Abstract
ABSTRACTEffects of dietary concentrate level and grass hay source were determined to evaluate a method (www2.luresext.edu/goats/research/suppconc.html) of predicting negative associative effects between feedstuffs in Boer goat wethers. Forage DM intake (g/kg BW0.75) was similar (P = .157) between growing and yearling wethers (34.9 and 30.8) and ranked 0 and 15 > 30 > 45 g/kg BW0.75 of concentrate dry matter (48.5, 41.8, 25.9, and 15.2, respectively). Age and concentrate level interacted in neutral detergent fibre digestibility (57.3%, 60.6%, 61.4%, and 58.4% for growing and 56.6, 62.9, 56.8, and 30.0% for yearling wethers with 0, 15, 30, and 45 g/kg BW0.75, respectively). There was a tendency (P = .074) for an interaction in metabolizable energy (ME) intake between age and concentrate level (361, 530, 634, and 709 for growing and 363, 547, 541, and 555 kJ/kg BW0.75 for yearling wethers with 0, 15, 30, and 45 g/kg BW0.75); values predicted for treatments with concentrate were 563, 631, and 619 for growing and 575, 684, and 697 kJ/kg BW0.75 for yearling wethers with 15, 30, and 45 g/kg BW0.75, respectively. In conclusion, ME intake was accurately predicted for the low level of concentrate with both animal types and the moderate level with growing wethers.
Highlights
In most ruminant production systems, reproducing females acquire the majority of nutrients and energy from grazed or harvested forage (Minson 1990)
Though it is known that associative effects result from potential change in both intake and digestion of basal forage, the decreases in forage intake predicted by LINC are intended to encompass the sum effect of decreases in forage intake and(or) digestion so that total metabolizable energy (ME) intake is predicted accurately
Inclusion of soybean meal in the concentrate should have averted associative effects resulting from the creation or accentuation of a deficiency of ruminally available nitrogenous compounds
Summary
In most ruminant production systems, reproducing females acquire the majority of nutrients and energy from grazed or harvested forage (Minson 1990). This is generally true for weaned animals, there are settings where diets high in concentrate are fed, such as finishing feedlot cattle in the USA (Galyean & Goetsch 1993). In order to maximize efficiency of utilization of forage and concentrate in mixed diets, there is need to accurately predict both negative and positive associative effects between different types of feedstuffs (Sahlu et al 2009). Though it is known that associative effects result from potential change in both intake and digestion of basal forage, the decreases in forage intake (i.e. substitution) predicted by LINC are intended to encompass the sum effect of decreases in forage intake and(or) digestion so that total ME intake is predicted accurately
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