A simple method to estimate feed required for maintenance of small ruminants
A simple means to estimate feed required for maintenance by Katahdin (K) sheep and Spanish (S) goats (initial BW = 30.6±0.40 and 21.8±0.27 kg, respectively; 8 mo old) by frequent BW measurement and adjustment of feed offered was evaluated. Ten K and S wethers in 1.05 × 0.55 m pens were fed grass hay (64.1% NDF, 10.4% CP, and 55.4% TDN; DM basis), initially at 58 and 55 g/kg BW0.75 (air-dry basis; i.e., ME intake of 427 and 452 kJ/kg BW0.75, respectively), at 0800 h for 5 wk. Three times weekly BW was measured at 1300 h in 50-g increments, and hay fed was varied thereafter by 0-5% (i.e., ≤ 40 g/d) to maintain BW. Breed (732 and 538 g for K and S, respectively; SE=11.5) and wk (625, 653, 632, 623, and 641 g for wk 1, 2, 3, 4, and 5, respectively; SE=9.4) affected daily air-dry intake (ADI; P<0.001), although breed × wk did not (P=0.508). Variation among days in ADI differed between breeds in wk 2 (SD=4.68 and 14.5 g; P=0.002) and 5 (SD=64.6 and 31.1 g for K and S, respectively; P=0.044). Body weights were smoothed using LOWESS and fitted by a segmented polynomial with the middle segment constrained to a flat line. Regression coefficients of the first and third segments and the two join points were estimated using nonlinear regression. The average of the first and second join points was 16 and 28 d, respectively, indicating BW stability between these times. Also, ADI of each wether was regressed against ADG in 2- and 3-day periods based on unsmoothed BW in wk 2-5, 3-5, 2-3, 2-4, 3-4, and 4-5. The only weeks without an intercept different from 0 (P>0.10) were 2-5 and 2-4. Hence, the intercept of wk 2-4 regressions was used to determine feed required for maintenance, with values of 727 and 538 g ADI (SE=11.6), corresponding to a ME requirement for maintenance of 447 and 426 kJ/kg BW0.75 for K and S, respectively. Variability was homogenous between breeds (P=0.867), although intercept SE averaged 6.0 and 12.9 g ADI for K and S, respectively. In conclusion, after 2 wk of adaptation, frequent weighing and change in offered feed for 2 wk may offer a relatively simple means of estimating maintenance feed needs of small ruminants.
Maintenance, goats, sheep