Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2009
Sammendrag
35 ammekyr av rasen Hereford inngikk i et forsøk hvor man ønsket å studere betydningen av fôringsstrategi i innefôringsperioden på fôrforbruk, fruktbarhet og kalvehelse. Kyrne ble gruppert etter hold ved innsett. Gruppa med høyest hold ble fôret for nedgang med inntil 1,8 holdpoeng i innefôringsperioden, mens gruppa med middels hold ble fôret for nedgang med inntil 1,3 holdpoeng fram til beiteslipp.Fôringsforsøket viste at strategien med å redusere fôrtilgangen for å spare vinterfôr og utnytte kyrnes energireserver til et visst nivå, kan gi tilfredsstillende produksjonsresultater hos både ku og kalv. Av dyrevelferdsmessige årsaker bør en stor del av grovfôrrasjonen bestå av lavenergifôr slik at kyrne får tilfredstilt sitt behov for vomaktivitet og tidsfordriv gjennom hele døgnet.
Forfattere
Ievina SturiteSammendrag
In Norway, the goal of 15% organic food production within 2015 is too ambitious if the current growth rate of organic farmland is continued. Hence, a study of bottlenecks within organic farming systems in Northern Norway, and farmer"s preconditions to convert was conducted in spring 2007. A questionnaire was sent to certified and former certified organic farmers, and a control group of conventional farmers. For organic farmers the most important bottlenecks were public regulations and organic price premiums. Conventional farmers feared yield decrease, restricted forage availability and extra work. In 2008, interviews with selected farmers and officials in local municipalities were conducted to explore the reasons for large differences between certified organic farmland.
Forfattere
Ievina SturiteSammendrag
Nitrogen (N) er kvantitativt det viktigste næringsstoff for vekst og reproduksjon. Nitrogenfikserende planter er avgjørende for å forsyne andre planter med N og for at fôr skal bli en bedre proteinkilde. Hvilke faktorer påvirker potensialet for biologisk nitrogenfiksering og hvordan overlever kløveren den lange nordnorske vinteren?
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Annette BärSammendrag
Skjøtselsplanen for Engan/Ørnes og Kjelvik gir en beskrivelse av de botaniske verdiene og kommer med faglige funderte anbefalinger for restaurering, skjøtsel og drift. Planen baserer seg på feltbe-faringer og eksisterende litteratur. Det ble også tatt hensyn til arealbruk og innspill fra grunneiere. De biologiske verdiene på Engan/Ørnes består i et variert, småskala dreven kulturlandskap. Lands-kapet er preget av en mosaikk av intensiv og ekstensiv slåtte- og beitemark. Botanisk sett er bratt-bakkene spesielt interessante pga et forholdsvis høyt biologisk mangfold. Fokus for skjøtselstiltak og fremtidig drift er å ta vare på disse arealer gjennom kontinuerlig og ekstensiv drift. I tillegg skal spesielt gjengrodd beitemark restaureres og tas i bruk igjen. Det innebærer også en del tynning og rydding av lauvoppslag. Det er viktig å slå veikantene regelmessig.Typisk for Kjelvik er ekstensive, artsrike slåttemark på innmarka og beitepreget bjørkeskog i utmarka. Områder bærer preg av gjengroing. Anbefalinger for skjøtsel tar utgangpunkt i tradisjonell slått på innmarka etter en restaureringsfase hvor krattet fjernes. Utmarka anbefales beitet. Både ekstensiv slått og beite kan også brukes i formidling av hvordan gården tidligere ble drevet.
Forfattere
Eivind UlebergSammendrag
QTL mapping experiments aim to find the genes or mutations that contribute to phenotypic variance. This knowledge is important for biological understanding and can be utilized, e.g. for medical or breeding purposes. QTL mapping methods can be categorised as linkage analysis (LA) methods, linkage disequilibrium (LD) based methods and methods combining linkage and linkage disequilibrium analysis (LLD). The basic difference between LA and LD analysis is the calculations of the probability that two animals carry genes that are identical-by-descent (IBD) at a given point on the chromosome. LA is based on within family IBD, whereas LD is based on population-wide IBD probabilities. LA analysis is dependent on recombinations that can be observed in the genotyped data, which limits the accuracy. LD is based on historical recombinations and can find short confidence intervals, but is likely to result in false positives due to spurious associations between markers and QTL. To avoid the problems of separate LA or LD analysis, approaches combining linkage and linkage disequilibrium mapping (LLD) have been proposed. The main objective of this thesis has been to make maximum use of genotyping information from QTL mapping experiments for detecting as many as possible QTL and position them as precisely as possible. Specific issues addressed have been single versus multiple mapping methods (paper 1), the effects of including the causative mutation amongst the markers in QTL mapping experiments (paper 2) and developing a statistical test to distinguish causative from non-causative SNPs (paper 3).In paper 1 single and multi QTL fine-mapping methods were compared in a situation where two QTL were located in the analysed region. The single QTL method had problems differentiating between two QTLs when these were closely located, which often resulted in discovery of a ghost QTL between the real ones, or no clear QTL discovery. The multi QTL approach found evidence of both QTLs even when these were close (15cM). Although these differences to some extent may be explained by the different statistical approaches used by the two methods, the main conclusion from this paper is that multi QTL mapping methods should be applied when analysing QTL data. Paper 2 investigated the effect of including the causative SNP amongst the markers in a QTL mapping experiment. Both power and precision was greatly increased by including the causative mutation. When the causative mutation was not included amongst the markers the LLD method had clearly better precision and power than the association method. The increased power from including the causative SNP as marker was larger with association mapping than LLD mapping, and when the causation was included amongst the markers the methods had similar power and precision. These differences were partly due to the test-statistics, as the association method tested directly on the markers, while the LLD method tested the midpoints of the marker brackets. Including the causative mutation as marker increases the possibility of discovering QTLs of smaller effects.The increased power and precision obtained by including the causative SNP amongst the markers, was in paper 3 used to develop a test to confirm causative SNPs. The ‘Causative SNP Test" obtained a power of 28 % in this study, while the power of QTL detection was 97 %. The low power of CST was due to strong LD between the analyzed markers. All confirmed SNPs were truly causative and correctly positioned by the CST test. Thus, if positive, this test provides a lot of evidence for causality.Results from QTL mapping experiments so far indicates that most complex traits are controlled by many genes, with mainly small effects on variance. Currently available genome sequences and sample sizes has limited power to detect QTLs with small effects and thus, reported QTLs so far only explains small proportions of observed phenotypic variance for most traits. Future prospects of complete genome sequences will increase the power to find QTLs. The recent strong focus on genome-wide association studies (GWAS) will be expected also for future experiments. This study has shown that future QTL mapping experiments should use multi QTL approaches, to avoid bias from additional QTLs. As the power of QTL mapping is greatly increased by including the causative mutation amongst the markers, one should also aim to design experiments that have high power to distinguish causative from non-causative mutations. Experiments where the relationship between the individuals is low, as is generally the case in human GWAS studies, seem to achieve this. The causality can in the next step be tested by the proposed CST test.
Sammendrag
Only small differences were found in milk composition from farms with different grassland management, except for the concentration of phytoestrogens that was highest on organic farms with short-term grassland. Milk fatty acid composition and milk content of phytoestrogens was strongly affected by farming system
Forfattere
Håvard SteinshamnSammendrag
Det er ikke registrert sammendrag
Forfattere
Håvard SteinshamnSammendrag
Det er ikke registrert sammendrag
Forfattere
Håvard SteinshamnSammendrag
The review confirms that feeding legume silage leads to higher DMI and milk production than grass. White clover is superior to red clover and red clover to lucerne in milk yield relative to intake. Milk fat content is lower on red clover than on grass diets and red clover yield milk with lower protein content than white clover and lucerne. Red clover yields milk with higher proportion of the fatty acids C18:2n-5 and C18:3n-3 than grass and higher content of equol than grass and white clover.