Relationships among nutritive value of selected forages, diet composition and milk quality in goats grazing in a Mediterranean woody rangeland

Woody rangelands are important forage resources for grazing goats in the Mediterranean basin. Goats are well adapted in these heterogeneous and complex ecosystems due to their particular anatomic characteristics, metabolic efficiency and browsing ability. However, the mechanism of grazing behavior and forage selection in goats is quite complex and depends on several factors. The present study deals with the seasonal changes of chemical composition in the selected forages and ingested diets as well as their effects on milk yield and composition of goats grazing in a Mediterranean woody rangeland. Hand plucked forage samples similar to those consumed by the goats were collected for chemical analysis. The nutritive value of consumed forages, in combination with the different feeding and grazing system per trial period, influenced milk quality and performance. The replacement of feed supplementation with an increase of the contribution of grazing in the rangeland could maintain the milk yield and quality at the late stage of lactation. In addition, this paper focuses on the influence of the chemical composition of selected forages on the diet selection of goats using a modeling approach. The model showed a high interpretative accuracy and explanatory value (R2 = 0.923) and was able to distinguish the goats' most important criteria for selecting among the forage plant species in relation to several factors. The results indicate that the dietary preferences of goats were influenced, not only by the seasonality of nutritive value and availability of forages in the rangeland, but also by the plant origin of each nutrient source. The selection of Quercus frainetto was highly correlated with its NDF content. Herbaceous species, Cistus creticus and other woody species were mainly selected due to their CP content. The ADL content seemed to have the lowest influence of all nutritive variables on the selection among groups of plant species. The modeling approach, apart from the understanding of grazing behavior of goats, offers additional information that can be useful to the shepherds in order to manage more effectively the feeding and grazing system of their goat's flock

A modeling approach for estimating seasonal dietary preferences of goats in a Mediterranean Quercus frainetto–Juniperus oxycedrus woodland

Goats are characterized as selective feeders due to their specific feeding behavior, thus the study of their seasonal preferences in a Mediterranean oak-juniper ecosystem is of great interest. The current research was conducted in an open oak forest in Megalo Dereio region, northeastern Greece which was grazed mainly by a flock of 650 local breed goats. Grazing behavior data as the number of bites per plant species were recorded using a direct observation method in late spring (May), middle of summer (July) and late autumn (November) of 2010 and 2011. Additionally, a modeling approach was followed in order to study the factors influencing the dietary preferences of goats. Inference – by adopting the Bayesian paradigm – was based on the best multinomial response logistic regression model, selected by the suitable model assessment criteria. According to the results, seasonal and yearly effects were both important in explaining the grazing behavior of goats, with season being the dominant factor. The model’s estimation accuracy was additionally assessed by the comparison of the calculated model-based dietary preferences with the corresponding observed values. The model could be a useful tool to estimate the seasonal changes of dietary preferences of grazing goats