VALEUR ALIMENTAIRE DE L'HERBE DES PRAIRIES TEMPORAIRES AUX STADES D'EXPLOITATION POUR LE PATURAGE. II. - QUANTITÉ INGÉRÉE PAR LES VACHES LAITIÈRES

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Abstract
Altogether 4602 individual measurements were made of the amount of herbage eaten. The forage studied were divided into 3 groups: ryegrass, which included the samples of ryegrass or of meadow fescue, in association with white clover; cocksfoot, which included the samples of cocksfoot in association with white clover, and grasses and lucerne, which included the samples of cocksfoot or tall fescue associated with lucerne. Intakes of fresh matter ranged from 7.34 to 15.70 kg 100 kg liveweight. It was less when dry matter content of the forage was more, or when the contents of crude fiber or of ballast (indigestible organic matter) as percentage fresh matter increased. The changes in contents of dry matter and of crude fiber accounted for 80% of the difference in intake of fresh matter. The intake of dry matter ranged from 1.69 to 2.84 kg/100 kg liveweight and was on average 2.17 kg. The ryegrass group were eaten better than the cocksfoot or the grass and lucerne. The intake of dry matter increased significantly with digestibility for the grass and lucerne group, but was independent of digestibility for the other forages. It increased significantly with dry matter content for the ryegrass group but was independent of dry matter content for the other forages. Intake of dry matter was independent of the crude protein content of the forages; it was reduced significantly as the content of indigestible organic matter of the forages of the grasses and lucerne group increased. Intake of digestible organic matter was from 1.0 to 2.0 kg/100 kg liveweight. It was greater for the ryegrass groups than for the cocksfoot, and especially for the grasses and lucerne groups. It tended to increase with digestibility of the forage. Intake of digestible crude protein ranged from 0.105 to 0.455 kg/100 kg liveweight. It was greater for cows given the grasses and lucerne than for those given grasses alone or with white clover. It increased markedly during successive cycles and depended much more on the digestible crude protein content of the forage than on the amount of dry matter eaten. Intake of digestible crude fiber increased significantly with digestibility of the grasses with lucerne. The ratio of the amount of digestible crude fiber eaten to the dry matter content of the forage increased significantly with digestibility of the ryegrass, cocksfoot and grass-lucerne groups. Intake of indigestible organic matter was from 0.30 to 0.77 kg/100 kg liveweight and of indigestible crude fiber was from 0.08 to 0.26 kg/100 kg liveweight. These amounts did not therefore limit the intake of herbage. They increased significantly when the dry matter content of the forage increased or when its digestibility decreased. Thus for forages of the same digestibility more must be eaten when the dry matter content is greater. The total intake of dry matter from herbage and concentrate ranged from 1.75 to 3.00 kg/100 kg liveweight. The intake of herbage, used at the pasture stage, by dairy cows showed wide variation, of which the main causes are discussed. The intake of fresh material could be estimated very accurately. The differences in intake of dry matter seemed to depend on the dry matter seemed to depend on the dry matter content of the forage and was weakly related to digestibility and chemical composition of the forage. It depends on the rate of breakdown of the cellulose of the forage in the rumen and it is possible that there is a difference in palatability among forages.