This study was focused on genetic evaluation of longevity in Croatian Simmental cattle using linear and survival models. The main objective was to create a genetic model that is most appropriate to ...describe the longevity data. Survival analysis, using piecewise Weibull proportional hazards model, used all information on the length of productive life including censored as well as uncensored observations. Linear models considered culled animals only. The relative milk production within herd had a highest impact on cows’ longevity. In comparison of estimated genetic parameters among methods, survival analysis yielded higher heritability value (0.075) than linear sire (0.037) and linear animal model (0.056). When linear models were used, genetic trend of Simmental bulls for longevity was slightly increasing over the years, unlike a decreasing trend in case of survival analysis methodology. Average reliability of bulls’ breeding values was higher in case of survival analysis. The rank correlations between survival analysis and linear models bulls’ breeding values for longevity were ranged between 0.44 and 0.46 implying huge differences in ranking of sires.
The aim of this study was to identify frequencies of alleles and genotypes, to evaluate their frequency in population of Holstein-Friesian cows, and to investigate association of κ-casein genotypes ...with longevity and lifetime production of cows. Blood samples were collected from 192 Holstein cows which have finished their production. Cows were reared at one farm in Vojvodina in Serbia. In the current study the following ratios of κ-casein genotypes were found: 0.50 were AA, 0.40 were AB and 0.10 were BB. Frequencies of alleles A and B were 0.70 and 0.30, respectively. Based on these results, it can be concluded that cows with heterozygous genotype AB had the longest life (2809 days) with the highest number of productive days (2062), while the cows which were homozygous recessive of genotype BB had the shortest life expectancy (2627 days) and the lowest number productive days (1878). The same trend was observed with regard to the production results of cows of these genotypes, where statistically significant differences have been observed (P<0.05) in the most traits between cows of heterozygous and homozygous genotypes, while between cows of dominant and recessive homozygous genotype statistically significant differences were not observed (P>0.05). The effect of dominant genes in observed traits was greater than the additive effect of genes. From the ratio of the additive and dominant gene effects, it can be seen that the average degree of dominance in observed traits was positive.
University textbook Principles of Animal Breeding is intended for students of agriculture and veterinary medicine. The material is the adapted curricula of undergraduate and graduate level studies in ...the framework of which the modules Principles of animal breeding as well as Basics of genetics and selection of animals attended are listened. The textbook contains 14 chapters and a glossary of terms. Its concept enables combining fundamental and modern knowledge in the breeding and selection of animals based on balanced and quality manner. The textbook material can be divided into several thematic sections. The first one relates to the classical notions of domestic animals breeding such as the history of breeding, domestication, breed, hereditary and non-hereditary variability and description of general and production traits. The second section focuses on the basic concepts in population and quantitative genetics, as well as biometrics. The third unit is dedicated to the principles of selection and domestic animals improving. The fourth unit relates to the current concepts and objectives of the molecular markers use in domestic animals selection and breeding. The above material has been submitted to the Croatian universities, but so far it has not been published as a textbook. The Ministry of Science, Education and Sports of Republic of Croatia approved financial support for the textbook publication.
Comparison of productive parameters of two analyzed groups (the first generation of imported gilts and the gilts born on the domestic farm) was conducted on a nucleus farm that imported the gilt ...lines from the TOPIGS breeding program. For the purposes of the nucleus pig farm, TOPIGS gilts were imported from Netherlands. The nucleus farm where the analysis of the two groups’ productive parameters was conducted imported the ancestral and grandfather lines to produce the parenting generation TOPIGS 40 sows which are bred with a Pietrain line of boars. The TOPIGS 40 sow is an animal based on A-line and B-line characterized by high fertility rate, excellent maternal characteristics, good capacity for growth, and quality meaty body. The analysis of productive parameters of the two observed groups of gilts (the first generation of 105 imported gilts and 88 gilts born on the domestic farm) resulted in significantly higher number of total born, born alive and weaned piglets after the first farrowing (P<0.001) as well as significantly higher number of total born and born alive piglets at third farrowing (P<0.05). The results of the observed qualities confirm the fact that, apart from the unquestionable genetic potential, other factors such as adaptation, accommodation conditions, microclimate, nutrition, and management have a significant effect on the increase of production results.
Different AT milk recording schemes, with purpose of detection of scheme with the highest lactation milk yields prediction accuracy as well as with simplest practice application, were compared in ...this study. Analysed data were collected from November 2004 till November 2006 on 15 family farms in Croatia according to A4 milk recording scheme by the field assistants of the Croatian Livestock Centre. Measuring at test-day included measurement of milk yield and taking one sample for milk composition analysis at each milking (evening and morning). During research, total of 769 cows were included in research. More than 50 % of all cows were Holstein breed (58.9 %), while the rest of the cows belonged to the Simmental breed. For prediction of daily milk yields two methods were used: M I. = linear regression of daily on partial values with taking into account the interval between successive milkings; M II. = doubling of partial values. The Test Interval Method (TIM) was used for prediction of lactation values. As evaluation criteria for comparison of schemes, correlation and difference between estimated and true milk yields were used. Scheme S II., that is use of first morning, then evening test-day record, in case of doubling the partial yields, showed as scheme with the highest prediction accuracy. Regardless of milk recording scheme, use of method M I. in daily milk yields prediction, resulted in high accuracy and low milk yields, milk fat and protein bias prediction in standard lactation. Research results implicate the use of method M I. in daily milk yields prediction, as well as possibility of different AT milk recording schemes combination in practice.
The aim of this study was to compare different statistical methods for the estimation of daily and 305-day lactation milk, fat and protein yields of Holstein and Simmental cattle breeds using an ...alternative milk recording scheme. Data included 6,824 individual test-day milk yield records collected according to the A4 milk recording method on 668 cows reared on 15 family farms. Daily milk, fat and protein yields were estimated using several statistical methods with regard to breed. The 305-day lactation yields were calculated from estimated daily yields using the Test Interval Method. The correlation between estimated and true yields, as well as the mean difference among estimated and true yield were used as the evaluation criteria for estimation methods. The linear regression of daily to partial milk, fat and protein yields while taking into account the interval between successive milkings was shown to be the most accurate model for estimating daily values, either from morning or evening records. The simple doubling of morning or evening records overestimated and underestimated the daily yields, respectively. When 305-day lactation milk, fat and protein yields were compared no difference between evaluated methods were found. Also, a separate estimation of daily and 305-day lactation yields according to breeds did not result in increased estimation accuracy.
Test-day records as a tool for subclinical ketosis detection Gantner, V., Josip Juraj Strossmayer University in Osijek, Osijek (Croatia). Faculty of Agriculture; Potocnik, K., University of Ljubljana, Domzale (Slovenia). Biotechnical Faculty, Zootechnical Department; Jovanovac, S., Josip Juraj Strossmayer University in Osijek, Osijek (Croatia). Faculty of Agriculture
Acta veterinaria,
(2009), 2009-00-00, Letnik:
59, Številka:
2-3
Journal Article
Recenzirano
Odprti dostop
The purpose of this study was to determine the prevalence of subclinical ketosis as well as the effect of subclinical ketosis on daily milk yield in Slovenian Holstein cows using monthly test day ...records.
Glavni ciljevi ovoga istraživanja bili su genetsko vrednovanje dugovječnosti simentalskih bikova u Hrvatskoj pomoću metode analize preživljavanja i linearnih mješovitih modela te usporedba korištenih ...metoda. Analizom preživljavanja, temeljenom na piecewise Weibull modelu proporcionalnih rizika korišteni su svi dostupni podaci o trajanju produktivnog vijeka krava, uključujući i krave koje se još uvijek nalaze u proizvodnji i čiji datum izlučenja nije bio poznat u trenutku završetka istraživanja. U slučaju modifikacija linearnih modela, razmatrane su samo izlučene životinje. Uspoređujući primijenjene metode, analiza preživljavanja rezultirala je višim vrijednostima heritabiliteta (0.075) u odnosu na linearni model oca (0.035) kao i na individualni linearni model (0.056). Genetski trend bikova za dugovječnost imao je rastući karakter (linearni modeli), dok je uporabom analize preživljavanja genetski trend bio opadajući. Prosječne pouzdanosti procijenjenih uzgojnih vrijednosti bikova za dugovječnost na temelju linearnih modela bile su niže u odnosu na iste procijenjene piecewise Weibull modelom proporcionalnih rizika. Korelacije ranga između uzgojnih vrijednosti bikova procijenjenih različitim metodama kretale su se u rasponu od 0.44 do 0.46.
Different statistical models were compared to estimate daily milk yield from morning or evening milking test results. The experiment was conducted on 14 family farms with 325 recorded cows. The ...amount of explained variance was higher for models including the effects of partial milk yield, the interval between successive milking, the interaction between partial milk yield and the milking interval and the farm (R
2
= 0.976 for AM, R
2
= 0.956 for PM) than for models including partial milk yield effect only (R
2
= 0.957 for AM, R
2
= 0.937 for PM). Estimates of daily milk yield from linear models were more accurate than those obtained by doubling single milking weights. The results show that more complex model gives the best fit to the data. Differences between models according to determination and correlation coefficient were minor. Further investigations on larger sets of data are needed to draw more general conclusion.
The objective of this study was to evaluate relationship between milk yield in the first three lactations regarding levels of milk yield in the first lactation and levels of age at the first calving. ...Prediction of milk yield in later lactation based on milk yield in the earlier one was also carried out. The data used in this study were 5743 lactation yields collected from 1995 to 2003. All cows finished the first three lactations. Mean value of milk yield in the first lactation was 5283.5 kg, 6033.5 kg in the second and 6338.4 kg the third one. The milk yield estimation coefficients between the first and second lactation was 1.164, between the first and third was 1.231, and 1.079 between the second and third. The levels of milk yield in the first lactation highly significant influenced the value of estimation coefficient between first three lactations, while the age at first calving influenced less significantly. Determination coefficient (R2) values for models used in prediction ranged from 0.348 to 0.396.
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