Twenty-eight pregnant Hereford heifers, whose mean stage of gestation was 171 ± 1 · 2 days, were removed from pasture, allotted to two groups of nine and one group of 10 animals, and confined in bare yards. A group of six non-pregnant heifers was also included in the experiment. The animals were changed to an all-grain ration during a period of two weeks. Thereafter, all groups received crushed sorghum grain, supplemented with 1 per cent. ground limestone. One pregnant group received 6 lb per bead per day fed daily (Group I), another was fed twice-weekly at the same rate (Group II) and the other was fed daily at the rate of 10 lb per head per day (Group Ill). The group of non-pregnant after 24 weeks of grain feeding, when the mean stage of lactation of animals suckling calves was 70 days.
There was little evidence of digestive disturbances due to all-grain feeding. From the commencement of all-grain feeding, the mean weight loss prior to calving was 54 and 70 lb in Groups I and II respectively, compared with a weight gain of 85 lb in Group III heifers during this period. After 24 weeks the average body-weight loss for those animals suckling calves at the conclusion of the experiment was 228, 257 and 87 lb for Groups I, II and III respectively. During the same period the heifers in the non-pregnant Group IV lost an average of 68 lb.
The average birth weight of calves was 57, 55 and 68 lb for Groups I, II and III respectively. There were no deaths in calves after birth. The average weight gain in calves during the first 28 days after birth, when they had access only to their dams' milk, was 17 · 5, 13 · 7 and 32 · 6 lb for Groups I, II and Ill respectively.
The overall incidence of dystokia, still-births and retained placenta was 15 · 4, 15 · 4 and 7 · 7 per cent. respectively.
. Mean 24-hr milk production at the conclusion of the experiment, based on a 4-hr hand-milking interval, was 1500, 1455 and 3502 g for Groups I, II and III respectively.
On the basis of body-weight changes in heifers both prior to calving and throughout the whole experimental period, milk production of heifers, weight of calves at birth and growth of calves to 28 days, the performance of Group Ill was significantly better than that of Groups I and II. There were no significant differences between Groups I and II.
Blood samples were obtained from all heifers when they were transferred from pasture to the experimental yards, at the beginning of all-grain feeding, and during the twelfth and twenty-fourth weeks of all-grain feeding. Determinations were made for haemoglobin, packed cell volume, blood inorganic phosphorus; serum calcium, magnesium, total protein, albumin and globulin; plasma chloride, sodium and potassium. Additional blood samples were obtained from animals in Group IV to determine plasma non-esterified fatty acids at 4-weekly intervals. Some of these determinations were made on blood from the calves when their mean ages were 6 and 10 weeks. There were significant differences within and between groups at different sampling periods in some of the constituents analysed but the levels found did not indicate a pathological condition at any stage.
The initial mean liver vitamin A reserves in all heifers were adequate (298 μ,g/g;. They decreased after 24 weeks on grain containing virtually no carotene, but even in the lactating animals were still considered adequate after this period (mean 150 /.Lg/g). No vitamin A reserves were detectable in the still-born calves.
The heifers gained weight rapidly when returned to pasture at the conclusion of all-grain feeding.
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