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- Title
Nitrogen and dry matter digestibility of high and low forage diets in dairy heifers.
- Authors
Daubert, J. M.; Moody, M. L.; Zanton, G. I.; Heinrichs, A. J.
- Abstract
Diets fed to growing dairy heifers normally contain high levels of forages and are fed at ad libitum consumption. Feeding high concentrate diets in a restricted manner to achieve optimal ADG however can be more efficient because of reduced metabolic losses associated with digestion and lower feed costs per unit of energy. The objective of this experiment was to determine the DM and N digestibility of 2 diets with differing forage to concentrate ratios in dairy heifers. A 77% corn silage, 23% grain TMR (11.1% CP, 67.9% TDN, 40.9% NDF) and a 67% grain, 33% corn silage TMR (12.0% CP, 67.7% TDN, 37.9% NDF) were fed to 8 Holstein heifers (5 and 12 mo, 172 kg and 337 kg BW). Diets were fed at restricted intake (BW.75) twice daily. A split plot design was used with the ages of heifers as the whole plot and the sub-plot of treatment, administered in a 2 period Balaam's design. Periods were 21d in length with 17d of adaptation and 4d total fecal and urine collection. Urine was collected via indwelling urinary catheters and feces were collected immediately at hourly intervals, stored in an airtight container, and weighed daily, mixed, sub-sampled, dried, and ground. DM digestibility was greater for low forage diets (74.3% vs. 70.7%; P <0.02). DM digestibility was higher for older than younger heifers (74.3% vs. 70.7%; P <0.05). N intake was 90.8g for the high forage diet and 100.9g for the low forage diet (P <0.04). N digestibility was not different between treatments (57.5%, low forage vs. 55.1%, high forage; P >0.20). Retained N was higher for low forage than high forage diets (35.5g vs. 26.2g; P <0.03) and was higher for older than younger heifers (36.5g vs. 25.2g; P<0.05). From these data we conclude that high concentrate diets are more digestible with greater retained N than high forage diets with equal nitrogen digestibility for both ages of heifers studied.
- Subjects
FORAGE plants; FORAGE; HEIFERS; CONCENTRATE feeds; URINARY catheters; IMPLANTABLE catheters
- Publication
Journal of Animal Science, 2006, Vol 84, p160
- ISSN
0021-8812
- Publication type
Article