Mature-equivalent Protein Yield Research Articles

Efecto de la duración del período seco en la posterior producción y reproducción en vacas Holstein

El registro de los partos de vacas Holstein desde enero 1983 a diciembre 2006 que comprende 1190 rebaños con 384717 partos, se utilizaron para evaluar los factores que afectan la duración del período seco y el efecto de los actuales días secos en las posteriores producciones y reproducciones de las vacas Holstein iraníes. Los análisis estadísticos de los días secos y características productivas y reproductivas en este estudio se realizaron con modelos lineales mixtos. La duración del período seco (DD) de las vacas se agrupa en 14 clases desde menos de 10 días hasta > 130 días. El promedio de DD fue de 100.46 días en vacas Holstein iraníes. Las vacas primíparas tuvieron el menor DD y la media de DD disminuyó a lo largo de los años de 1983 a 2006 y las de parición de verano tenían el DD más corto (p <0.001). Las vacas dentro de las clases DD de 51-60 y 61-70 tuvieron el mayor rendimiento real de leche, la producción de leche en equivalente-madura, producción de leche ajustada, producción de grasa ajustada, producción de proteína y el rendimiento ajustado a equivalente-madura de proteína (p <0.05 ). Además, las vacas dentro de la clase de 0-10 DD tuvo el mayor porcentaje de grasa ajustada, porcentaje de grasa en equivalente-madura y el porcentaje de proteína ajustado (p <0.05). Nuestros resultados actuales muestran una reducción en el intervalo entre partos y en la edad al parto en las vacas con menor longitud de días secos que en otras con una duración del period seco más largo (p <0.05). Teniendo en cuenta la reciente iniciativa de acortar los períodos secos, vale la pena destacar que con 51 a 70 DD se proporciona un rendimiento máximo en vacas Holstein iraníes.

Genetic and phenotypic trends for age at first calving and milk yield and compositions in Holstein dairy cows

Abstract. Calving records from the Animal Breeding Center of Iran collected from January 1990 to December 2007 and comprising 207 106 first calving events of Holsteins from 2 506 herds were analysed using linear sire models to estimate genetic trends for age at first calving (AFC) and milk traits. Genetic trends were obtained by regressing yearly mean estimates of breeding values on year of birth. In general, there were decreasing genetic trends for AFC, fat percentage and protein percentage over the years but there were increasing genetic trends for milk yield, mature-equivalent milk yield, fat yield, mature-equivalent fat yield, protein yield and mature-equivalent protein yield over the years. On the other hand, there was a decreasing phenotypic trend for AFC but estimates of phenotypic trends were positive for milk yield and compositions over the years. It seems that the decline in calving age in this study over time resulted primarily from increased turnover rate and increased culling of heifers that failed to get pregnant. On the other hand, increasing trend for yield traits over time in this study indicated that Iranian dairy producers were successful in choosing progressively better semen and sires from imported and local sources over the years.

Genetic parameters and trends in the Chilean multibreed dairy cattle population.

Estimates of additive and nonadditive multibreed co-variance components, genetic parameters, and predicted genetic values for first lactation 305-d mature equivalent (ME) milk yield, fat yield, and protein yield were computed using data from a sample of 3316 cows from the Chilean Holstein-other breeds multibreed population. Variances and covariances were estimated by 2-trait REML analyses using a Generalized Expectation-Maximization algorithm applied to multibreed populations. Multiple estimates of additive genetic, nonadditive genetic, and environmental variances from 2-trait analyses were averaged to yield a single variance estimate for each trait and effect. Heritabilities were moderate for all traits in Holstein, other, and Holstein x other crossbred groups. Interbreed interactibilities (ratio of nonadditive genetic to phenotypic variances) were all near zero. Multibreed additive, nonadditive, and total genetic trends were estimated using the complete dataset (56,277 cows). Upward trends between 1990 and 2000 existed for all traits, genetic effects, and breed groups, except for 305-d ME protein yield in 1/4 Holstein, indicating that Chilean dairy producers were successful in choosing progressively better semen and sires from imported and local sources over time.

Genetic and phenotypic relationships among milk production and composition traits in primiparous Holstein cows in two different herd environments

Genotype by environment interactions for mature equivalent milk yield (MEM), mature equivalent protein yield (MEP), mature equivalent fat yield (MEF), protein percentage (P%), fat percentage (F%), and lactation mean somatic cell score (LMSCS) were studied using 248 230 first parity records of Holstein cows calving from 1987 to 1994, daughters of 588 sires in 3042 herds. Herds were classified into low and high yield environment classes. Genetic parameters were estimated with bivariate linear mixed models using the multiple trait derivative free software ( mtdfreml). For low yield environment herds, heritabilities for MEM, MEP, MEF, P%, F% and LMSCS were 0.22, 0.20, 0.23, 0.51, 0.58 and 0.11, while for high yield environment herds they were 0.30, 0.27, 0.27, 0.56, 0.56 and 0.09. All genetic correlations, except between MEM and P% and F%, were different in low and high yield environment herd classes. These results indicate that differences in management between the two herd environment classes modify the genetic expression of the traits studied and their genetic association. This suggests that, when these traits are considered in a selection index, appropriate weights for these traits depend on the herd environment class. These results also indicate that different correlated responses for MEP, MEF and LMSCS are expected in high relative to low yield environment herds when selection is based on MEM only.

COMPARISON OF FINNISH AND CANADIAN AYRSHIRE PROVEN BULLS

Semen from four Finnish and four Canadian progeny-tested Ayrshire bulls was used to breed cows and heifers in 50 cooperating Ayrshire herds in Quebec and Ontario in 1972 through 1974. Among the 690 calvings, 2.5% were stillbirths, 2.0% were difficult, 1.1% were malpresentations and 11.4% were unobserved. The percent easy calving among live births was 97% with no significant difference between bull groups or sex of calf. Male calves average 36.4 kg at birth compared with 34.7 kg for females. In the Quebec data, 69% of calvings were to the first service, 23.7% to the second service and 7.2% to a third or later service with no significant difference between bull groups. Heart girth and withers height before calving averaged 164 cm and 119 cm, respectively, in Quebec herds at an average age of 24.6 mo. In Ontario herds, heart girth and withers height after calving averaged 177 cm and 126 cm, respectively, at an average age of 31.6 mo. Taped weight at first calving averaged 420 kg in Quebec herds. None of the measurements of growth showed significant (P > 0.05) differences between groups, although there were significant (P < 0.05) differences among bulls within group. BCA milk and fat averaged 141 and 139, respectively, with a 4.1 ± 3.5 and 4.5 ± 3.3 BCA superiority for Canadian sires in milk and fat, but these differences were not significant (P > 0.05). Mature equivalent protein yield in Quebec heifers averaged 180 kg with a superiority of 10.0 ± 8.5 kg for Canadian sires. Differences between the Finnish and Canadian bulls tested for calving ease, growth and lactation performance were not significant. For conformation, Canadian-sired heifers scored significantly higher (P < 0.05) for final score and all 10 scorecard components and were significantly (P < 0.05) larger, taller, more stylish and more rapid in milking out. No evidence was found to justify extensive use of Finnish Ayrshire bulls in the Canadian population. Key words: Dairy cattle, Ayrshire, Finnish, Canadian, Sire comparison