni rezultati upućuju na to da bi se podatci kontrole proizvodnosti mogli koristiti za procjenu emisije metana kod mliječnih simentalskih krava, što omogućuje analizu populacije i genetsku evaluaciju mliječnih goveda za emisiju metana. S obzirom na utvrđenu vrlo visoku varijabilnost u procijenjenim vrijednostima emisije metana u odnosu na korišteni statistički model te s ciljem visoke točnosti genetske evaluacije, preporučuje se definiranje modela procjene tjelesne mase, unosa suhe tvari i emisije metana na temelju parametara (ocjene eksterijera te zapisi na kontrolni dan) populacije pojedinih mliječnih goveda. Model će omogućiti genetsku evaluaciju mliječnih goveda za emisiju metana, kao i selekciju krava s manjom emisijom metana. Primjena navedenoga u konačnici će dovesti do ekološki prihvatljivije proizvodnje mlijeka