B. Berglund

Genetic and Environmental Correlations Among Female Fertility Traits and Milk Production in Different Parities of Swedish Red and White Dairy Cattle

The main objective of this study was to estimate genetic correlations between fertility and production traits in first, second and third lactations as well as between fertility traits measured in the same way at different ages. The fertility traits studied were: number of inseminations per service period, number of treatments for reproductive disturbances, interval between first and last inseminations, interval between calving and first insemination, and interval between calving and last insemination. Early milk production was measured as the average of the energy-corrected milk yield at the second and third monthly testdays in a lactation. The number of records was approximately 450 000, 350 000, 180 000 and 75 000 in the heifer period, first, second, and third lactations, respectively. A linear, trivariate model that included the effects of herd-year, year, month, age and sire of the cow was applied. To reduce the effect of ongoing selection, 305-days kg protein production in first lactation was included as a variate in all of the analyses. Correlations between the herd-year effects indicated that factors of herd-year level conducive to increased production had a tendency to increase the number of inseminations as well as the number of reproductive treatments, although there was an earlier start and termination of the insemination period. Genetic correlations between fertility traits and production were in the range of 0.2-0.4, all of them unfavourable and higher at later parities. The genetic correlations between fertility traits in the heifer period and the same traits in first lactation were 0.7. Genetic correlations between the first and second lactation varied between 0.7 and 0.9, and between the second and third lactation they were all 0.9 or higher. In conclusion, fertility and production traits need to be selected for simultaneously if fertility is going to be maintained along further genetic improvement on production, and such selection should include fertility results from lactating cows.

Somatic cell count as a selection criterion for mastitis resistance in dairy cattle.

Abstract The purpose of this study was to investigate whether it is possible to increase the resistance to clinical mastitis by selecting for bulls siring daughters whose milk has a low somatic cell count. Data from the animal disease recording scheme, including all veterinary treatments for clinical mastitis, were used in the analysis. A total of 1462 progeny tested Swedish Red and White bulls (SRB), and 911 Swedish Friesian bulls (SLB), with nearly 750 000 effective daughters, were included. Effects of alternative selection criteria on response to clinical mastitis were studied by using selection index theory. Correlations between relative breeding values for clinical mastitis and somatic cell count were 0.45 for SRB bulls and 0.41 for SLB bulls. Corresponding genetic correlations were indirectly estimated to be 0.79 and 0.71. The relationships were found to be linear. It was concluded that it is possible to improve resistance to clinical mastitis by selecting for a low somatic cell count. Due to the higher heritability of the somatic cell count selection based on this was more efficient than selection directly on clinical mastitis to improve mastitis resistance when only small progeny groups (less than 100 daughters) were available. However, a combination of both measures was about 20% more efficient than the former alone. There were no significant differences in relative breeding values for clinical mastitis between bulls differing in their proportion of Holstein-Friesian genes.

Relationship between somatic cell count and milk yield in different stages of lactation

The association between somatic cell count (SCC) and daily milk yield in different stages of lactation was investigated in cows free of clinical mastitis (CM). Data were recorded between 1989 and 2004 in a research herd, and consisted of weekly test-day (TD) records from 1,155 lactations of Swedish Holstein and Swedish Red cows. The main data set (data set A) containing 36,117 records excluded TD affected by CM. In this data set, the geometric mean SCC was 55,000 and 95,000 cells/mL in primiparous and multiparous cows, respectively. A subset of data set A (data set B), containing 27,753 records excluding all TD sampled in lactations affected by CM, was created to investigate the effect of subclinical mastitis (SCM) in lactations free of CM. Daily milk yields were analyzed using a mixed linear model with lactation stage; linear, quadratic and cubic regressions of log(2)-transformed and centered SCC nested within lactation stage; weeks in lactation; TD season; parity; breed; pregnancy status; year-season of calving; calving, reproductive, metabolic and claw disorders; and housing system as fixed effects. A random regression was included to further improve the modeling of the lactation curve. Primiparous and multiparous cows were analyzed separately. The magnitude of daily milk loss associated with increased SCC depended on stage of lactation and parity, and was most extensive in late lactation irrespective of parity. In data set A, daily milk loss at an SCC of 500,000 cells/mL ranged from 0.7 to 2.0 kg (3 to 9%) in primiparous cows, depending on stage of lactation. In multiparous cows, corresponding loss was 1.1 to 3.7 kg (4 to 18%). Regression coefficients of primiparous cows estimated from data set B were consistent with those obtained from data set A, whereas data set B generated more negative regression coefficients of multiparous cows suggesting a higher milk loss associated with increased SCC in lactations in which the cow did not develop CM. The 305-d milk loss in the average lactation affected with SCM was 155 kg of milk (2%) in primiparous cows and 445 kg of milk (5%) in multiparous cows. It was concluded that multiparous cows in late lactation can be expected to be responsible for the majority of the herd-level production loss caused by SCM, and that preventive measures need to focus on reducing the incidence of SCM in such cows.

Causes of Stillbirth and Time of Death in Swedish Holstein Calves Examined Post Mortem

This study was initiated due to the observation of increasing and rather high levels of stillbirths, especially in first-calving Swedish Holstein cows (10.3%, 2002). Seventy-six Swedish Holstein calves born to heifers at 41 different farms were post mortem examined in order to investigate possible reasons for stillbirth and at what time in relation to full-term gestation they had occurred. The definition of a stillborn calf was dead at birth or within 24 h after birth after at least 260 days of gestation. Eight calves were considered as having died already in uterus. Slightly less than half of the examined calves (46.1%) were classified as having died due to a difficult calving. Four calves (5.3%) had different kinds of malformations (heart defects, enlarged thymus, urine bladder defect). Approximately one third of the calves (31.6%) were clinically normal at full-term with no signs of malformation and born with no indication of difficulties at parturition or any other reason that could explain the stillbirth. The numbers of male and female calves were rather equally distributed within the groups. A wide variation in post mortem weights was seen in all groups, although a number of the calves in the group of clinically normal calves with unexplained reason of death were rather small and, compared with e.g. those calves categorised as having died due to a difficult calving, their average birth weight was 6 kg lower (39.9 ± 1.7 kg vs. 45.9 ± 1.5 kg, p ≤ 0.01). It was concluded that the cause of stillbirth with a non-infectious aetiology is likely to be multifactorial and difficult calving may explain only about half of the stillbirths. As much as one third of the calves seemed clinically normal with no obvious reason for death. This is a target group of calves that warrants a more thorough investigation in further studies.SammanfattningObduktionsstudie av dödfödda SLB-kalvar - dödsorsaker och dödstidpunkt.Andelen dödfödda kalvar har ökat och den genomsnittliga frekvensen hos förstakalvande SLB är nu 10.3% (2002). Detta utgjorde bakgrunden till att denna studie initierades där 76 dödfödda SLB-kalvar från förstakalvare i 41 olika besättningar obducerades med syfte att fastställa dödsorsak samt tidpunkt i förhållande till födseln. Definitionen av en dödfödd kalv var att den efter fullgången dräktighet (minst 260 dagar) var död vid födseln eller inom 24 timmar efter födseln. Åtta kalvar (10,5%) bedömdes ha dött redan i livmodern. Knappt hälften av kalvarna (46,1%) bedömdes ha dött på grund av svår kalvning. Fyra kalvar (5,3%) hade olika typer av missbildningar (2 hjärtmissbildningar, 1 förstorad thymus, 1 urinblåsedefekt). Nära en tredjedel av kalvarna (31,6%) var fullt utvecklade och utan några tecken på missbildningar, kalvningssvårigheter eller andra or saker som kunde förklara dödfödseln. Fördelningen av tjur- resp. kvigkalvar inom de olika kategorierna var i stort sett lika. Variationen i födelsevikter var stor inom alla kategorier, men den genomsnittliga födelsevikten var ca 6 kilo lägre för den tredjedel kalvar som föddes fullt utvecklade med oförklarad dödsorsak. Det konkluderades att orsaken till dödfödslar (med en icke-infektiös sjukdomshistoria) är multifaktoriell och att svåra kalvningar bara förklarar cirka hälften av dödfödslarna. Att det hos en så stor andel som en tredjedel av kalvarna tycks finnas någon form av oförklarat vitalitetsproblem gör att orsakerna till dödsfallen för denna grupp av kalvar behöver studeras ytterligare i framtida studier.

Genetic improvement of dairy cow reproductive performance.

The welfare of cow along with profitability in production are important issues in sustainable animal breeding programmes. Along with an intense/intensive selection for increased milk yield, reproductive performance has declined in many countries, in part due to an unfavourable genetic relationship. The largely unchanged genetic trend in female fertility and calving traits for Scandinavian Red breeds shows that it is possible to avoid deterioration in these traits if they are properly considered in the breeding programme. Todays breeding is international with a global selection and extensive use of the best bulls. The Nordic countries have traditionally recorded and performed genetic evaluation for a broad range of functional traits including reproduction. In recent years many other countries have also implemented genetic evaluation for these traits. Thus, the relative emphasis of dairy cattle breeding objectives has gradually shifted from production to functional traits such as reproduction. Improved ways of recording traits, e.g. physiological measures, early indicator traits, assisted reproductive techniques and increased knowledge of genes and their regulation may improve the genetic selection strategies and have large impact on present and future genetic evaluation programmes. Extensive data bases with phenotypic recordings of traits for individuals and their pedigree are a prerequisite. Quantitative trait loci have been associated to the reproductive complex. Most important traits, including reproduction traits are regulated by a multitude of genes and environmental factors in a complex relationship, however. Genomic selection might therefore be important in future breeding programmes. Information on single nucleotide polymorphism has already been introduced in the selection programmes of some countries.

Effects of complex vertebral malformation on fertility in Swedish holstein cattle.

AbstractComplex vertebral malformation (CVM) is an autosomal recessive inherited defect in the Holstein breed. It causes intra-uterine mortality through the entire gestation period leading to repeat breeding and involuntary culling of cows and thereby economic losses. The defect was first reported in Denmark in 1999 and a direct DNA test for the defect has been available since February 2001. The aim of this study was to investigate if Holstein bulls heterozygous for the CVM gene had reduced reproductive performance, measured as non-return rate (NRR) and in a daughter fertility index. All genotyped Swedish Holstein bulls born between 1995 and 1999 were included. Altogether 228 bulls were analysed, of which 53 bulls, i.e. 23%, were confirmed CVM carriers. A statistically significant difference between carriers and non-carriers in the relative breeding value for NRR was observed for 168 days NRR (101.1 ± 0.9 vs. 103.1 ± 0.6, p < 0.05). There was no difference for 28 days NRR whereas the difference approached significance for 56 days NRR. No significant effect of the paternal CVM genotype on the daughter fertility index was shown probably due to the complexity of traits this index is composed of. In conclusion, the study showed that carriers of the CVM defect have an inferior NRR compared with non-carriers.SammanfattninEffekterna av CVM på fruktsamheten hos svensk Holstein. Complex vertebral malformation (CVM) är en genetisk defekt i Holsteinrasen som först rapporterades från Danmark 1999. Den orsakar fosterdödlighet genom hela dräktighetsperioden och leder på så sätt till ekonomiska förluster genom omlöpningar och ofrivillig utslagning av kor. Ett markör-test för defekten har funnits tillgängligt från september 2000 och endirekt gen-test sedan februari 2001. Alltsedan dess testas alla tjurar i Sverige för defekten och bärare används ej i aveln. Syftet med denna studie var att retrospektivt undersöka om man kunde se en skillnad i fruktsamhet mellan Holstein tjurar som var bärare av CVM-genen jämfört med icke-bärare. Alla CVMtestade tjurar som använts i den svenska AI-organisationen som var födda mellan 1995 och 1999 ingick istudien. Analysen omfattade 228 tjurar varav 53 stycken d.v.s. 23% var bärare av CVM-genen. En statistisk signifikant skillnad i 168 dagars icke-omlöparfrekvens erhölls mellan bärare och icke-bärare (101,1 ± 0,9 vs. 103,1 ± 0.6, p & 0,05). Det var ingen skillnad mellan grupperna för 28 dagars NR men den närmade sig signifikans vid 56 dagars NR. Ingen effekt av CVM på dotterfruktsamhetsindexet kunde påvisas. Det beror sannolikt på att detta index är sammansatt av flera olika egenskaper varav CVM barakan påverka antalet inseminationer per insemineringsomgång. Sammanfattningsvis visade studien att bärare av CVM-genen hade en signifikant sämre fruktsamhet mätt som icke-omlöparfrekvens, jämfört med CVM-fria tjurar. Eftersom nya defekter uppstår vartefter illustrerar detta exempel vikten av att rapportera in alla misstänkta missbildningar och av att ha kontrollprogram för genetiska defekter så att åtgärder kan sättas in på ett tidigt stadium innan de förorsakat alltför stora negativa konsekvenser.

Optimising lactation cycles for the high-yielding dairy cow. A European perspective

Abstract Few investigations have been performed where effects of a planned increase of the calving interval have been elucidated. In order to study these matters, a research project has started at the Swedish University of Agricultural Sciences (SLU). The study involves researchers both at the Agricultural and Veterinary Faculties at SLU as well as from the dairy industry in Sweden. Experiments are being performed within two experimental herds (approximately 150 cows) belonging to SLU. We are now in the middle of a three-year study comparing 12- and 15-month calving intervals (herd 1) or 12- and 18-month calving intervals (herd 2). In herd 2, two milking frequencies (2 vs. 3 per day) are combined with the two calving intervals. Long-term effects on health, reproduction, milk production (including milk quality) and production efficiency are studied in detail. The plan is to study individual cows in three consecutive years. Interactions with management system and breed will also be investigated. Results from the first lactation show no significant differences in fertility between treatments. So far, milking three times per day has not given a more persistent lactation compared with milking two times a day. Some cases of salty taste of milk have been noticed.

Genome-wide associations for fertility traits in Holstein-Friesian dairy cows using data from experimental research herds in four European countries

Genome-wide association studies for difficult-to-measure traits are generally limited by the sample population size with accurate phenotypic data. The objective of this study was to utilise data on primiparous Holstein-Friesian cows from experimental farms in Ireland, the United Kingdom, the Netherlands and Sweden to identify genomic regions associated with traditional measures of fertility, as well as a fertility phenotype derived from milk progesterone profiles. Traditional fertility measures investigated were days to first heat, days to first service, pregnancy rate to first service, number of services and calving interval (CI); post-partum interval to the commencement of luteal activity (CLA) was derived using routine milk progesterone assays. Phenotypic and genotypic data on 37 590 single nucleotide polymorphisms (SNPs) were available for up to 1570 primiparous cows. Genetic parameters were estimated using linear animal models, and univariate and bivariate genome-wide association analyses were undertaken using Bayesian stochastic search variable selection performed using Gibbs sampling. Heritability estimates of the traditional fertility traits varied from 0.03 to 0.16; the heritability for CLA was 0.13. The posterior quantitative trait locus (QTL) probabilities, across the genome, for the traditional fertility measures were all <0.021. Posterior QTL probabilities of 0.060 and 0.045 were observed for CLA on SNPs each on chromosome 2 and chromosome 21, respectively, in the univariate analyses; these probabilities increased when CLA was included in the bivariate analyses with the traditional fertility traits. For example, in the bivariate analysis with CI, the posterior QTL probability of the two aforementioned SNPs were 0.662 and 0.123. Candidate genes in the vicinity of these SNPs are discussed. The results from this study suggest that the power of genome-wide association studies in cattle may be increased by sharing of data and also possibly by using physiological measures of the trait under investigation.

Genetic and Environmental Correlations Among Female Fertility Traits, and Between the Ability to Show Oestrus and Milk Production in Dairy Cattle

Genetic and environmental correlations were estimated both between the ability to show oestrus and milk production, and among different fertility traits (heat-intensity score, number of days between consecutive inseminations, number of inseminations per service period, interval between calving and first or last insemination, and interval between first and last insemination). Milk production was measured as the average of the energy-corrected milk yield on second and third monthly test days. The number of records were approximately 450000, 350000, 180000 and 75000 in the heifer period, first, second and third lactations, respectively. A linear, trivariate model that included the effects of herd-year, year, month, age and cows sire was applied. The results indicated that further selection for increased milk production is not expected to deteriorate heat intensity. The number of days between calving and first insemination, the number of inseminations and the heat intensity were complementary, and can be recommended for a selection index for fertility.

Live Weight Changes, Feed Consumption, Milk Yield and Energy Balance in Dairy Cattle during the First Period of Lactation

Abstract The purpose of this study was to estimate any breed differences and to investigate the interrelationships between live weight changes, feed consumption, milk production in kg energy corrected milk (kg ECM) and the therefrom calculated energy balance with emphasis on the first part of lactation. Altogether 508 lactations were studied for 153 cows from the same herd in first to fifth lactation of the following Swedish dairy cattle breeds: Swedish Red and White (SRB), Swedish Friesian (SLB), reciprocal F1-crosses of the two breeds, and Swedish Jersey (SJB). The gamma function (Y n=an b·ecn) was fitted to each animals records in order to derive secondary traits from the functions. A Mixed Model Procedure was used to estimate breed and parity effects and variance components. The average goodness of fit to the function, as assessed by the R 2 value, was best for milk production data, followed by feed consumption, while lower R 2 values were obtained for live weight changes and especially for energy ba...