Hay belongs to roughage. Such food is given to guinea pigs mainly in winter. Very valuable is the so-called “vitamin hay”, rich in carotene, which is harvested from well-leafed alfalfa, clover, and shade-dried nettle. Use “vitamin hay” for feeding pregnant and lactating females and young animals.
It is necessary to pay attention to the quality of the hay: the color should be green, and the smell should be pleasant and fragrant. Before feeding, the hay must be examined, its quality, shelf life are determined, hay dust is removed. This should be done without fail, since all this affects the nutritional value of hay and its assimilation by animals.

The “age” of hay is determined by the degree of drying and discoloration of some of the herbs it contains. For example, plantain remains green during the first month after mowing, after 4 months it turns brown, after 7 months it dries up and turns black, after 8 months it easily breaks and crumbles into powder when rubbed in the palms.
A goose foot, in which the upper surface of the leaf is smooth, green, and the lower one is velvety white, remains white in the first months after mowing, then turns yellow and after 9 months turns black, and the entire leaf becomes brittle and easily grinds into powder. After mowing, the black-headed cornflower retains moisture in the stems for 3 months, then for some time the moisture remains only in the heads, and only after some time the plant dries out completely, becomes brittle.
Hay should not be soggy. Soaked, it loses its characteristic dry aroma and changes color. Thus, hay harvested from steppe plants takes on a pale green or grayish green color; from meadows – brownish-green or almost black. There should be no poisonous or harmful herbs in the hay.
Rotten, moldy hay is also not suitable for feeding to animals. If no specks are found when examining brown or blackened hay, it means that the hay is only soaked. Rotten hay has a specific smell, which is especially intensified if you rub the bunch with your hands. It should be borne in mind that well-dried and ventilated rotten hay may not have a putrid smell, and then it can be mistaken for soaked, if you do not take into account the specks, which under no circumstances disappear.