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Because of high costs and labour requirements along with the highly variable nutritional value of live feeds, we investigated the possibility of early weaning for barramundi (Lates calcarifer Bloch) larvae aimed at reducing the use of Artemia. Two commercial microdiets, Gemma Micro (Skretting, Australia) and Proton (INVE, Belgium) were compared for growth and survival of larvae using three weaning protocols, until 33 days posthatch (dph). Enriched rotifers were fed to larvae in all protocols through mouth opening until 21, 18 and 30 dph (protocols 1, 2 and 3, respectively). At 13 dph, enriched Artemia metanauplii were introduced to weaning protocols 1 and 2, and continued until 29 and 24 dph, respectively, whereas protocol 3 did not receive Artemia. Microdiet was initiated at 20, 16 and 13 dph in protocols 1, 2 and 3, respectively. Barramundi larvae grew successfully to 33 dph when co‐fed rotifers and microdiet, and significantly larger larvae resulted from feeding Gemma Micro rather than Proton, when Artemia were not used. However, larvae weaned onto Proton using a longer period of Artemia provision were significantly larger than larvae reared according to all other protocols. Survival was significantly higher in all Gemma Micro protocols when compared with Proton protocols. This was in part due to higher cannibalism when using Proton compared with Gemma Micro (22.8 ± 0.9% and 9.2 ± 0.6%, respectively). Cannibalism became more noticeable in all protocols when the larvae reached 7–8 mm standard length and further increased after the cessation of live feed. Tank biomass production was the highest when larvae were weaned onto Gemma Micro including a short period of Artemia provision as a result of a combination of high growth and survival. However, similar biomass production resulted when larvae were weaned directly from rotifers onto Gemma Micro and/or from a prolonged Artemia period onto proton. The success of weaning barramundi larvae directly to microdiet from rotifers, thus eliminating the need for Artemia, was influenced by the microdiet. Relatively higher levels of free amino acids and lipids were believed to contribute to increasing larval growth and survival. Larvae that were fed Gemma Micro showed higher growth when Artemia were utilized for a shorter period, while Proton‐fed larvae benefited from an extended Artemia feeding period.

Live weight, milk yield, fat, protein and lactose percentage of 236 cows and heifers of four breeds of dairy cattle were recorded at 2-week intervals, starting within a week after calving, during the winter and spring of 1972/73. Lactation curves of the form X(n) = Xn b e cn were fitted to each animal's records, where X, b, c are constants, e the base of natural logarithms and X(n) the value of the character at the nth 2-week interval. Correlations between the curves, and between deviations from the curves, showed that the production of milk, fat, protein and lactose was negatively correlated with live-weight change in the long term, but that deviations from the curves were not correlated. There were significant positive correlations between milk yield and size, and between potential compositional quality and size (the values of X in the model). Of the four breeds studied, Friesian, Ayrshire, Guernsey and Jersey, adult Friesian cows required less dietary energy per kg of total solids produced than any other group, according to the principles of the metabolizable energy system of calculating energy requirements. During the period of negative energy balance, an average 10% to 15% of energy output in the form of milk was derived from the mobilization of body reserves.

The rectal temperatures, pulse rates and milk yields of 44 Ayrshire and 38 Friesian cows were recorded during oestrus and compared with values obtained after oestrus had ceased. The fat, solids-non-fat (SNF) and protein percentages and the cell counts of milk samples were also compared. Forty of the cows were housed in cubicles and 42 were kept loose in yards. During oestrus rectal temperatures and pulse rates were significantly raised and milk yields were lowered. Milk had, on average, significantly higher fat contents and cell counts and lower SNF and protein contents than post-oestrous milk. The differences due to oestrus between the cows kept in cubicles and yards were minimal, but the Ayrshire cows tended to show more significant effects than the Friesians, except in the milk cell counts, where the difference was higher in the Friesians.

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