The gastrointestinal tract is a complex and dynamic ecosystem. Commensal microorganisms (C), which proliferate in the intestine from birth, are crucial for gut homeostasis while non commensal (NC) microorganisms are transient and enter the organism from the environment and foods. We studied comparatively the influence of oral administration of C and NC Lactobacillus fermentum and Lactobacilus acidophilus on the gut-associated lymphoid tissue (GALT) of conventional mice. To determine the importance of the selection of probiotic host-specificity bacteria with immunomodulating capacity, we examined the interaction with the gut by transmission electron microscopy and FITC-labelled bacteria. We compared the immunomodulation capacities of C and NC strains by studying the number of IgA secreting cells and cytokine profile. No differences were found in the number of IgA+ cells; however, the pattern of cytokine response to C and NC bacteria was different. With regard to proinflammatory cytokine (IFNγ and TNFα), we found that TNFα was mainly produced by NC bacteria, while C bacteria were able to elicit mainly IFNγ. The regulatory cytokines (IL-10 and IL-4) were induced with different patterns for both C and NC strains. No differences in the pathway of internalization to the gut between C and NC were found. In summary, we determined that C and NC bacteria interact with the intestine in the same way; both C and NC bacteria were able to reinforce the surveillance of the gut mucosal immune system. The cytokine profile showed that C bacteria would be involved in the regulation of intestinal homeostasis rather than in the immune activation as the NC bacteria.

Amperometric sensors may be used in milk analysis but electrochemical interference from compounds other than the analyte is an on-going problem. A survey was made of the level of electrochemical activity (potential interference) in milk from a herd of dairy cows grazing on summer pasture. It was a ubiquitous feature of the aqueous phase of whey and de-proteinized milk over about 3 months. The nature of the interference was studied by differential pulse voltammetry and responses to ascorbic acid oxidase and uricase. The principal source of interference appeared to be uric acid.

Supplementation with a high dose (600 g/d) of rumen inert conjugated linoleic acids (RI-CLA) inhibits milk fat synthesis in total mixed ration (TMR)-fed dairy cows immediately post partum. However, effects of RI-CLA on milk fat and bioenergetic parameters during the transition period in grazing cows have not been investigated. Multiparous Holstein cows (n=39) grazing pasture were randomly assigned to one of three treatments: (1) pasture (PAS), (2) PAS+540 g/d Hyprofat (palm oil; HYPRO) and (3) PAS+600 g/d RI-CLA. HYPRO and RI-CLA supplements were isoenergetic, fed twice daily at 7.00 and 16.00 and provided 0 and 125 g CLA/d, respectively. Treatments began 27±10 d prepartum and continued until 36±1 days in milk (DIM). There was little or no overall effect of RI-CLA on content or yield of milk protein and lactose. RI-CLA supplementation decreased overall milk fat content and yield with RI-CLA-induced milk fat depression (MFD) becoming significant by day 3 when compared with PAS and by day 6 when compared with HYPRO. MFD continued to increase in severity during the first 24 d post partum after which MFD reached a plateau (~40%; RI-CLA v. HYPRO). Pasture-fed cows produced less milk (19·4 kg/d) than the lipid-supplemented groups and although there were no overall differences in milk yield between RI-CLA and HYPRO (22·3 kg/d) a curvilinear relationship (R2=0·57) existed between the RI-CLA-induced milk yield response and extent of MFD. RI-CLA tended to increase milk yield (1·8 kg/d) compared with HYPRO until MFD exceeded 35% (~day 21), after which point the positive milk yield response was eliminated. Milk fat trans-10, cis-12 CLA content averaged 0·25 g/100 g in the RI-CLA treatment, was temporally independent, and was undetectable in PAS and HYPRO treatments. Based on the milk fat 14[ratio ]1/14[ratio ]0 ratio, RI-CLA decreased the overall Δ9-desaturase system compared with PAS and HYPRO. Compared with HYPRO, RI-CLA had no effect on plasma glucose, insulin, leptin, or NEFA concentrations. Results indicate that a high RI-CLA dose decreases milk fat synthesis and tends to increase milk yield immediately post partum in pasture-fed cows; however, excessive MFD (>35%) appears to be associated with a diminished milk yield response.

This work describes the effect of the hydrolysis time and pressure (0·1–400 MPa) on the proteolysis of β-lactoglobulin A (β-lg A) with trypsin, either conducting hydrolysis of β-lg under pressure or hydrolysing β-lg that was previously pressure treated. Pressurisation, before or during enzyme treatments, enhanced tryptic hydrolysis of β-lg. Trypsin degraded pressure-modified β-lg and pressure-induced β-lg aggregates, favouring proteolysis to the intermediate degradation products: (Val15-Arg40), (Val41-Lys69)S-S(Leu149-Ile162) and (Val41-Lys70)S-S(Leu149-Ile162). These were further cleaved at the later stages of proteolysis to yield: (Val15-Tyr20), (Ser21-Arg40), (Val41-Tyr60), (Trp61-Lys69)S-S(Leu149-Ile162) and (Trp61-Lys70)S-S(Leu149-Ile162). Particularly, in the tryptic hydrolysates of pre-pressurized β-lg, two other fragments linked by disulphide bonds: (Lys101-Arg124)S-S(Leu149-Ile162) and (Tyr102-Arg124)S-S(Leu149-Ile162), were found. These corresponded to rearrangement products induced by SH/SS exchange between the free thiol group of Cys121 and Cys160, that normally forms the disulphide bond Cys66-Cys160. In the light of these results, structural modifications of β-lg under high pressure are discussed.

An examination of the economic impacts of reduced milk production associated with Johne's disease on Johne's-positive and Johne's-negative dairy operations indicated that, if Johne's disease had not existed in US dairy cows in 1996, then the economic surplus of Johne's-negative operations would have been $600 million±$530 million lower, while the economic surplus of Johne's-positive operations would have been higher by $28 million±$79 million, which was not significantly different from zero. The data available for projecting changes in surplus were not sufficiently precise to allow an exact statement on whether Johne's-positive operations would have been better or worse off economically, in terms of the value received for producing more milk if they had not been affected by Johne's disease. The changes in producer surplus, based upon eliminating specific epidemiological risk factors for Johne's disease, were disaggregated between Johne's-positive dairy operations exposed to the risk factor and all other US dairy operations. Eliminating the risk factor of having any cows not born on the operation would have had a significant positive effect on the economic surplus of Johne's-positive operations that had any cows not born on the operation.