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A factorial experiment has been carried out to determine the effects of varying the level of vacuum, air admission, and reserve air on milking rate and the amount of strippings, in high pipeline, low pipeline, and large diameter low pipeline milking machines. The low pipeline and the large diameter low pipeline machines were found to milk 10.1 and 12.1 per cent faster, respectively, than the high pipeline machine. The large diameter low pipeline operating without air admission was 6.3-7.5 per cent faster than the low pipeline machine operating with and without air admission. Milking rate was 16.1 per cent faster at 15 than at 12 inches Hg vacuum and about 6 per cent faster at 17 and 5 cubic feet per minute (c.f.m.) reserve air than at no reserve air. The admission of air at the claw piece resulted in 9 per cent faster milking with the high pipeline and 9.5 per cent slower milking with the large diameter low pipeline machine. There was no difference in milking rate in the low pipeline machine with or without air admission. The fastest milking rate was observed with the large diameter low pipeline without air admission. However, this system probably has no real advantage over the low pipeline providing the diameter of milk pipe of the latter is sufficient to cope with high rates of milk flow.

SummaryInvolution of the mammary gland was initiated by stopping milking in 8 cows in the eighth to tenth month of lactation, in 4 ewes which had been lactating less than 7 weeks and in a further 6 ewes lactating more than 12 weeks. In all animals the concentrations of immunoglobulins in the mammary secretion—IgG1, IgC2, IgA and IgM—increased as involution progressed. In the cows and in those ewes in early lactation there was a transitory increase in selective transfer of IgG1during the initial phase of involution. Subsequently, the glandular epithelium completely lost its ability to selectively transfer IgG1, and the results indicated that the loss of structural integrity of the epithelium characteristic of advanced involution allowed a ready equilibration of proteins between the secretion and interstitial fluid. There was no suggestion of a transitory increase in selective transfer of IgC1in those ewes involuted late in lactation.Immunology and Cell Biology (1972) 50, 535–539; doi:10.1038/icb.1972.46

SummaryTo determine whether selective absorption of immunoglobulin occurs in newborn unanaesthetised calves, the concentrations of IgG1, IgG2, IgM and IgA were measured in thoracic duct lymph shortly after the feeding of colostrum. In the 13 calves studied it was found that the concentrations of IgG1, IgG2, IgM and IgA in lymph expressed as a proportion of the concentration of the same immunoglobulins in the colostrum fed were not significantly different. It is concluded that immunoglobulins in the molecular weight range of 150,000 to 1,000,000 are absorbed non-selectively in the calf.Australian Journal of Experimental Biology and Medical Science (1971) 49, 629–633; doi:10.1038/icb.1971.69

SummaryHuman serum albumin, 7S globulin, slow IgG and fast IgG were Labelled with [131I] iodine and injected intravenously into a total of 19 ewes. The mean (whey : serum) ratios for human serum albumin, 7S globulin (mainly fast IgG), slow IgG and fast IgG were respectively 0·044, 0·052, 0·025 and 0·062. There was a sharp increase in the (whey : serum) ratios for human serum albumin, and slow IgG compared with fast IgG as the glands became inflamed following the infusion of virulent staphylococci or α-haemolysin into the test sinus. Thus 12hr. after infection the (whey : serum) ratio for slow IgG and human serum albumin had increased 250–500% above pre-infection values while the ratio for fast IgG had increased by only 160%.Each under half became acutely inflamed within 4hr of the infusion of α-haemolysin. At this time the (whey : serum)ratios for slow IgG were increased 317–640% above the pre-infection values, whereas those for IgG were increased only 135–188%.There result suggest that a Selective mechanism of transfer for fast IgG into milk similar to that existing during colostrum formation continues into lactation and that acute inflammation inhibits this mechanismAustralian Journal of Experimental Biology and Medical Science (1968) 46, 285–294; doi:10.1038/icb.1968.23

The time of appearance of appendicular ossification centres in the Peppin-type Merino foetus has been established using radiological methods on 68 foetuses of known age. A standard of reference of the aging process or maturation process of bone has been drawn up using the number of ossification centres present and the contour changes of certain of these centres as a yardstick. Osseous maturation is thus given a numerical score. Measurements of tibial and body length have also been taken. The entire data (the four variables being age, body length, tibial length, and osseous maturation score) have been subjected to a correlation analysis. Very high correlation coefficients were obtained, ranging from +0.98 to +0.99. It is thus clearly seen from the results of the analysis that body length, tibial length, or osseous maturation measurements are of equal value in assessing the age of the foetus. Furthermore, because of these high correlations a combined regression equation would be pointless.