Non-linear change in body condition score over lifetime is associated with breed in dairy cows in Germany

Abstract

Optimal body condition is crucial for the well-being and optimal productivity of dairy cows. However, body condition depends on numerous, often interacting factors, with complex relationships between them. Moreover, most of the studies describe the body condition in Holstein cattle, while condition of some breeds, e.g. Simmental (SIM) and Brown Swiss (BS) cattle, have not been intensively studied yet. Body condition score (BCS) proved to be one of the most effective measures for monitoring body condition in dairy cows. Alterations in BCS were previously mainly studied over a single lactation period, while changes over the lifetime were largely ignored. This study was designed to report BCS of German SIM and BS cows in the light of the broadly accepted BCS in German Holstein (GH) cows and to explore patterns of change in BCS over the productive lifetime of animals. BCS was modeled via linear mixed effects regression, over- and undercondition of animals were studied using mixed effects logistic regressions and condition of animals was explored with the multinomial log-linear model via neural networks. All models included an interaction between breed and age. We found BCS of SIM and BS to be higher than BCS of GH. Our results show that BCS of BS cows did not change over the lifetime. In contrast, the BCS of GH and SIM was found to have a non-linear (quadratic) shape, where BCS increased up to the years of highest productivity and then decreased in aging cows. Patterns of change between SIM and GH, however, differed. GH do not only reach their highest BCS earlier in life compared to SIM, but also start to lose their body condition earlier. Our dataset revealed that 23% of the animals scored were over- and 14% underconditioned. The proportion of cows that were overconditioned was high (>10% of cows) for every breed and every age, while severe underconditioning (>10% of cows) occurred only in middle aged and old GH. Moreover, we found that the probability of underconditioning of animals over lifetime increases, while the overconditioning decreases from the middle to older ages. Our findings highlight the importance of understanding the non-linear nature of BCS, and uncover the potential opportunity for improving the performance and welfare of dairy cows by adjusting their nutrition, not only during lactation, but also highly specific to breed and age.

Keywords: Body condition; Brown Swiss cattle; Overconditioning; Simmental cattle; Underconditioning.

Fig. 1

A - Distribution of animals (% (n)) over three breeds and three regions (East, North and South). B - Density of BCS (Body condition score) per breed per region. Breeds are: GH - German Holstein, SIM - Simmental and BS - Brown Swiss cattle.

Fig. 2

Results of the univariate model of the association between breed (GH - German Holstein, SIM - Simmental and BS - Brown Swiss cattle) and BCS (Body condition score). A - predicted values of BCS. B - estimated marginal means (least-squares means) of BCS per breed with 95% confidence intervals. C - pairwise comparisons of breeds among each other.

Fig. 3

Breed specific evolution of variable age in our dataset in regard to BCS (Body condition score), where breeds are: GH - German Holstein, SIM - Simmental and BS - Brown Swiss cattle. All subplots show predicted values of BCS. Subplot B shows the results of a non-linear additive model, while subplots A, C and D display results of linear mixed-effects models. A model in subplot D, having a non-linear component in the form of the second polynomial degree for age, is technically still linear, because it allows for a linear combination of predictors.

Fig. 4

A - Predicted values of BCS (Body condition score) per breed (GH - German Holstein, SIM - Simmental and BS - Brown Swiss cattle) per age category (described in material and methods). B - estimated marginal means of BCS. C - post-hoc tests of the final model representing contrasts (differences) in BCS between age categories for a particular breed.

Fig. 5

Dynamics of under- (A, B, C) and overconditioning (D, E, F) of breeds (GH - German Holstein, SIM - Simmental and BS - Brown Swiss cattle) in different age groups (see material and methods). A, D - predicted values of BCS (Body condition score) per age category. Condition categories are based on the optimal BCS range per breed per lactation stage as described in Table 1. B, E - pairwise comparisons of age categories among each other. C, F - pairwise comparisons of breeds among each other. G - dynamics of all conditions of breeds in different age groups by the means of non-parametric multinomial neural network based model. Dashed lines indicate the threshold of a percentage of animals in a herd, below which the herd is considered well managed (Kelogg, 2010).