Hydrogenation is the chemical or biological process (biohydrogenation by rumen microbes like Butyrivibrio fibrisolvens) where molecular hydrogen is added across double bonds of unsaturated fatty acids to convert them into saturated fatty acids.

Biological Value (BV) is defined as the percentage of absorbed nitrogen that is retained by the animal's body for growth and maintenance:

$$\text{BV} = \frac{N_{\text{retained}}}{N_{\text{absorbed}}} \times 100 = \frac{N_{\text{intake}} - (N_{\text{fecal}} - N_{\text{MFN}}) - (N_{\text{urinary}} - N_{\text{EUN}})}{N_{\text{intake}} - (N_{\text{fecal}} - N_{\text{MFN}})} \times 100$$

Peristalsis consists of coordinated rhythmic wave-like contractions of circular and longitudinal smooth muscle layers in the esophageal wall that propel the food bolus downward toward the stomach.