1. In a series of virulence experiments a comparison was made between the resistance to infection of 551 mice fed on raw and 495 mice fed on pasteurized milk, each dietary being supplemented by a mineral mixture and a whiteflour biscuit. In one set of experiments the mice were inoculated intraperitoneally with about 100 or 1000 living Bact. typhi-murium and observed for a fortnight; in another set they were fed by the mouth with about 100–200 million living organisms of the same strain and observed for 4 weeks. All animals dying during, and all survivors killed at the end of the experiments were bacteriologically examined for evidence of specific infection.

2. In the intraperitoneal inoculation experiments the results obtained with the raw and pasteurized groups respectively were as follows: Proportion of animals dying of specific infection 51·83 and 51·20 per cent; proportion of all animals found to be specifically infected at death or when killed 95·29 and 91·57 per cent; average survival time of animals dying of specific infection 8·06 and 6·93 days. The proportions of animals dying of specific infection when standardized for weight distribution were 55·1 and 50·6 per cent respectively.

The effect of equal and unequal milking intervals (12 + 12, 10 + 14 and 8 + 16h) was investigated in milch ewes. The treatments were applied to 9 ewes using a double 3 × 3 Latin square. The daily production of milk and fat was unaffected by the changes in milking interval.

Details are given of a histochemical technique suitable for the identification of lipoproteins in cheese based on their property of forming insoluble complexes with sulphated polysaccharides.

Average values for the total phosphorus content of sera from unsalted butter samples and for the phosphorus contents of the various fractions of the sera after partition with trichloroacetic acid were: total P, 83·6 mg./100g.; acid-soluble P, 32·4 mg./100 g.; inorganic P, 28·8 mg/100 g.; acid-insoluble P, 51·2 mg./100 g.; and phospholipid p, 33·6 mg./100 g.

There was no evidence that decomposition of the phospholipids or other organic phosphorus compounds occurred in salted or unsalted sweet-cream butters during storage at –10° C. for 8 months.

Total bacterial counts of the milk from individual cows were measured for three groups of ten winter housed cows at three milkings. The teats were either (i) left unwashed or (ii) washed with disinfected water (60 ppm available iodine) and dried with individual paper towels or (iii) washed with plain water and then dried with a single fabric cloth impregnated with a polymeric bisguanide and a quaternary ammonium compound. The mean total bacterial counts/ml for the groups were 5820, 2108 and 1116 respectively. Treatments (ii) and (iii) were also compared for their ability to prevent the inter-teat transfer of bacteria. Before teat washing and drying, one teat of each cow was deliberately contaminated with Streptococcus agalactiae. Significantly fewer teats (5/30) became contaminated with Str. agalactiae when treatment (iii) was used for teat washing and drying compared with treatment (ii) (20/30).

The addition of 10% of sodium chloride to milk caused an average drop in pH of 0·42 unit. Different workers have found very variable relations between the pH of cream and the pH of salted butter churned from it. When 10% of sodium chloride is added to 0·2% solutions of sodium citrate or sodium phosphate there is a drop in pH of the order of 1 unit. When an alkaline solid phase is present as in the serum of neutralized cream and butter, and in milk, this change in pH may be diminished or reversed, possibly by increased solubility of the alkaline precipitate in sodium chloride solution. Factors are listed which will cause the pH of salted butter to differ from that of the cream from which it was made. In the churning of alkaline creams there occurs in the butter an increase in the proportion to the serum water of calcium phosphate and of other solids-not-fat.

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.

Effects of the reaction variables pH, temperature, time, enzyme concentration and solids concentration on the hydrolysis and solubilization of lactalbumin slurries by Alcalase have been determined. Reaction progress curves, solubilization v. time, were very unusual with a maximum solubilization of 96% occurring at a short reaction time corresponding to a degree of hydrolysis of 11–12%. Further hydrolysis beyond this point produced a rapid decrease in solubilization to about 67%, followed by a further gradual increase in solubilization with prolonged hydrolysis. The unusual solubilization profile was also produced by increasing enzyme concentration at fixed reaction time. The effects of pH, temperature and solids concentration were similar to those found in the hydrolysis and solubilization of other insoluble proteins. The implications of the results for the design and operation of an enzymic hydrolysis process are discussed.

This study tested the hypotheses that machine milked dairy sheep have a high prevalence of teat-end hyperkeratosis (TEH), which contributes to udder health problems. A random sample of 1360 milking ewes from 28 dairy sheep farms was monitored. Milking procedures, milking parlour characteristics and maintenance were recorded during a designated on farm audit; records were obtained through observations and interviews with farmers. Number of ewes/milker, ewes/milking unit and milkings/milking unit were calculated. Vacuum level, pulsation rate and ratio were measured. Four combinations of vacuum level and pulsation rate were defined; <40 kPa and <150 cycles/min (VP1), <40 kPa and ≥150 cycles/min (VP2), ≥40 kPa and <150 cycles/min (VP3), ≥40 kPa and ≥150 cycles/min (VP4). California Mastitis Test (CMT; scores 0–4) was done on all ewes. Then the udder of each ewe was assessed for TEH (scores 1–4) and ewes were assigned into three groups according to TEH severity (no or mild, medium and severe TEH). Severe TEH (scores 3 and 4) prevalence at teat-level was ca. 13%. TEH severity was associated with the combination of vacuum level and pulsation rate; ewes milked with VP4 combination were more likely to have a one-level increase on TEH severity compared to ewes milked with VP2 and VP3 combinations. More ewes/milker and less ewes/milking unit increased the likelihood of a one-level increase on TEH severity. Finally, ewes with severe TEH were more likely to have a one-level increase on CMT score. Therefore, our hypotheses that TEH is prevalent in dairy ewes and contributes to udder health problems were confirmed. Additionally, farmers can reduce TEH prevalence by optimising the way they milk and their milking parlour.

We investigated whether prepartum levels of serum bone biomarkers are related to the degree of parturient hypocalcaemia and risk of milk fever (MF) in dairy cows with advancing parity. A total of 58 late-pregnant cattle were assigned to four groups: nulliparous, primiparous, multiparous in the 2nd lactation and multiparous in the 3rd–5th lactation. The multiparous cows were further assigned to MF and non-MF groups according to the onset of MF. Serum samples were obtained from the cows during the 3 weeks prepartum to 5 d postpartum period for the measurement of serum calcium (Ca) and three bone biomarkers: tartrate-resistant acid phosphatase isoform 5b (TRAP5b), osteoprotegerin (OPG) and bone isoenzyme of alkaline phosphatase (ALP3). The ratios of OPG to TRAP5b (O/T ratio) and ALP3 to TRAP5b (A/T ratio) were calculated. The data from all cattle showed that the severity of hypocalcaemia at parturition increased with advancing parity/age. The MF cows had elevated serum TRAP5b activity and a decreased O/T ratio after parturition, suggesting an increased number of osteoclasts due to osteoclastogenesis, in response to severe hypocalcaemia. The MF cows showed lower serum ALP3 activity during the 3 weeks prepartum than the non-MF cows, therefore, prepartum osteoblast function was likely weak in the MF cows. During the 2–3 weeks prepartum, serum ALP3 activity and the A/T ratio had moderate associations with the serum Ca concentration at day 0 (day of calving) in the multiparous cows, and receiver operating characteristic curve analysis revealed that ALP3 activity had excellent ability to predict MF. In conclusion, prepartum serum ALP3 activity is a promising biomarker to predict MF in multiparous cows.

Records of 81 heifers, daughters of 6 bulls, were examined to determine the regressions of milk yield, corrected for lactation length, on initial liveweight and age at calving.

Age was found to have no significant effect and was discarded in the final analysis.

The regression equations were similar for the different groups of half-sibs, except for one group whose members had not been fed according to milk yield. After removal of this group, a highly significant positive relationship between lactation yield and liveweight at calving was found ‘within bull groups’. The mean values of groups of halfsibs did not show this relationship, and significant differences in milk yield still persisted between groups after adjustment for liveweight differences.

It was concluded that herd improvement by choosing heifers solely on the basis of liveweight shortly after calving appears unlikely to be effective unless the sire's potential is known and the feeding during lactation takes into account the greater maintenance requirements of heavier animals.

The keeping quality of milk is a factor which is of considerable importance from the commercial aspect, yet the relationship which exists between the keeping quality and the bacteriological standards as laid down in the Milk Special Designations Order, 1936, has not been fully explored. Wilson compared the keeping quality at 17·5°C. of samples of mixed morning and evening milk with the reduction times at different temperatures and found, in each case, a relatively poor correlation. Since the samples consisted of mixed morning and evening milk it is not possible to state the age of the milk when the tests were commenced. Much of the Tuberculin Tested milk sold in the Provinces is bottled on the farm, and consequently the milk produced in the morning is bottled separately from that produced in the evening.

1. An investigation was carried out, using objectively measurable stimuli, to examine the method of assessing the size of the mammary glands of calves by palpation. The method was that described by Swett.

2. The results indicate that the estimated sizes may be very different from the true sizes, although the two are generally highly correlated. In most cases the estimated sizes are significantly smaller than the true sizes.

3. Different judges give very different estimated sizes for the same true sizes, thus it is not justifiable to compare directly glands which have been stated to be of the same size by different judges.

A technique for monitoring the movement of the teatcup liner during milking, using video recordings, has been investigated. The liner was videoed through a transparent shell and the recordings were subsequently processed frame by frame by an image analyser. The width of the liner and its variation with pressure difference across the liner walls were calculated at several locations along the liner length, and analysis of these results allowed the pressures at which the liner buckled and the walls touched to be determined and some estimate of the degree and duration of liner collapse to be made.

Between August and May-the butter-making season in New Zealand-the average vitamin Dcontent of the butterfat varied between 10 and 64 i.u./100g and during the corresponding months in Great Britain (February-November) the values were between 15 and 39 i.u./100g. At the beginning and end of the season the values in both countries were similarly low but in mid-season New Zealand values were up to twice those for Great Britain. Within each country the vitamin D values were highly correlated with hours of sunshine and, for both countries, with total radiation, which includes the diffuse radiation in ‘skyshine’ and also allows for variation in sunshine intensity. The higher content of vitamin D in New Zealand butter in mid-season was attributed to a higher level of total radiation.

In a paper by Mattick & Shattock (1) it is stated that: ‘The suspicion exists in the minds of those who investigated cases of gastro-enteritis that streptococci of the faecal type isolated from suspected cheese may have been responsible for the disease.’ They examined thirty cheeses and found that the faecal types of streptococci were common, and that the haemolytic varieties were rare. Since then the question has arisen as to the identity of the haemolytic streptococci found in cheese examined for the presence of the pathogenic streptococci. While we have never had occasion to examine cheese suspected of harbouring pathogenic organisms, the presence of haemolytic varieties of streptococci, their identity, and their role in cheese œcology is of general interest.

1. An investigation was made of the effect on the casein number of (a) advanced lactation, (b) storage of the milk sample at room temperature and in the refrigerator, and (c) storage of the sample at room temperature after the addition of the following preservatives: potassium dichromate, mercuric chloride, formaldehyde, crystal violet and sodium azide.

2. The casein number method of mastitis diagnosis is not applicable to cows in advanced lactation. It did not distinguish between infected and uninfected quarters, as all quarters in the drying-off stage produced milk with a number below normal. At the end of lactation the mean casein, soluble protein plus non-protein, and total nitrogen contents were 21, 86, and 36% greater respectively than when the cows were in full milk.

3. There was a decrease in the casein number of the milk samples on keeping at 16–18° C. or with preservatives owing to the hydrolysis of casein to proteose-peptone and non-protein nitrogenous substances. For the diagnosis of mastitis from the casein number, samples should not be kept at room temperature for more than a few hours before analysis. Keeping at 0–2° C, and at room temperature with the addition of 0·2, 0·05, and 0·01 g. potassium dichromate, formalin or mercuric chloride respectively per 100 ml. of milk, prevented significant reduction of the casein number for 24–48 hr.