The effects of supplemental calcium salts of rapeseed oil fatty acids (FA) and rapeseed oil on ruminal metabolism and apparent digestibility of lipids in the small intestine were studied using three multiparous Holstein x Friesian cows in a 3 x 3 Latin square design. Cows fitted with ruminal, duodenal, and ileal cannulas were fed restricted amounts of a control diet (C) containing 65% corn silage and 35% concentrate mix or diet C with supplemental calcium salts of rapeseed oil FA (S) or diet C supplemented with rapeseed oil (O). Fatty acid contents were 1.9, 8.4, and 7.6% for diets C, S, and O, respectively. The average flow of total FA to the duodenum was lower than the intake for supplemented treatments, suggesting catabolism of FA by ruminal microbes. Fatty acid flows at the duodenum were higher (P < .10) for diets supplemented with fat than for diet C, except for C18: 3(n-3) and straight-chain and branched-chain C15 and C17. Fat treatment affected total and individual FA flow to the ileum, except C14:0 and C18:2(n-6) and excreted amount of individual FA, except C14:0, C16:0, and total C18:1. In our trial, the addition of fat, regardless of origin, affected small intestinal digestibilities of C14:0 and C18:2(n-6) and did not affect changes in the amount of FA in the hindgut.

The aim of this experiment was to study the effects on digestion of a supply of Ca salts of vegetable oil as a fat source for ruminants. Total tract digestibility and ruminal digestion were studied using three ruminally and duodenally fistulated dairy cows in a Latin square design. Diets compared were a control diet (C) based on corn silage and concentrate, and the C diet supplemented with calcium salts of rapeseed oil (S) or supplemented with rapeseed oil (O). Organic matter digestibility was lower (P < .05) for diet O than for diet C; diet S was intermediate and not different (P > .05) from diet C. Treatment did not affect (P > .05) the proportion of OM digested in the rumen, total N and microbial N flow at the duodenum, or efficiency of N microbial synthesis. In situ degradation of DM and NDF was higher for diet S than for diet C. The molar concentration of ruminal acetate was lower (P < .05) for O than for C and S. Under the conditions of this trial, supplemental calcium salts rich in polyunsaturated fatty acids did not decrease ruminal digestion.

SUMMARYTwo groups of nine wethers, three of which were fitted with rumen cannulas, were used in a digestion trial at the INRA centre in Theix, France, in 1988. Group 1 received 65% maize silage and 35% concentrates; group 2 received 65% hay and 35% concentrates. Concentrates were based on either cereals rich in starch, or by-products rich in fibre and were given either alone or supplemented with lipids as calcium soaps. The fatty acid content of lipid-supplemented diets wasc.9·5 and 8·5% of dry matter, of which 85 and 89% was provided by calcium soaps, for maize silage and hay diets, respectively. For each group, the four diets were tested in four successive periods from January to June 1988.Total digestibility of dry and organic matter, acid detergent fibre (ADF) and neutral detergent fibre (NDF) was measured in six wethers of each group by total faeces collection. On cannulated wethers, volatile fatty acid content and composition, pH and NH3-N in rumen liquor were determined four times a day;in saccodegradability of dry matter, ADF and NDF of the forage eaten by the wethers was estimated by the kinetics of incubation in the rumen.In vivoandin saccoresults showed that dry matter and organic matter digestibilities were not modified by the nature of concentrates. Cell wall digestibility was higher for fibre concentrates than for starchy concentrates, by 4·1 and 6·2 percentage units for NDF in maize silage and hay groups, respectively. Volatile fatty acids (VFA) and ammonia concentrations were higher and pH was lower with the maize silage than with the hay diet.Lipid supply slightly increased cell wall digestibility in the group fed maize silage by 7·5 and 2·0 percentage units for starch and fibre concentrates, respectively. This surprising increase was related to an improvement inin saccodegradability. In all diets, lipid supply increased pH, but variations in VFA concentration and pattern were low. Interactions between the nature of concentrate and lipid supply were moderate, but were higher in the group fed maize silage than in the group fed hay, especially for total digestibility.

L’une des limites à l’utilisation des matières grasses dans l’alimentation des ruminants tient aux perturbations qu’elles engendrent dans la digestion des glucides dans le rumen. Pour éviter cet inconvénient, diverses formes de protection des lipides sont apparues. Cet article récapitule les effets de l’addition des graisses animales (en moyenne 941 g/j) et d’huiles végétales (693 g/j) encapsulées, et de savons de calcium (593 g/j), dans la ration des vaches laitières sur les quantités ingérées, la production et la composition du lait. L’addition de matières grasses protégées entraîne une diminution des quantités ingérées plus faible pour les savons de calcium (0,55 kg MS/jour) que pour les graisses ou les huiles encapsulées (1,1 à 1,3 kg MS/jour). Ces diminutions sont comparables à celles observées avec des matières grasses non protégées. L’incorporation de graisses encapsulées ou de savons de calcium accroît la production laitière d’environ 1 kg/jour, alors que celle d’huiles encapsulées ne la modifie pas. L’addition de graisses encapsulées ou de savons de calcium réduit le taux protéique de 1,8 et 1,2 g/kg, respectivement, alors que les huiles encapsulées ne le modifient pas. Cette différence est une conséquence des variations de production laitière, la quantité de protéines sécrétée n’étant modifiée par aucun des trois suppléments. L’encapsulation des lipides entraîne un accroissement important du taux butyreux avec les graisses (4,0 g/kg) et les huiles (6,4 g/kg). L’augmentation de sécrétion d’acides gras longs est en effet supérieure à la réduction de la synthèse de novo d’acides gras courts et moyens. L’accroissement variable de la sécrétion d’acides gras polyinsaturés reflète l’efficacité de la protection contre l’hydrogénation ruminale. L’addition de savons de calcium n’accroît pas le taux butyreux ; selon les essais, l’inhibition de la synthèse de novo est compensée par une sécrétion accrue soit d’acide palmitique, soit d’acide oléique.

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