Feeding behaviour, digestibility, energy balance and productive performance of lactating goats feed forage-based and forage-free diets

Six lactating Saanen goats have been used in a Latin Square design to evaluate a grass-based diet (G), a hay-based diet (H) and a nonforage diet (NF). On a dry matter, grass and hay contributed for 55% of the diets and had 13.7 and 16.1% CP, 55.4 and 49.4% NDF, 38.0 and 31.6% ADF, respectively. Diet NF had beet pulp, cracked carob beans and whole cottonseed as main ingredients, with more than 75% of the particles greater than 2 mm. Independently of the dietary treatment, the goats spent more time eating than ruminating. Diet NF proved to be effective in stimulating chewing activity, despite a trend for a lower chewing activity for eating (178, 185, 125 min/kg DMI for diets G, H and NF, respectively), but not for ruminating (84, 80, 80 min/kg DMI for diets G, H and NF, respectively). Feed intake did not differ among diets, while regarding digestibility diet NF had the highest values for DM (74.1%), OM (75.7%) and non-fibrous carbohydrates (92.0%), but the lowest for ADF (44.5%). For treatments G, H and NF milk yields were 3011, 3688 and 3212 g/d (P<0.05 between H and G), while milk fat and protein were respectively 3.37, 3.24, 2.96% (P<0.05 between G and NF) and 3.11, 3.32, 3.29%. Milk urea N was lower for diet NF (18.8, 18.6, 12.7 mg/100 ml, P<0.001). Diet NF increased the concentration of the short chain fatty acids of milk fat and decreased the content of C18:0, C18:1 and C18:3 in comparison to the other two diets. No difference among treatments was recorded for CLA. Intake energy was digested to a lesser extent for diet G (68.9, 70.0, 72.7%, P<0.05 between G and NF) due to its poor quality forage. Urinary energy losses reflected the corresponding protein contents of the diets, while no difference was recorded for methane production. ME resulted higher for diet NF (60.0, 60.7, 65.1% of the intake energy, P<0.01), while heat production and milk energy yield were similar in the three treatments. Diet NF had a higher ME content (11.13, 11.26, 11.93 MJ/kg DM, P<0.05), while no significant difference among the diets was recorded in terms of kl (0.64, 0.70, 0.69) and NEl (7.20, 7.93, 8.30 MJ/kg DM). It is concluded from the study that a nonforage diet with an adequate amount of structured fibre could substitute a ration based on poor quality forage in lactating goats; however, good forage seems to enhance milk performance to a greater extent.