Reduced-Fat Distillers Grains: How Much Can We Feed To Growing Dairy Heifers?

Nov 30, 2015

By Jill Anderson

Assistant Professor SDSU Dairy Science Department

Past research at the SDSU Dairy Science Department has shown that dried distillers grains with solubles (DDGS) are a good replacement for corn and soybean meal in dairy heifer diets without causing changes in daily gain. However, the high fat content (10-15%) of traditional DDGS has made their incorporation as the main concentrate difficult in limit-fed heifer rations. The development and increasing availability of reduced-fat distillers dried grains with solubles (RFDDGS) could allow them to be incorporated at much greater proportions. Heifer growth has been shown to be maintained by feeding RFDDGS, demonstrating that it is a good feedstuff for dairy heifers. But in past research, RFDDGS has only been incorporated into diets at inclusion rates of approximately 20% of diet dry matter (DM). This raises questions on how replacing energy and protein from forage with energy and protein from RFDDGS affects growth performance and what is the optimum or maximum dietary inclusion.

Methodology

Recent research within the SDSU Dairy Science department studied the effects on dairy heifer growth performance of feeding RFDDGS in replacement of forage in limit-fed rations. Forty-eight Holstein heifers (199 days of age) were assigned to 1 of 3 treatment diets for 16 weeks and fed individually with Calan gates and boxes (see Figure 1.). Treatment diets included: 1) 30 % RFDDGS with 68.5% grass hay (30DG), 2) 40% RFDDGS with 58.5% grass hay (40DG), and 3) 50% RFDDGS with 48.5% grass hay (50DG). All diets also included mineral mix at 1.5% of dietary dry matter (DM). Diets were limit-fed at 2.65, 2.50, and 2.35% of body weight on a DM basis for 30DG, 40DG, and 50DG, respectively to have similar intakes of crude protein and energy among treatments. Ration intakes were measured daily throughout the study and heifers were weighed and measured every two weeks.

Findings

Results (Table 1) demonstrated that intake decreased with increasing dietary concentrations of RFDDGS (linear effect). There were no differences in body weight or daily gain among treatments. As dietary concentrations of RFDDGS increased there was also an increase in gain: feed ratio across treatments. When frame growth rates were compared there were differences in withers height, paunch girth, and body condition score. There was also a tendency for hearth girth to be different among treatments. However, differences were numerically small.

Table 1. Growth performance results of Holstein heifers fed increasing amounts of RFDDGS in replacement of grass hay.

聽	Treatments1			SEM2	P-Values3
Item	30DG	40DG	50DG	聽	Treatment	Week	Treatment 脳 Week	Linear	Quadratic
# of heifers	16	16	16	聽	聽	聽	聽	聽	聽
DM intake, lbs/d	14.3	13.7	11.8	0.26	<0.01	<0.01	1.00	<0.01	0.50
Body Weight, lbs.	582.2	586.9	587.3	10.96	0.69	<0.01	1.00	0.44	0.72
ADG4, lbs/d	1.96	2.07	2.14	0.18	0.43	-	-	-	-
Gain:Feed	0.31	0.35	0.40	0.003	<0.01	<0.01	0.94	<0.01	.02
Withers Height, in	47.6	47.9	47.9	0.12	<0.01	<0.01	0.99	<0.01	0.03
Hip Height, in	49.1	49.1	49.1	0.14	0.74	<0.01	1.00	0.98	0.44
Heart Girth, in	55.5	55.4	55.5	0.16	0.22	<0.01	0.95	0.81	0.08
Paunch Girth, in	67.9	68.5	67.9	0.51	0.02	<0.01	0.99	0.98	<0.01
Body Length, in	44.3	44.4	44.5	0.25	0.18	<0.01	1.00	0.06	0.85
Hip Width, in	14.0	14.1	14.1	0.12	0.57	<0.01	1.00	0.46	0.45
BCS5	3.11	3.12	3.07	0.02	<0.01	0.59	0.82	<0.01	0.02
1聽30DG=low RFDDGS (30%), 40DG=mid RFDDGS (40%), and 50DG=high RFDDGS (50%)聽 2聽SEM= Standard error of the mean 3聽P<0.05 indicates a significant effect. P鈮?.10 indicates a tendency for effect 4Average daily gain (=BW Change/d) was calculated & analyzed using Regression procedures in SAS 9.3. 5聽Body condition score: 1 = emaciated to 5 = obese.

Conclusion

This study demonstrated that feeding diets with 50% inclusion of RFDDGS did not compromise dairy heifer growth. Limit-feeding diets with greater inclusion rates of RFDDGS improved gain to feed ratios while maintaining frame growth without increasing body condition score, demonstrating that replacing forage with RFDDGS does not negatively affect heifer growth performance. There were impacts on metabolic profile, nutrient utilization, and onset of puberty which will be discussed in other articles and data on post-trial long-term performance of these heifers is still being collected.

Acknowledgements

This research was funded by the Minnesota Corn Research and Promotion Council and Minnesota Agricultural Utilization Research Institute with support from the SDSU Agriculture Experiment Station.

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