Effects of grain sorghum planting density and processing method on nutrient digestibility and retention by ruminants
2001
Defoor, P.J. | Cole, N.A. | Galyean, M.L. | Jones, O.R.
Grain sorghum grown in 38-cm rows (high density (HD)) or 76 cm rows (normal density (ND)) was treated as follows: steam-flaked (SF), high-moisture-harvested followed by rolling and ensiling (HM) or dry-rolled (DR) (USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas, USA; [date not given]). Resulting grains were evaluated using lambs (Saint Croix; n=10) in two 5 × 5 Latin square digestion trials. Treatment diets contained either SF-HD, SF-ND, HM-HD, HM-ND or DR-ND grain sorghum in 2 trials; a 90 or a 60% concentrate diet was fed in each trial. High-density planting increased (P<0.10) the apparent absorption of P relative to ND planting for both 60 and 90% concentrate diets. Steam flaking decreased (P<0.10) the apparent absorption of P in the 90% concentrate diet and decreased (P<0.10) the apparent absorption of N in both the 90 and 60% concentrate diets. Despite differences in N digestibility, steam flaking and HM ensiling resulted in similar (P>0.10) N retention as a percentage of N intake in both trials. However, changes in the distribution of N between faeces and urine among processing methods could affect N content of manure and alter nutrient management strategies. These results indicate that both planting density and grain processing can alter the apparent absorption of grain sorghum P by ruminants. Furthermore, it seems that grain processing can alter the route of N excretion in ruminants without changing total N retention.
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