Abstract
We estimated ruminal crude protein degradation of twelve feedstuffs commonly used in China using in vitro and in vivo methods. The in vivo net protein utilization (NPU) levels of corn, sorghum, barley, wheat, Chinese wild rye grass, corn stalk, rice straw, soybean straw, soybean meal, distillers’ dried grains with solubles (DDGS), Brewers’ spent grains, and sunflower meal were 52.57, 49.68, 65.38, 72.58, 82.41, 72.26, 68.57, 76.95, 54.75, 56.27, 29.03 and 41.88%, respectively. The linear regression between NH3-N incorporated into microbial proteins and gas production after incubation (6, 12, and 24 h) was significant (r = 0.9948 and P < 0.001, r = 0.9874 and P < 0.01, and r = 0.9912 and P < 0.01, respectively). Based on the linear regression equations, we estimated in vitro protein degradability (IVPD) and generated the regression equations between IVPD and NPU. The linear regression equations between IVPD and NPU after 6 h incubation in the energy, protein, and roughage feed groups were Y = 0.5633X + 33.20 (R2 = 0.8517, P < 0.05), Y = 0.8482X+ 34.81 (R2 = 0.8650, P < 0.05), and Y = 1.6295X − 17.70 (R2 = 0.909, P < 0.05), respectively. The in vitro gas production method is useful for the determination of protein degradation in feedstuffs.
Highlights
Amongst all methods used to evaluate protein quality in ruminant feedstuffs, in vivo estimates are the most reliable
Among the protein feed group, Crude protein (CP) concentration was higher in soybean meal and sunflower meal than in dried grains with soluble (DDGS) and Brewers’ spent grain
The CP, acid detergent fiber (ADF), and Neutral detergent fiber (NDF) of soybean meal obtained in this study were similar to those reported by NRBC6
Summary
Amongst all methods used to evaluate protein quality in ruminant feedstuffs, in vivo estimates are the most reliable. The in vitro gas production technique[14,15] has been use to evaluate rumen CP degradability of feeds via ammonia-N and gas production measurements recorded by incubating feedstuffs in buffered rumen fluid. By improving this technique (e.g., through method innovation, instrument upgrades, and data handling), the in vitro gas production technique has been widely used to predict digestibility of ruminant feedstuffs[16,17,18,19]. The objectives of this study were to (1) determine the chemical composition of twelve common beef cattle feedstuffs commonly used in China and (2) predict protein digestibility by using in vitro gas production technique and in vivo data derived from digestion trials in an attempt to assess the accuracy of the in vitro gas production technique
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