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Genomska selekcija je postala rutinska metoda pri mlečnih pasmah govedi. Z uvedbo genomske selekcije generacijski interval vsaj prepolovimo, kljub manjši točnosti plemenskih vrednosti, se genetski napredek poveča. Tako hitreje pridemo do želenih rezultatov posameznih živali, črede in populacije. Nadziramo lahko tudi širjenje dednih napak in preprečujemo oz. omejujemo parjenje v sorodu. V okviru diplomskega dela bomo predstavili pomen genomske selekcije in možnosti za izvajanje le-te v Sloveniji. S pomočjo vprašalnika smo od slovenskih rejcev pridobili njihovo mnenje o uporabi genomske selekcije, o prednostih in slabostih, ki jih genomska selekcija prinaša rejcem, rejskim organizacijam in strokovnim službam. Rezultati vprašalnika so pokazali, da se rejci zavedajo prednosti in priložnosti, ki jih daje genomska selekcija (npr. poznavanje monogenskih lastnosti ter lastnosti, možnost zgodnje odbire živali na osnovi genomskih plemenskih vrednostih). Hkrati pa se soočajo tudi s slabostmi in ovirami za širšo uporabo genomske selekcije (majhne populacije težko vzpostavijo dovolj veliko referenčno populacijo. V prihodnje bo potrebno več naporov vložiti v boljše poznavanje uporabne vrednosti genomske selekcije, boljše informiranje rejcev in bolj razumljive izpise rezultatov genotipizacije. Genomic selection is a rutinized selection method in dairy cattle breeding. Genomic selection increases genetic gain mainly by halving the generation interval, which allows faster results at the individual and herd-level. With genomic selection, we can also prevent the spread of genetic diseases and improve the genetic breeding value of the herd. In this paper, we present the importance of genomic selection and the possibilities of its implementation in Slovenian cattle populations based on scientific papers. With the help of a questionnaire, we obtained the opinion of Slovenian breeders on the use of genomic selection, and on the advantages and disadvantages of genomic selection for breeders, breeding organizations, and professional services. The cost of genotyping is the decisive factor for the use of genomic selection in Slovenia. The questionnaire showed that breeders are aware of the possibilities and advantages of genomic selection (e.g. information on monogenic diseases and traits, early selection of the best animals based on genomic breeding values. At the same time, they are aware of the disadvantages and barriers toe wider application of genomic selection (e.g. cost of genotyping , lower reliability of genomic breeding value prediction). In the future, we will need to invest more in educating breeders about the value of genomic prediction and selection, and in communicating genotyping resultsmore widely and clearly.

In tropical environments, dairy cattle production is constrained by several factors, including climate. The seasonal loss of milk due to heat stress is a recurring challenge for many dairy producers. The objective of this study was to detect heat stress thresholds, milk yield loss and individual animal variations using random regression models for dairy cattle from test-day milk records. Data were obtained from the Kenya Livestock Breeders Organization for the years 2000–2017 and merged with weather data. The weather parameters were grid-interpolated solar and meteorological data obtained from the National Aeronautics and Space Administration/Prediction Of Worldwide Energy Resources (NASA/POWER). After editing, the records comprised 49 993, 45 251 and 36 136 test-day records for first, second, and third lactations, respectively, for the four main dairy breeds: Friesian (68.0%), Ayrshire (21.1%), Jersey (7.6%) and Guernsey (3.3%). Variance components were estimated using Restricted Maximum Likelihood in ASReml software. Random regression models with third-order Legendre polynomials were fitted to the average and individual lactation curves and the reaction norms. An extended factor analytic variance structure for the random cow effects was used to estimate (co)variances between days in milk and thermal load. The daily average temperature (TA) and temperature humidity index (THI) were identified as the most suitable thermal load indicators for assessing milk yield losses. Considering a one day lag, the estimated heat stress thresholds were about 22 °C and 69 index units for TA and THI, respectively. Almost no differences were observed for estimated residual variances between the thermal load indicators, indicating there was no better model fit by TA or THI. The heat stress thresholds and milk loss patterns are important for management of dairy production systems in the tropics with climatic conditions similar to this study. Data recording should be improved as a tool to monitor the expected impacts of climate change and mitigation measures.

Early-life nutrition affects calf development and thus subsequent performance. The aim of this study was to examine the effect plane of nutrition on growth, feeding behaviour and systemic metabolite concentrations of artificially reared dairy bull calves. Holstein-Friesian (F; n=42) and Jersey (J; n=25) bull calves with a mean±SD age (14±4.7 v. 27±7.2 days) and BW (47±5.5 v. 33±4.7 kg) were offered a high, medium or low plane of nutrition for 8 weeks using an electronic feeding system which recorded a range of feed-related events. Calves were weighed weekly and plasma samples were collected via jugular venipuncture on weeks 1, 4 and 7 relative to the start of the trial period. The calves offered a high plane of nutrition had the greatest growth rate. However, the increased consumption of milk replacer led to a reduction in feed efficiency. Holstein-Friesian calves offered a low plane of nutrition had the greatest number of daily unrewarded visits to the feeder (P

Cilj diplomskega dela je bil proučiti in analizirati vplive telesnih lastnosti na dolgoživost in mlečnost pri mlečnih oz. kombiniranih pasmah govedi. Različne študije navajajo, da imajo lastnosti vimena, okvirja in nog pomemben vpliv tako na mlečnost kot tudi na dolgoživost krav molznic. Tako imajo krave z obsežnim in čvrsto pripetim vimenom, korektnimi nogami in čvrstimi parklji običajno večjo mlečnost in boljšo dolgoživost. Velikost okvirja živali ima pozitiven vpliv na količino prirejenega mleka, po drugi strani pa ima negativen vpliv na dolgoživost živali. Podobno velja za kot in odprtost reber. V nalogo smo vključili analizo slovenskih krav, ki so v svojem življenju priredile preko 100.000 kg mleka. Življenjsko mlečnost preko 100.000 kg mleka je doslej doseglo 129 krav, od tega 96 krav črno-bele pasme, 18 krav rjave pasme, 4 krave lisaste pasme in 11 križank. Največjo povprečno življenjsko mlečnost kot tudi najkvalitetnejše mleko med omenjenimi kravami so dosegle krave lisaste pasme. Analizirana skupina 129 krav je bila v primerjavi z ostalimi sovrstnicami v 1. laktaciji bolje ocenjena za lastnosti okvirja, vimena in nog, kar ugotavljajo tudi v drugih podobnih študijah. Med telesnimi lastnostmi imajo največji vpliv na dolgoživost, življenjsko prirejo mleka ter življenjsko dobo korektni biclji in parklji ter odlična pripetost vimena pod trebuhom, močna centralna vez, primerna globina vimena, ter čim večja višina in širina mlečnega zrcala. The aim of this B. Sc. Thesis was to study and to analyse the influences of conformation traits on longevity and milk production of dairy and dual-purpose cattle breeds. According to different studies, udder traits, stature and feet & leg traits have an important influence on milk yield and longevity of dairy cows. Cows with strong fore udder attachment, correct feet and proper legs usually have higher milk production and better longevity. The size of the stature of the animal is positively related to the milk yield, but on the other hand it has a negative influence on longevity of the animal. The same is considered for the angularity. Slovenian cows, which have given over 100,000 kg of milk in their life, were studied. Until 2016, 129 cows have reached this goal. 96 of them were Holsteins, 18 Brown Swiss, 4 Simmental breed and there were also 11 crossbreed cows, that have yield over 100,000 kg of milk in their life time. Simmental breed cows have reached the highest average lifetime milk, fat and protein production among aforementioned cows. In comparison with the rest of their peers, the analysed group of 129 high-productive cows has achieved better scores for the udder traits, feet & legs traits and stature, when assessed in their first lactation. The same findings have also been established in other similar studies. Proper feet and pasterns, excellent fore udder attachment, strong central ligament, appropriate udder depth, and very high and wide rear udder have the greatest influence on longevity and lifetime milk yield among all type traits.

Beef production from cull cows is an additional source of income for dairy farms and greatly contributes to red meat production, but the sources of variation of live animal characteristics and the carcass traits of cull cows have rarely been examined. This study investigated the effects of the farm type, breed, age at slaughter (AGE) and calving to culling interval (Calv_Cull) on the body traits and carcass characteristics of dairy and dual-purpose cull cows. Data from 555 cull cows from 182 herds belonging to five farm types, characterised by a combination of housing and feeding systems, were recorded and analysed. Dairy breeds, such as Holstein Friesian and Brown Swiss, and dual-purpose breeds (Simmental, Rendena) were included in the trait assessments. The day before slaughter, the cows were weighed and scored for body condition (BCS) and fleshiness, and then, their heart girth and wither height were measured. At the slaughterhouse, the carcass weight (CW), dressing percentage (DP), carcass conformation and fatness scores, carcass price per kg and carcass total value were obtained. On average, the cows were slaughtered at nearly 71±27 months of age, 285±187 days after the last calving; 615±95 kg BW; and provided a 257±51 kg CW. Nearly 50% of the cows fell within the BCS range of 2.75 to 3.50, and the carcasses were mostly graded in the lowest class of conformation and fatness scores. Cull cows from free-stall farms had a higher DP, carcass conformation score and price than those from traditional tie-stall farms. The breed influenced the AGE, live animal characteristics and carcass traits. Cows from dairy breeds were younger at slaughter, had a lower BCS and fleshiness, and greater body measurements, but a lower DP and carcass price than those from dual-purpose breeds, although differences between the breeds were found within both groups. The age of the cows at slaughter influenced the Calv_Cull and increased the BW, body measurements and CW, but not the fleshiness and fatness appreciation (both in vivo and postmortem) or carcass price. The increasing Calv_Cull improved the BW, BCS, fleshiness, CW and carcass conformation and fatness. In conclusion, the decision to cull dairy cows should also take into account the factors that affect their carcass value in regards to improving the carcass price of cows.

Cattle are one of the main instruments for economic (e.g., milk, meat, and cattle sale) and social (e.g., marriage, death, dispute settlement, and gift giving) exchange in Uganda. They serve as the main source of livelihood for a large majority of rural Ugandans, especially in the cattle corridor. Recent statistics demonstrate that the livestock sector contributes 13.1 percent of the agricultural gross domestic product (GDP) and 5 percent of the national GDP. Since 1991, the output of the livestock sector has grown on an average of 2.2 percent per annum, with most of the growth coming from the dairy sector. Dairy is an important and growing sector of Uganda's economy, and it is increasingly proving to be a lucrative livelihood option for a large number of households engaged in milk production and trade. Frequent realization of risks, however, impacts the performance of the supply chain. Effective management of these risks will require increased efforts to mitigate the identified risks and strengthen coping mechanisms. However, rather than a stand-alone risk management strategy, these efforts should be an integral component of a broader dairy development policy and strategy.

Om de geschiktheid op vleesproduktie-kenmerken te beoordelen werden 2 series met in totaal 72 Brown Swiss-MRY-kruislingen en 25 MRY-dieren gemest als vleeskalf. Tijdens de mestperiode welke varieerde van 144 tot 172 dagen, waren de kalveren individueel gehuisvest in boxen en werden ze individueel gevoerd met kunstmelk

De samengevatte literatuur betreft twee onderwerpen: vergelijkingen in de Verenigde Staten tussen de melkveerassen Brown Swiss en Braunvieh wat betreft melkgift en vruchtbaarheid en kruisingsproeven tussen deze rassen in Oostenrijk, Duitsland, Zwitserland en Denemarken

The heritability of milk yield and fat percentage was calculated of herd-registered cattle in Friesland. The estimates were based on daughter-dam comparisons. Comparisons covered the first three lactations. The average heritability estimates of milk yield within sires, and according to the different kinds of soil, were 35.50 and 37.38 %, with daughter-dam regression and dam-daughter correlation, respectively. Under the same conditions the figures for fat percentage were 76.52 and 81.58 %, respectively.When the effect of different soils was ignored, average heritability estimates for milk were 36.58 and 38.60 %, respectively. The corresponding figures for fat percentage were 76.40 and 81.60 %, respectively.If the figures were not calculated on within-sire basis, the average heritability for milk yield was 39.60 and 40.60 %; whereas for fat percentage the estimates were 84.44 and 83.52 %, as calculated from daughter-dam regression, and damdaughter correlation, respectively.The most reliable estimates of heritability were by the within-sire daughterdam regression calculated for each of the different soil types.

Original imports of Black Pied cattle were of various types and productive potential and could hardly be called Friesians. South African Frieslands contain blood from Afrikaner, Bechuana and Damara cattle and so are very heterogeneous. Uncontrolled breeding with native and with several imported breeds continued until about 1905, resulting in total degeneration of some outstanding native breeds. After 1905, with the foundation of a herd association this haphazard crossing slowly decreased. The register played an important part but was of no scientific merit and required reorganisation. Many Friesland herds in South Africa are very heterogeneous, both phenotypically and genotypically. Outstanding Friesland herds were always linebred and originated mainly from Jan 3265 FRS, Ceres 4497 FRS and Albert 1306H FRS. The openness of the register permitted registration of grades and ought to be abandoned. A few uniform herds of Frieslands were already available in South Africa. The new registration system of 1933 was more national, requiring a basic conformation and production score. But the scoring system ought to be revised to emphasize general features of conformation rather than figures. The 'Preferent Sire' award should be supplied only after a very thorough test of all progeny.

Birthweight was very important for growth until 12 months of age, particularly in bull calves which were heavier fed than heifer calves. Correlation between birthweight and bodyweight in bull calves was ± 0.5.The early first calving of heifers in the Netherlands (24 months of age) decreased birthweight of the first calf considerably, being 5 kg less than of calves born of cows. This difference in calfweight increased to 24 kg at 12 months of age. Autumn calves were at birth 2.5 kg heavier than spring calves. This difference increased in the first year of life to 48 kg, presumably through the difference in environmental conditions.Average weight, diameter and length of calves' hair at birth fluctuated between years. The sire had a definite influence on coat characters of offspring. The cattle breeds used in this study, Friesian and the Meuse-Rhine-Yssel, differed in coat type: the Friesians had a thinner shorter fibre with less medullation. The differences between coat types at birth were not significant.

Birthweight was very important for growth until 12 months of age, particularly in bull calves which were heavier fed than heifer calves. Correlation between birthweight and bodyweight in bull calves was ± 0.5.The early first calving of heifers in the Netherlands (24 months of age) decreased birthweight of the first calf considerably, being 5 kg less than of calves born of cows. This difference in calfweight increased to 24 kg at 12 months of age. Autumn calves were at birth 2.5 kg heavier than spring calves. This difference increased in the first year of life to 48 kg, presumably through the difference in environmental conditions.Average weight, diameter and length of calves' hair at birth fluctuated between years. The sire had a definite influence on coat characters of offspring. The cattle breeds used in this study, Friesian and the Meuse-Rhine-Yssel, differed in coat type: the Friesians had a thinner shorter fibre with less medullation. The differences between coat types at birth were not significant.

Various aspects of the ease of milking of more than a thousand cows were studied with a Gascoigne individual-quarter milking machine (pulsation ratio 3:1, pulsation rate 60 cycles per minute). Progeny groups from 17 bulls used in artificial insemination (420 heifers) were recorded twice and 75 cows on 9 different farms were tested on 16 occasions during lactation.Wide variation existed in peak flow (x = 2.13,σ= 0.70, C.V. = 33 %) and average flow (x = 1.70,σ= 0.58, C.V. = 34%). From paternal half-sib correlations, high heritability estimates of 0.65 ± 0.11 and 0.56 ± 0.10 were found for these features. Selection on peak flow could be especially effective. An accurate progeny test could be based on a sample of 25 daughters, while individual cows (bull dams) could be tested very accurately with 4 test milkings (repeatability 0.7). A correction for a standard milk yield of 7 kg was necessary for comparison.There was a sufficient variation in percentage milk in fore quarters x = 43.5,σ= 6.05, but heritability was lower (0.26 ± 0.28). No significant correlation was found with peak flow, machine time and quantity of stripping. Selection on this character was of minor importance.The average stripping yield by hand was 361 ml with wide variation, but very low heritability (0. 12 ± 0.24). Selection on this character was almost impossible.

Original imports of Black Pied cattle were of various types and productive potential and could hardly be called Friesians. South African Frieslands contain blood from Afrikaner, Bechuana and Damara cattle and so are very heterogeneous. Uncontrolled breeding with native and with several imported breeds continued until about 1905, resulting in total degeneration of some outstanding native breeds. After 1905, with the foundation of a herd association this haphazard crossing slowly decreased. The register played an important part but was of no scientific merit and required reorganisation. Many Friesland herds in South Africa are very heterogeneous, both phenotypically and genotypically. Outstanding Friesland herds were always linebred and originated mainly from Jan 3265 FRS, Ceres 4497 FRS and Albert 1306H FRS. The openness of the register permitted registration of grades and ought to be abandoned. A few uniform herds of Frieslands were already available in South Africa. The new registration system of 1933 was more national, requiring a basic conformation and production score. But the scoring system ought to be revised to emphasize general features of conformation rather than figures. The 'Preferent Sire' award should be supplied only after a very thorough test of all progeny.

Blood groups are genetically determined components of the red blood cells. In cattle there were 13 loci known to determine blood groups and some of these loci had large series of alleles. There were also 14 other loci known to determine proteins and enzymes in blood and milk of cattle.The author examined how the distribution of blood groups in the Dutch Friesian population had been influenced by the restrictions of breeders. He found that parent cattle were paired independently of blood group. In offspring there was no selection for a certain phenotype until the end of the first year.There were clear differences in the frequency of some genes between adult bulls and cows. The gene for blood group A was less frequent in bulls and that for blood group F was less frequent in cows. This occurred in some foreign breeds of cattle.The distribution of blood groups over the population was not even. There were differences in gene frequency between breeding areas and in the breeding areas there were large differences between artificial insemination stations. Differences within farms and within breeding pedigrees were even greater. These differences could be ascribed largely to the use of one or only a few sires.

The heritability of milk yield and fat percentage was calculated of herd-registered cattle in Friesland. The estimates were based on daughter-dam comparisons. Comparisons covered the first three lactations. The average heritability estimates of milk yield within sires, and according to the different kinds of soil, were 35.50 and 37.38 %, with daughter-dam regression and dam-daughter correlation, respectively. Under the same conditions the figures for fat percentage were 76.52 and 81.58 %, respectively.When the effect of different soils was ignored, average heritability estimates for milk were 36.58 and 38.60 %, respectively. The corresponding figures for fat percentage were 76.40 and 81.60 %, respectively.If the figures were not calculated on within-sire basis, the average heritability for milk yield was 39.60 and 40.60 %; whereas for fat percentage the estimates were 84.44 and 83.52 %, as calculated from daughter-dam regression, and damdaughter correlation, respectively.The most reliable estimates of heritability were by the within-sire daughterdam regression calculated for each of the different soil types.