Analysis of water intake, dry matter intake and daily milk yield using different error covariance structures

Abstract

The aim of the present study was to investigate the daily measured traits milk yield, water intake and dry matter intake with fixed and random regression models added with different error covariance structures. It was analysed whether these models deliver better model fitting in contrast to conventional fixed and random regression models. Furthermore, possible autocorrelation between repeated measures was investigated. The effect of model choice on statistical inference was also tested. Data recording was performed on the Futterkamp dairy research farm of the Chamber of Agriculture of SchleswigHolstein. A dataset of about 21 000 observations from 178 Holstein cows was used. Average milk yield, water intake and dry matter intake were 34.9, 82.4 and 19.8 kg, respectively. Statistical analysis was performed using different linear mixed models. Lactation number, test day and the parameters to model the function of lactation day were included as fixed effects. Different structures were tested for the residuals; they were compared for their ability to fit the model using the likelihood ratio test, and Akaike's and Bayesian's information criteria. Different autocorrelation patterns were found. Adjacent repeated measures of daily milk yield were highest correlated (p 1 5 0.32) in contrast to measures further apart, while for water intake and dry matter intake, the measurements with a lag of two units had the highest correlations with p 2 5 0.11 and 0.12. The covariance structure of TOEPLITZ was most suitable to indicate the dependencies of the repeated measures for all traits. Generally, the most complex model, random regression with the additional covariance structure TOEPLITZ(4), provided the lowest information criteria. Furthermore, the model choice influenced the significance values of one fixed effect and therefore the general inference of the data analysis. Thus, the random regression 1 TOEPLITZ(4) model is recommended for use for the analysis of equally spaced datasets of milk yield, water intake and dry matter intake.

Analysis of water, feed intake and performance of lactating sows

“…The error covariance was modelled due to the fact that repeated daily measurements within the lactation of sow were assumed to contain autocorrelated repeated measures (Kramer et al, 2008b;Littell et al, 1998;Littell et al, 2006). The covariance of the residual term was modelled with the spatial (exponential) structure (SP(EXP)).…”

Gestión hídrica en el sistema familiar lácteo de la subcuenca Amecameca en el Estado de México.

“…These values correspond to the second stage "Dynamic" of the methodology. Water consumption for watering animals that was obtained in the FDS of the Amecameca Sub-Basin is higher (5.6 l of water per liter of milk) in comparison with what was reported by various authors (Kume et al, 2010;Kramer et al, 2008;Nosetti et al, 2002;Meyer et al, 2004) (Table 1), because most of the studies reported were carried out with factors and conditions that were totally different than those evaluated in this research; for example, geographic region, milk production systems, type of diet, irrigation to obtain fodder, period of lactation, physiological stage, climate, season of the year, among others. The value obtained in this study represents more than double what was reported by Kume et al (2010), with a value of 2.66 liters of water per liter of milk per bovine head of breeding stock.…”

“…Estos valores corresponden a la segunda etapa "Dinámica" de la metodología. El consumo de agua para abrevar que se obtuvo en el SFL de la Subcuenca Amecameca es mayor (5.6 l de agua por L de leche) en comparación con lo reportado por diversos autores (Kume et al, 2010;Kramer et al, 2008;Nosetti et al, 2002y Meyer et al, 2004) (Cuadro 1), debido a que la or no more than five employees), and humid (they are the establishments that require a consumption of 76 to 150 m 3 bimonthly to perform their activities). According to the Gazette of the Estado de México Government (2012), ranches and establishments were classified within the humid use.…”

“…Consumo voluntario de agua de bebida por vaca (L agua/L leche) Uso de agua de servicio por vaca Kramer et al (2008) 2.36 Kume et al (2010) 2.66 Sánchez (1965) 9.60 l agua/vaca Meyer et al (2004) 2.62 Nosetti et al (2002) 0.95 l agua/ vaca Spörndly E. y E.Wredle (2005) 1.94 Valores obtenidos 5.60 1.00 l agua/ l de leche Fuente: elaboración propia. u Source: authors' elaboration.…”

Group housing for lactating sows with electronically controlled crates: 1. Reproductive traits, body condition, and feed intake

“…Therefore, the error covariance needed to be modeled. Acceptable residuals were performed with the first-order heterogeneous autoregressive structure (Littell et al, 2006;Kramer et al, 2008;Kruse et al, 2010).…”