INCORPORATION OF MILK CONTENT TRAITS INTO A BREEDING PROGRAM

lako se općenito priznaje da bi uzgojni cilj u sastavu mlijeka trebalo usmjeriti na povećanje (ili neizmijenjeni) postotak bjelančevina i smanjenje postotka masnoće, većina uzgojnih programa ide u prilog visokih postotaka masnoće, bilo posredno ili neposredno putem selekcije na visoki postotak bjelančevina. Čak pri selekciji na jednu osobinu, na postotak bjelančevina, zbog visoke korelacije između osobina sadržaja i veće varijabilnosti postotka masti odnosna reakcija postotka masnoće može biti veća nego neposredno povećanje postotka bjelančevina. U Finskoj se postotci osobina razmatraju u domaćem uzgoju već od 1988. Prihvaćen je i cilj smanjenja postotka masnoće i kao posljedica toga bikovi rođeni nakon 1990. imaju oko 25% jedinica niži sadržaj masnoće u mlijeku nego bikovi rođeni između 1985. i 1987. Godine 1990. ustanovljen je uzgojni program otvorenog prijenosa jezgre embrija koji je primijenio alternativni uzgojni cilj u sastavu mlijeka. Cilj je bio podići omjer bjelančevina: masnoća u mlijeku, povećavajući sadržaj bjelančevina dok se u isto vrijeme održavao nepromijenjen postotak masnoće. lzabrane su relativne težine za osobine koje su davale jednaku važnost stvaranju i postotku bjelančevina s istovremenom negativnom težinom za postotak masnoće. Za vrijeme od četiri godine rada provedeno je ispiranje 291 krave, te je prenijeto 1607 embrija. Do sada je rođeno 746 telića. Godine 1995. prvih 95 ET kćeri ocijenjeno je prema nacionalnom programu modela životinja. Njihovi BLUP postotci bjelančevina bili su +.14 iznad skupine junica oteljenih iste godine, a BLUP-ovi dobivenih bjelančevina bili su 12 kg iznad srednje vrijednosti analogne skupine. Uzgojne vrijednosti postotka masnoće bile su na istoj razini kao u klasi te godine.Although it is commonly agreed that the breeding goal in milk composition should be towards increased (or unaltered) protein-% and decreased fat-%, in most breeding programs high fat percentage is favored either directly or indirectly via selection for high protein-%. Even in single trait selection for protein-%, due to high correlation between content traits and a bigger variability in fat-% the correlated response in fat-% can be larger than direct inprovement in protein-%. In Finland the percentage traits have been considered in the national breeding since 1988. The goal to decrease fat-% has been adopted, and as a result bulls born after 1990 have about -.25% -units lower fat content of milk than bulls born 1985-87. In 1990 an open nucleus embryo transfer breeding program was established that employed alternative breeding goal in milk composition. The aim was to raise the protein to fat ration in milk by increasing the protein content while the same time keeping the fat-% unaltered. Relative weights for traits were chosen that gave equal importance to protein yield and percentage, with simultaneous negative weight on fat-%. During the four years of operation 291 cows have been flushed, and 1607 embryos have been transferred. Till now 766 calves have been born. In 1995 first 95 ET-daughters were evaluated with national animal model program. Their protein-% BLUPs were +. 14 above the group of heifers born same year, and the protein yield BLUPs were 12 kg above analogous group mean. The fat-% breeding values were in same level as in the year class

The relationships between early lactation energy status indicators and endocrine fertility traits in dairy cows

The relationships between dairy cow milk-based energy status (ES) indicators and fertility traits were studied during periods 8 to 21, 22 to 35, 36 to 49, and 50 to 63 d in milk. Commencement of luteal activity (C -LA) and interval from calving to the first heat (CFH), based on frequent measurements of progesterone by the management tool Herd Navigator (DeLaval), were used as fertility traits. Energy status indicator traits were milk beta-hydroxybutyrate (BHB) concentration provided by Herd Navigator and milk fat: protein ratio, concen-tration of C18:1 cis-9, the ratio of fatty acids (FA) C18:1 cis-9 and C10:0 in test-day milk samples, and predicted plasma concentration of nonesterified fatty acids (NEFA) on test days. Plasma NEFA predictions were based either directly on milk mid-infrared spectra (MIR) or on milk fatty acids based on MIR spectra (NEFAmir and NEFAfa, respectively). The average (standard deviation) C-LA was 39.3 (+/- 16.6) days, and the average CFH was 50.7 (+/- 17.2) days. The correlations between fertility traits and ES indicators tended to be higher for multiparous (r < 0.28) than for primiparous (r < 0.16) cows. All correlations were lower in the last period than in the other periods. In period 1, correlations of C-LA with NEFAfa and BHB, respectively, were 0.15 and 0.14 for primiparous and 0.26 and 0.22 for multiparous cows. The associations between fertility traits and ES indicators indicated that negative ES during the first weeks postpartum may delay the onset of luteal activity. Milk FPR was not as good an indicator for cow ES as other indicators. According to these findings, predictions of plasma NEFA and milk FA based on milk MIR spectra of routine test-day samples and the frequent measurement of milk BHB by Herd Navigator gave equally good predictions of cow ES during the first weeks of lactation. Our results indicate that routinely measured milk traits can be used for ES evaluation in early lactation.Peer reviewe

Estimation of individual animal SNP-BLUP reliability using full Monte Carlo sampling

Calculation of individual animal reliability of estimated genomic breeding value by SNP-BLUP requires inversion of the mixed model equations (MME). When the SNP-BLUP model includes a residual polygenic (RPG) effect, the size of the MME will be at least the number of genotyped animals (n) plus the number of SNP markers (m). Inversion of the MME in SNP-BLUP involves computations proportional to the cube of the MME size; that is, (n + m)3, which can present a considerable computational burden. We introduce a full Monte Carlo (MC) sampling-based method for approximating reliability in the SNP-BLUP model and compare its performance to the genomic BLUP (GBLUP) model. The performance of the full MC approach was evaluated using 2 data sets, including 19,757 and 222,619 genotyped animals selected from populations with 231,186 and 13.35 million pedigree animals, respectively. Genotypes were available in the data sets for 11,729 and 50,240 SNP markers. An advantage of the full MC approximation method was its low computational demand. A drawback was its tendency to overestimate reliability for animals with low reliability, especially when the weight of the RPG effect was high. The overestimation can be lessened by increasing the number of MC samples

Bias in genetic evaluation using random regression test-day model

The effect of an upgraded Finnish evaluation model on bias in estimated breeding values for protein yield was investigated. Evaluations based on repeatability animal model and on random regression test-day model without and with heterogeneous variance adjustment were compared. Comparisons were based on the average difference between pedigree indices and the future estimated breeding values, based on own or on daughter performance records. This was defined as empirical bias. The pedigree indices were computed from reduced data sets where four years of the most recent data were excluded. Results showed an upward bias in the protein yield pedigree indices for Ayrshire young sires of 2.2 kg, 2.5 kg and 1.8 kg from the repeatability animal model, random regression test-day model and random regression test-day model with heterogeneous variance adjustment, respectively. Pedigree indices for daughters of young sires were upward biased, whereas pedigree indices for daughters of proven sires were slightly underestimated when heterogeneous variance was not accounted. Inclusion of test-day yields from the fourth lactation onwards increased the bias. Moving from repeatability animal model to random regression test-day model did not reduce the bias, whereas adjustment of heterogeneous variance reduced bias.

Relationship between clinical mastitis, somatic cell score, and production for the first three lactations of Finnish Ayrshire

vo

Symposium review: Single-step genomic evaluations in dairy cattle

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Genetic parameters for Finnish blue fox population: litter size, age at first insemination and pelt size

Pelt size has increased rapidly in the Finnish blue fox population during the last decade. However, average number of pups per mated female has slightly decreased after the mid-1990s. In this study we estimated genetic parameters of litter size in the first two parturitions, age of female at first insemination, and pelt size with a linear multitrait animal model. Heritability of litter size in first and second parturition was 0.06 and 0.10, respectively. Heritability estimate for age at first insemination was 0.15 and for pelt size 0.29. Genetic correlation between pelt size and first litter size was 0.30, between first and second litter size 0.76, and between second litter size and age at first insemination 0.70. Thus, genetic correlation between fertility and pelt size was unfavorable.