The rôle of protein in food intake regulation is complex in ruminants. Previous research has shown that a deficiency in degradable nitrogen (N) could affect microbial activity and decrease intake. On the other hand, an increase in metabolizable protein content of the diet seems to stimulate food intake in lactating dairy cows. The aim of this experiment was to determine whether metabolizable protein supply plays a direct rôle in the stimulation of food intake. Treatments comprised two infusions of soya protein isolate (800 g/day) either into the rumen (RP) or into the duodenum (DP), which were compared with two iso-energy infusions of glucose (880 g/day) either into the rumen (RG) or into the duodenum (DG). Four ruminally and duodenally cannulated cows producing 36·5 kg/day of milk were assigned to a 4 ✕ 4 Latin-square design with periods of 4 weeks. Duodenal infusions of protein (DP) significantly increased (P < 0·05) dry-matter intake (DMI) ( +1·9 kg/day), rate of intake ( + 8·2 g DMI per min), milk yield ( + 4 kg/day), protein content ( + 2·3 g/kg) and protein yield ( +191 g/day) compared with the glucose infusion in the duodenum (DG). No significant effect was observed with ruminal infusion of protein (RP) compared with the glucose infusion in the rumen (RG). The protein infusions had no effect (P > 0·05) on the apparent digestibility of dry matter, organic matter, neutral-detergent fibre or acid-detergent fibre and also no or only small effects on ruminal fermentation variables. Plasma concentrations of most of the essential amino acids increased significantly with the duodenal infusion of protein, whereas ruminal infusion of protein had no significant effect. It is concluded that direct supply of metabolizable protein stimulates intake independently of ruminal digestion effects.

Ten Hereford ✕ Friesian steers prepared with rumen, duodenal and ileal cannulae were offered ad libitum access to either grass (G), white clover (W) or red clover (R) silage or mixtures of the grass silage with the clover silages (GW and GR; 60: 40 dry matter (DM) basis). The experiment was conducted as a two-period change-over design within each clover treatment, with grass silage as an experimental control. The clover silages had higher concentrations of DM, nitrogen (N), and total fatty acids and lower concentrations of fibre (P < 0·05) than the grass silage. Rumen fermentation characteristics were similar between treatments apart from a slight elevation of n-butyric acid levels with white clover silage diets (P < 0·05). Duodenal flows of DM, organic matter (OM), total and microbial nitrogen (MN) were significantly higher (P < 0·05) with the white clover silage treatments compared with the grass silage diet. However there were no significant differences in the efficiency of microbial protein synthesis with a mean value of 27·1 g MN per kg OM apparently digested in the rumen. Duodenal flows of total fatty acids per unit intake were not significantly different, although there was a trend (P < 0·1) for increased flows with the white clover silage diets. Duodenal flows of cis-vaccenic acid (P < 0·01), linoleic acid (P < 0·05), α-linolenic acid (P < 0·05) and cis-9 trans-11 conjugated linoleic acid (CLA) (P < 0·05) were higher for the clover silages, particularly white clover silage. The increased flows of α-linolenic and linoleic acids remained significant after correcting for differences in DM intake. Biohydrogenation of linoleic (mean = 0·83) and α-linolenic (mean = 0·86) acids was extensive for all diets but the latter was significantly lower (P < 0·01) for the diets based on red clover silage. These results suggest potential for modifying the fatty acid composition of ruminant products by feeding clover silages.

The effect of carbohydrate supplementation on rumen utilization of ammonia-treated straw was studied in four rumen-cannulated ewes (42•0 (s.e. 2•80) kg live weight) in a Latin-square design. Diets were a 50: 50 mixture of ammoniated barley straw and a concentrate made up with different ratios of barley grain and citrus pulp, namely M1 (100: 0), M2 (66: 33), M3 (33: 66) and M4 (0: 100). Concentrates also included soya-bean meal and urea to make diets isonitrogenous. Diets were given in one meal in the morning at 0•8 kg/day. There were no significant differences among treatments in daily weighted means of rumen pH and concentration of volatile fatty acids. Acetate, propionate and butyrate molar proportions were not different among treatments, but proportions of isobutyrate (P < 0•05) and isovalerate (P < 0•10) were higher for M1 and M2. Ammonia concentration immediately before feeding was lower (P < 0•05) for M3 and M4 (72•1 and 51•3 mg/l) than for M1 and M2 (97•0 and 107•9 mg/ l). Total rumen bacterial concentration was higher (P < 0•05) with the highest barley proportion, whereas enzymatic activity against structural carbohydrates of particle-associated bacteria did not differ significantly among treatments. Digestibility of neutral-detergent fibre increased (P < 0•05) with the increase in the proportion of citrus pulp in the concentrate (0•647, 0•674, 0•684 and 0•693 for M1, M2, M3 and M4; s.e. = 0•0086). Urinary excretion of purine derivatives decreased linearly (P < 0•05) as the proportion of citrus pulp in the diet increased, while faecal excretion of purine bases was not significantly affected by dietary treatments.

Sheep rearing is a traditional occupation of about 85 000 shepherd families on the Deccan plateau in the Maharashtra State of India. They rear Deccani (D) sheep which usually bear only single lambs. Prolificacy is an important trait for the efficiency of meat producing sheep. It was decided to evaluate and utilize Indian sheep genetic resources with a view to improving the efficiency of sheep production on the Deccan plateau. A crossbreeding experiment was conducted over 4 years, using rams of the D, Bannur (B) and Garole (G) breeds and D and B ewes with the aim of developing recommendations for the appropriate breed combination of a likely composite. It was found that crossing with G reduces live weight and growth rates significantly compared with D but lambs sired by G rams were more resistant to naturally acquired gastro-intestinal nematode infections and to artificial challenge with Haemonchus contortus than those sired by D or B rams. The G breed, being from a humid environment is, however, not adapted to the semi-arid Deccan plateau. The higher productivity (in terms of weight of lamb weaned) of twin-bearing ewes compared with those bearing singles was evident even in extensive rearing conditions. The finding of increased resistance to gastro-intestinal nematodes in the G breed, which also carries a major gene for prolificacy, highlights the potential for inclusion of G in a composite breed. Negative effects on growth and survival from inclusion of the Garole need to be carefully managed.

Amino acids stimulate the growth rate and growth yield of ruminal micro-organisms, but the basis of this stimulation, in terms of amino acids which most limit growth, has never been fully established. Here, for the first time, a deletion approach was investigated using in vitro incubations of mixed ruminal micro-organisms supplied with a mixture of xylose, starch and cellobiose as energy sources and ammonia plus a complete amino acids mixture or mixtures with a single amino acid omitted as nitrogen sources, enabling the evaluation of the impact on ruminal fermentation of the deletion of a single amino acid from a complete amino acids mixture. Significant effects (P < 0·05) on total gas production were observed after 10 h of incubation when glutamate, glutamine, isoleucine, leucine, phenylalanine, serine, tryptophan or tyrosine were deleted from the amino acids mixture. The only significant effect of an amino acid deletion on volatile fatty acid production at 10 h was with serine (P < 0·05), although the effect of omitting others, including arginine, isoleucine, leucine and phenylalanine, approached significance (P < 0·01). The removal of leucine caused a 0·09 decrease in growth yield (P < 0·05); no other deletion affected the yield significantly (P > 0·05). Net gas production for each treatment was calculated by subtracting gas production in the absence of carbohydrates from gas production in their presence, thus eliminating gas production from amino acids from the values. At all times up to 10 h, the most significant effects on net gas production were found when serine, leucine, or the aromatic amino acids were omitted from the amino acids mixture. Thus, the deletion approach confirmed that no single amino acid limits ruminal fermentation more than any other, although a few, principally phenylalanine, leucine and serine, have a particularly significant rôle in the ruminal fermentation rate of soluble, rapidly degraded materials and/or microbial growth efficiency.

A 5 ✕ 5 Latin square was conducted with ruminally and duodenally cannulated Dohne Merino wethers consuming wheat straw to determine the effect of different rumen degradable protein (RDP) levels on forage intake, fermentation characteristics, nutrient flow and digestion. The wethers had ad libitum access to water and wheat straw (32 g crude protein (CP) per kg dry matter (DM); 742 g neutral-detergent fibre (NDF) per kg DM) that was offered twice daily, immediately after intraruminal infusion of the supplements at 07:00 and 19:00 h. The supplemental RDP (calcium caseinate; 900 g CP per kg DM) levels were: 0, 40, 80, 120 and 160 g/day. Each period consisted of 14 days of adaptation and 6 days of sampling. Forage and total organic matter (OM) intakes increased in a linear manner (P < 0•01) with increasing supplemental RDP levels. Digestible organic matter intake (DOMI) displayed a quadratic increase with elevated amounts of RDP (P < 0•01). The effects of treatments on rumen and total tract digestion, as well as fluid dilution rate were minimal. Microbial nitrogen (MN) flow to the duodenum and microbial efficiency increased quadratically (P < 0•04) with increased RDP supplementation. Rumen ammonia nitrogen (NH3-N) concentrations increased linearly (P < 0•01) and total volatile fatty acids (VFA) tended to increase linearly (P = 0•07). In conclusion, RDP supplementation to Dohne Merino wethers consuming wheat straw generally enhanced rumen fermentation and forage intake. A total RDP intake (sources: calcium caseinate and wheat straw) of 3•30 g/kg M0•75 or 0•12 of DOM maximized DOMI.

The aim of this experiment was to determine the mechanisms involved in changes in the production of cashmere as a consequence of genetic selection. Skin follicle parameters and pattern of cashmere growth were compared in two selected lines of Scottish cashmere goats and a randomly bred control line. One line, the fine line, had been selected for low fibre diameter, and this had resulted in lower fibre diameter, but the weight of cashmere produced had also been reduced. Selection for fibre quantity and quality to give maximum financial return (the value line) had increased cashmere weight without a significant increase in cashmere diameter.

Skin follicle density and the ratio of secondary to primary follicles (S/P ratio) were measured at 5 months of age in 25 female kids from each line. The density of follicles in the value line was greater (P · 0.05) than that in the fine or control lines (means were 21·8, 19·8 and 20·1 follicles per mm2 respectively, s.e.d. 0.73). S/P ratio increased (P · 0.001) from control to fine to value lines (means were 6.5, 7.7 and 8.4 respectively, s.e.d. = 0.30).

The rate of cashmere growth (length), peak cashmere length, the duration of the cashmere growing period and dates of initiation and cessation of growth were measured in the same 25 goats from each line between 2 and 3 years of age. These traits were estimated from the regression of measurements of staple length taken at approximately 6-weekly intervals from the start of the growing period until peak staple length was reached. Measurements were made on the shoulder, mid side and hip. There was no difference in cashmere growth rate between the selection lines (average 0·29 (s.e. 0.006) mm/day). Cashmere growth started earliest in the value line and latest in the fine line but the date of cessation of growth was not different. This affected the duration of the growing period which was 183, 163 and 214 days (s.e.d. 9.6, P · 0.001) for the control, fine and value lines respectively. Peak staple length of cashmere was longest in the value line.

Increased weight of cashmere in the value line was brought about through an increase in the number of secondary follicles and by an increase in the length of cashmere due to an increase in the duration of the growing period.

In order to develop a behavioural test as well as gain information about behavioural response to novel food, we performed four experiments with cattle kept in tie-stalls and observed the behaviour (approach/avoidance, self-grooming and consummatory behaviour) for 10 (experiment 3 and 4) or 30 (experiment 1 and 2) min after provision of novel food.

In experiment 1, the effects of the novelty of the feeding method were tested using nine heifers provided with 2 kg of their usual food from the usual fodder truck or from a basket made of plastic. The novel feeding method induced increased sniffing, decreased duration of eating and increased self-grooming.

The effects of the degree of novelty of a food were examined in experiment 2 using heifers (no. = 8 to 12) and three concentrations of fish oil (1•5, 6 or 24 g/kg) and eucalyptus oil (5, 20 or 80 drops per kg) added to the usual food. Increasing the concentration of eucalyptus oil in the food led to changes in behaviour, while the addition of fish oil led to a less clear response. However, both suggested that the behaviour reflected the degree of novelty in the food. Behavioural responses to two novel foods (4 kg carrots v. 80 drops per kg of eucalyptus oil added to the usual food) as well as individual characteristics and repeatability within 72 h were examined in experiment 3. The behavioural responses to the novel foods differed, showing a higher level of approach and attempts to eat the carrots, and responses to the two different novel foods were not correlated. At the second provision, the acceptability of the carrots was greater, however responses to carrots showed an acceptable repeatability.

Finally, the cardiac (heart rate) and behavioural responses to usual food and novel food (4 kg carrots) were compared in experiment 4. Provision of novel food led to behavioural signs of motivational conflict and neophobia while the heart rate tended to be lower than when the cows were provided with usual food.

These results provide evidence that behavioural responses to novel food in cattle include signs of motivational conflict between eating motivation and neophobia, reflecting the degree of novelty in the test situation including the feeding method. However, palatability of the food might also affect the responses, and the data on heart rate suggest that novel food is not a fear-inducing stimulus.

The objectives of this study were (1) to estimate herbage intake in spring and late summer in Danish Friesian steers during their first grazing season on ryegrass/white clover pasture and (2) to investigate the effect of different winter feeding levels on subsequent herbage intake in Danish Friesian steers weighing more than 450 kg. In experiment 1, herbage intake was estimated in 18 to 20 steers with a mean live weight of 210 kg (s.e. 8•0 kg) and 312 (s.e. 8•9) kg in May/June and August respectively. In experiment 2, 22 steers were allocated to two feeding treatments in their second winter with expected daily live-weight gain of 500 g (LOW) and 800 g (HIGH). The steers weighed 440 (s.e. 15•8) kg (LOW) and 531 (s.e. 9•2) kg (HIGH) at the time of turn-out on to a ryegrass/white clover pasture. Herbage intakes were estimated in June using, as in experiment 1, the alkane bolus technique. Faeces and herbage samples were analysed for alkanes to estimate herbage intake, digestibility and botanical composition of intake. The weight gains (kg/day) were 1•156 (s.e. 0•69) and 1•054 (s.e. 0•87) in May/June and August respectively (experiment 1) and 1•592 (s.e. 0•137) and 1•273 (s.e. 0•116) in June in LOW and HIGH respectively (experiment 2). Daily herbage intake (kg dry matter (DM) per steer) estimated by alkanes C32 /C33 were 5•2 (s.e. 0•26), 9•4 (s.e. 0•28) in May/June and August (experiment 1) (P < 0•001) and 12•0 (s.e. 0•50) and 10•4 (s.e. 0•41) in LOW and HIGH (experiment 2) (P < 0•05) respectively. The diet of steers contained primarily ryegrass leaves (0•70 to 0•90) and ryegrass stems (0•10 to 0•30) and clover (0 to 0•02 and 0•18 in experiment 1 and experiment 2 respectively). It was concluded that (1) steers during their first grazing season can maintain herbage intake per kg live weight during the grazing season from May to August, and (2) steers weighing more than 450 kg are able to increase herbage intake along with compensatory growth.