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Summary. Shade-type preferences by Holstein–Friesian cows were investigated under natural climatic conditions. The trial was conducted in south-east Queensland, Australia, over 88 days in summer. Forty-two cows were placed in a dirt-floored yard (zero grazing) provided with different shade types. Shade types provided were a 3 m high galvanised iron roof, Sechium edule (choko) vines on a 3 m high trellis, 70% shade cloth on a 3 m high frame and natural shade trees. The floor area under the shade structures was concrete. An unshaded area (the remainder of the yard) was also provided. Each cow was scored for coat colour based on the proportion of black and white. Number of cows using a particular shade type and their respiration rates were recorded daily at 1300 hours. Ambient temperature, relative humidity, solar radiation and wind speed were also measured. Cows selected the galvanised iron roof most frequently when temperatures rose above 30°C, with no significant differences between the other shade types. At temperatures below 30°C, animals did not seek shade. As ambient temperature, solar radiation and relative humidity rose, respiration rate rose. Cows with a high percentage of black coat preferred shade, while those with a high percentage of white coat did not seek shade.

The present study was conducted to compare the efficacy of five different reaction conditions on the guanidination of lysine in casein and to establish optimum lysine:O‐methylisourea (OMIU) for maximum guanidination of lysine in casein and soya bean meal. The results indicate that the presence of glycine–NaOH buffer is not required for guanidination of proteins at pH 10·5. A OMIU concentration of 0·4 M was found to be as effective as 0·6 M for guanidination. Both OMIU–hydrogen sulphate and free OMIU were equally effective reagents in terms of conversion of lysine to homoarginine. The use of OMIU–hydrogen sulphate for guanidination and the use of ethanol to recover guanidinated protein, however, resulted in the formation of crystalline sodium sulphate, a known purgative agent, in the guanidinated material, and therefore are not recommended if the guanidinated protein is to be used in animal trials. The molar ratio of lysine: OMIU required for efficient lysine conversion to homoarginine varied for different protein sources. Ratios required for maximum conversion for casein and soya bean meal were determined to be 1:10 and 1:16, respectively. A simple procedure developed for the large‐scale guanidination (5–10 kg batches) of proteins is also described. The results showed that guanidination of proteins can be easily scaled up from 20 g to 5–10 kg and that large‐scale guanidination is feasible and efficient.

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