Supplementation of alfalfa silage with different energy-rich concentrates in diets for lactating dairy goats
Lactating Saanen does were fed diets based on ad libitum alfalfa silage (SA) to study the effects of including fixed amounts of three different energy-rich concentrates: wheat grain (T), sorghum grain (S), and dehydrated citrus pulp (PC), in a 4 x 4 Latin Square with four replicates. Sixteen does (45 ± 10 d postpartum and producing 2.016 ± 0.58 kg/d of 4% fat corrected milk, FCM) housed in individual pens under roof, received the following diets: 1) SA (33.9% DM, 19.9% CP, 44% NDF); 2) SAT (52.4% DM, 19.8% CP, 33.7% NDF); 3) SAS (50.9% DM, 17.9% CP, 37% NDF); and 4) SAPC (52.5% DM, 16.1% CP, 39.1% NDF), resulting in respective forage-to-concentrate ratios (F:C) of 100:0. 65:35, 67:33, and 64:36. Daily DM intake from silage was greater for SA than for the other three treatments combined (2.55 vs. 2.33% of body weight, BW) whereas total DM intake (g/kg BW0.75) was lower (74.9 vs. 95.4). Yields of FCM or fat-protein-corrected milk were affected positively by concentrate supplementation, but milk protein concentration (g/L) or yield (g/d) were not. Chewing efficiency (min/g NDF consumed per kg BW0.75) improved from 20.4 to 15.0 (P <0.05) as a result of F:C decrease from 100:0 to 65:35, independent of the type of concentrate supplementation. Results suggest that the daily feeding routine (four offerings of alfalfa silage and two of concentrates) had greater impact on animal performance than the physical-chemical properties of dietary concentrates. In this study levels of 20 to 27% ADF and 33 to 44%NDF in diets for Saanen goats proved to be adequate to maintain normal rumen function and productive performance.