Submitted to: Small Ruminant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2004
Publication Date: 7/1/2004
Citation: Luo, J., Goetsch, A.L., Nsahlai, I.V., Moore, J.E., Galyean, M.L., Johnson, Z.B., Sahlu, T., Ferrell, C.L., Owens, F.N. 2004. Voluntary feed intake by lactating, angora, growing and mature goats. Small Ruminant Research. 53:357-378.
Interpretive Summary: Using databases of treatment means from the literature, methods to predict feed intake by lactating, Angora, growing and mature goats were developed, based on body weight (BW), dietary metabolizable energy concentration (MEC) and dietary crude protein concentration (PTCP) (Angora and mature goats). A factorial approach was used together with a calculated constant overall efficiency of metabolizable energy (ME) utilization based on assumptions of ME requirements and efficiencies of use for maintenance, BW change, change in tissue mass, fiber gain and lactation, along with adjustments based on PTCP and ratios of independent variables being used. Equations were also developed via multiple regression analysis using BW, MEC, production levels and their ratios and PTCP as independent variables. Accuracy of prediction was similar for the two methods. Because of the relatively large number of observations in this study, these methods should be useful for predicting voluntary intake of various diets by a variety of goats in or near thermoneutral conditions and with pen or stall settings. This efficiency approach also should be of value under other settings where maintenance energy requirements are different, as with grazing or acclimatization, with appropriate changes in ME requirements.
Technical Abstract: Databases amassed from the literature were used to predict feed intake by lactating, Angora, growing and mature goats, using 221, 54, 282 and 99 treatment means, respectively. One prediction approach was based on a calculated constant overall efficiency of ME utilization (k) considering biotype (meat, >/_50% Boer; dairy; indigenous; Angora), BW (kg; all goats), 4% fat-corrected milk (FCM, kg; lactating), BW change or ADG (kg; lactating, growing and mature), dietary ME concentration (MEC, MJ/kg DM; all goats), tissue gain (TG, kg; Angora) and clean mohair fiber gain (FG, kg; Angora). For lactating goats, assumptions included efficiency of ME utilization for maintenance and activity: 0.503 + (0.019 x MEC); efficiency of ME use for gain (kg): 0.75; efficiency of use of mobilized ME for lactation: 0.84; efficiency of use of dietary ME for lactation: 0.589; tissue energy concentration (TEC): 23.9 MJ/kg; ME requirement for maintenance and stall or pen activity (MEmREQ): 0.5013 and 0.4227 MJ/kg BW0.75 for dairy and other goats, respectively; and all mobilized tissue energy used for lactation. Assumptions for Angora goats that differed from lactating goats were efficiency of ME use for tissue gain (TG; kg/day): 0.006 + (0.0423 x MEC); efficiency of use of ME (dietary and mobilized tissue) for clean fiber gain (FG): 0.151; TEC = 4.972 + (0.3274 x kg BW); MEm: 0.473 MJ/kg BW0.75; ME used for FG: FG x 157 MJ/kg; and all mobilized tissue energy used for FG. Mean k for Angora goats was 0.525 (S.E. = 0.0112), and prediction accuracy was improved by adjusting for dietary CP concentration. Assumptions for growing goats included: kg: 0.006 + (0.0423 x MEC); efficiency of use of mobilized tissue energy for maintenance: km; and MEmREQ: 0.489, 0.580 and 0.489 MJ/kg BW0.75 for meat, dairy and indigenous goats, respectively. Mean k estimated from a random development data set resulted in unbiased prediction of intake for an evaluation data set without observations removed. Assumptions for mature goats were the same as those for growing goats except for a MEmREQ of 0.462 MJ/kg BW0.75. k was 0.632 (S.E. = 0.00448). Because of the relatively large number of observations in this study, these methods should be useful for predicting voluntary intake of different diets by a variety of goats in or near thermoneutral conditions fed in pens or stalls.