Production performance, nutrient digestibility, and milk fatty acid profile of lactating dairy cows fed diets containing triticale silage of different maturities and different dietary forage levels

Abstract

This study aimed to evaluate the production performance, the milk fatty acid profile, and the nutrient digestibility of high-producing dairy cows fed high-forage (HF) or low-forage (LF) diets containing triticale silages harvested at either the boot stage (BT) or the soft-dough stage (SFT) of maturity. A 10-ha field was seeded with 105 kg/ha of triticale. Half of the field was harvested at BT and the other half at SFT. The harvested forage was ensiled in separate concrete-walled bunker silos for at least 60 d. The BT silage had 97.0% OM, 9.6% CP, 61.0% NDF, 42.0% ADF, 8.9% ADL, and 1.6% starch, whereas the SFT silage had 97.3% OM, 8.3% CP, 63.0% NDF, 44.0% ADF, 10.2% ADL, and 3.7% starch. The similar nutritional compositions of the 2 silages might be related to splitting the field in 2 halves that reflected differences in growing conditions of the crop. The animal study involved 8 primiparous (584 ± 21 kg BW and 105 ± 11 DIM) and 16 multiparous (710 ± 57 kg BW and 105 ± 18 DIM) Holstein cows. The experiment was a replicated 4 × 4 Latin square design with 21-d periods, with a 2 × 2 factorial arrangement of treatments. The HF diets were formulated to contain 55% dietary forage, and the LF diets were formulated to contain 38% dietary forage. Cows were housed in a freestall barn and fed once daily. Cows fed BT and SFT diets had similar DMI, but cows fed LF diets had higher DMI than cows fed HF diets. Feeding BT diets resulted in more milk production (43.5 vs. 42.4 kg/d) and higher milk protein (1.30 vs. 1.23 kg/d) and lactose yields (2.13 vs. 2.04 kg/d) compared with feeding SFT diets. Energy-corrected milk yield did not differ between BT and SFT diets. Cows fed HF diets produced less milk (41.1 vs. 43.0 kg/d) but tended to increase milk fat concentration (4.56% vs. 4.37%) compared with cows fed LF diets. Milk protein concentration was similar between cows fed HF and LF diets, but cows fed HF diets increased lactose concentration (5.02% vs. 4.80%). Triticale maturity did not affect NDF digestibility, but LF diets improved NDF digestibility (45.2 vs. 41.7%). No difference existed in de novo fatty acids between cows fed the BT and SFT diets despite the higher concentrations of CLA trans-10, cis-12 fatty acid and slightly higher concentrations of C18:1 trans-10 fatty acid. Under the conditions of this study, production performance did not appear to be sensitive to diets with triticale silage harvested at different maturity stages, and this occurred with both HF and LF diets.