[Experimental studies on the ketogenic effect of high doses of proteins in dairy cows]

A 14-month feeding experiment was conducted with 16 high-yielding cows, each given a daily supplement of 2 kg soya meal regardless of milk yield or the stage of lactation, in comparison with 8 normally-fed cows. At monthly intervals various parameters of carbohydrate, fat and protein metabolism and of liver function were determined. At the end of the trial, samples of liver were obtained by biopsy for morphological and histochemical examination. Supplementation had a pronounced effect on milk yield and fat content, averaging over 900 kg of milk and 0.2% fat content more than during the preceding year. The parameters of metabolism revealed clear signs of subclinical ketosis, particularly during the first third of the trial period. Changes were greatest during the 3rd and 4th months of the trial, when the protein content of the ration was particularly high (over 3 kg) and when the energy supply ratio was particularly unfavourable (PEQ 300). At the end of the trial some abnormalities were detected in individual animals in the biochemical properties of blood and urine, and the morphological, histochemical and ultrastructural appearance of the liver. These changes included increases in KK, BTS and bilirubin concentrations in the blood; ketonuria, proteinuria; perilobular fat infiltration with glycogen depletion; changes in succinate dehydrogenase and acid phosphatase activities. In most animals the liver seemed to have become adapted to a high protein intake.

Corticosteroids in nocturnal blood plasma of cows in the field related to stage of lactation and plasma acetoacetate

Two materials of nocturnal blood plasma samples, each representing more than 100 cows unselected with respect to health condition, showed acetoacetate variations within a wide range, overlapping with the range for animals with clinical ketosis. Within each of the two materials a statistically significant (P smaller than 0.001) negative correlation (r equal to minus 0.30) was obtained between plasma corticosteroids and log acetoacetate. The lowest corticosteroid and the highest acetoacetate averages were obtained for animals which were within the first month of the lactation cycle. With increasing time post-partum the two components varied inversely, a maximum in corticosteroids coinciding with a minimum in acetoacetate in cows which had calved 2 1/2 to 3 months before the date of sampling. At this stage the mean plasma sugar was about 10 per cent higher than in early lactation. The corticosteroid ranges for different levels of acetoacetate overlapped extensively. Still cows with acetoacetate smaller than or equal to 0.6 mg/100 ml gave significantly higher corticosteroid averages than the rest of the material. But in animals exceeding the 0.6 mg limit no relationship was found between the severity of the ketonaemia and the steroid level. Thus, no difference was obtained between cows with clinical ketosis and animals which were moderately ketonaemic. Some change in adrenal function may be associated with the development of ketonaemic conditions in cows. But no proof has been provided of a direct adrenal involvement in the transformation of a case of subclinical ketosis to the clinical stage.

Performance of Holstein and crossbred dairy cattle in Louisiana. III. Health and viability

Viability and health disorders were compared for straightbred Holsteins and crosses between Holsteins, Brown Swiss, Jerseys, and Red Sindhis. In addition, effects of mating systems and effects of various parts of Red Sindhi heredity on these traits were evaluated. Losses before first calving per 100 females born alive were: Holsteins 22; Holstein-sired crosses 20: Brown Swiss-sired crosses 26; daughters of crossbred sires group I (sires had from 1/4 to 1/16 Red Sindhi heredity) 24; and group II (sires were all European breeds) 31. Losses in first-gestation from abortions and stillbirths were: Holsteins 20% and crossbreds 9%. In first lactation, incidence of foot rot and anaplasmosis was higher among Holsteins (13% and 16%) than in crossbreds (5% and 8%) whereas the incidence was less among crosses with Red Sindhi heredity (3% and 2%) than in all European breed crosses (9% and 17%). When progeny produced by criss-crossing to purebred sires were compared with progeny from random mating to crossbred sires, the former had a greater incidence of mastitis (30% versus 19%) and anaplasmosis (11% versus 2%). There was no differences between Holsteins and crossbreds in overall viability. However, there was considerable variation between breeds at the various ages.