Reproductive sustainability in Norwegian Red cows

Cow fertility is among the most important economic factors in dairy production, and a key trait in export of Norwegian Red (NR). Successful reproduction is the result of complex interactions of many factors affected by genetics as well as environment. This project delivered knowledge and tools to improve dairy cow fertility which are needed to prevent negative consequences of changes towards larger herd size, higher milk yield per cow and more efficiency pressure in Norwegian dairy herds. Early embryo mortality is a major factor contributing to decline in reproductive efficiency. In this project we identified causes and risk factors for early embryo death. We did a clinical study where NR heifers were synchronized, superovulated, and inseminated, and collected embryo. Two groups of bulls, with high and low non-return% respectively, were used for insemination. The resulting embryos were gene sequenced and results showed that the sire had a significant effect on early embryo development (blastocyst stage). Gene expression of several genes in pathways related to embryo development were different in the two groups. Fertility problems due to endometritis is an increasing problem internationally. In this project we studied occurrence of subclinical endometritis in NR and identified risk factors and associations to cow fertility. Results from a large field study including cytology testing of 1800 cows showed a prevalence of subclinical endometritis of 28 %. This was surprisingly high given the overall god fertility in the NR population. We estimated heritability of subclinical endometritis and showed that there is genetic variation for this trait in NR. However, cheaper and easier ways of measuring subclinical endometritis is needed before this can be considered included in a breeding program. Fertility has been an important trait in the breeding program for NR since the 1970s. Breeding values for cow fertility is in the routine genetic evaluation and included in the total merit index for NR, while male fertility has been evaluated phenotypically. We have done the first genetic analyses of male fertility traits and estimated genetic parameters for semen characteristic traits for NR. All analysed semen production and sperm quality traits showed genetic variation and results illustrate the potential for genetic evaluation for male fertility. Genomic breeding values for semen production and sperm quality traits may be useful when selecting bull calves to become future AI bulls and allow monitoring genetic trends for these traits. Cow fertility is an important trait in the breeding program for NR. The current fertility traits have low heritability, and are among the most challenging traits in genomic selection. Better and more precise phenotypes is needed. We have analyzed data from activity tags used for heat detection of NR cows and aim to use this to develop more reliable measures of cow fertility, and thereby increase genetic gain in NR. Results from the first genetic analyses cow activity data shows that these data can be used for genetic evaluation of cow fertility. Access to routinely collected data from these sensors are needed before implementation can be considered.

Prosjektet har levert ny kunnskap innen mange ulike aspekt av fruktbarhet hos storfe som kan være med å sikre god fruktbarhet for framtidas mjølkeku. Embryotap har stor betydning for økonomien i mjølkeproduksjonen. Prosjektet har vist at far(oksen) har en vesentlig betydning for embryoutviklingen i det tidlige stadiet (blastocyststadiet). Selv om oksenes sædkvalitet gjennomgår kvalitetskontroll på seminstasjonen er det variasjon i ikke-omløps%. Vi har vist at genuttrykk på blastocyststadiet er påvirket av far. Okser med høy versus lav ikke-omløps % gav ulikt genuttrykk i tidlige embryo og flere av genene som ble ulikt uttrykt var knyttet til pathways som kan forklare at det er ulike utviklingspotensialet hos embryo. Prosjektet har kartlagt utbredelsen av subklinisk endometritt, årsaksfaktorer og effekten dette har på fruktbarheten på NRF kyr i Norge. Prevalensen var overraskende høy (28%) sett i sammenheng med den relativt gode fruktbarheten NRF kyr har. Vi har vist at det finnes genetisk variasjon i motstandsevne mot subklinisk endometritt i NRF. Hvis en finner enklere og billigere metoder for å måle egenskapen er det er mulig å inkludere den i avlsarbeidet. I prosjektet har vi også studert livmorens mikrobiom i tiden ved første inseminasjons etter kalving hos kyr med og uten subklinisk endometritt. Det er sett på ulike prøvetakingsmetoder og konkludert med at en relativt enkel svaberprøve fra skjeden kan gi en god indikasjon på forholdene i livmoren. Det er levert en doktoravhandling på genetiske analyser av oksefruktbarhet. For første gang er det beregnet arvegrader og genetiske korrelasjoner for sædproduksjon og sædkvalitetsegenskaper for NRF okser. Dette gi et grunnlag for at Geno kan implementere slike egenskaper i sine rutine-beregninger av avlsverdier. Genomiske avlsverdier for sædproduksjon og sædkvalitetsegenskaper kan brukes for å selektere oksekalver som skal bli framtidas seminokser, og til å overvåke utvikling av oksefuktbarhet i populasjonen. Ny teknologi, som aktivitetsmålere for brunstkontroll, gir nye muligheter innen husdyravl. I dette prosjektet har vi jobbet med å finne nye og mer presise fenotyper for fruktbarhet, som kan gi sikrere avlsverdier og større avlsframgang for fruktbarhet. De første genetisk analysene av aktivitetsdata for NRF og viser at data fra aktivitetsmålere kan brukes for å beregne avlsverdier for kufruktbarhet. Løsninger for rutinemessig innsamling av data fra sensorer som aktivitetsmålere må på plass før dette kan tas i bruk i avlsarbeidet

Cow fertility is an important economic factors in dairy production, and a key trait in export of Norwegian Red (NR). Successful reproduction is a result of complex interactions of many factors affected by genetics as well as environment. This project will deliver knowledge and tools to improve dairy cow fertility which are needed to prevent negative consequences of changes towards larger herd size, higher milk yield per cow and more efficiency pressure in Norwegian dairy herds. Early embryo mortality is a major factor contributing to decline in reproductive efficiency. Further, the incidence of endometritis in NR is unknown. Embryo loss and endometritis result in increased number of services per conception, decreased non return rate and increased interval from calving to last service. Endometritis will lead to delayed onset of estrus and increased interval from calving to first service. These problems are of economic importance and may increase the use of antibiotics and reproductive hormones in dairy farms. In this project, we will identify causes and risk factors for early embryo death and endometritis and study occurrence of subclinical endometritis in NR. Breeding values for cow fertility is in the routine genetic evaluation and included in the total merit index for NR, while male fertility has been evaluated at the performance test station. We analysed male fertility traits and estimate genetic parameters for semen characteristic traits for NR based on data from the test station. Knowledge of genetic associations between these male fertility traits and other traits in the NR breeding goal is needed. We will also assess the potential for genomic evaluation for male fertility in NR. Cow fertility is an important trait in the breeding program for NR. The current fertility traits have low heritability, and are among the most challenging traits in genomic selection. Better and more precise phenotypes is needed. Data from activity tags can provide more reliable measures of cow fertility, and we will examine how we can utilize these data to improve phenotypimg of fertility and thereby increase genetic gain in NR.