Energy content of reduced-fat distillers grains for lactating dairy cows

Abstract Text: The corn-ethanol industry has started to produce distillers grains and solubles which contain a reduced concentration of fat (RFDDGS) but the impact of this feed on the supply of energy to the cow has not been studied in depth. Eight Holstein and 8 Jersey multiparous, lactating cows were used to complete 56 energy balances to determine the energy content of rations containing RFDDGS. A repeated switchback design was used to compare treatments with and without RFDDGS. On a DM basis treatments consisted of 24.2 % corn silage, 18.4 % alfalfa hay, 6.94 % brome hay with either 22.9 % rolled corn and 14.8 % soybean meal, or 4.51 % rolled corn, 14.5 % RFDDGS, and 0 % soybean meal (DM basis). The inclusion of RFDDGS increased DMI from 21.7 ± 0.70 kg/d to 23.3 ± 0.68 kg/d (P < 0.01) but did not affect milk production (30.4 ±1.46 kg/d; P = 0.11). However, 3.5% FCM tended (P = 0.10) to be different (33.0 ± 1.27 and 34.2 ± 1.25 kg/d for Control and RFDDGS treatment, respectively). Milk energies were 1.44 ± 0.50 Mcal/d higher with RFDDGS (P = 0.01). Energy lost as methane was reduced (P = 0.01) by 0.28 Mcal/d with the addition of RFDDGS. Heat loss averaged 30.4 ± 0.55 Mcal/d and did not differ by treatment (P = 0.94).  Energy retained as tissue energy was found to be -0.22 ± 1.48 Mcal/d for the Control and 6.78 ± 1.43 Mcal/d for the RFDDGS treatment (P < 0.01). Intakes of digestible and metabolizable energies were lower (P < 0.01) for the Control (2.70 and 2.36 ± 0.05 Mcal/kg DM, respectively) compared to RFDDGS (2.86 and 2.54 ± 0.05 Mcal/kg DM). There was also a treatment by breed interaction for digestible, metabolizable and lactational net energies (P < 0.01) with a greater difference between treatments with Holstein cows than Jersey cows. Differences between treatments in Holsteins were 12.0 ± 2.09, 11.7 ± 1.98 and 11.3 ± 1.90 Mcal/d (P  < 0.01), and Jerseys were 4.16 ± 2.14, 4.32 ± 2.04 and 5.47 ±1.96 Mcal/d (P= 0.06, 0.04 and 0.01), for digestible, metabolizable and lactational net energies, respectively. These energy estimates suggest higher energy content of diets containing RFDDGS than diets containing a mixture of corn and soybean meal in lactating dairy cows.

Keywords: Reduced-fat distillers grains with solubles, Energy balance, Methane