Effects of long-term restricted feeding on digestion and energy utilization in Balady vs. Shami goats

Abstract

Twenty four non-lactating goats (Age=3.5±0.08 years; Balady goats, n=12 and Shami goats, n=12) were used to evaluate the effects of long-term nutrient restriction on digestion and energy utilization. Six animals of each goat breed were fed a concentrated mixture and alfalfa hay diet (50:50 as DM basis) to meet metabolizable energy (ME) of maintenance (MEm, CON). The other six animals were fed 50% of this amount relative to actual BW (RES). Animals were individually housed for a 90-day period and then moved to metabolic cages in two sets of 12 animals each, three per treatment and breed for each set. Total Energy expenditure (EE) was estimated by a heart rate (HR) monitor for 48h after its individual calibration by oxygen consumption with a face mask open-circuit respiratory system. Body weight and digestibility were negatively affected by long-term restricted feeding, without differences in digestibility between goat breeds. Energy expenditure was greater for CON vs. RES (417 vs. 355kJ/kgBW0.75/day respectively, P<0.001) and lower for Balady goats compared to Shami goats, particularly in terms of RES intake treatment (312 vs. 399kJ/kgBW0.75/day respectively, P<0.01). As a result, the energy balance (EB) was similar for both goat breeds on treatment CON, while it was greater (P<0.05) for Balady goats than Shami goats when they received RES treatment (−133 vs. −208kJ/kgBW0.75/day respectively, P<0.01). In conclusion, Balady goats, but not Shami goats, have the ability to reduce their EE in order to improve their EB as a mechanism of adaptation when their ME intake is restricted below MEm requirements.