USE OF DISTILLERS GRAINS IN PRECISION-FED DAIRY HEIFERS
Open Access
- Author:
- Suarez, Francisco Xavier
- Graduate Program:
- Animal Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Arlyn Judson Heinrichs, Thesis Advisor/Co-Advisor
Arlyn Judson Heinrichs, Thesis Advisor/Co-Advisor - Keywords:
- dairy
rumen
distillers
heifer - Abstract:
- Objectives of this study were to determine effects of feeding differing forage to concentrate ratios (F:C) and corn dry distillers grain with solubles (DDGS) inclusion rates on digestion, rumen fermentation and chewing activities, in precision–fed dairy heifer rations. A split plot design with F:C as whole plot and DDGS inclusion level as sub–plot was administered in a 4–period (19 d) 4 × 4 Latin square. Eight rumen cannulated Holstein heifers (12.5 ± 0.5 mo and 344 ± 15 kg, age and BW, respectively) housed in individual stalls were allocated to 2 F:C (50:50 LF or 75:25 HF; DM basis) and to a sequence of DDGS inclusion (0, 7, 14 and 21%; DM basis). Forage was a mix of 50% corn silage and 50% grass hay (DM basis). Diets were fed to allow for 800 g/d BW gain and fed 1X/d. Chewing behavior was visually monitored for 48 h at 5–min intervals. Rumen contents were sampled at –2, 0, 2, 4, 6, 8, 10, 12, and 20 h after feeding for pH determination. Total rumen evacuation was performed at –2 and 5 h after feeding. Statistical analyses were conducted using the MIXED procedure of SAS. DMI linearly decreased as DDGS increased (6.6 to 6.1 ± 0.1 kg/d; P < 0.01). LF rations had greater apparent digestibility (AD) of DM (66.7 vs. 63.2 ± 0.8%; P = 0.02) and OM (69.0 vs. 65.2 ± 0.6%; P < 0.01). AD responded quadratically for DM, OM, ADF and NDF with 14% DDGS inclusion level having the highest values. Rumen concentration of ammonia tended to be higher for HF (7.7 vs. 6.5 ± 0.4 mg/dL; P = 0.07) and tended to increase as DDGS increased (6.5 to 8.1 ± 0.6 mg/dL; P = 0.08). Nitrogen retention decreased with increasing levels of DDGS (40.9 vs. 27.9 ± 4.4 g/d; P = 0.01). Molar proportions (% of total VFA) of acetate tended to be greater for HF (65.8 vs. 64.0 ± 0.6%; P = 0.07) and decreased as DDGS increased (65.4 to 63.9 ± 0.5%; P < 0.01); propionate increased as DDGS increased (18.8 to 20.6 ± 0.3 %; P < 0.01). Acetate to propionate ratio decreased as DDGS increased (3.5 to 3.1 ± 0.1; P < 0.01). Rumen protozoa count decreased as DDGS increased (24.4 to 11.9 ± 3.2 × 104/mL; P < 0.01). No differences were found for rumen pH, and bacterial CP flow estimated by purine derivatives. Time spent eating tended to be longer for HF (151 vs. 112 ± 14 min/d; P = 0.09) and was not different for DDGS inclusion. Ruminating time did not differ by forage leveland linearly increased as DDGS increased (421 to 450 ± 15 min/d; P = 0.03). Total chewing time tended to be longer for HF (593 vs. 516 ± 28 min/d; P = 0.10) and to increase linearly as DDGS increased (553 to 579 ± 23 min/d; P = 0.09). Wet rumen digesta weight (46.6 vs. 37.6 ± 2.2 kg; P = 0.03) and volume (51.5 vs. 41.5 ± 2.5 L; P = 0.03) were greater for HF. We found that nutrient AD responds quadratically to DDGS level. Ammonia concentration and molar proportion of propionate increased; while molar concentration of acetate, acetate to propionate ratio, and rumen protozoa number decreased with increasing levels of DDGS. LF rations had greater DM and OM AD. Total chewing time increased by the addition of DDGS and higher F:C. DDGS influenced ruminating time with no effect on eating time while F:C affected eating time. Higher F:C increased rumen digesta weight and volume. Forage and DDGS levels did not affect rumen pH. Moderate levels (14% of DM) of DDGS appear to be more suitable for use in dairy heifer rations yielding the highest digestibility, however with a decrease in nitrogen retention.