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Five different straws consisting of two varieties of winter barley, two varieties of spring barley and one variety of winter wheat were chosen due to differences in degradation characteristics determined by using nylon bags incubated in the rumen of cattle and describing the straw using the equation: p = a + b (1 – e–ct). To increase variation in degradability, batches of the same straws were also treated with anhydrous ammonia in a sealed oven.The straws were subsequently offered ad libitum to groups of steers given a daily supplement of 1·5 kg concentrate and untreated straws were supplemented with urea. The dry-matter intake (DMI) of the straws varied from 3·4 to 5·7 kg/day, the digestible DMI from 1·4 to 3·5 kg/day and growth rate from 106 to 608 g/day.By using multiple regression of a, b, c from the exponential equations characterizing degradability of the straw, the correlation coefficients with DMI, digestible DMI and growth rate were 0·88, 0·96 and 0·95 respectively.

1. The object of the experiment was to determine the effects of varying the quantities of herbage available to cows on their diet and milk production.2. Four groups of five Ayrshire cows were strip grazed for three periods of 3-4 weeks on areas calculated from sample cuts to supply (A) 25, (B) 35, (C) 45 or (D) 55 lb. dry matter per cow per day. These periods were interspersed between four standard periods of 2-3 weeks, in which all the cows were strip grazed on 50-60 lb. dry matter per head per day.3. Measurements of milk production and of herbage consumption, by the chromic oxide-faecal nitrogen technique, were made for the last 12 or 16 days of experimental and last 8 days of standard periods. The observations made in the standard periods were used as covariates in the analyses of those made in the experimental periods.

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I. In the first of two experiments four sheep were fed on dried grass and oat straw in the following combinations: (I) straw eaten to appetite and an equal quantity given via a rumen fistula, (2) straw eaten and grass by fistula, (3) grass eaten and straw by fistula, (4) grass eaten and grass by fistula. Mean daily dry-matter intakes (g/kg metabolic live weight, W0,75) for the four treatments respectively were: 13.3, 23.2, 47.8 and 59.4. Dry-matter digestibility coefficients (%) were 37'2, 53.1, 53.3 and 71.3. Changing the digestibility of the diet without changing the component eaten ( I TI. 2; 3 TI. 4) had a large effect on intake, but changing the component eaten without changing digestibility (2 z ) . 3) caused a twofold change in intake. The latter result implied a difference in palatability between the feeds.2. The quantities of digesta in the rumen, determined by removal before and after feeding, were generally twice as great for treatments 3 and 4 as for I and 2. There were corresponding differences between treatments in the rates of passage of stained particles of feed and of chromic oxide.3. In the second experiment the treatments were the same except that meadow hay replaced oat straw. Mean daily dry-matter intakes (g/kg W0"5) were 41.7, 55.1, 59'9 and 68.7 for treatments I to 4 respectively, and digestibility coefficients were 54'0, 61.3, 62.3 and 72.0. In this experiment there appeared to be only a small difference in the palatability of the feeds.The term 'palatability' cannot be defined exactly since it is a concept rather than an exact scientific term (Marten, 1969). The palatability of a food is considered to reflect those of its characteristics which invoke a sensory response in the animal. In nutritional science a food is often said to be palatable if it is selected in preference to other foods offered simultaneously. However, in the experiments to be described the question examined was whether or not the ruminant's sensory response to a food affects the quantity of that food it eats when offered no alternative food.Teitelbaum & Epstein (1963) examined this question in rats by allowing them to feed themselves solely by stomach tube. The rats had the same calorie intake under these conditions as when they ingested the same diet orally, and it was concluded that sensory stimuli were not essential for the regulation of food intake. The same conclusion was reached by Janowitz & Hollander (1955), who found that, when dogs were given intragastrically a liquid feed supplying either 50, roo or 175 % of their normal calorie intake, their calorie intake as solid food was reduced in proportion, so far as this was possible. The liquid feed was given 6 h before the daily meal of solid food, so oral intake was not limited by gastric distension. More recently, Baile & Mayer ( I 967) have given a liquid diet to goats, the food being either consumed entirely by mouth or given partly through a rumen fistula for 2 d at a time. In this experiment also, oral intake was reduced by amounts approximately equal to tho...

SUMMARYOn three occasions in May—July one half of a ryegrass pasture was grazed intensively by cattle and the other was mown. In August and September these areas, designated fouled (F) and clean (C) respectively, were each strip-grazed by two groups of five cows. One group on each area had a herbage allowance of 11·4 kg dry matter per cow per day (C11 and F11) and the other 20·4 kg (C20 and F20).Before the August-September grazing the fouled area had 2·8% of its surface covered by faeces. After this grazing 23 % of the F n area and 34 % of the F20 area were classified as having been rejected by the cows. However, the upper parts of the sward on these rejected areas were in fact grazed. There were only small differences in N and soluble-carbohydrate contents between the herbages offered and rejected.Organic-matter digestibility (%) and intake (kg/cow per day) for the four groups were: C11, 73·0 and 10·5; C20, 74·9 and 11·7; F11 , 74·4 and 9·6; F20, 77·0 and 10·6. The C11 cows consumed all the herbage allowed to them, but the F11 rejected 13%. Digestible organic matter intake was affected more by grazing intensity than by fouling; this was the case also for milk yield, milk composition and the live-weight change of the cows.

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