Effects of main reproductive and health problems on the performance of dairy cows: a review

This review focuses on the potential effects of twinning, dystocia, stillbirth, abortion, retained placenta and metritis on the productive and reproductive performances in dairy cattle. These are diverse disorders that are similar in that they all can result in impaired performance of dairy cows. Reproductive problems occur frequently in lactating dairy cows and can dramatically affect reproductive efficiency in a dairy herd. Poor reproductive performance is a major cause of involuntary culling and therefore reduces the opportunity for voluntary culling and has a negative influence on the subsequent productivity of a dairy herd. Reproductive performance is influenced by the interactive effect of environment, management, health, and genetic factors. In addition, diseases mainly affect dairy cow productivity by decreasing reproductive efficiency, shortening the expected length of productive life and by lowering milk production. Deciding whether to breed, treat, or cull dairy cows showing one or more of these problems is a challenge for both veterinarians and dairy producers. In addition, there is considerable debate among dairy scientists and bovine practitioners regarding the economic impact of these problems in a dairy operation and the most effective management or therapeutic intervention for treating them. Because of this controversy, dairy managers should focus on prevention and control of risk factors associated with each problem rather than on prescriptive therapeutic interventions

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

Calving records of Holstein cows from January 1983 to December 2006 comprising 1,190 herds with 384,717 calving events were used to evaluate factors affecting the dry period length and effect of current dry days on the next productive and reproductive performances of Holstein cows. Statistical analyses of dry days, productive and reproductive traits in this study were performed as linear mixed models. Dry period length (DD) of cows was grouped into 14 classes from 130 days. Average DD was 100.46 days in Holstein cows. Primiparous cows had the lowest DD and the mean of DD decreased over the years from 1983 to 2006 and summer calvers had the shortest DD (p <0.001). Cows within the DD classes of 51-60 and 61-70 had the greatest actual milk yield, mature equivalent milk yield, adjusted milk yield, adjusted fat yield, mature equivalent milk yield, adjusted protein yield and mature equivalent protein yield (p <0.05). Also, cows within the DD class of 0-10 had the greatest adjusted fat percentage, mature equivalent fat percentage and adjusted protein percentage (p <0.05). Our current results showed a reduction in calving interval and age at calving after cows had shorter dry days than with other longer dry period lengths (p <0.05). Given the recent advocacy for shortened dry periods, it is worthwhile to emphasize that 51 to 70 DD does provide maximal performance in Holstein cows.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

Introducing a sinusoidal equation to describe lactation curves for cumulative milk yield and composition in Holstein cows

6 páginas, 3 tablas, 1 figura.The aim of the work reported here was to investigate the appropriateness of a sinusoidal function by applying it to model the cumulative lactation curves for milk yield and composition in primiparous Holstein cows, and to compare it with three conventional growth models (linear, Richards and Morgan). Data used in this study were 911 144 test-day records for milk, fat and protein yields, which were recorded on 834 dairy herds from 2000 to 2011 by the Animal Breeding Centre and Promotion of Animal Products of Iran. Each function was fitted to the test-day production records using appropriate procedures in SAS (PROC REG for the linear model and PROC NLIN for the Richards, Morgan and sinusoidal equations) and the parameters were estimated. The models were tested for goodness of fit using adjusted coefficient of determination , root mean square error (RMSE), Akaike's information criterion (AIC) and the Bayesian information criterion (BIC). values were generally high (>0.999), implying suitable fits to the data, and showed little differences among the models for cumulative yields. The sinusoidal equation provided the lowest values of RMSE, AIC and BIC, and therefore the best fit to the lactation curve for cumulative milk, fat and protein yields. The linear model gave the poorest fit to the cumulative lactation curve for all production traits. The current results show that classical growth functions can be fitted accurately to cumulative lactation curves for production traits, but the new sinusoidal equation introduced herein, by providing best goodness of fit, can be considered a useful alternative to conventional models in dairy research.The authors wish to acknowledge the Animal Breeding Centre and Promotion of Animal Products of Iran for providing the data used in the current study

A sinusoidal equation as alternative to conventional growth functions to describe the evolution of growth in quail

10 páginas, 4 tablas, 3 figuras.Aim of study: The aim of the present study was to introduce a sinusoidal equation into poultry science by applying it to temporal growth data from quail. Material and methods: To examine the performance of the sinusoidal equation in describing the growth patterns of quail, four conventional growth functions (Gompertz, logistic, López and Richards) were used as reference in this study. Comparison of models was carried out by analysing model behaviour when fitting the curves using nonlinear regression and assessing statistical performance. Maximum log-likelihood estimation, mean squared error, Akaike and Bayesian information criteria were used to evaluate the general goodness-of-fit of each model to the different data profiles. Main results: The selected sinusoidal equation precisely describes the growth dynamics of quail. Comparison of the growth functions in terms of the goodness-of-fit criteria revealed that the sinusoidal equation was one of the most appropriate functions to describe the age-related changes of bodyweight in quail. Research highlights: To the best of our knowledge there are no studies available on the use of sinusoidal equations to describe the evolution of growth in quail. The sinusoidal equation used in this study represents a suitable alternative to conventional growth functions to describe the growth curves for a range of strains/lines of male and female Japanese quail