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SummaryLong-term undernutritional stress is often a feature of sheep and beef cattle production, but has only become a major feature of dairy cattle husbandry in the United Kingdom in recent winters when food was short and expensive. An experiment was carried out to study the effects of long-term underfeeding during pregnancy and early lactation on some blood constituents, milk yield and composition and body weight of dairy cattle. Two groups of cattle were fed at 60 and 40% of the estimated requirements for maintenance and pregnancy or lactation for 13 weeks before and 13 weeks after calving, and one group was fed at the maintenance level only for the same period. A control group was fed at 100% of estimated requirements for this period. All groups were subsequently fed at the control level for a further 24 weeks.The experiment showed that cows undergoing long-term nutritional deprivation were able to maintain concentrations of blood constituents within narrow limits; the concentrations of such constituents as glucose or non-esterifled fatty acid did not reflect energy deficit or surplus. The animals remained clinically healthy during the underfeeding and recovery periods. The results suggest that debility occurring under field conditions in association with reduced food supply may be due to a multiplicity of factors or to severe imbalance of specific nutrients, rather than to energy or protein deficit alone.There was a difference in efficiency of utilization of energy of 19% between cows in the most severely underfed groups which maintained lactation and those which were not able to maintain lactation. There was evidence that this difference in efficiency was detectable within a few weeks of the start of the period of reduced nutrition. Animals which were less affected in the early stages of food deprivation were also those which maintained the advantage through the deprivation and recovery periods.

An experiment was performed with two groups of nine British Friesian cows to compare the effect of calving in fat or thin condition on (1) the mobilization and functional activity of subcutaneous adipose tissue, (2) the mobilization of skeletal muscle, (3) the development and resolution of fatty infiltration of the liver and (4) the chemistry and haematology of blood. Sampling was performed at various times during the dry period and subsequent lactation. There were no differences between groups in the amount of adipose tissue mobilized between 4 weeks before and 26 weeks after calving. The lipogenic and lipolytic capacities of isolated adipocytes were also not different between groups at any time although major changes occurred in both over the calving period and during early lactation. Acetate oxidation to carbon dioxide was higher in adipocytes isolated from thin cows particularly after calving. More muscle fibre area was lost in the fat cows compared with the thin cows between 4 weeks before and 4 weeks after calving and the fat cows had greater infiltration of fat in the liver at 1 and 4 weeks after calving than the thin cows. The mean white-cell count was lower and the packed-cell volume was higher in the fat cows than in the thin cows at 1 week after calving. The major differences between groups in blood composition were increased concentrations of copper, non-esterified fatty acids, bilirubin and enzymes such as ornithine carbamyl transferase in the fat cows after calving. These results suggest that fat and thin cows respond differently to the metabolic demands of early lactation and that some of these differences render fat cows more susceptible to disease.

SUMMARYThe blood composition of 45 cows with more than 20% fat in the liver (moderate fatty liver) was compared with that of 83 cows with less than 20% fat in the liver (mild fatty liver). The cows were sampled at 1 week after calving and were from three Friesian and one Guernsey herds. Blood concentrations of non-esterified fatty acids, bilirubin and aspartate amino-transferase were significantly elevated in cows with more than 20% in the liver whereas concentrations of glucose, cholesterol, albumin and magnesium were all significantly reduced. Blood samples from cows in two of the herds were analysed for ammonia, insulin and D(-)3-hydroxybutyrate. Cows with moderate fatty liver in these two herds had significantly lower insulin concentrations and higher D(-)3-hydroxybutyrate concentrations than those with mild fatty liver. Using an equation based on blood concentrations of non-esterified fatty acids, glucose and aspartate aminotransferase it was possible to assign correctly three out of four cows to either the mild or moderate fatty liver groups.

SummaryAn experiment was carried out to study the effects of underfeeding during late pregnancy and early lactation on the structure and chemistry of liver and muscle of dairy cows. Two groups of cattle were fed at 60 and 40% of estimated requirements for maintenance and pregnancy or lactation for 13 weeks before and 13 weeks after calving, and one group was fed at maintenance level only for the same period. A control group was fed at 100% of estimated requirements for the same period. All groups were subsequently fed at the control level for a further 24 weeks.Underfeeding resulted in significant changes in muscle and liver of dairy cows. In particular, there was a decrease in liver cell volume in the underfed groups and a persistence of post-parturient fat in the moderately underfed cows. Muscle fibre diameter was reduced and there was a loss of fast twitch oxidative glycolytic fibres in the underfed cows.

SUMMARYLipid production across the liver was measured in catheterized dairy cows in vivo in the fed state and during 6 days of fasting. Production rates were calculated from the lipid concentrations in arterial, portal and hepatic-venous plasma and from the rates of plasma flow in the portal vein and the hepatic veins.There was a consistent net hepatic output of triacylglycerol and a net hepatic uptake of free fatty acids in the fed state.In the fasted state there was a significant change to a net hepatic uptake of triacylglycerol and an increased hepatic uptake of free fatty acids. Both factors are likely to result in an accumulation of triacylglycerol in the liver.

A drug-resistant strain ofT. vivaxwas transmitted through a series of four duikers (S. grimmia) and a gazelle (G. rufifrons) byG. palpalisandG. tachinoides. The cyclical transmission of the strain in cattle, started in earlier work, was continued for control purposes. Infections with the drug-resistant strain in the antelope were of the same type as those produced by field strains ofT. vivaxin the same host species, and infection rates in tsetse flies fed at early stages of infection on the antelope were similar to those found in flies fed on cattle infected with the drug-resistant strain. The strain retained resistance to diminazene aceturate at a dose rate of 7-0 mg/kg and quinapyramine sulphate at 5'0 mg/kg in the absence of the drugs for 7 months in tsetse flies and antelope, and for a total period of 29 months in tsetse flies and cattle.We wish to thank Dr A. A. Amodu, Director of the Nigerian Institute for Trypanosomiasis Research, for permission to publish this paper.

SYNOPSISThe investigation described in this paper considers the influence of social class and the infant's birth order on maternal care, and then, in the light of these findings, examines the association between quality of maternal care and infant development. The study population comprised 89% of all births during an 18-month period in a defined administrative area in Glamorganshire. Possible explanations for the findings are discussed.