Genetic associations were estimated between pathogen-specific cases of clinical mastitis (CM), lactational average somatic cell score (LACSCS), and patterns of peaks in somatic cell count (SCC) which were based on deviations from the typical lactation curve for SCC. The dataset contained test-day records on SCC in 94 781 lactations of 25 416 cows of different parities. Out of these 94 781 lactations, 41 828 lactations had recordings on occurrence of pathogen-specific CM and on SCC, and 52 953 lactations had recordings on SCC only. A total of 5 324 lactations with cases of CM were recorded. Analysed pathogens were Staphylococcus aureus, coagulase negative staphylococci, Escherichia coli, Streptococcus dysgalactiae, Streptococcus uberis, and culture-negative samples. Pattern definitions were based on three or five consecutive test-day recordings of SCC. They differentiated between short or longer periods of increased SCC, and also between lactations with and without recovery. Occurrence of pathogen-specific CM and presence of patterns of peaks in SCC were both scored as binary traits. Variance components for sire, maternal grandsire, and permanent animal effects were estimated using AS-REML. The estimated heritability for overall CM was 0·04, and similar heritabilities for pathogen-specific CM were estimated. Heritabilities for the patterns of peaks in SCC ranged from 0·01 to 0·06. Heritabilities for LACSCS were 0·07 to 0·08. Genetic correlations with patterns of peaks in SCC differed for each pathogen. Generally, genetic correlations between pathogen-specific CM and patterns of peaks in SCC were stronger than the correlations with LACSCS. This suggests that genetic selection purely on diminishing presence of peaks in SCC would decrease the incidence of pathogen-specific CM more effectively than selecting purely on lower LACSCS.

Twelve 6-month-old growing female goats and sheep were used in this study. Blood samples were obtained in the morning before goats and sheep were given food and then at 2-h intervals for 24 h (part I). This procedure was repeated 2 weeks later (part II). Concentrations of osteocalcin (OC), activities of total (tAP) and bone-specific alkaline phosphatase (bAP), degradation products of C-terminal telopeptide of type-I collagen (CrossLaps™ CL), and carboxyterminal telopeptide of type-I collagen (ICTP) were measured in serum.

In both parts of the study, all bone marker concentrations were significantly higher in goats than in sheep. The OC concentrations in goats increased in the late afternoon/evening and decreased thereafter to reach values similar to those obtained at the beginning. The ICTP concentrations in goats slowly decreased until 14:00 h, increased, and decreased again. The concentrations in sheep decreased continuously but not significantly, towards the morning sampling. The CL concentrations increased in both sheep and goats during the night but at 06:00 h started to decrease to levels found at the beginning of testing. The bAP activities decreased in goats from 20:00 to 22:00 h. Changes in the concentrations of bone markers were mainly observed in goats of this study. As documented for bone resorption and formation in other species, circadian rhythms were evident for concentrations of ICTP, CL, bAP and OC. The present study indicates that growing goats may have a physiologically higher bone turn-over than growing sheep, because the bone marker concentrations were always higher.

The effects of different sequences of food restriction and fattening have been studied on plasma metabolites and hormones in double-muscled Belgian Blue bulls. Twenty animals were divided into five groups. The first group (control, CG) was given, ad libitum, a fattening diet based on sugar-beet pulp. In G2 and G3, fattening was interrupted after 103 and 187 days, respectively, by a period of food restriction lasting about 2 months during which the animals received a maintenance ration. They were finished with the same diet as CG. The last two groups, G4 and G5, received a limited amount of the restriction diet to support 0·5 and 0 kg gain per day, respectively, for 4 months, before being fattened as CG. Plasma glucose, alpha-amino nitrogen, non-esterified fatty acids, urea, creatinine, thyroxine (T4), 3, 3’, 5’-tri-iodothyroxine (T3), and insulin-like growth factor-1 (IGF-1) were measured in blood samples taken every 2 weeks. Plasma GH and insulin profiles were measured in serial blood samples obtained at three different times during growth. Animals that showed compensatory growth had lower plasma urea, associated with high levels of T3, T4 and IGF–1. Animals from G2 and G3 failed to show compensatory growth. In Belgian Blue bulls, compensatory growth is markedly affected when food restriction is severe or fattening interrupted.

We aimed to determine whether the dietary carbohydrate source altered body fat composition and distribution in finishing lean (Landrace) and obese (Iberian) swine. To this end, twenty-four finishing castrated male pigs (12 Iberian and 12 Landrace; 108 kg live weight) were offered two diets differing in the main carbohydrates source, maize (diet M) or acorn-sorghum-maize (diet A). Diets were formulated to have the same nutrient content, except for carbohydrate fractions: diet M contained higher amount of starch (537 v. 389 g/kg) but less non-starch polysaccharides (118 v. 148 g/ kg) than diet A. At an average weight of 133 kg live weight pigs were slaughtered and their carcasses were sampled to study lipogenesis, backfat and intramuscular fat composition. Iberian pigs showed a higher voluntary food intake than Landrace pigs (3·6 v. 2·4 kg/day; P < 0·001) but no significant differences in the daily weight gain. Diet M tended to promote the highest food intake (P = 0·09). Iberian pigs showed higher (P < 0·01) lipogenic enzyme activities, backfat thickness (71·7 v. 31·9 mm) and intramuscular fat content (40 to 95 g/kg fresh muscle) than Landrace pigs, which was associated with their higher food intake. Furthermore, fat depots from Iberian pigs had higher (P < 0·001) monounsaturated fatty acids (MUFA) and lower (P < 0·05) polyunsaturated (PUFA) proportions than those from Landrace pigs. The backfat thickness of pigs given diet M tended to be higher (P = 0·07) than that of pigs given diet A, without differences in the intramuscular fat content. The higher backfat thickness found for diet M was correlated with a lower PUFA proportion in diet than for diet A (P < 0·001). We conclude that body fat content, composition and lipogenic enzyme activities are markedly influenced by the animal breed and to a lesser extent by dietary characteristics.

Carotenoid pigments are good biomarkers of grass-feeding in sheep. However, as grazing lambs may be concentrate-finished, we investigated the effect of concentrate finishing after grazing on the carotenoid concentration of fat in sheep, and its significance for discriminating lamb production systems. In experiment 1 with 32 lambs, four feeding treatments were compared: G = grazing, C = feeding a concentrate-based diet, GSC = short concentrate-finishing period after grazing, and GLC = long concentrate-finishing period after grazing. The concentrate supply was regulated to have similar average daily gain for all treatments. In experiment 2, 42 ewes were given a low carotenoid diet after pasture feeding, for 0, 8, 22, 42, 84 or 126 days. The feeding level was adjusted to maintain body weight and body condition score. The nature and concentration of carotenoids was analysed by HPLC on diets and lambs’ perirenal fat. The reflectance spectrum of perirenal fat was measured at slaughter. Lutein was the only carotenoid in lamb fat. In experiment 1, the intensity of light absorption by lutein was linearly related with its concentration in the fat (P < 0·001) and was negatively correlated with the duration of the finishing period. The design of experiment 2 avoided the confounding effect of fat gain during the finishing period and examined the effect of the duration of this period by itself. There was no effect of stall-feeding duration on the intensity of light absorption by carotenoids in the fat in experiment 2, demonstrating that the effect of stall-feeding duration in fattening lambs was mediated via a dilution of existing fat with whiter fat rather than through pigments coming out of the fat. The concentration of lutein and the intensity of its light absorption in the fat decreased with lamb body-weight gain during the finishing period (P < 0·01 and P < 0·05 respectively) and increased with plasma carotenoid content at the end of the grazing period (P < 0·001). Because of the inter-individual variability in carotenoid absorption, the use of the reflectance spectrum of the fat alone may cause some concentrate finished grazing lambs to be classified as C lambs shortly after the beginning of the stall-feeding period, whereas others may be considered as G lambs for a long period of time. However, the combined use of plasma carotenoid content at slaughter together with the reflectance spectrum of the fat improves reliability in the discrimination of grass-fed, concentrate-fed and concentrate-finished grazing lambs, by taking advantage of the differences in the rate of reduction in carotenoid concentration in blood and fat.

A total of 74 pigs representing three commercially available crossbred types, Landrace (50%), Pietrain (50%) and Meishan (25%), were given food ad libitum over a 25- to 115-kg growth period and serially slaughtered for physical and chemical analysis in five groups at 32, 42, 63, 82 and 114 kg live weight (W). Results are presented in the order of pig type as above. Pig types grew at similar overall rates of live body gain, but the Meishan type ate more food and had greater back fat depth. The Pietrain type was least fat. Dissected fatty tissue grew substantially faster than the carcass as a whole; allometric exponents being 1·64, 1·34 and 1·52 (P < 0·05) for the Landrace, Pietrain and Meishan types respectively. Dissected lean tissue gains were 0·419, 0·427 and 0·308 kg daily (P < 0·01), and dissected fatty tissue gains were 0·251, 0·158 and 0·218 kg daily (P < 0·05); the Meishan type being slowest for lean gain and the Pietrain type slowest for fatty tissue gain. The Pietrain type had the largest cross-sectional area of the longissimus dorsi muscle, and the Meishan type the smallest. The pelvic limb of the Meishan type lost density (as measured by specific gravity) fastest, and that of the Pietrain slowest as the pigs grew. The Meishan type had a lower proportion of its carcass lean and a higher proportion of its carcass fat in the pelvic limb than did the other two types. For each kg of live-weight gain, 0·037, 0·041 and 0·032 kg (P < 0·05) of chemical protein was deposited in the pelvic limb of the three types respectively. Equivalent values for chemical lipid were 0·041, 0·035 and 0·041 (P < 0·05). The Meishan type retained protein at a relatively slower rate in the pelvic limb than in the body as a whole. The Pietrain type had the greatest ultimate protein mass in the pelvic limb. Estimation of whole body protein content as a linear function of pig live weight gives coefficients of 0·154, 0·178 and 0·168 kg (P < 0·05) for the three types respectively. Equivalent values for whole body lipid content were 0·269, 0·214 and 0·274 (P < 0·05). Best estimates of the daily rates of protein retention in the body of the whole live pig were 0·152, 0·197 and 0·142 kg/day for the Landrace, Pietrain and Meishan types respectively.

The objective of this study was to evaluate the ability of the plant extracts Yucca shidigera, Quillaja saponaria and a combination (a blend of capsicum, carvacrol and cinnamaldehyde) to stimulate piglet and sow performance when used as supplements in the diets of lactating sows. These extracts were selected for their potential benefits to health, appetite and digestion. Eighty hybrid sows were housed in conventional indoor farrowing crates from day 107 of gestation until weaning. Sows were allocated according to parity, live weight, fatness and past reproductive performance, to one of four dietary treatments: control (C), combination (COM, 100 g/t food), yucca (Y, 200 g/t), quillaja (Q, 250 g/t). Between days 107 to 114 of gestation, sows received 2·5 kg food per day of their respective diet. During lactation food was offered ad libitum with sow food intake (FI) recorded daily. Faecal samples were obtained from sows daily in order to measure diet digestibility using titanium dioxide as an external marker. Piglet live weight and sow P2 backfat were recorded on days 1, 7, 14 and 21 and at weaning on day 23 (s.e.2·5). Piglet live weight and rectal temperature were measured at birth and 24 h of age. Piglet growth between birth and 24 h was significantly affected by sow treatment. Litters from COM sows held the greatest advantage (117 v. C 99, Q 77, Y 107 g per pig per day, P < 0·01, s.e. = 7·9). Piglet body temperature at birth was also higher in COM litters when compared with treatment C (38·58 v. 37·95oC, P < 0·05)). Q and Y piglets were intermediate between the two. Sow treatment had no effect on piglet performance between day 1 and 14 of lactation. However, between days 15 and 21, piglets from COM sows again significantly outperformed all other treatments (COM 290, C 246, Q 235, Y 255 g per pig per day, P < 0·001, s.e. = 9·3). Piglet weights on day 21 were also significantly greater for the COM sows (6878 g v. C 6584 g, Q 6330 g, Y 6498 g, P < 0·05 s.e. = 132). No benefit was seen from supplementation with either yucca or quillaja extracts on piglet growth. Sow FI and P2 backfat loss between parturition and weaning were unaffected by treatment. However, diet digestibility was enhanced by all supplements during week 1 of lactation in terms of dry matter, organic matter and crude protein. It is concluded that some plant extracts may enhance piglet and sow performance prior to weaning.

A deterministic, dynamic pig growth model is described that predicts the effects of genotype and the thermal and nutritional environments on food intake, growth and body composition of growing pigs. From the daily potential for protein gain, as determined by pig genotype and current state, the potential gains of the other chemical components, including ‘desired’ lipid gain, are calculated. Unconstrained voluntary food intake is predicted from the current protein and lipid contents of the pig, and the composition of the food, as that which is needed to permit potential growth to be achieved. The model allows compensatory lipid gain. The composition of the food is described in terms of its digestible energy content (DEC), ideal digestible crude protein content (IDCPC) and bulkiness. Both energy and protein can be limiting resources and the bulk of the food may constrain intake. The animal’s capacity for bulk is a function of its size. The thermal environment is described by the ambient temperature, wind speed, floor type and humidity and sets the maximum (HLmax) and minimum (HLmin) values possible for heat loss. A comparison with heat production (HP) determines whether the environment is hot (HP > HLmax), cold (HP < HLmin) or thermoneutral (HLmin < HP < HLmax). A constraint on intake operates in hot environments, while in cold environments, there is an extra thermal demand. If conditions are thermoneutral no further action is taken. Daily gains of each of the chemical components are calculated by partitioning energy intake between protein and lipid gains according only to the energy to protein ratio of the food. The model builds on the work of others in the literature as it allows predictions on how changes in: (i) the kind of pig; (ii) the animal’s current state, which is particularly relevant in cases of compensatory growth; (iii) the dietary composition, and; (iv) the climatic environment, affect food intake and growth, whilst maintaining simplicity and flexibility.

A deterministic, dynamic pig growth model predicting the effect of genotype, and the thermal and nutritional environments on food intake, growth and body composition of growing pigs was tested and evaluated against experimental data from the literature. Four sets of experiments meeting the necessary requirement of feeding the pigs ad libitum and reporting sufficient information on trial conditions were chosen to test the model. The parameters used in the model to describe the kind of pig were protein weight at maturity (Pm) the Gompertz rate parameter (B) and the ratio of mature lipid weight (Lm) to Pm. Values for Pm and B used to apply to the pigs in the four experiments were selected as those which gave the maximum daily gains equal to those reported at thermoneutral temperatures on diets not limiting in protein. The value of Lm was chosen as that which gave a value for food conversion ratio close to that seen in the experiment, again at a thermoneutral temperature and on a non-limiting diet. The model was run for each of the experiments from the given start weight until slaughter weight was reached. All pigs were assumed to have their desired bodily composition at the start of the experimental period, which is determined by their genetic descriptors and weight. From the conditions of the experiments, average daily gain (ADG) average daily food intake (ADFI) food conversion ratio (FCR) final body weight, body composition, average daily gains of each of the chemical body components and heat production (HP) were predicted. Generally as temperature increased or the crude protein content of the food increased, ADFI, ADG and the fatness of the pig decreased, whilst protein content increased. Quantitative differences between the model predictions and the observations, were probably due to the greater sensitivity of the model to temperature. This is likely to reflect the omission of long-term adaptation and acclimatization, or to incorrect estimation of the wetness of the pig’s skin. However, model predictions were generally in good quantitative agreement with the observed data over the wide range of treatments tested. This gives support to the value and accuracy of the model for predicting pig performance when the thermal and nutritional environments are manipulated.

The intake of immunoglobulin G (IgG) by sucking piglets from colostrum was estimated over the first 24 h of sucking by the weigh-suck-weigh technique using experimentally determined correction factors for metabolic and urinary losses and was related to appearance of IgG in piglet plasma. Colostrum immunoglobulin G (IgG) concentrations declined rapidly from 61 mg/ml at the start of sucking to 9·0 mg/ml after 24 h sucking. IgG was first detected in piglet plasma after 4 h sucking, increased to a maximum after 12 to 16 h sucking and thereafter declined. In piglets allowed to suck from birth, there was no significant relationship between estimated IgG intake and plasma IgG concentration suggesting that IgG intake did not limit acquisition of IgG by the piglet. When sucking was delayed by 8 or 12 h, colostrum intakes by piglets were not different from piglets allowed immediate access to the udder but IgG intakes were significantly (P < 0·001) decreased. Total plasma IgG (g/kg live weight) did not decline significantly as a result of delayed sucking. In conclusion, under the experimental conditions employed, the appearance of IgG in piglet plasma was limited by factors other than by colostrum IgG intake.

An 8-week feeding trial was conducted to determine the dietary copper (Cu) requirement of juvenile hybrid tilapia, Oreochromis niloticus 5 O. aureus. Purified diets with eight levels (0, 1, 2, 3, 4, 8, 12 or 20 mg Cu per kg diet) of supplemental Cu were given to tilapia (mean initial weight 0·79±0·03 g). Each diet was given to three replicate groups of fish. The rearing water contained 0·98 µg Cu per l. Weight gain was highest in fish given diets supplemented with 2 mg Cu per kg diet, followed by the group given 1 mg Cu per kg diet, then the unsupplemented control group, and was lowest in the 20 mg Cu per kg diet group. The differences between each of these four groups were significant (P < 0·05). Food efficiency (FE) of fish showed a similar trend to that of weight gain. Blood haemoglobin (Hb) and haematocrit (Hct) concentrations were lowest in fish given ≥ 12 mg Cu per kg diet, followed by fish given the unsupplemented control diet and highest in fish given 2 mg Cu per kg diet (Hb) and 2 and 3 mg Cu per kg diet (Hct). Plasma ceruloplasmin activity was higher in fish given 1 and 2 mg Cu per kg diet, followed by 3 to 12 mg Cu per kg diet and the control group, and lowest in fish given 20 mg Cu per kg diet. The body Cu content in fish generally increased as the dietary Cu supplementation level increased. Analysis by broken-line regression of weight gain percent and by linear regression of the whole-body Cu retention of fish indicated that the adequate dietary Cu concentration in growing tilapia is about 4 mg Cu per kg diet.

A first group of three horses was given diet 1 (D1) allowing 1180 g per 100 kg body weight (BW) of a pelleted food rich in fibre (P1) and 556 g per 100 kg BW of straw during a 20-day period to allow for adaptation. A second group of four horses were given diet 2 (D2) allowing 1180 g per 100 kg BW of a pelleted food rich in cereals (P2) and 1000 g per 100 kg BW of meadow hay during the same period. Digesta was collected from the stomach, duodenum, jejunum, ileum, caecum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, and small colon, and faeces were collected under general anaesthesia 2·5 h after the ingestion of the morning pelleted meal. The concentration of total anaerobic, cellulolytic and lactic acid-utilizing bacteria, lactobacilli and streptococci were determined in all these segments except for the duodenum, left ventral colon, right dorsal colon and small colon. D-/L-lactic acid, volatile fatty acids and pH were measured in all anatomic segments of the digestive tract (from stomach to small colon). The caecal concentration of total anaerobic bacteria was the lowest (7·9 5 107 colony-forming units (c f. u.) per ml), whereas that of the stomach was the highest (1·4 5 109 c f. u. per ml) (P < 0·001). Cellulolytic bacteria did not exceed 3·0 5 102 c f u. per ml in the ante-caecal segments whereas in the hindgut the average concentration was 5·3 x 105 c f u. per ml (P < 0·001). Likewise, VFA concentrations were also greater in the large intestine (on average, 96·3 mmol/l v. 8·8 mmol/l in the ante-caecal segments) (P < 0·001), confirming the limited extent of fibre degradation in these ante-caecal segments. Lactobacilli, streptococci and lactate-utilizing bacteria colonized all the digestive tract; the stomach and the small intestine tended to host the greatest numbers of these bacteria, which suggests a high interference of micro-organisms with the digestion of readily fermentable carbohydrates. Compared with the other ante-caecal segments, the stomach ecosystem seemed the most affected by the composition of the last pelleted meal ingested: the concentrations of lactobacilli and lactate-utilizing bacteria were higher (P < 0·05) with P2. The lower concentration of D-/L-lactate with P2 (P < 0·05) was concomitant with a greater proportion of propionate (P < 0·05), probably related to a greater fermentation of lactate. In the large intestine of horses given D2, cellulolytic bacteria tended to be lower, whereas VFA concentrations were higher (P < 0·05). The lower [NDF/starch] ratio of D2 was probably less propitious for the proliferation of cellulolytic bacteria but was compensated by the higher cellulose intake brought by the hay.

Sixteen early to mid lactation Finnish Ayrshire dairy cows were used in a cyclic change-over experiment with four 21-day experimental periods and a 4 5 2 factorial arrangement of treatments to evaluate the effects of heat-treated rapeseed expeller and solvent-extracted soya-bean meal protein supplements on animal performance. Dietary treatments consisted of grass silage offered ad libitum supplemented with a fixed amount of a cereal based concentrate (10 kg/day on a fresh weight basis) containing 120, 150, 180 or 210 g crude protein (CP) per kg dry matter (DM). Concentrate CP content was manipulated by replacement of basal ingredients (g/kg) with either rapeseed expeller (R; 120, 240 and 360) or soya-bean meal (S; 80, 160 and 240). Increases in concentrate CP stimulated linear increases (P < 0·05) in silage intake (mean 22·5 and 23·8 g DM per g/kg increase in dietary CP content, for R and S, respectively) and milk production. Concentrate inclusion of rapeseed expeller elicited higher (P < 0·01) milk yield and milk protein output responses (mean 108 and 3·71 g/day per g/kg DM increase in dietary CP content) than soya-bean meal (corresponding values 62 and 2·57). Improvements in the apparent utilization of dietary nitrogen for milk protein synthesis (mean 0·282 and 0·274, for R and S, respectively) were associated with higher (P < 0·05) plasma concentrations of histidine, branched-chain, essential and total amino acids (35, 482, 902 and 2240 and 26, 410, 800 and 2119 µmol/l, respectively) and lower (P < 0·01) concentrations of urea (corresponding values 4·11 and 4·52 mmol/l). Heat-treated rapeseed expeller proved to be a more effective protein supplement than solvent-extracted soya-bean meal for cows offered grass silage-based diets.

This study assessed the efficacy of the n-alkane technique to estimate intake and diet composition in animals given single foods or a choice of two. In the first experiment intakes of pelleted ryegrass and lucerne, given either alone or as a choice, were measured in lambs housed indoors in individual pens. Each of the three feeding treatments was given to 12 lambs at two degrees of maturity (0·30 and 0·45 of estimated mature sizes). The 12 lambs were constituted as three replicates of the two sexes of each of two breeds. The measured intakes were compared with those estimated using the n-alkanes C31 and C33, found naturally in the foods, and C32, which was given as a dose. On the choice treatment diet composition was estimated using a non-negative least squares procedure and data on C31 and C33 alone. The agreement between actual and predicted intake was good: R2 of 0·938 for log-linear regression with a residual standard deviation of 0·0845. Intake of lucerne when offered alone was slightly yet significantly over-predicted. The proportion of ryegrass in the diet was also accurately predicted (R2 of 0·950 and residual s.d. of 0·0398). Using the data on C27 and C29, in addition to that on C31 and C33, gave a poorer agreement with the observed diet compositions. The low and similar levels of C27 in the two foods meant that this n-alkane provided little extra information that could be used to estimate diet composition. In a second experiment faecal samples were collected every 4 hours over a 24-h period in six lambs on ad libitum, and in six lambs on a restricted quantity, of pelleted ryegrass. There was no significant diurnal variation in the ratios of either C31 or C33 to C32 on either ad libitum or restricted feeding. The time of faecal collection within a day should not therefore affect the reliability of the predictions. The study confirmed the value of using n-alkanes in methods to determine the intake of forages by sheep, and that the time of faecal collection within the day does not affect the reliability of these predictions. The results also confirm the utility of the n-alkane method for estimating diet choice, at least with two-component mixtures.

Four groups of eight primiparous ewes and their single lambs were grazed for 2 weeks on pasture containing one of four novel grass species – perennial ryegrass, timothy, cocksfoot and red fescue. When subsequently grazed in a field with randomized plots of the four species, both ewes and lambs spent longer grazing the species to which they had been accustomed than was spent by ewes and lambs accustomed to other species. This effect was proportionately greater for the lambs than the ewes, and the lambs responded most to experience of cocksfoot and red fescue. Both ewes and lambs spent most time grazing perennial ryegrass and timothy, and least time grazing red fescue, with cocksfoot intermediate. It is concluded that perennial ryegrass and timothy are grazed by ewes and lambs in preference to cocksfoot and red fescue, but that a two week period of experience will increase the attractiveness of the less-preferred species, particularly to lambs.

Forty single lambs were either artificially reared indoors or were at pasture with their mothers until weaning at 3 months of age, after which one half of each group were joined by five adult, dry ewes, to examine the effects of grazing experience and presence of adult ewes on the response to the introduction of novel grass species. Lamb groups sequentially grazed paddocks with one, two, three and then four grass species in four 1-week periods, and grazing and ruminating times and pasture biting rates were recorded during daylight hours. In the first period the lambs grazed only perennial ryegrass, then timothy, cocksfoot and finally red fescue were introduced in periods 2 to 4 respectively. The total time that lambs spent grazing and ruminating were both increased (P < 0·001) by grazing experience and to a lesser extent by the presence of adult ewes. Pasture biting rate was considerably increased by experience, and to a lesser extent adult presence, with a synergistic effect between these two factors (P < 0·001). Timothy and to a lesser extent perennial ryegrass were the most preferred species, and lambs spent less time grazing cocksfoot than either of these two, and even less time grazing red fescue (P < 0·001). Experience of grazing particularly increased the time spent grazing cocksfoot and red fescue (P < 0·001), but the presence of adult ewes did not increase the time lambs spent grazing novel species (P = 0·59). The pasture biting rate was greater on species that the lambs preferred grazing (P < 0·001), but neither experience nor ewe presence increased the biting rate on novel species in the period of their introduction. It is concluded that although both grazing experience and, to a lesser extent adult presence, increased the total time spent grazing and the pasture biting rate, only grazing experience increased the acceptability of novel species.

The objective of this trial was to examine the daily herbage requirement and grass dry matter intake (DMI) of dairy cows of different levels of milk production with rotational grazing and optimum grazing conditions. The daily herbage allowance (DHA) that was required was defined as the allowance that permitted the herds to graze to a post-grazing sward height (SHA) of 70 mm. Four herds of 15 primiparous Holstein-Friesian cows were assembled with similar characteristics but different milk production potentials. The herds grazed separately and were offered a DHA such that the SHA was 70 mm for all herds. The daily yield per cow, for the 4 weeks prior to the start of the experiment (PMY), was 17·4, 19·8, 21·8 and 24·3 kg milk (s.e.0·20, P < 0·001), 0·72, 0·78, 0·87 and 0·93 kg fat (s.e. 0·021, P < 0·001), 0·59, 0·66, 0·71 and 0·77 kg protein (s.e. 0·009, P < 0·001) for herds 1 to 4, respectively. The experiment began on 30 June and finished on 16 August. The swards offered were 18-day re-growths following a previous defoliation by grazing. Herbage mass pre- and post-grazing was 2143 (s.e.33·3) and 622 (s.e.18·2) kg dry matter (DM) per ha above 40 mm, respectively and were similar for the four herds. The DHA was 21·2, 21·9, 22·9 and 23·9 (s.e. 0·13, P < 0·001) kg DM per cow above 40 mm. Individual cow grass DMI was determined once during the experimental period using the alkane technique. Experimental milk yield (EMY) was 15·1, 17·4, 18·6 and 20·8 (s.e. 0·33, P < 0·001) kg per cow per day. DMI was 14·5, 15·4, 15·5 and 16·1 (s.e. 0·47, P > 0·05). Variations in DMI were best described by the relationship: DMI = 0·85 (s.e. 3·038) + 0·32 (s.e. 0·082) ✕ EMY + 0·012 (s.e. 0·0054) ✕ experimental live weight + 2·10 (s.e. 0·738) ✕ weight gain + 0·020 (s.e. 0·0085) ✕ days in milk (residual s.d. = 1·477 and r = 0·75). EMY was linked to DMI and PMY according to the expression: EMY = –0·64 (s.e. 1·532) + 0·256 (s.e. 0·0865) ✕ DMI + 0·705 (s.e. 0·0620) ✕ PMY (residual s.d. = 1·204 and r = 0·872). It is concluded that higher yielding herds require higher DHA and this is associated with higher DMI of those herds.