Utilisation digestive par le veau préruminant de laits de remplacement contenant de l'ultrafiltrat de lactosérum comme seule source de lactose

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Abstract
During 2 trials (A and B), the apparent digestibility of milk replacers in which lactose was supplied either from dried whey or whey ultra-filtrate was compared. In order to know the influence of the solubility of proteins, the latter were mainly provided by insoluble (A) or soluble (B) fish protein concentrates. In a 3rd experiment (C), the effect of adding emulsifiers to the milk replacer containing ultrafiltrate and insoluble concentrate, was studied. In trials A and B, replacement of whey by ultrafiltrate had a depressive effect on the performances (16% on an average on live weight gain) and on the fecal consistency (11.8% of days with diarrhea vs. 1.4). In trial A, the apparent digestibility decreased strongly with introduction of the ultrafiltrate (P < 0.001) from 92.9-89.2%, from 86.3-82.7% and from 86.9-78.2% respectively for organic matter, N and fat. In trial B, the digestibility of the 2 diets was much more satisfactory than in trial A; only that of N decreased significantly (from 92.2-90.1%) with introduction of the ultrafiltrate. In trial C, addition of emulsifiers improved the digestibility from 87.2-91.8% for organic matter (P < 0.001) from 78.3-83.3% for N (P < 0.05) and from 72.1-88.1% for fat (P < 0.001). Neither digestibility of the N free extract or that of lactose were altered. Whey ultrafiltrate must be introduced in smaller amounts than whey into milk replacers for preruminant calves. Use of soluble protein concentrates and of emulsifiers would be favorable for keeping digestibility at a high level.