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1. Digesta were collected from eleven preruminant calves fitted with re-entrant (four calves in Expt 1 and three in Expt 2) or single cannulas (four calves in Expt 1) in the terminal ileum. Collection periods lasted 24 h (Expt 1) or 96 h (Expt 2).2. Two milk-substitutes (fish and soya bean) and a control diet were given to the calves. In the control diet, protein was entirely provided by skim-milk powder. In the other two diets, protein was provided mainly by a partially hydrolysed white-fish protein concentrate or a soya-bean protein concentrate prepared by extracting soya-bean meal with hot aqueous ethanol.3. In Expt 1, flow rates of fresh matter, dry matter, nitrogen and ash exhibited two maxima between 6 and 8 h after the morning meal and between 4 and 6 h (control and soya-bean diets) or 6 and 8 h (fish diet) after the evening meal. Minimum pH values were observed at times of maximum flow rate. Variations observed in the flow rates and pH values were larger with fish and especially soya-bean diets than with the control diet.4. The apparent digestibility of the three diets in the terminal ileum was significantly higher in Expt 2 than in Expt 1 : for N, the values were 0.92, 0.83 and 0.75 (Expt l), and 0.94, 0.87 and 0.88 (Expt 2) with the control, fish and soya-bean diets respectively.5. The amount of N apparently absorbed in the terminal ileum represented 90-96% of the amount that disappeared from the whole digestive tract in Expt 1 and 95-99% in Expt 2.6. In Expt 1 the amino acid (AA) composition of digesta changed little with the flow rate when the calves were given the control diet (from 158 to 179 g glutamic acid/kg AA). With the fish and soya-bean diets the AA composition was similar to that observed with the control diet when the flow rate was minimum, but differences became apparent as the flow rate increased (281 and 161 g glutamic acid/kg AA for the soya-bean and control diets respectively with maximum flow rate). In Expt 2, the mean compositions of the digesta were very similar to the means obtained in Expt I.7. Different comparisons with dietary, endogenous and bacterial proteins indicated that for the three diets a common mixture containing approximately 65% endogenous and 35 % bacterial proteins reached the terminal ileum. The quantity of dietary protein added to this mixture appeared to be very low with the control diet, but it increased with the flow rate in the case of the fish and soya-bean diets.8. In Expt 2, the additional undigested protein in the small intestine was richer in glycine with the fish diet and in glutamic acid and aspartic acid with the soya-bean diet compared with the control diet. This undigested fraction probably originated mainly from the fish solubles and the glycinin of soya bean respectively. 9. With the control diet the apparent digestibility of threonine and cystine was always lower than the mean value for all AA while that of methionine was higher (0.92, 0.82 and 0.96 respectively). Digestibility of all AA was higher for the control diet than corresponding values ...

-By modifying the forces (hydrophobic and electrostatic interactions, hydrogen bonding and presence of micellar calcium phosphate) responsible for the structure and the stability of casein micelles, alkalinisation induces a disruption of casein micelles in milk. The objective of this work was to compare the alkalinisation-induced physico-chemical changes of casein micelles of buffalo and cow milks with a special attention to the mineral fraction. The whiteness and viscosity were determined as global characteristics of milk. The aqueous and micellar phases of milks were ascertained for the distributions of the concentrations of nitrogen, casein molecules, calcium, inorganic phosphate and water as their supramolecular and molecular characteristics. These parameters were measured at six pH values between pH 6.7 and 10.8. Between pH 6.7 and 10.8, the whiteness decreased from 73.5 to 50.9 and from 71.3 to 50.9 units and the viscosity increased from 1.8 to 10.2 and from 1.5 to 4.8 mPa·s for buffalo and cow milks, respectively. Simultaneously, > 90% of nitrogen contents were in the supernatants of ultracentrifugation at pH 9.7 and 8.6 for buffalo and cow milks, respectively. Chromatographic analyses showed that caseins were totally solubilised at these pH values. Calcium and inorganic phosphate concentrations progressively increased in the supernatants of ultracentrifugation and decreased in the ultrafiltrates. At alkaline pH, the negative charge of caseins increased and the inorganic phosphate ion changed its ionisation state from HPO 4 2− to PO 4 3− form. This form has a greater affinity for calcium and can demineralise casein micelles. The consequences were modifications of protein-protein and protein-minerals interactions resulting in micellar disruption. The dissociations took place at pH 9.7 and 8.6 for buffalo and cow milks, respectively. These differences were due to higher concentrations of casein and minerals in buffalo than in cow milk, which were also our criteria of selection of the former as a model. casein micelle / buffalo milk / cow milk / mineral / alkalinisation 摘要 -碱化作用对水牛乳和牛乳酪蛋白胶束物理化学性质的影响○ 分子间作用力 (疏水 和静电作用、氢键和胶束磷酸钙的存在) 的改变会影响酪蛋白胶束的结构和稳定性，碱化作 用使得乳中酪蛋白胶束破坏○ 本研究比较了碱化作用对水牛乳和牛乳物理化学性质和酪蛋 白胶束中矿物元素的影响○ 以白度和黏度作为综合指标来评价乳的表观特性○ 并测定了乳 水相和胶束相中氮、酪蛋白分子、钙、无机磷酸盐和水分的分布○ 这些参数的测定是在 pH 6.7-10.8 (6 个 pH 间隔)○ 在 pH 6.7-10.8, 水牛乳的白度从 73.5 单位 降到 50.9 单 位，牛乳的白度从 71.3 单位降到 50.9 单位，而水牛乳的黏度从 1.8 mPaAEs 增加 10.2 mPaAEs，牛 *Corresponding author (通讯作者): frederic.gaucheron@rennes.inra.fr Dairy Sci. Technol. 89 (2009)

Heat shock proteins (HSP) play a central role in the protection of cells, tissues or organs subjected to various types of stressors. Different nutrients have been recently shown to exert their protection through the induction of HSP. Because these nutrients alleviate alterations of the intestine after weaning in pigs, this study was designed to obtain basic information on the expression of HSP 27, heat shock cognate 70 (HSC 70), HSP 70 and HSP 90 along the gastrointestinal tract (GIT) of young pigs and to study the effect of weaning on this expression. Pigs were weaned at 28 or 21 d and slaughtered at various times postweaning. All HSP were expressed in the GIT segments studied before and after weaning. However, the expression of HSP 27 and HSP 70 was transiently increased in the stomach and duodenum between 6 and 12 h postweaning and between 24 and 48 h in the mid-jejunum, ileum and colon. Their expressions were transiently decreased in the ileum. Expression of HSP 90 increased in the stomach and jejunum but decreased in the duodenum, ileum and colon. Similar results were obtained at both ages of weaning. We conclude that the HSP studied are present all along the gut of pigs and that their expression is modulated through weaning according to spatial-temporal patterns. The modulation by nutrients of HSP and their protective role on the GIT remain to be investigated in pigs.