Sentence:  This you shall do concerning his ordinary keeping at home, where the Horse hath rest, and that you may dispose of hours as you please; but if you be either in Travel, or Sport, or other occasion, so that you cannot observe these particular times, then you must divide the main and whole quantity of Meat into fewer parts and greater quantities, and give them at the best conveniency; ever observing to give the least quantity before Travel; as a third part before <WSD>Mounture</WSD>, and the two other after you come to rest. 
Meaning of the word marked with <WSD> tags:  The act or process of mounting.