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

• Main Authors: Gianni Matteo Crovetto, Alberto Tamburini, Luciana Bava, Luca Rapetti
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2010-01-01
• Series: Italian Journal of Animal Science
• Subjects: Goat, Nonforage diet, Chewing activity, Energy balance, Milk
• Online Access: http://www.aspajournal.it/index.php/ijas/article/view/228

Six lactating Saanen goats have been used in a Latin Square design to evaluate a grass-based diet (G), a hay-based diet<br />(H) and a nonforage diet (NF). On dry matter, grass and hay contributed for 55% of the diets and had 13.7 and 16.1%<br />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<br />as main ingredients, with more than 75% of the particles greater than 2 mm.<br />Independently of the dietary treatment, the goats spent more time eating than ruminating. Diet NF proved to be effective<br />in stimulating chewing activity, despite a trend for a lower chewing activity for eating (178, 185, 125 min/kg DMI<br />for diets G, H and NF, respectively), but not for ruminating (84, 80, 80 min/kg DMI for diets G, H and NF, respectively).<br />Feed intake did not differ among diets, while regarding digestibility diet NF had the highest values for DM (74.1%), OM<br />(75.7%) and non-fibrous carbohydrates (92.0%), but the lowest for ADF (44.5%). For treatments G, H and NF milk yields<br />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,<br />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<br />ml, P<0.001). Diet NF increased the concentration of the short chain fatty acids of milk fat and decreased the content of<br />C18:0, C18:1 and C18:3 in comparison to the other two diets. No difference among treatments was recorded for CLA.<br />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<br />quality forage. Urinary energy losses reflected the corresponding protein contents of the diets, while no difference was<br />recorded for methane production. ME resulted higher for diet NF (60.0, 60.7, 65.1% of the intake energy, P<0.01), while<br />heat production and milk energy yield were similar in the three treatments. Diet NF had a higher ME content (11.13,<br />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,<br />0.69) and NEl (7.20, 7.93, 8.30 MJ/kg DM).<br />It is concluded from the study that a nonforage diet with an adequate amount of structured fibre could substitute a ration<br />based on poor quality forage in lactating goats; however, good forage seems to enhance milk performance to a greater<br />extent.