摘要:

The use of derivative-free methods to give maximum likelihood estimates of bivariate (co)variance parameters is illustrated. An algorithm is given to estimate the four variance and two covariance parameters of two random effects associated with each trait when both traits are measured on all animals and the same fixed and random model hold for both traits. By reparameterising in terms of canonical heritabilities and a transformation matrix, a six-dimensional problem is reduced to a two-dimensional problem. It is shown how to derive the estimate of the transformation matrix given the values for the canonical heritabilities. Maximization is then only over the two dimensions of canonical heritabilities and the transformation matrix. The use and the properties of the method are illustrated with examples from simulated selection experiment data.

ISSN:0906-4702    

DOI:10.1080/09064709209410128

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Records form Finnish Ayrshire cattle were used to estimate variances and covariances of milk traits by the restricted maximum likelihood (REML) method using the individual animal model (IAM). Two data sets were analyzed. The first data set consisted of 1423 sires and 16363 cows, of which 11911 had records on first lactation. The heritabilities estimated from this data set for milk yield, protein yield, protein content and fat content were 0.40, 0.31, 0.63 and 0.68, respectively. The second data set was a subset of first data set with herds with less than ten observations excluded and consisted of 1335 sires and 11262 cows with 8140 first, 5688 second and 3717 third lactation records. The heritability estimates from the second data set under a repeatability model for milk yield, protein yield, protein content and fat content were 0.30, 0.26, 0.59 and 0.66, respectively. The repeatability estimates for the same traits were 0.53, 0.51, 0.67 and 0.76, respectively. The second data set was also used to estimate genetic and phenotypic correlations among milk traits in first lactation. Both genetic and phenotypic correlations among protein yield and protein and fat content traits were small. The genetic correlation between milk yield and protein content was -0.61, between milk yield and fat content -0.50 and between protein content and fat content 0.67. Absolute values of phenotypic correlations for the same pairs of traits were somewhat smaller than respective genetic correlations.

ISSN:0906-4702    

DOI:10.1080/09064709209410129

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Different selection strategies were studied to improve milk traits and to reduce the frequency of clinical mastitis and somatic cell count. The results indicate that it is better to use both clinical mastitis and somatic cell count in the selection index to improve the resistance of animals to mastitis and to improve the quality of milk. Selection for protein yield simultaneously with selection against mastitis or somatic cell count would result in increased milk, fat and protein yields, increased protein content, decreased fat content and decreased frequency of clinical mastitis and somatic cell count. Maximizing the total net economic profit based on the current pricing system in Finland would not decrease somatic cell count or frequency of clinical mastitis.

ISSN:0906-4702    

DOI:10.1080/09064709209410130

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Multivariate REML analysis was used to treat the results of a selection experiment for lean tissue growth rate that included 393 purebred Swedish Yorkshire gilts. Heritabilities were estimated to be 0.51, 0.33, 0.45 and 0.41 for pubertal age, litter size, mean piglet birth weight and weight loss during first lactation, respectively. There was a negative genetic correlation between pubertal age and growth rate and a positive one between pubertal age and leanness. The genetic correlation was positive between growth rate and piglet weight and negative between litter size and piglet weight. Age at puberty, litter size and piglet weight showed a positive genetic correlation with weight loss during lactation.

ISSN:0906-4702    

DOI:10.1080/09064709209410131

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Danish experiments with growing pigs from the last 40 years are presented to enlighten some of the problems connected with carcass fat quality. In the experiments a variety of feeds have been used, supplying varying amounts of fat differing greatly in fatty acid composition. Generally, whende novofatty acid synthesis, resulting in saturated and monounsaturated fatty acids, is predominant, the back fat will be very firm, while the deposition of dietary polyunsaturated fatty acids will produce soft backfat. The relationship between the amount and composition of dietary fat and the content and profile of intramuscular fat seems complicated. Oats, rapeseed, sunflower seed, animal fat and vegetable oil should only be included in limited amounts in the diet to avoid high occurrence of unacceptable soft backfat and rancidity of the carcass. The iodine value (IV) of backfat is shown to be related to the iodine value product (IVP) of the dietary fat through the following equation: IV=47.1+0.14 × IVP/day (R2=0.86).

ISSN:0906-4702    

DOI:10.1080/09064709209410132

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In Norway 40–50% of trotters start to race before the age of five years. This clearly represents a preselection process which may affect the ability to estimate the true genetic trend on the basis of mixed linear model methods. This problem was conceptually examined by stochastic simulation and the animal model by assuming positive genetic and environmental correlations between a preselection criterion and transformed earnings. Inclusion of data on started horses, only, in the analysis (a selected data approach) resulted in a severe underestimation of the true genetic trend, while addition of zero unrankable earnings for horses culled prior to races (a dummy data approach) reduced the bias from preselection. The dummy data approach appeared robust to changes in preselection intensity over time, but sensitive to increasing phenotypic variance in transformed earnings due to inflation. The latter problem was taken into account by expressing the phenotypes as standard normal deviates within birth year.

ISSN:0906-4702    

DOI:10.1080/09064709209410133

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The variation in progesterone secretion during the luteal phase and pregnancy in blue fox vixens was analyzed. Progesterone was measured in blood plasma once or twice a week using radioimmunoassay. The material was allocated into three groups; five mated, but barren, blue fox vixens, six mated vixens with implantation zonès in the uterus, but no cubs at parturition, and 26 normally parturient vixens. The progesterone profiles for the three different groups of females showed a steady increase in progesterone immediately after mating. Maximum values were observed on days 8–12 of pregnancy. Then the progesterone levels decreased gradually until delivery around day 52. The levels of progesterone were found to be significantly different (P<0.05) between non-pregnant and pregnant females from day 22 after mating. The plasma progesterone level seems to be affected by the presence of conceptuses.

ISSN:0906-4702    

DOI:10.1080/09064709209410134

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Plasma prolactin secretion during the luteal phase and pregnancy was studied in 11 mated but non-parturient and 26 parturient blue fox vixens. Prolactin was measured in blood plasma once or twice a week using a heterologous double-antibody radioimmunoassay. Data for all females were fitted with an animal model. In both groups of females, prolactin concentrations increased slowly during the early post mating period. For the parturient vixens the prolactin values increased further until parturition, whereas there was only a slight increase in the non-parturient vixens. Statistically significant differences (p < 0.05) were observed in prolactin release between the non-parturient and parturient animals from day 36 after mating. A possible role of prolactin may exist in the luteotrophic complex maintaining pregnancy in blue fox vixens, because higher levels of plasma prolactin and progesterone appeared in the parturient vixens compared to the non-parturient during the second half of gestation.

ISSN:0906-4702    

DOI:10.1080/09064709209410135

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Presmolt Atlantic salmon (Salmo salar), 16–17 months old and weighing 65 ± 5 g, were fed either a control diet or a diet containing equal portions of pyruvate and α-ketoglutarate replacing 10% of the total feed dry weight. In a pilot experiment the keto acid diet had been fed to 5-month-old salmon during 5 weeks without adverse effects on growth and the body amino acid content. Nitrogen excretion was markedly diminished. In the major experiment the 16–17-month-old presmolt salmon were divided into four groups. After one week on the diets one control and one keto acid group were continuously exposed to 17-β-estradiol by implanting a capsule containing the hormone. After further 4 weeks the fish were killed. The vitellogenin concentration in the plasma was 50.5 ± 5.1 mg and 56.7 ± 5.2 mg/ml for the hormone treated fish fed the control and the keto acid diet, respectively. Liver glycogen content decreased during hormone treatment, but the fish fed on the keto acids were less affected. Upon exposure to estradiol the activity of tyrosine aminotransferase (EC 2.6.1.5) and malic enzyme (EC 1.1.1.40) was diminished in both feeding groups. Phosphoenolpyruvate carboxykinase (EC 4.1.1.32) was elevated in activity after feeding the keto acid diet but was unaffected by hormone treatment. Isocitric dehydrogenase (EC 1.1.1.42) and glutamate dehydrogenase (EC 1.4.1.3) were elevated in activity after hormone treatment of the fish fed on the keto acids. Fatty acid synthetase (EC 2.3.1.38) as well as glucose-6-phosphate dehydrogenase (EC 1.1.1.49) plus 6-phosphogluconate dehydrogenase (EC 1.1.1.43) were unchanged by dietary and hormonal conditions. The high vitellogenin synthesis in the liver was reflected in a decrease in protein content per g wet weight of muscle. Proteins of sarcoplasmic origin were more affected by estradiol treatment than those of myofibrillar origin. No differences between the dietary conditions were noted. Muscle glycogen content was elevated in the fish fed on the keto acids without an effect by estradiol. In summary, a utilization of dietary pyruvate and α-ketoglutarate in carbohydrate metabolism seemed to occur. Pyruvate and α-ketoglutarate can be used as an alternative carbohydrate source in the diet. The advantage of such a diet is the diminished nitrogen excretion by the fish into the water without a negative effect on growth and vitellogenin synthesis.

ISSN:0906-4702    

DOI:10.1080/09064709209410136

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0906-4702    

DOI:10.1080/09064709209410127

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor