Grape seed extract (GSE), a rich source of polyphenols, is reported to possess antioxidant, anti-inflammatory and immunomodulatory properties. The objective of the present study was to determine whether GSE could attenuate the heat stress-induced responses of jejunum epithelial cells (JEC) in cattle. The JEC of a steer (Simmental ×  Qinchuan) were exposed to heat stress for 2 h in the absence (0 μg/ml) or presence (10, 20, 40 and 80 μg/ml) of GSE in the culture medium. When cultured at 40°C, JEC supplemented with GSE exhibited increased glutathione peroxidase activity (P= 0·04), viability (P= 0·004), and mRNA expression of epidermal growth factor (EGF; P= 0·03) and EGF receptor (EGFR; P= 0·01). Under the same conditions, the cells exhibited decreased mRNA expression of IL-8 (P= 0·01) and TNF-α (P= 0·03) and decreased protein concentrations of IL-1β (P= 0·02), Toll-like receptor 4 (TLR4; P= 0·04) and heat shock protein 70 (HSP70; P< 0·001). When cultured at 43°C, JEC supplemented with GSE exhibited increased catalase activity (P= 0·04), viability (P< 0·001), and mRNA expression of EGF (P< 0·001) and EGFR (P< 0·001) and decreased protein concentrations of IL-1β (P< 0·001), TLR4 (P= 0·03) and HSP70 (P< 0·001), as well as mRNA expression of IL-8 (P< 0·001), TLR4 (P= 0·002) and TNF-α (P< 0·001). Temperature × GSE concentration interactions were also observed for the concentrations of IL-1β (P< 0·001), IL-8 (P< 0·001), TNF-α (P= 0·01) and HSP70 (P= 0·04) and viability (P< 0·001) of JEC. The results of the present study indicate that GSE can attenuate the responses of JEC induced by heat stress within a certain range of temperatures.

Use of synthetic feed additives, including synthetic vitamin D3 (D3) in the feed for cows and other ruminants, is not consistent with the international principles of organic farming. If dairy farmers wish to produce in accordance with the organic principles, production animals would be left with only their endogenous production of D3 from summer sunlight as a source of D3. To examine the impact of supplemental synthetic D3 from the feed on the D3 status of dairy cattle in organic production in Nordic countries, 20 high-yielding dairy cows and 30 dairy steers were divided into two groups: one supplemented with synthetic D3 in the feed and one not supplemented with synthetic D3. Vitamin D3 status of the animals was assessed by measuring the concentration of the liver-derived 25-hydroxyvitamin D3 (25OHD3) in plasma. Results showed that 25OHD3 concentration in plasma from dairy cattle as well as from steers decreased during winter for both supplemented and unsupplemented groups. Unsupplemented cows and steers had approximately 2 ng 25OHD3 per ml plasma during winter, whereas supplemented animals had between 10 (cows) and 30 (steers) ng/ml. During summer and autumn there was no additive effect of supplementing with synthetic D3 since unsupplemented and supplemented animals had the same D3 status at this time of year. In all cows summer concentrations of 25OHD3 were 20–25 ng/ml and in all steers 40–50 ng/ml plasma. The decrease in vitamin D3 status during winter indicates that cows and steers are able to store D3 only to a limited extent. The results also show that cows or steers fed supplemental D3 according to Swedish recommendation throughout the year are not able to maintain their summer value of 25OHD3 during winter.

The objectives of the two experiments were to determine the respective effects and interactions of diet type (grass v. maize diets) and physical activity (grazing v. zero grazing) on lipogenic enzyme activities and adipose cell size in subcutaneous, perirenal and intermuscular adipose tissues and on plasma metabolites and hormones in Charolais steers. After weaning, the steers were assigned to two (Experiment 1, n = 24) or three (Experiment 2, n = 24) groups, with steers in Experiment 1 grazed grass or indoors maize-silage-fed and steers in Experiment 2 grazed grass, indoors cut grass- or indoors maize-silage-fed. Both experiments lasted for 23 months. All grass-fed animals were fed grass silage during the two winter seasons. During the two summer seasons, steers fed on grass were rotationally grazed on a perennial rye-grass pasture while steers fed on cut grass were fed indoors on freshly cut grass alone. Steers fed on maize silage were fed maize silage indoors during the entire experiment. All animals were reared for similar body weight and growth rates and slaughtered at the same age (31 to 32 months). Activities of lipogenic enzymes were significantly lower in the three adipose tissue sites of steers fed cut grass compared with maize silage, although there were less-marked effects in intermuscular adipose tissue. Plasma insulin and glucose concentrations were also lower in steers fed cut grass whereas plasma leptin concentration was similar. As body fat content was not affected by nutritional treatment, it is suggested that the decrease in potential lipogenic activity was associated with the nature of the diet and not to differences in available net energy. In other respects, grazed grass compared with eating cut grass did not affect lipogenic enzyme activities but decreased plasma leptin concentrations in the older steers and increased plasma non-esterified fatty acids and glucose concentrations without affecting adipose tissue weight and adipose cell size.

The aim of this study was to evaluate the effects of two dietary supplements (monensin and a live yeast culture) on acid-base balance in steers maintained in a commercial feedlot system, considering effects over the finishing productive cycle. Steers (no. =42) were allotted randomly to one of the three study groups: (1) control group (no supplementation, C), (2) monensin supplementation (MON), and (3) live Saccharomyces cerevisiae strain 47 supplementation (SACC). Venous blood samples were collected for the measurement of acid-base parameters and l-lactate. Production parameters were also used as a complementary tool for understanding the internal changes associated with supplementation. During the finishing period, MON steers tended to gain more efficiently than C and SACC steers. In the C group, the finishing-period diet caused a progressive decline in blood bases, in line with the high-grain diet consumption. In contrast, supplemented animals did not show this trend, although lower HCO3− and base excess values were registered in SACC steers than in MON, indicating that ionophore supplementation is less effective for reducing blood base consumption than yeast supplementation. In our study, the lack of the expected response to yeast supplementation may be attributable to the high crude protein content of the ration, a common feature of commercial feedlot industries.

The objective of this study was to evaluate effects of natural zeolite (clinoptilolite) on nutrient digestibility, carcass attributes and performance of Holstein steers given a diet containing urea. Forty-five Holstein steers (309 (s.d. 11·2) kg) were given diets as follows: control diet based on maize and soya-bean meal (SBM); treatment 2 (T2), control diet (without SBM) containing 20 g/kg urea; treatment 3 (T3), control diet (without SBM) containing 20 g/kg urea and 30 g/kg zeolite. Just before feeding, ruminal ammonia levels were low in all treatments. At 2·5 h post feeding, steers given T2 and T3 diets had higher ( P<0·05) ruminal ammonia concentration than the control. At 5·5 h post feeding, steers on T3 diet had the highest ruminal ammonia concentration, which was higher ( P<0·05) than the value for steers given T2 diet. Plasma urea nitrogen level increased post feeding for all treatments. At 3 h post feeding, the level for steers given T2 diet was higher ( P<0·05) than those on control and T3 diets but at 6 h post feeding, the level was higher for steers on T3 diet. No differences ( P>0·05) were observed in dry-matter intake among treatments. Live-weight gain and gain: food ratio were highest ( P<0·05) for steers on the control diet, with no differences ( P>0·05) between steers given T2 and T3 diets. Including zeolite in a diet containing urea had no effect ( P>0·05) on total tract digestibility coefficients of dry matter, organic matter and crude protein but increased ( P<0·05) digestibility of neutral-detergent fibre and acid-detergent fibre. Hot carcass weight and kidney, pelvic and heart fat weight of steers were highest in control, intermediate in T3 and least in T2 ( P<0·05). No differences ( P>0·05) were found in longissimus muscle area and fat thickness over longissimus muscle among treatments. Including 30 g/kg of zeolite in a diet containing 20 g/kg of urea decreased ruminal ammonia nitrogen concentration, plasma urea nitrogen level and increased fibre digestibility but its effect on feedlot performance was negligible.

Advancing maturity of forage maize is associated with increases in the proportion of dry matter (DM) and starch and decreases in the proportions of structural carbohydrates in the ensiled crop. Three maize silages (286 (low, L), 329 (medium, M) and 379 (high, H) g DM per kg fresh weight) plus a concentrate formulated to give isonitrogenous intakes were offered to Holstein-Friesian steers fitted with a cannula in the dorsal sac of the rumen and a ‘T’ piece cannula in the proximal duodenum in an experiment with a cross-over design that allowed four collection periods. Nutrient flow to the duodenum was estimated using chromium-EDTA. Steers consumed approximately 0·6 kg DM per day less of diet L compared with the other two diets (P=0·026), resulting in less DM being digested (P=0·005) but digestibility did not differ between diets. Similar results were obtained for organic matter. There were no differences between diets in the intake or digestibility of neutral-detergent fibre. Intake, duodenal flow and faecal output of starch were greater for steers offered diets M and H compared with those given diet L (P<0·05). In all diets rumen digestion contributed to over 90% of total digestion of starch, although rumen digestibility declined significantly with advancing maize maturity (P=0·002). Molar proportions of acetic acid were higher in diet H (P<0·05) whilst proportions of propionic acid and n-butyric acid were higher in diets M and L. There were no significant differences between diets in mean rumen pH or ammonia concentrations. Mean circulating concentrations of insulin were higher (P=0·009) in cattle given diets L and M compared with diet H. There were no differences between diets in the mean circulating concentration of growth hormone, or the frequency, amplitude and duration of growth hormone pulses, or the mean circulating concentrations of IGF-1. Changes in forage composition that accompany advancing maize maturity affect overall silage digestion and circulating concentrations of insulin.

Simmental × Holstein-Friesian steers were offered four forage diets. These comprised grass silage (G); proportionately 0·67 grass silage, proportionately 0·33 maize silage (GGM); 0·33 grass silage, 0·67 maize silage (MMG); maize silage (M) from 424 (s.d. = 11·5) kg to slaughter at a minimum weight of 560 kg. Forages were mixed and offered ad libitum. Steers were offered 2 kg of a concentrate daily, the concentrate being formulated such that all steers had similar crude protein intakes across dietary treatments. A sample of steers was slaughtered at the beginning of the experimental period to allow the calculation of the rate of gain of the carcass and its components. Carcass dissection of a sample of steers allowed the development of a prediction equation of carcass composition based on thoracic limb dissection of all carcasses. Forage dry matter intake and live-weight gain increased linearly as maize silage replaced grass silage in the forage mixture, resulting in improvements in food conversion ratio (all P = 0·001). Killing-out proportion increased with maize silage inclusion (P < 0·001) but fat and conformation scores did not differ significantly between diets. However, increasing maize inclusion in the diet resulted in a greater weight (P = 0·05) and proportion (P = 0·008) of fat in the carcass, and significant increases in internal fat deposition. The inclusion of maize led to a progressive increase in the daily gains of carcass (P < 0·001), and significant increases in the daily gains of both fat (P < 0·001) and lean tissue (P < 0·001). Fat colour was more yellow in cattle given diets G and GGM than diets MMG and M(P < 0·001) and colour intensity was lower on diet M than the other three diets (P < 0·001). There were no significant differences in any aspects of eating quality between diets. Therefore, maize silage has the potential to reduce the time taken for finishing beef animals to achieve slaughter weight with no apparent detrimental effects on subsequent meat quality.

Sixty Angus steers (413 ± 8.0 kg) were used to determine the effects of copper (Cu), maize type, and finishing system (confinement v. pasture) on performance, carcass characteristics, and fatty acid composition of longissimus muscle in steers. Steers in confinement were given individually high concentrate diets containing either typical or high-oil maize, using Calan gate feeders. Steers grazing pasture (tall fescue) were maintained in four pastures with each pasture containing five steers. Salt was used to limit concentrate intake in pasture steers to approximately 0.6 of that observed in confinement steers. One half of the steers in each treatment received a CuO needle bolus at the initiation of the study while the remaining steers received no supplemental Cu. Equal numbers of steers per treatment were harvested after 91, 112 or 133 days on food. Rate of gain was lower (P < 0.01; 1.2 v. 1.6 kg/day) for pasture-fed steers compared with steers receiving typical maize. Cu supplementation increased (P < 0.05) ADG in steers given typical maize (1.8 v. 1.5 kg/day) and those on pasture (1.3 v. 1.1 kg/day) but not in steers given high-oil maize diets (1.5 v. 1.5 kg/day). Gain, dry-matter intake and gain/food did not differ between steers given typical or high-oil maize. Plasma cholesterol concentrations were lower (P < 0.01) in steers given typical maize relative to steers given high-oil maize. Steers receiving a Cu bolus had higher plasma (P < 0.05) and liver (P < 0.01) Cu concentrations than steers not receiving a Cu bolus. Steers receiving typical maize had lower (P < 0.05) liver Cu concentrations than steers receiving high-oil maize. Steers finished on pasture with limited concentrate had conjugated linoleic acid (CLA) concentrations in longissimus muscle that were approximately three times higher (P < 0.01) than steers given typical maize. Cu supplementation tended (P < 0.10) to increase muscle CLA. Longissimus muscle from pasture-fed steers was lower (P < 0.01) in C16: 0 and higher (P < 0.05) in C10: 0, C17: 0, C18: 3, C20: 3 and total polyunsaturated fatty acids than steers given typical maize. Muscle C18: 1 trans and C17: 0 tended to be reduced (P < 0.10) by Cu supplementation. These results indicate that finishing cattle on pasture with limited grain increases CLA in longissimus muscle and that Cu supplementation also alters the fatty acid composition of muscle.

An experiment was conducted with 42 Montbéliard steers to determine if nutritionally induced interrupted growth could influence muscle characteristics of steers and hence meat quality. A restriction/refeeding path was designed in order to induce a discontinuous growth path. At 9 months of age, 21 steers were given a restricted amount of diet for 3 months and were then slaughtered (R steers; no. = 10; intake: 5·28 kg dry matter (DM) per day) or subjected to a 4-month ad libitum refeeding period (R/F steers; no. = 11; intake: 8·99 kg DM per day) with the same diet (11·03 to 11·12 MJ metabolizable energy (ME) per kg DM) prior to slaughter. An additional 21 control steers were offered the same diet but in amounts that allowed them to gain continuously between 9 and 12 months of age, and were then slaughtered (C steers; no. = 10; intake: 7·08 kg DM per day) or maintained on a continuous feeding protocol through to 16 months of age prior to slaughter (C/C steers; no. = 11; intake: 8·07 kg DM per day). M. semitendinosus (ST), m. longisssimus thoracis and m. triceps brachii (TB) were collected for biochemical and histochemical analyses. R steers had a lower average daily gain (ADG; P 0·001), a lower final weight (P 0·01) and a leaner carcass (P 0·01) than C steers. Upon refeeding, R/F steers had a higher ADG than C/C steers (P 0·05) and underwent compensatory growth resulting in compensation of body weight and composition at 16 months. In muscles, glycolytic lactate dehydrogenase activity was lower in R steers (P 0·01) and restored in R/F steers compared with control steers. Among oxidative enzymes, cytochrome-c oxidase activity was higher in the TB of R/F compared with C/C steers (P 0·001) indicating a muscle-specific metabolic adaptation to the feeding level. There was little effect of the nutritional treatment on muscle fibre size and type except for an increase in the frequency of hybrid fibres in R and R/F groups (P 0·05). Total and insoluble collagen content were affected by restriction (P 0·001) in a muscle-specific manner: insoluble collagen content was lower in ST, but total and insoluble collagen contents were higher in TB of R compared with C animals at 12 months of age. No differences were recorded in lipid contents nor in proteasome activities. The data suggest that an alternation of relatively mild nutritional restriction and ad libitumfeeding had only a small effect on muscle characteristics. However, muscles respond differentially to changes in feeding level.

The objectives of this study were to investigate the effects of vitamin A (retinol) on growth hormone (GH) secretion and circulating insulin-like growth factor-1 (IGF-1) concentration in Japanese Black steers. Thirteen 10-month-old Japanese Black steers were divided into two groups: high vitamin A (H) group and low vitamin A (L) group. The animals in the H group were injected with 20 ml retinol palmitate (303 mg as retinol) intramuscularly every month throughout the experimental period. The steers in the L group were injected with vitamin A similarly at the age of 10 to 14 months. All steers were given vitamin A with the food (approx. 100 μg as retinol per kg diet) at the age of 21 to 30 months to prevent clinical vitamin A deficiency. Blood samples for analyses of vitamin A and IGF-1 were collected every 2 months. Series of blood samples for analyses of GH were collected at 15-min intervals over a 6-h period from each animal at the age of 10, 20, and 30 months. Although there was no difference in food intake between the two groups (P > 0·05), the average daily gain of the H group was greater (P < 0·001) than that of the L group. The carcass weight and subcutaneous fat thickness of the H group were significantly greater (P < 0·05) than those of the L group. The longissimus muscle area (P < 0·01) and marbling score (P < 0·001) of the L group were significantly greater than those of the H group. The serum retinol concentrations of the L group were significantly lower (P < 0·01) than those of the H group from the age of 16 months. The serum IGF-1 concentrations of the L group gradually decreased and were significantly lower (P < 0·01) than those of the H group from the age of 18 months. The overall mean concentration, peak height, area under the curve, and nadir of GH in both groups decreased with age. However, there were no significant differences (P > 0·05) in overall mean GH concentration, peak number, peak height, area under the curve, or nadir between the two groups. These results indicate that vitamin A affects the IGF-1 levels, with little or no intermediary effect on GH.

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.

Muscle chemical analysis and muscle identification both were attempted by using visible and near infrared reflectance spectroscopy (NIRS). Seventy-eight beef muscles (m. longissimus dorsi) from Hereford cattle were used. The samples were scanned in a NIRS monochromator instrument (NIRSystems 6500, Silver Spring, MD, USA) in reflectance mode (log 1/R). Both intact and minced muscle presentation to the instrument were explored. Predictive equations were made using ISI software (Infrasoft International, Port Matilda, PA, USA) and muscle identification was performed by Principal Component Analysis (PCA) and Soft Independent Modelling of Class Analogy (SIMCA). The coefficient of determination in calibration (R2CAL) and standard error in cross validation (SECV) for the intact sample presentation were 009 (SECV: 15·6), 0·89 (SECV: 46·9), 0·48 (SECV: 23·9) for moisture (M), fat and crude protein (CP) on g/kg fresh weight basis respectively. R2CAL and SECV for minced sample presentation were 0·41 (SECV: 161), 0·92 (SECV: 43·4), 0·71 (SECV: 20·5) for M, fat and CP on g/kg fresh weight basis respectively. Qualitative analysis of optical information through PCA and SIMCA analysis showed differences in muscles resulting from two different feeding systems.

Eight Hereford ✕ Friesian steers were used to investigate the effect of feeding Lolium perenne (L) forage containing elevated levels of water-soluble carbohydrate (WSC) on rumen metabolism and nitrogen (N) absorption from the small intestine. The steers were offered ad libitum access to one of two varieties with matched heading dates (Ba11353, high WSC, HS; AberElan, intermediate WSC, control) cut at different times of the day to accentuate WSC differentials, zero-grazed for 21 days. This was followed by a 14-day period where the animals were on grass silage to provide a covariate intake. Although the total N concentration was similar for the two grasses, all other measured values were significantly different. The dry matter (DM) concentration of HS was greater than that of the control (202 v. 167 g DM per kg; P 0·01). WSC and in-vitro dry matter digestibility (IVDMD) were 243 and 161 g/kg DM, and 0·61 and 0·56 for HS and control, respectively. In contrast, acid- and neutral-detergent fibre were 251 and 296 g/kg DM and 480 and 563 g/kg DM for HS compared with control, respectively. DM intake was increased (9·3 v. 6·7 kg/day; P 0·001) for HS animals and this contributed significantly towards higher flows of non-ammonia N to the duodenum as well as increased absorption of amino acids from the small intestine. This DM intake response was partly due to the elevation in DM concentration of HS. However fresh weight intake was increased proportionately by ca. 0·15 (P 0·05) in animals on HS compared with control. Rumen ammonia levels were lower (14·0 and 26·4 mg N per l; P 0·001) and concentrations of rumen propionate higher (P 0·01) and acetate lower (P 0·01; increasing the glucogenic: lipogenic volatile fatty acid ratio) in animals on HS compared with control. However, the efficiency of microbial protein synthesis (15·9 and 17·8 g microbial nitrogen per kg organic matter apparently digested) and flow of N to the duodenum per unit N intake (0·84 and 0·93) for HS and control, respectively, were similar across both diets.

The objective of this study was to determine the effects on animal performance and rumen digestion characteristics of supplementing cattle grazing autumn grass offered at two levels of allowance, with concentrates formulated from different carbohydrate sources. Seventy-two steers (494 (s.e. 38·4) kg) were assigned to one of six treatments which were arranged in a two grass allowances (5·5 or 11 kg grass dry matter (DM) per head per day) by three concentrate types (starch, starch + fibre or fibre-based diets) factorial design. The experiment commenced on 22 August and had a mean duration of 84 days. Concentrates were formulated to have similar metabolizable energy and crude protein and animals were offered 5 kg per head daily. Grass allowances were offered daily and concentrates were offered individually. Six rumen fistulated steers were used concurrently in a Latin square design to determine the effect of the diets on rumen digestion characteristics. Grass and concentrates degradabilities were measured using the nylon bag technique. The concentrate DM was degraded at 0·189, 0·102 and 0·094 per h for the starch, starch + fibre and fibre-based diets, respectively. Concentrate carbohydrate source and grass allowance did not affect (P > 0·05) degradation rate of grass DM or nitrogen in the rumen, rumen fluid pH, rumen fluid concentration of volatile fatty acids, total lactic acid or ammonia concentration or plasma concentration of glucose, urea or beta-hydroxybutyrate. Animals offered the low grass allowance had larger (P < 0·05) diurnal variation in the rumen fluid acetate: propionate ratio than those offered the high grass allowance. Increasing grass allowance increased (P < 0·01) carcass gain whereas concentrate type had no effect. There was no interaction between concentrate carbohydrate source and grass allowance on any of the production variables measured. It is concluded that the rumen environment in cattle grazing autumn grass buffered the effects of concentrate carbohydrate degradability such that similar productivity was achieved with each concentrate.

The aim of this experiment was to quantify the relationship between autumn grass supply and concentrate supplementation level on grass intake and animal performance. One hundred and ten continental steers (567 kg) were assigned to 10 treatments. The experimental design was a three grass allowances (6, 12 and 18 kg dry matter (DM) per head daily) by three concentrate levels: (0, 2·5 and 5 kg per head daily) factorial with a positive control group offered concentrates ad libitum and no grass. Grass allowance was offered daily and concentrates were given individually. The experiment began on 22 August and all animals were slaughtered after a mean experimental period of 95 days. Grass intake was calculated using the n-alkane technique and diet digestibility using ytterbium acetate as an indigestible marker. There was an interaction (P < 0·05) between grass allowance and concentrate level for grass intake. At the low grass allowance there was no effect of offering animals supplementary concentrates on grass intake, at the medium and high grass allowances, supplementary concentrates reduced grass intake by 0·43 and 0·81 kg DM respectively per kg DM concentrate offered. Increasing grass allowance increased (P < 0·001) complete diet organic matter (OM) digestibility at all concentrate levels and supplementary concentrates increased (P < 0·001) complete diet OM digestibility only at the low grass allowance. Both offering animals supplementary concentrates (P < 0·001) and increasing daily grass allowance (P < 0·001) increased their carcass growth rate. Relative to the animals offered the low grass allowance and no concentrate, supplementing with concentrate increased carcass growth by 116 g/kg concentrate DM eaten whereas increasing the grass allowance, increased carcass growth by 38 g/kg DM grass eaten. As a strategy for increasing the performance of cattle grazing autumn grass, offering supplementary concentrates offers more scope than altering grass allowance.

There is evidence that, in cattle, rapid compensatory growth after a period of growth restriction may increase the variability of beef quality and that variability is greater in breeds which reach larger body size at maturity. This experiment investigated the effect of compensatory growth following a period of winter growth restriction on carcass quality in steers of small and large mature size grazed on pasture. Angus (no. = 120) and South Devon ✕ Angus (SD✕ A; no. = 110) steers were allocated to non-restricted or restricted growth treatment groups and for 126 days over winter their grazing was managed to achieve mean live-weight gains of approximately 0·7 kg/day or to maintain live weight for each group respectively. Steers were slaughtered at the start (no. = 10 per breed) and end (no. = 20 per nutrition group (10 from each breed)) of the winter period for carcass evaluation. Thereafter, remaining steers were grazed together at a high pasture allowance to maximize growth and were slaughtered for carcass evaluation as they reached target live weights (Angus, 590 kg; SD✕ A, 620 kg). SD✕ A steers grew faster ( P < 0·05) during both the winter and finishing periods and reached target slaughter live weights approximately 20 days earlier than Angus steers. SD✕ A steers also had leaner carcasses than Angus steers at each slaughter although there was no significant difference in meat quality between breeds. However, there was a significant effect of restriction treatment on carcass weight and meat quality. The non-restricted steers grew faster, had heavier carcasses and more tender steaks than restricted steers, although there was no significant difference in carcass fatness (adjusted for hot carcass weight). Muscle calpain activities were positively correlated with live-weight gain during the finishing period suggesting increased potential for post-mortem myofibrillar proteolysis and therefore increased meat tenderness. However, in the present experiment this was confounded by an increase in shear force with age-at-slaughter, especially in the non-restricted steers. Nevertheless, steers which were heaviest at the start of the experiment reached slaughter live weight earliest, were leaner than average and had higher calpain system activities at slaughter regardless of breed or restriction treatment. Furthermore, in the non-restricted group, high initial live weight and early slaughter was associated with lower pH and more tender meat. In conclusion, although restriction affected meat quality attributes, it appears that live weight prior to food restriction also had a considerable effect on carcass characteristics at slaughter. Therefore, the characteristics of the early growth phase prior to the finishing period may have important consequences for meat quality.

A study was carried out to examine the relationship between silage intake and rumen degradability characteristics of silage. The dry matter (DM), neutral-detergent fibre (NDF), acid-detergent fibre (ADF), hemicellulose and nitrogen (N) degradability characteristics of 136 silages were determined using polyester bags in three rumen fistulated beef cross steers. The bags were incubated for 0, 6, 12, 24, 48 and 72 h. Intakes of these silages, by steers, were reported by Steen et al., 1998. The relationships between silage DM intake (g/kg metabolic live weight) and DM, fibre and N degradability characteristics of the silages were poor (R2 < 0·32). Degradability characteristics of the silages were highly negatively correlated with fibre concentration of the silages (R < –0·82) and highly positively correlated with the soluble N minus ammonia concentration (R < 0·77). Some of the degradability characteristics were highly correlated with organic matter digestibility, particularly the proportion of DM, fibre and N degraded after 72 h (R = 0·75 to 0·85). In view of the poor relationship between silage intake and degradability, the results of this study question the rôle of degradation characteristics of DM, fibre and N in the rumen on silage intake.

As part of an investigation of factors responsible for a previously reported lower efficiency of carcass lean gain in steers offered grass silage diets, 16 Simmental × Friesian steers (515 (s.e. 6·4) kg) were offered perennial ryegrass silage ad libitum (C0) or silage plus rolled barley at 200 (C20), 400 (C40) or 600 (C60) g/kg total diet dry matter (DM). Barley-supplemented diets were intake-restricted to provide equal DM and metabolizable energy (ME) intakes to those offered C0. Eight steers were selected at random to determine the ME contents of the diets by open-circuit respiration calorimetry. The other eight steers were offered the same diets and were blood-sampled at 20- to 60-min intervals, for 10 h, to monitor changes in the concentrations of a number of nutritionally related plasma metabolites and hormones. Estimated ME intakes in these steers were 85·7, 83·1, 84·4 and 86·2 (s.e. 0·91) MJ/day from diets C0, C20, C40 and C60 respectively. Rumen-fistulated Hereford × Friesian steers provided 24-h rumen data for the same diets offered at equal amounts of ME per kg metabolic live weight.

Mean 24-h plasma concentrations of insulin and insulin-like growth factor 1 (IGF-1) were linearly and positively related (P < 0·01 and P < 0·001 respectively) and glucagon quadratically related (P < 0·05) to the proportion of barley in the diet. Plasma insulin increased after feeding on all diets but concentrations on diets C40 and C60 were significantly higher than those on C0 and C20 at all post-feeding sampling times up to 9 h after feeding. Plasma IGF-1 concentrations increased above pre-feeding levels following feeding of the higher barley diets (C40 and C60; P = 0·053) but remained unchanged in steers offered C0 and C20. Mean plasma concentrations of glucose were unaffected by diet but those of β-hydroxybutyrate (BOHB) and urea were positively and negatively related respectively (both P < 0·001) to the proportion of barley in the diet. Plasma BOHB and urea concentrations also changed with time after feeding (P < 0·001). Amongst the rumen parameters measured (pH; ammonia and volatile fatty acid concentrations and proportions) only the mean 24-h concentrations and proportions of butyrate were positively related to the proportion of barley in the diet (P = 0·051 and P < 0·05 respectively). All rumen parameters were affected by time after feeding (acetate, P < 0·01; others, P < 0·001) but there was no interaction between treatment and time for any parameter.

The effect of genotype on the size of adipocytes and on the lipogenic enzyme activities in different fat depots in Asturiana, Avilena, Morucha, Parda Alpina, Pirenaica, Retinta and Rubia Gallega steers was studied (six animals per breed). Steers were weaned at about 6 to 8 months of age and 220 to 260 kg live weight (LW). During the fattening period the steers were given commercial concentrates and straw, both ad libitum, until slaughter at 470 kg average LW. Adipocyte size and activity of the following lipogenic enzymes were studied: glycerol 3-phosphate dehydrogenase (G 3-PDH); fatty acid synthase (FAS); NADP-malate dehydrogenase (MD), glucose 6-phosphate dehydrogenase (G 6-PDH) and NADP-isocitrate dehydrogenase (ICDH) in the omental, perirenal, subcutaneous and intermuscular adipose depots. Also the perirenal fat depot was removed and weighed and the 10th rib was dissected. Differences between breeds were significant for the amount of fat in the different adipose depots (P < 0·001), for adipocyte size (except in intermuscular depot) and for G 3-PDH, FAS, MD, ICDH (P < 0·001) and G 6-PDH (P < 0·01). In general, steers of breeds that had more fat also had bigger adipocytes and higher lipogenic enzyme activities. In this way, Asturiana breed (lean breed) had smaller adipocytes and lower lipogenic enzyme activities than Morucha breed (fatter breed). Finally, adipocytes from the perirenal depot were the biggest and showed the highest G 3-PDH and FAS activities while adipocytes from the intermuscular depot had the smallest size and the lowest lipogenic activities.

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.