Diet choice by goats as effect of milk production level during late lactation

Abstract

The diet self-regulation ability of goats during late lactation has been studied with regard to their production level. Two groups of seven Girgentana goats producing 1100 6 157 g/day (H group) and 613 6 138 g/day (L group) were housed in individual pens and were given alfalfa pelleted hay (1.5 kg), whole grains of maize (0.5 kg), barley (0.5 kg), faba bean (0.5 kg) and pelleted sunflower cake (0.5 kg) on a daily basis. During a 7-day pre-experimental period, goats received a mixed ration based on the same feeds used during the experimental period (1.5 kg of hay and 0.4 kg of each concentrate). Individual choice of feeds was continuously recorded for 7 days using a 24-h IR video surveillance system equipped with four video cameras. The nutrient intake in both groups was much higher than needed. Goats in the H group ate more (2016.3 v. 1744.3 g dry matter (DM)/day) and selected less hay (26.9% v. 34.6% DM), more high-protein feeds (faba bean and sunflower cake: 14.0% and 15.9% v. 8.8% and 7.9% DM, respectively) and less maize (21.5% v. 25.0% DM), reaching a higher CP concentration in the diet (17.3% v. 15.0% DM) compared with the goats in the L group. During the 24-h trial period, hay was more constantly selected (on average never reaching ,20% of the total hourly basis feeding time, apart from the first hour after feed administration) compared with concentrate feeds. This feeding behaviour has probably exercised a 'curative' effect that enabled the goats to continue to take in very high levels of starch and protein, without manifesting any symptom of metabolic disease. Shifting goats from the pre-experimental diet, based on a mixture of the same feeds used during the experimental period, to the free-choice feeding caused more than 20% increase in milk production in both groups. From the results of the intake, we are unable to conclude that the goats can select their diet to meet their requirements, as goats consumed much more than needed. However, when free to choose their diet, the animals improved milk performance, despite the late-lactation stage.Keywords: goats, milk production level, free-choice feeding, selective behaviour, late lactation ImplicationsThe diet self-regulation ability of goats during late lactation was studied with regard to the production level. Five feeds were individually offered to the goats in a free-choice feeding system. The nutrient input was much higher than needed. The study highlighted the ability of goats to self-regulate, during the day, their diet for quality, more than quantity, to reach a 'curative' effect of the selected diet against metabolic discomfort. Indeed, shifting goats from a feeding system, based on a mixture of the five feeds, to the free-choice feeding system caused an increase of milk yield, despite the latelactation stage. In the light of the positive response of goats to the free-choice system, the research could stimulate further studies aimed to optimize the free-choice feeding system, searching for the best combination between less protein-rich feeds and m...

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