How individual sorting behaviour in dairy goats might modify dietary nutritive characteristics?
Abstract
Goats are able to adapt to various environments due to their developed sorting behaviour. They are able to select the most nutritive fractions of a forage. This study aimed to test if this sorting behaviour and the resulting nutritive value are part of an animal’s personality i.e. if they differ between, but are repeatable within individuals. Eight earlylactating Alpine goats (week 1, 3, 8 and 14 post kidding) were housed in individual pens and fed corn silage, alfalfa hay and concentrate in three separate troughs. Roughages were fed ad libitum. Samples of intake and refusals were taken during five consecutive days and analysed for lignocellulose content (ADF) and for morphological fractions (stems and leaves for alfalfa hay and five fractions for corn silage: stalk and fine leaves, stalk and medium leaves, husk, cob and grain). Percentage of refusals was around 25% for each forage. For hay, goats preferred leaves as they sorted against stems (43.0% stem in the offered hay vs 80.7% in the refusals), with a between-goat standard deviation of 7.23 and a significant goat effect. Three animals were very selective with around 90% of refusals constituted by stems, whereas one had only 68% of stems in its refusal. The outcome was that ADF of hay decreased by 49 g/kg DM, between the hay offered and the hay ingested (347 vs 298 g/kg DM) with a significant between-goat effect (decrease per goat ranging from 34 to 62 g/kg DM). According to intra-roughages relationships based on the INRA 2018 tables, the mean energy value of the alfalfa hay was therefore improved by 0.12 UFL (between 0.08 and 0.15 UFL/kg DM), and the fill value decreased by 0.076 (between 0.05 and 0.10 UEL/kg DM). The personality aspect was more pronounced for corn silage, especially for sorting against husks and cobs. Silage ingested was less fibrous than offered (167 vs 182 g ADF/kg DM), with individual values ranging from 143 to 182. Thus, the mean improvement of the energy value was 0.03 UFL/kg DM (maximum 0.07/kg DM for one goat) and the fill value decreased by 0.059 UEL (maximum 0.160/kg DM). Sorting behaviour may be a personality trait in dairy goats which might enhance the nutritive value of roughages fed ad libitum.