|Tovar-Luna, I -|
|Puchala, R -|
|Sahlu, T -|
|Goetsch, A -|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 17, 2010
Publication Date: January 1, 2011
Repository URL: http://hdl.handle.net/10113/48593
Citation: Tovar-Luna, I., Puchala, R., Sahlu, T., Freetly, H.C., Goetsch, A.L. 2011. Effects of level of feeding on energy utilization by Angora goats. Journal of Animal Science. 89(1):142-149. Interpretive Summary: The energy requirements of Angora goats are poorly defined. Angoras differ from meat and dairy goats in that a large proportion of the nutrients that they receive are used for growing mohair. The objective of this experiment was to determine the effect of feeding level on efficiency of energy utilization by Angora goats. Efficiency of energy utilization for mohair growth did not differ across feed levels suggesting that a constant efficiency estimate may be used across feeding levels. Energy required for maintenance is lower than current guidelines for Angora goats. Incorporation of this research into predictors of nutrient requirements will improve the nutrient recommendations for Angora goats.
Technical Abstract: Twelve mature Angora does were used in a replicated 3 × 3 Latin square to determine effects of feeding level on energy utilization. Fiber growth was determined in the first 4 wk of 6-wk periods, preceded by 14 or 18 d of adaptation. Metabolizability and gas exchange measures occurred in wk 4, followed by feeding near maintenance then fasting in wk 5 and 6 to determine the ME requirement for maintenance (MEm). A 60% concentrate diet was fed at levels to approximate 100, 125, and 150% of assumed MEm. Digestibility and metabolizability were not affected by treatment with different levels of offered feed and subsequent intake near MEm. Heat energy (HE) during fasting (261, 241, and 259 kJ/kg BW0.75; SEM = 8.7), efficiency of ME use for maintenance (71.6, 69.6, and 69.2%; SEM = 2.29), and MEm (365, 344, and 377 kJ/kg BW0.75 for 100, 125, and 150%, respectively; SEM = 10.3) were similar among treatments. Tissue (non-fiber) gain was lowest among treatments (P < 0.05) for 100% (-0.6, 23.7, and 29.8 g/d), although clean fiber growth only tended to vary among treatments (5.60, 6.57, and 7.36 g/d for 100, 125, and 150%, respectively; SEM = 0.621). Intake of ME was greater (P < 0.05) for 125 and 150 than for 100% (6.87, 8.22, and 8.41 MJ/d for 100, 125, and 150%, respectively). Total HE was greater for 150 vs. 100 (P < 0.05) and 125% (P < 0.07; 6.03, 6.31, and 6.77 MJ/d), and mobilized tissue energy was low but greater (P < 0.05) for 100 vs. 125 (P < 0.05) and 150% (P < 0.07; 0.16, 0.01, and 0.04 MJ/d for 100, 125, and 150%, respectively). Efficiency of ME use for fiber growth was similar among treatments (17.2, 16.3, and 17.7% for 100, 125, and 150%, respectively; SEM = 1.61). In conclusion, efficiency of ME use for fiber growth was similar to the NRC recommendation regardless of feeding level, although MEm was lower perhaps because of experimental conditions employed. Energy appeared partitioned to fiber growth, although preferential usage was not complete possibly because energy metabolism for tissue and fiber accretion reached a plateau with the highest feeding level.