A total of 6620 monthly test day records of SCC, milk yield, and protein percentage from single lactations of 2374 Spanish Churra ewes from 10 flocks was used to estimate genetic and environmental parameters. A subset of 4278 records containing data from healthy udders (SCC < or = 250,000 cells/ml) was also analyzed. Genetic parameters were estimated by REML using an animal model. Herd test date, parity, and lactation stage contributed significantly to variation of most variables, and birth type significantly affected milk yield only. The SCC increased markedly as parity number and stage of lactation increased. Heritabilities (+/- SE) for test day milk yield, log SCC, protein percentage, and log SCC (< or = 250,000 cells/ml) were 0.18 (0.03), 0.09 (0.02), 0.16 (0.03), and 0.03 (0.02), respectively. The corresponding repeatabilities were 0.54, 0.38, 0.38, and 0.10. Genetic correlations of log SCC with milk yield and protein percentage were -0.23 and 0.18, respectively. Phenotypic correlations were -0.15 and 0.16. Genetic and environmental reduction of SCC for dairy ewes could be achieved using practices similar to those for dairy cows. The negative genetic correlation between milk yield and SCC suggested that selection for increased milk yield alone is expected to result in a decrease in SCC.

A total of 3231 lactation records of somatic cell counts (SCC), milk yield, and protein percentage for 2379 Spanish Churra ewes from 10 flocks were used to estimate genetic and environmental parameters. Genetic parameters were estimated by REML with a multitrait repeatability animal model. A lactation measure of SCC was obtained as the mean of test day log SCC adjusted for stage of lactation. Heritabilities for SCC, milk yield, and protein percentage were 0.12, 0.24, and 0.17, respectively. The corresponding repeatabilities were 0.35, 0.49, and 0.38. Heritability and repeatability estimates of SCC obtained from this study fell within the range frequently reported for dairy cows. Therefore, as practiced for dairy cattle, future possibilities for sire evaluation to improve udder health status using lactation measures of SCC for dairy sheep are not rejected, although hygienic practices are regarded as more important. Genetic correlations of SCC with milk yield and protein percentage were -0.15 and -0.03, respectively. The genetic correlation between milk yield and protein percentage was -0.47. The low genetic correlations of SCC with milk yield and protein percentage may indicate that breeding decisions to improve milk and protein yields of Churra ewes are not expected to have an effective correlated response in SCC.

A data file with 11,547 lactations for 2602 Spanish Churra ewes, daughters of 100 sires and 2179 dams, was used to estimate genetic and phenotypic parameters of total and partial lifetime traits with a multiple-trait animal model using REML. These ewes first lambed between 1992 and 1998 and belonged to 27 flocks enrolled in the nucleus scheme of the breed. The study took into account 4 life span traits, 2 productive traits, and 2 reproductive traits. Lifetime revenues from milk and lambs were calculated. Daily traits for both milk and revenues of lifetime, productive life, and useful life were also calculated. Partial lifetime traits were considered for the first 3 parities. The model included flock and birth year within flock as fixed effects and animal as a random effect. Both fixed effects contributed significantly to variation of all total lifetime traits. Milk production level was included in the model as a covariable to adjust life span traits. Heritability estimates for life span traits were low (0.02 to 0.06), indicating few possibilities for direct genetic selection. Genetic and phenotypic correlations among life span traits averaged 0.90 and 0.87, respectively. Heritabilities for daily milk and revenue traits were always higher than those for their corresponding lifetime traits. Heritability for milk yield per day of useful life was 0.25 (+/-0.04). Heritability estimates for partial lifetime performance traits increased notably when more parities were included (from the first parity to the first 3 parities). Their genetic and phenotypic correlations with total lifetime traits also increased gradually when more information was considered. These results indicate that possibilities for early genetic selection for some lifetime traits are not totally excluded.

Genetic parameters were estimated using REML in a multiple-trait animal model including genetic direct and maternal effects for birth and weaning weights, pre-weaning daily weight gain and three linearly scored traits (muscularity, skeletal size and general appearance) in 3,428 Charolais calves. The three complex type traits were scored at weaning on a nine-point scale.Fixed effects considered were herd-year-season of birth, sex of the calf and parity number of the dam. The fixed effect of weaning season and the linear covariate of age at weaning were considered for all variables except for birth weight. All fixed effects contributed significantly (P < 0.001) to variations in all traits except for the effect of weaning season which was not significant for the general appearance score. The percentage of variance explained by the model averaged 50.74% for the considered traits. Average birth and weaning weights and pre-weaning daily weight gain were 42.95, 278.21 and 1.11 kg, respectively, while muscularity, skeletal size and general appearance scores averaged 5.33, 5.19 and 5.36, respectively. Direct heritability estimates were 0.36, 0.36, 0.22, 0.50, 0.52 and 0.52 for the six traits, respectively. The corresponding maternal heritabilities were 0.37, 0.32, 0.18, 0.18, 0.15 and 0.13, respectively. Direct genetic correlations among these traits varied from low and negative (-0.11) between birth and weaning weights to extremely high and positive (0.95) between muscularity and skeletal size scores. Type traits can be effectively used to improve the efficiency of beef production for Charolais calves in Spain.Additional key words: general appearance, genetic correlation, growth traits, heritability, muscularity, skeletal size. ResumenEstimación de parámetros genéticos del peso al nacimiento, peso al destete, ganancia diaria nacimiento-destete y tres caracteres morfológicos en ganado vacuno de raza charolesa en España Se han estimado los parámetros genéticos de los caracteres, peso el nacimiento, peso al destete, ganancia media diaria predestete, y tres caracteres morfológicos lineales (desarrollo muscular, desarrollo esquelético y aptitud funcional) en 3.428 terneros Charoleses usando REML en un modelo animal multicarácter, incluyendo efectos genéticos directos y maternos. Los tres caracteres de tipo fueron registrados en una escala lineal de uno a nueve puntos. Los efectos fijos considerados en el modelo son rebaño-año-estación de parto, sexo del ternero y el número de parto de la vaca. Se consideró el efecto fijo estación de destete y la covariable edad al destete para todas las variables, excepto para el peso de nacimiento. Todos los efectos fijos fueron significativos (P < 0,001) en todas las variables, excepto el efecto estación de destete, que no fue significativo para el carácter aptitud funcional. El porcentaje de varianza explicada por el modelo fue en promedio el 50,74% para los caracteres estudiados. Las medias de los caracteres peso al nacimiento, peso al destete y ganancia media diaria predestete f...

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A data file on 36,396 lactations was used to determine the strength of the phenotypic relationship between productive, reproductive and lifespan traits for 7935 Spanish Churra ewes. These ewes first lambed between 1989 and 1997 and belonged to 23 flocks. The study took into account four lifespan traits (lifetime, productive life, useful life and lifetime score), three productive traits (total milk yield produced during lifetime, lambs weaned during ewe lifetime and total revenues from sold milk and weaned lambs during lifetime) and two reproductive traits (age at first lambing and mean interval between successive lambings). Moreover, milk yield and revenues from sold milk and weaned lambs were calculated per day of lifetime, productive life and useful life. Partial lifespan traits were considered for the first three parities. The model included flock, birth year within flock and season of birth of the ewe as fixed effects. The first two effects contributed significantly to variation in all traits, while season significantly affected lifespan traits, productive traits and age at first lambing. Milk production level was added to the model for lifespan traits only. It significantly contributed to explaining the variation in all lifespan traits with high percentage of variance explained averaging 14.91%. Lifetime averaged 2324 d. Productive life accounted for 57% of lifetime while useful life represented 50% of productive life. Age at first lambing averaged 622 d and average days dry during lifetime was 560. During lifetime, ewes gave an average of 4.6 parities, 6.5 weaned lambs and 636 l of milk. Average revenue from milk and lambs during lifetime was 673 euros. Milk/day of lifetime, productive life and useful life averaged 0.26, 0.51 and 0.93 l, respectively. The corresponding per-day revenues from sold milk and weaned lambs were, 0.27 euros, 0.55 euros and 1.01 euros, respectively. Lifespan and productive traits had strong relationships (rp among these traits ranged between 0.75 and 0.95). Two-parity and three-parity per-day milk yield had moderately high correlation (0.70-0.83) with total lifetime per-day milk yield traits. Therefore, good use of these traits would be helpful in determining best individuals early in life.