The objective was to elucidate the influences of two analytical methods, which employed neutral detergent or enzymes, on the digestion of carbohydrate fractions in the rumen and post-rumen of steers. Structural carbohydrates in diets and digesta were directly measured using both procedures and the contents of non-fibre carbohydrates (NFC) and non-fibre non-starch polysaccharides (NFSP) were estimated by subtracting the structural carbohydrates and other components from the organic matter. Carbohydrate sources were Italian ryegrass and rolled barley in the control diet and, in each of other three diets, Italian ryegrass and rolled barley plus either beet pulp, citrus pulp or soya-bean hulls. All diets contained similar proportions of dry matter as crude protein, structural carbohydrates and NFC but the starch proportion of the NFC was different in each diet, as follows: control (0·62), beet pulp (0·48), citrus pulp (0·30) and soya-bean hulls (0·63). Four Holstein steers with ruminal, duodenal and Heal cannulas were offered the four diets in a 4 × 4 Latin-square design. Estimated digestibilities of the structural carbohydrates in the rumen and the whole tract were greater (P < 0·01) when the detergent method was used than when the enzymatic method was used. The maximal difference in the ruminal digestion among the four diets was only 0·05 by the detergent method but 0·17 by the enzymatic method. Conversely, the digestibility of NFC in the rumen, as estimated from the detergent structural carbohydrates was less (P < 0.01) than that estimated from enzymatic structural carbohydrates with no evident differences among the four diets. Starch digestibility in the rumen was extensive for all diets but the ruminal digestibility of NFSP was much lower in the control and soya-bean hull diets, especially when it was estimated using the detergent method. The duodenal flow of microbial protein was greater (P < 0·05) for the beet pulp and citrus pulp diets than for the control. The acetate concentration of the ruminal fluids ranged from 84 for the control diet to 128 mmol/l for the soya-bean hulls diet. The digestion of carbohydrate fractions and the fermentation characteristics in the rumen suggested that the enzymatic method is the more appropriate method for fractionating carbohydrates.

The influence of prior exposure to high salt diets on the salt appetite and the exhibition of stereotyped behaviour patterns was investigated with individually penned calves and tethered dairy cows. In the first experiment one half of a group of 12 calves received concentrates with the sodium content increased from 4 to 9 g/kg by the addition of NaCl up to weaning at 6 weeks, the other half had no supplementary NaCl added to the concentrates. Adding the NaCl increased the food intake of the calves, the time spent ruminating and live weight. Stereotyped behaviour patterns, such as self-grooming, licking the pen or buckets and ear sucking were reduced by adding NaCl. Calves were tested for their salt preference at 6 months of age by adding varying quantities of NaCl to silage. Exposing calves to supplementary NaCl in the concentrate pre-weaning increased the preferred sodium concentration of silage from 3 to 9 g/kg dry matter (DM). In the second experiment 36 tethered dairy cows received either a restricted concentrate and forage diet with a mean dietary sodium concentration of 2 g/kg DM, or the same diet but with the sodium content increased to either 7 or 12 g/kg DM by adding NaCl to the concentrates. There was no effect of NaCl on feeding or ruminating behaviour but the total amount of stereotyped behaviour, including mouthing or rubbing the tethering chain or bars, self-grooming and nosing or pawing the ground, decreased with increasing salt in the diet. It is concluded that increasing the sodium content of the diet of young calves from 4 to 9 g/kg increased their subsequent salt appetite and that increasing the salt content of the diet of calves or cows in restricted housing conditions can reduce the amount of stereotyped oral behaviour.

The colon of the simple-stomached animal comprises a gradually changing microbial environment, using the residues of digestion as substrates for fermentation. As carbohydrate sources decline along the length of the colon, the microflora degrade proteins to use as an energy supply, resulting in the formation of undesirable and potentially toxic metabolites. This study has examined the possibility of using dietary starches as a means of extending carbohydrate fermentation along the colon in order to reduce the effects of protein degradation, and the influence of these starches on the numbers of microbial groups within the total population. The study was carried out in weaned piglets, using native and retrograded forms of maize and waxy maize starches, containing proportionately about 0·25 and 0·01 amylose respectively. It was found that protein degradation in the mid and distal regions of the colon was best reduced by the inclusion of the retrograded form of waxy maize, although these data did not achieve significance. However, it was found that a reduced population of the protein-degrading Bacteroides spp. resulted from the inclusion of waxy maize rather than maize in the diets, (proximal colon P < 0·01 ; mid colon P < 0·001 , distal colon P < 0·05), while the retrograded waxy maize produced increased lactobacillixoliform ratios throughout the colon, which may result in an improved resistance to infection by intestinal pathogens. Retrogradation of these starches reduced the coliform populations throughout the colon, with significant (P < 0·05) effects observed in the proximal and distal regions. The data suggest that, of the starches tested, reduced protein-degrading activity and improved pathogen resistance may be achieved with retrograded waxy maize.

Endogenous ileal amino acid flows were determined in pigs fitted with simple T-cannulas using either the regression method (meat and bone meal (MBM) as the protein source at five levels of inclusion) or following protein-free alimentation. Amino acid flows were compared with those determined by feeding animals a diet the sole nitrogen source of which was enzyme-hydrolysed casein (EHC), followed by centrifugation and ultrafiltration of the ileal digesta. The EHC was a mixture of free amino acids and oligopeptides (molecular weight 5000 Da). For the EHC treatment, the ileal digesta precipitate plus retentate was used to determine the endogenous flows. The ultrafiltration step excludes unabsorbed dietary amino acids from the measure of endogenous loss. Chromium III oxide was the reference marker in all diets. Estimates of endogenous nitrogen and amino acid flows determined under protein-free alimentation and the comparable flows determined using the regression method were similar. However, endogenous flows of amino acids for the EHC-fed pigs were generally significantly higher (F < 0·01) than values found for pigs on the protein-free diet and were higher than values obtained after extrapolation for pigs given the MBM-based diets. Mean endogenous ileal nitrogen flow for the EHC-fed animals was 2526 (s.e. 33.9) compared with 1711 (s.e. 25.5) mg/kg dry-matter intake for pigs receiving the protein-free diet.

Two experiments were designed to study the influence of an increase in energy supply on the utilization of exogenous glucose in food-restricted post-partum Charolais suckler beef cows. In experiment 1, 18 cows were given a basal diet (BD) providing 0·70 of energy requirements from calving with or without an energy supplement (SD) of 2 kg of rolled triticale grain starting at day 32 post partum. On day 42 post partum an injection of glucose (1·0 mmol/kg live weight) lasting 20 min resulted in a similar plasma glucose and cortisol profile in each diet group but a smaller plasma insulin increase in SD than in BD cows (146 (s.e. 37) v. 273 (s.e. 37) pmol/l, P < 0·05). Plasma non-esterified fatty acids concentrations were reduced by the glucose injection (P < 0·01). Experiment 2 compared the efficiency of an energy supplement in the form of concentrate (CS, maize grain, no. = 11) or forage (PS, maize silage, no. = 10) in oestrous-synchronized beef cows previously given a restricted diet. Glucose injection resulted in a small increase in insulin concentrations during infusion with a peak at 20 min (PS: 250 (s.e. 34) v. CS: 257 (s.e. 32) pmol/l, P > 0·05). No differences were observed between the two groups of cows for glucose, insulin and cortisol profiles (P > 0·05). Similar pregnancy rates after oestrous synchronization treatment were observed in CS and PS cows (6/11 v. 5/10). In conclusion, a period of supplementation sufficient to re-establish energy balance, but not the type of supplement, influences the insulin response to exogenous glucose in food-restricted post-partum Charolais beef cows.

Meals prepared from low glucosinolate rapeseed screenings (SCREEN) and from seed which had heated during storage (HEAT) were compared against commercial rapeseed meal (COM) for feeding value. Oil, crude protein (CP) and acid-detergent insoluble nitrogen contents in SCREEN, HEAT and COM, respectively, were (g/kg): 118, 246 and 13; 227, 315 and 436; and 17, 64 and 21. in situ dry matter (DM) and protein disappearance rates, soluble protein fraction and effective rumen degradability of protein (EDCP) were lower (P < 0·05) in HEAT than in SCREEN or COM. Comparing oil-extracted meals in situ, EDCP of HEAT was lower (P < 0·05) than EDCP of SCREEN or COM but protein and DM disappearance rates of HEAT were only lower (P < 0·05) than those of SCREEN. Four isonitrogenous barley-based diets (150 g/kg CP, DM basis), containing SCREEN, HEAT, COM or COM supplemented with rapeseed oil (OIL), were given to lambs. For DM, organic matter and neutral-detergent fibre apparent digestibilities, the diets ranked SCREEN > HEAT = OIL > COM (P < 0·05). Digestion and retention of nitrogen were lower (P < 0·05) in lambs given HEAT than in lambs given other diets. Food efficiency of lambs given HEAT was improved (P < 0·05) as compared with lambs given SCREEN or COM. Dressing proportions were higher (P < 0·05) with HEAT, SCREEN and OIL diets than with COM. Other than minor changes in fatty acid composition of subcutaneous fat with HEAT and OIL, carcass traits were not altered by treatment. Feeding SCREEN or HEAT did not adversely affect animal performance or food utilization.

The effects of energy source and level of digestible undegraded protein (DUP) in concentrates on silage intake and performance of lactating dairy cows, offered one of a range of grass silages differing in digestibility and intake characteristics, were evaluated in a partially balanced change-over design experiment involving 48 cows. Four silages were prepared using differing management practices prior to and during ensiling. All silages were treated with an inoculant additive. For silages A, В, С and D, dry matter (DM) concentrations were 199, 320, 313 and 223 (s.e. 4.6) g/kg, pH values 3.82, 4.03, 4·03 and 5·27 (s.e. 0.056), ammonia nitrogen (N) concentrations 58, 122, 66 and 356 (s.e. 13.2) g/kg total N and in vivo DM apparent digestibilities 077, 0.75 , 0.60 and 0.60 (s.e. 0·013) respectively. When offered as the sole diet to 12 dairy cows in a partially balanced change-over design experiment, silage DM intakes were 14.7, 14.7, 12.7 and 10.5 (s.e. 0·36) kg/day respectively for silages А, В, С and D. Six concentrates containing three starch concentrations, each at two levels of DUP, were formulated to have similar concentrations of crude protein, metabolizable energy (ME) and fermentable ME. For the low and high starch concentrates and low and high levels of DUP, starch concentrations were 22·5 and 273 g/kg DM and DUP levels were 44 and 60 g/kg DM respectively. Silages were offered ad libitum supplemented with 10 kg fresh concentrate per head per day. For silages А, В, С and D, DM intakes were 10.8, 11.2, 10·7 and 9·1 (s.e. 0·26) kg/day and milk yields 29.0, 27.6, 27.1 and 25.7 (s.e. 0.69) kg/day respectively. With the exception of milk protein concentration there were no significant (P > 0.05) silage type by concentrate energy source and/or level of DUP interactions on silage intake, milk output or composition. Concentrate energy source had no effect (P > 0.05) on silage DM intake, the yields of milk, fat, protein or fat plus protein or milk fat concentration. However, increasing starch concentration increased milk protein concentration (P < 0·001), urinary allantoin concentration (P < 0·01) and diet apparent digestibility (P < 0·001). Altering concentrate DUP level had no effect (P > 0·05) on silage DM intake, yields of milk, protein, fat or fat plus protein, milk f at concentrations or diet apparent digestibility. Increasing the level of DUP decreased milk protein (P < 0·05) concentration. It is concluded that with silages of varying digestibility, fermentation and intake characteristics, there were no concentrate energy source and/or level of DUP by silage type interactions on silage intake, milk yield or composition, or diet apparent digestibility with the exception of a silage type by concentrate level of DUP interaction on milk protein concentration. With out-of-parlour feeding of concentrates the results of the present study suggest that there is no evidence to justify the formulation of concentrates differing in energy source or level of DUP to complement individual silage types.

The study was conducted to investigate the adreno cortical capacity after injection of ACTH and the sensitivity of the pituitary and the adrenal to immobilization in neonatal pigs at different ages. Furthermore, the endocrine reactivity of the offspring was compared with the stress reactivity of their mothers. Four piglets were selected from each of six different litters and subjected to an immobilization test and an adrenal function test using synthetic ACTH1-24 at the ages of 7, 21 and 35 days; the six sows were also subjected to restraint and an ACTH stimulation test. Plasma β-endorphin, norepinephrine and epinephrine concentrations were measured in blood samples taken 2 min after restraint and cortisol concentrations were measured 60 min after ACTH administration. A highly sensitive adrenal response was demonstrated in both sows and piglets and adrenal reactivity showed also a considerable consistency over time within sows. In neonatal pigs, the cortisol response to ACTH was greatest on day 7 and decreased up to day 35. Plasma epinephrine and norepinephrine levels after the 2-min immobilization were also higher at day 7 compared with the other ages (P < 0·01). Piglets from sows, classified as high reacting according to their cortisol or epinephrine response, also showed significantly higher cortisol levels after ACTH challenge at all ages and significantly higher epinephrine levels after restraint at day 7 than piglets from low reacting sows. The results show an age-related change of pituitary-adrenocortical and sympatho-adrenomedullary responses in neonatal pigs and an absence of a stress hyporesponsive period at all ages studied. The results also indicate different levels of excitability in the offspring depending on the maternal stress reactivity.

An experiment was conducted to measure the response of goat kids to supplementary feeding of their dams with protected fat (calcium soap of fatty acids). At birth, 22 single male goat kids were distributed in two groups according to the dams’ diet supplemented with 0 (dam control diet, DCD) or 100 (dam protected fat, DPF) g/day of protected fat through lactation. Higher energy intake of dams given protected fat caused higher fat content of their milk (P < 0·01) and the fatty acid profile was affected with a reduction of lauric acid (P < 0.01) and myristic acid (P < 0.01) and an increase in palmitic acid (P < 0.01). Goat kids were suckled by their dams from birth until the end of the experiment and had access to a creep food from 7 days of age. Kids were slaughtered at 45 days of age. There was no significant response (P > 0Ό5) in terms of kid mean live-weight gain, being 172 g (DPF) compared with 148 g (DCD). Fatty acid composition of the perirenal fat showed some differences between groups. Fat composition of group DPF was significantly higher in palmitoleic, oleic and linoleic acid content. In addition, myristic, palmitic and stearic acid had lower values. Fat of goat kids of the DPF group was more unsaturated (43·3 g per 100 g) than fat from animals of the DCD group (32·5 g per 100 g). In the DPF group, oleic acid comprised most of the unsaturated fatty acid due to its important increase compared with fat composition of the DCD group. In conclusion, fatty acid composition of fat depot in goat kids can he modified by feeding of the dams through lactation, which could be useful for possible changes according to market demand.

In order to investigate the rationale of manipulating post-ovulation progesterone (P4) concentrations, luteal activity was measured in 10 Holstein-Friesian cows treated with a progesterone-releasing device (CIDR, 1·9 g P4) inserted on the morning of day 2 post-oestrus for a period of 7 days and compared with 10 untreated control animals. Milk samples were collected daily during afternoon milking from 7 days pre- to 24 days post-oestrus and P4 concentrations were measured using enzyme-linked immuno-sorbent assay (ELISA). The milk P4 profiles were used to assess the effects of early post-oestrus P4 elevation on five intervals of the luteal phase. In the treated (T) and control (C) animals, the mean interval from oestrus to P4 rise (≥3 μg/l), was 2·38 (s.e. 0·18) and 4·90 (s.e. 0·28) days, respectively, (P < 0·01). The mean interval from oestrus to the attainment of peak P4 concentrations was not significantly different (P > 0·05) between the T (14·75 (s.e. 1-62) days) and С (14·30 (s.e. 0·70) days) animals, with cows in the T group showing a more variable (F7 9 = 4-30, P < 0·05) interval to the occurrence of the peak. The interval from peak P4 to corpus luteum (CL) regression (when P4 fell below ≥3 μg/l) was not significantly different between the T (4·13 (s.e. 1·30 days) and С (5·60 (s.e. 0·88) days) groups. Furthermore, CIDR insertion did not alter luteal phase length, number of days with P4 concentrations ≥3 μg/l (T = 16·50 (s.e. 0·80) v.C = 15·00 (s.e. 0·47) days) or the interval from oestrus to CL regression (T = 18·88 (s.e. 0·79) v.C = 19·90 (s.e. 0·41) days). We conclude that treatment with CIDR 2 days after oestrus successfully increased the availability of P4 to cows without significantly affecting luteal phase characteristics.

The Maasai of Kenya are typical of many pastoral communities in that they rely on milk as a major part of their diet. Milk production in three herds of Maasai cattle was studied from 1991 to 1996. Weekly measurements of milk extracted for human consumption were used to estimate lactation length, total offtake and mean daily production. Calf live-weight data were used to estimate total milk yield. Least-mean squares regression and analysis of variance tests were adopted to assess the effect of a number of variables on milk production parameters.

Data from a total of 650 lactations and 383 calvings were collected. Mean daily offtake was 891 ml. The length of lactation of frequently milked cows was 372 (s.e. 7·96) days. Total lactation offtake was estimated at 305 I. Herd, parity level and year of calving differences were observed. Multiple regression analyses indicated that some of the variation in daily offtake could be explained by stage of lactation, season of milking, herd, parity and year of calving. An average total yield of 2·73 I/day was estimated for the first 90 days of lactation. Of this, approximately 0·4 was used for human consumption. Overall, seasonality was seen as the major variable influencing production.

The study was carried out on a continuously stocked grass/white clover pasture, which was maintained at two sward heights: 3·5 cm (low; LSH) and 6·5 cm (high; HSH). Three oesophageal-cannulated and three other rumen-cannulated Merino sheep were allocated to each of the plots (LSH and HSH) in order to study the effects of sward height and advancing grazing season on rumen fermentation in grazing sheep. Three grazing periods (13 days) were considered: mid June, late July and early October. During each grazing period and after a preliminary period (7 days), samples of the grazed herbage and of grass hay were incubated in nylon bags in the rumen of each sheep for 0, 3, 6, 12, 24, 48, 72 and 96 h. On days 10 and 12 rumen fluid was sampled at the incubation time (11.00 h) and at 3, 6 and 12 h afterwards and pH, ammonia-nitrogen and volatile fatty acids (VFA) concentrations were determined. Sward height did not affect (P > 0·05) the degradation rate of dry matter (DM) and neutral-detergent fibre (NDF) from grazed herbage in any of the considered periods. Animals grazing LSH presented higher (P < 0·05) DM and NDF effective degradabilities (DMED and NDFED, respectively) during October but no differences were found during June and July. HSH grazing animals presented lower (P < 0·05) degradation rates of DM and NDF from grass hay during June and July than those found for LSH grazing sheep, with no differences (P > 0·05) observed during October. Sward height did not affect (P > 0·05) grass hay DMED and NDFED during July but during June and October HSH grazing sheep presented higher (P < 0·05) values. In general, DMED and NDFED from grazed herbage increased with advancing season, the lowest (P < 0·05) value being observed during June. Rumen ammonia-nitrogen concentrations were higher during October than during June and July for both sward heights but values were higher than 200 mg/l at any sampling time during all grazing seasons. Rumen pH values were within the range considered adequate for maintaining a normal cellulolytic activity at most of the sampling times, with the exception of sheep grazing LSH during October. Rumen VFA concentrations were within the range reported for other grazing studies and only a few differences between sward heights were found. Differences in rumen parameters are discussed in relation to both chemical composition of grazed herbage and pattern of intake.

Four dietary treatments were based on a flat-rate (5 kg/day) of concentrates with ad libitum grass silage. The concentrates were iso-energetic and iso-nitrogenous, based on either barley or unmolassed sugar-beet pulp and either extracted rapeseed meal (RSM) or a 1: 3 mixture of fish and soya-bean meals (F/S). These diets were offered to 61 multiparous Holstein-Friesian cows in a continuous design experiment from lactation weeks 4 to 22. Milk yields tended to he higher with RSM (25·1 v. 23·9 kg/day; s.e.d. = 0·64; P < 0·1), whilst milk fat (38·1 v. 40·0 g/kg; s.e.d. = 0·81) and milk protein (30·4 v. 31·3 g/kg; s.e.d. = 0·41) concentrations were significantly (P < 0·05) lower. There were no significant effects of treatments on the efficiency of conversion of food-nitrogen (N) to milk-N or on N-retention. A lower organic matter apparent digestibility (g/g) was found for RSM-based diets (0·738 v. 0·763; s.e.d. = 0·0096; P < 0·05). The diets were also offered to four fistulated dairy cows in a Latin-square-design experiment. Concentrate energy source had significant effects on rumen pH (P < 0·05) and ammonia-N concentration (P < 0·01), whilst protein sources had no effect; values were always in the optimal range (pH > 6 and ammonia-N > 50 mg/l). There was a significant interaction effect (P < 0·05) such that the N-degradability of the whole diet, estimated in vivo, was unaffected by energy source for RSM-based diets but highly dependent on energy source for FIS diets. Microbial protein yield was reduced on the RSM-based diets (179 v. 220 g/day; s.e.d. = 9·6; P < 0·001).

A 28-day experiment with 12 9-month-old cattle (275 kg initial weight, M1), used a 2 × 2 arrangement of treatments to compare the effect of doubling the ad-libitum quantity of long barley straw offered daily (25 or 50 g dry matter (DM) per kg M1) and sex/genotype (Limousin × Friesian steers or Friesian heifers) on intake and selection. All animals received a protein concentrate at 20 g DM per kg M10·75 per day. Prior to the experiment the cattle had grazed for 6 months and were given no pre-experimental change-over period. On day 1 animals were weighed (M1), allocated to treatment and penned individually. Animals were weighed on day 28 (M2). Doubling the amount offered did not affect straw intake (g DM per kg M3 per day; M3 = mean of M1 and M2) during days 22 to 28 (steers: 17·9, 17·2; heifers 14·3, 13·3; s.e. 0·50) but increased the proportion (g DM per kg DM offered) refused (steers: 258, 635; heifers: 412, 721; s.e. 22). During days 22 to 28, at each level of offer (25, 50), refused straw contained (g DM per kg DM) less leaf-plus-sheath than offered straw (25 g steers: 251, 430, s.e. 16·7; 50 g steers: 393, 450, s.e. 19·7; 25 g heifers: 304, 420, s.e. 7·2; 50 g heifers: 405, 446, s.e. 9·6). The sex/genotype effect on intake was attributed to differences in growth potential. Straw intakes increased significantly over the first 14 days, but there were no differences between days 15 to 21 and days 22 to 28. It is concluded that an excess-feeding strategy, involving a doubling of the ad libitum amount of barley straw offered did not result in growing cattle consuming more straw, in contrast to published results with sheep and goats. However, the cattle did show a limited ability to selectively consume leaf-plus-sheath in preference to stem but the improvement in diet digestible organic content (estimated in vitro) was presumably insufficient to stimulate intake.

In an investigation of factors responsible for the lower efficiency of carcass lean gain seen previously in steers offered grass silage diets 18 Simmental × British Friesian steers (361 (s.e. 5-35) kg) were offered one of three diets: a perennial ryegrass silage ad libitum and alone (S) or supplemented with rolled barley at 300 g/kg of total dry matter (SC) or supplemented as described but restricted (SCr) in quantity so as to provide the same dry matter (DM) and digestible energy (DE) intakes as for S. Eating (Eb), ruminating (Rb), standing (Sb) or lying (Lb) behaviour was quantified during four 24-h periods of manual observation. Eb was noted in more detail in a second experiment using computerized Calan-Broadbent gates and load cells to monitor times and rates of eating. Blood was taken via temporary indwelling jugular catheters at 30 to 60 min intervals on each of 4 days 1 month apart. Rumen fluid was sampled hourly for three 24-h periods from three rumen-cannulated steers given the same three diets in a separate 3 x 3 change-over design experiment.

Steers offered the restricted diet SCr ate most of their food in one extended meal within 6 h of feeding while two peak eating periods (morning and evening) were observed in steers offered the other two diets. Steers offered SCr spent more time in Sb (P < 0.05), and less time in Eb (P < 0·001) and Rb (P < 0·05) activities than did animals offered the two diets ad libitum (SC and S). Mean 24 h insulin-like growth factor-1 (IGF-1) concentrations and postprandial insulin concentrations were significantly higher with diet SCr than with diet S (P < 0·001) despite equal daily DM and DE intakes from each. Insulin appearance in the jugular vein reflected the pattern of food intake on all treatments. Rumen fermentation characteristics were largely unaffected by diet. Mean 24 h rumen volatile fatty acid, pH and ammonia concentrations did not differ between diets but post-prandial rumen pH tended to be lower in animals offered the SC and SCr diets.

Differences in patterns of food intake between animals offered food ad libitum and at a restricted level are likely to determine patterns of nutrient absorption and the secretion of nutritionally regulated splanchnic hormones. The higher proportions of Sb and Rb activities in steers offered the restricted diet represent an energy cost to these animals while the higher plasma IGF-1 and insulin concentrations also seen in these animals may collectively influence the partitioning of nutrients to the peripheral tissues and contribute to the increased efficiency of carcass lean deposition previously shown in animals offered such diets.

Development of all follicles with antral diameter ≥2 mm during the oestrous cycle was characterized in goats of the Murciana-Granadina dairy breed by daily transrectal ultrasonography. Of nine does initially synchronized in oestrus, six returned to oestrus and three did not. In the first six does, mean cycle length was 21·2 (s.e. 2-3) days. There were mean total numbers of 6·2 (s.e. 0·6) small (2 to 3 mm), 1·9 (s.e. 0·3) medium (4 to 5 mm), and 1·0 (s.e. 0·2) large follicles (≥6 mm) each day but only numbers of large follicles differed with day of cycle (P < 0·01). The diameters of the largest follicle (LF1), the second largest (LF2) and the remaining follicles (RF) varied with day of cycle (P < 0·01). The LF1 and LF2 varied with day in similar patterns but the difference in diameter between them (P < 0·05) was greatest on days 7 and 9 (2·3 mm) and days 19 to 23 (2·2 to 3·8 mm), and least on days 2, 15, 16 and 18 (0·5 to 0·8 mm). The relationship between the LF1 and LF2 to the RF differed only early or late in the cycle when concentrations of progesterone were low (P < 0.05). There was some evidence to support follicular growth in waves. Although the number of apparently new follicles detected (4·8 (s.e. 0·4) per day) did not vary with day of cycle, follicles emerging at 3 mm over a 48-h period that grew to a diameter of ≥6 mm were distributed non-randomly in three of six cyclic does. The three cystic does that did not return to oestrus by day 25 had large follicles (16 to 28 mm), fewer new follicles (3·3 (s.e. 1-1) per day; P < 0·01) than cyclic does (4·8 (s.e. 0·4) per day) and fewer follicles that became largest (4·0 v. 8·8 in cyclic does; P < 0·01).

The disappearance of neutral-detergent fibre (NDF) from six fibrous foods (lucerne hay, NaOH-treated barley straw, olive leaves, paprika meal, soya-bean hulls and sunflower hulls) when incubated in the rumen of sheep in nylon bags was investigated. Source of fibre, time of incubation and its interaction had a significant (P < 0·01) effect on NDF degradation. Stepwise regression analysis showed that the best single predictor for NDF degradation rate was the hemicellulose fraction of NDF (HEMndf). The variables selected to predict potential degradability and degradability of NDF at 72 h were the proportions of acid-detergent lignin in NDF (ADLndf, first step) and of acid-detergent cutin in ADL (ADCadl, second step). For NDF degradability at 12 h, the variables selected were the proportions of HEMndf, ADLndf and ADCadl, in the first, second and third step, respectively. The results showed that ADC is an important component to understand NDF degradability at both 12 and 72 h.

Comparative studies were performed on the in-situ rumen degradation rate (kd) and the in-situ rumen undegradable residue (U) of dry matter (DM) and crude protein (CP) in sheep and dairy cows. The effect of different treatmentsfor sheep were investigated together with the validity of using cow-based reference protein values of foods for sheep. The effect of different breeds (Texel ewes and crossbred ewes), dietary roughage: concentrate ratio and shearing (mild cold exposure) were investigated for sheep.

The in-situ rumen incubations were performed in accordance with standard operational procedures which were comparable for both species. The foods under consideration were hay and concentrates. Cows displayed lower (DM 0·53 , CP 0·86) Kds than sheep for concentrates.

For hay a clear trend between cows and sheep was not observed but cows displayed 0·40 lower Kds than Texel ewes and 0·30 higher Kds than crossbred ewes. For concentrates U levels did not differ between species but for hay cows had 0·45 higher U values than Texel ewes. Texel ewes showed 0·45 higher Kd and 0·35 lower U for DM and CP than crossbred ewes. Dietary roughage: concentrate ratio in sheep diets did not influence the Kds and Us of the foods under consideration. Shearing of crossbred ewes increased Kd of CP by 0·25 and reduced U for DM and CP by 0·20 and 0.24 .

In conclusion different in situ rumen degradation rates were found between dairy cows and sheep. This probably makes using reference protein values of foods invalid for sheep since they are based on data for cows. Differences (Kd andU) were also found between sheep breeds and between unshorn and shorn crossbred ewes (mild cold exposure). No effect on rumen degradation kinetics could be attributed to dietary roughage: concentrate ratio.

The effect of the physiological state and dietary protein level on urinary excretion of creatinine (C) and purine derivatives (PD) was studied in two experiments carried out with pregnant and lactating ewes to evaluate whether the PD/C ratio in urine can he confidently used as an index of PD excretion. In both experiments ewes were given ammonia-treated straw and concentrates including different levels of fish meal and the excretion in urine and milk and the plasma concentration of C, allantoin (AL), xanthine, hypoxanthine and uric acid was measured.

Creatinine excretion (in urine and milk) was higher in pregnant ewes than in those lactating (492 and 420 (s.e. 10.0) μmol/kg maternal live weight0.75) and no significant differences were found due to number of foetuses and dietary protein level. The coefficient of variation was 0·10 in both pregnancy and lactation and individual variation accounted for proportionately 0·78 and 0·93 of total variation. The AL/C ratio in urine was highly correlated with daily AL excretion (r = 0·90 and 0·78 in pregnant and lactating ewes, respectively). Changes in PD excretion with experimental treatments were mainly reflected in AL, as the main component (0-83) of total PD. Most of the variation in AL excretion was explained by differences in rumen fermentable organic matter intake (RFOMI) (R2 = 0·79) and AL excretion did not differ between treatments when expressed per kg of RFOMI. In contrast to this the ratio AL/digestible organic matter intake decreased with increasing levels of fish meal in the diet. Urinary PD excretion was better related to estimated PD kidney tubular load (r = 0·76) than to PD plasma concentration (r = 0·64).

The results suggest that creatinine excretion is scarcely affected by the number of foetuses in pregnancy and dietary protein level but if the AL/С in urine is used instead of total collection as an index of purines absorbed in the duodenum, differences in urinary creatinine excretion due to physiological state must be accounted for.

Polyethylene glycol-4000 (PEG) was used to inactivate tannins in Acacia cyanophylla Lindl foliage. In the first of two experiments, four groups of five Barbarine sheep were held in metabolism crates so that intakes, apparent digestibilities, nitrogen balances and urinary excretion of allantoin could be measured. The second experiment involved four groups of three male Queue Fine de l'Ouest sheep fitted with rumen cannulae and housed in individual pens to measure rumen fermentation parameters and dry matter in situ degradation of A. cyanophylla foliage. All animals received fresh A. cyanophylla foliage ad libitum and 330 g concentrate on a daily basis. In each experiment, three groups of sheep received 20 g PEG daily, either mixed with concentrate (PEG-concentrate), dissolved in drinking water (PEG-water) or sprayed as a solution on A. cyanophylla foliage at the point of feeding (PEG-treatment). The fourth group was not supplied with PEG (control). Dry-matter intake of A. cyanophylla was low (28·3 g/kg metabolic live weight (M0·75) per day) and increased in sheep given the PEG-concentrate diet (38·2 g/kg M0·75 per day). PEG-concentrate and PEG-water diets resulted in an improvement in protein utilization as indicated by an increase of crude protein apparent digestibility (2·1 and 1·9 fold, respectively), nitrogen retention (3·2 fold with both dietary treatments) and urinary excretion of allantoin (1·9 and 1·5 fold, respectively). Improvements obtained with PEG-treatment diet were low and in general not significant (P > 0·05). Low neutral-detergent fibre and acid-detergent fibre apparent digestibility coefficients of diets led to the conclusion that conventional detergent extraction techniques are questionable in determining the in vivo digestibility of cell wall constituents for tannin-rich forages. Results from rumen fluid analyses indicated that sheep given PEG-containing diets had higher ammonia-nitrogen and volatile fatty acid (VFA) concentrations (P < 0·05). These results, coupled with the increase of allantoin excretion gave clear evidence that the efficiency of microbial synthesis was improved with PEG addition. The absence of change in ruminal pH and molar proportions of individual VF A suggested similar fermentation patterns among all dietary treatments. PEG supply increased the slowly degradable fraction of A. cyanophylla foliage incubated in the rumen (P < 0·05), thus dry matter potential degradability (a + b) was highest in sheep given PEG-containing diets. It is concluded that the affinity of acacia tannins to PEG, increased the availability of degradable proteins, which resulted in an improvement of the nutritive value of acacia foliage. However, for practical situations, adding PEG to concentrate or to drinking water is recommended for sheep browsing A. cyanophylla trees in the field or fed indoors.