To measure the effect of partially replacing grass silage with urea-treated whole-crop wheat (WCW) four multiparous Holstein/Friesian lactating cows fitted with cannulas in the rumen and proximal duodenum were offered four diets in a Latin-square experiment. Grass silage (GS) was produced from the primary growth of a perennial ryegrass sward. Spring wheat (cv. Axona) was harvested at 603 g dry matter (DM) per kg and preserved with 20 (WCW-20) or 40 (WCW-40) kg urea per t DM. The diets were 6 kg DM of a dairy concentrate daily with one of four forages offered ad libitum The forage treatments were GS alone, a 2: 1 DM ratio of GS with WCW-40 (2: 1 40), or a 1: 2 DM ratio of GS with WCW-20 (1: 2 20) or WCW-40 (1: 2 40). Each period lasted 4 weeks with rumen and duodenal samples being taken on 2 days in the last week. Concentrations of milk fat and protein were increased by WCW inclusion. The digestibility in the rumen of DM, organic matter (OM) neutral-detergent fibre (NDF), acid-detergent fibre and starch fell with increasing WCW-40 inclusion in the diet. Flow of starch and non-ammonia nitrogen to the duodenum increased with WCW inclusion. It was estimated that the amounts of OM, starch, NDF and nitrogen digested post ruminally increased with WCW. With WCW there were increases in the rumen in the ratio of acetic acid plus n-butyric acid to propionic acid and in ammonia concentrations. The level of urea inclusion had no significant effects on rumen digestion. It is concluded that the large reduction in the contribution of the rumen to total OM digestion when WCW partially replaces grass silage may have implications for calculations of metabolizable protein supplies to animals given such diets. Possible means to improve food utilization include processing of the wheat grains and inclusion of readily fermentable carbohydrates in the diet to facilitate the utilization of the rumen ammonia.

The nutritive value of banana by-products (leaves, pseudostems and raceme stems) for goats was studied by rumen degradability and in vitro digestibility techniques, voluntary intake and maintenance trials. Banana by-products had both a relatively low degradability and digestibility, with derived metabolizable energy content (MJ ME per kg dry matter (DM)) of 6·54 for leaves, 6·66 for pseudostems and 8·24 for raceme stems. Daily voluntary intake (g DM per kg M0·75) was 66·4 for leaves, 19·3 for pseudostems, and 15·3 for raceme stems. On these results, pseudostems and raceme stems would provide less than 0·30 of maintenance ME needs of goats. However, rations based only on banana leaves should meet more than 0·85 of the maintenance energy needs.

The objective was to determine the effect of previous lambing date and subsequent month of mating on reproductive performance in Mule (Bluefaced Leicester × Scottish Blackface) ewes. Sixty-four ewes which had previously lambed in January (13 January (s.e. = 1 day)) and 80 ewes which had previously lambed in May (15 May (s.e. = 1 day)) were allocated equally to four mating periods (30 August to 17 September, 1 November to 19 November, 3 January to 21 January and 14 February to 4 March) in a 2 × 4 factorial design. From 20 days before and during their designated mating period, January- and May-lambing ewes were separately housed in straw-bedded pens under natural photoperiod and were given 1 kg per head per day dried grass pellets. A vasectomized ram was continuously present with each group for 17 days and was replaced by a raddled, fertility tested entire Suffolk ram at the start of the mating period. Ewes were mated at a single natural oestrus and those marked by the ram were recorded daily. Ovulation rate was measured by laparoscopy on day 6 after mating. For ewes which had previously lambed in January (16 per group), numbers by month of mating that showed oestrous behaviour, ovulated and were pregnant, respectively, were: September, 16, 15 and 12; November, 16, 15 and 14; January, 15, 15 and 10 and February, 15, 16 and 7. Mean (s.e.) ovulation rates by month of mating were 2·1 (0.16), 2·5 (0.19), 2·1 (0.09) and 2·2 (0.19) corpora lutea per ewe ovulating, and lambing rates by month of mating were 1·3 (0.25), 1·9 (0.25), 1·2 (0.24) and 0·8 (0.23) lambs per ewe to the ram. For ewes which had previously lambed in May (20 per group), numbers by month of mating that showed oestrous behaviour, ovulated and were pregnant, respectively, were: September, 13, 20 and 12; November, 20, 20 and 19; January, 20, 20 and 17 and February, 20, 20 and 13. Mean (s.e.) ovulation rates by month of mating were 2·0 (0.13), 2·3 (0.11), 2·1 (0.05) and 2·2 (0.11) corpora lutea per ewe ovulating, and lambing rates by month of mating were 1·0 (0.21), 2·1 (0.15), 1·5 (0.17) and 1·2 (0.21) lambs per ewe to the ram. Ovulation, pregnancy and lambing rates were not influenced by previous lambing date, but lambing rates were significantly (P < 0·01) reduced for ewes mated in September and February compared with November. Results demonstrate that in Mule ewes acceptable ovulation rates can be achieved throughout the period September to February but lambing rates are reduced when ewes are mated at the extremes of their natural breeding season. The main factor contributing to the reduction in lambing rates was an increase in the number of ewes failing to establish pregnancy as a consequence of ovulation without oestrous behaviour, fertilization failure and (or) total embryo loss.

The effects of diets formulated to have two rates of organic matter (OM) release and to be either synchronous or asynchronous with respect to their hourly release of nitrogen (N) and OM in the rumen on the growth, intake and metabolism of ewe lambs was studied. In experiment 1, the in situ degradation characteristics of N and OM for 16 food ingredients was determined. The foods varied considerably in their chemical composition and degradability coefficients of N and OM. Based on this information, four diets were formulated to differ in their rate of N and OM release in the rumen but to have a similar content of metabolizable energy (10·4 MJ/kg dry matter (DM)), crude protein (140 g/kg DM), daily ratio of N: OM released (34 g N per kg OM) and digestible undegradable protein (32 g/kg DM) but to be synchronous or asynchronous with respect to hourly N: OM ratio. The four diets were slow energy, synchronous (SS), slow energy asynchronous (SA), fast energy, synchronous (FS) and fast energy asynchronous (FA).

In experiment 2 the four diets were offered ad libitum to 24 ewe lambs of an initial live weight of 25 kg in a 2 × 2 factorial design. Lambs were slaughtered at 40 kg live weight. Animals offered diets FS and FA had a higher growth rate than those offered diets SA and SS (266 v. 225 g/day respectively; P < 0·05). There was a significant interaction between rate ofOM and N release on DM intake (DMI) with lambs offered diet FS consuming less than those offered FA (1·47 v. 1·67 kg DM per day; P < 0·05). Rate of energy release and synchrony had an effect on food conversion efficiency (FCE; kg gain per kg DMI) with lambs offered diets FS and FA having a greater FCE than those offered SS and SA (0·170 v. 0·146 respectively; P < 0·001) and those offered diets SS and FS had a greater FCE than those offered diets SA and FA (0·164 v. 0·152 respectively; P < 0·05). Diet had little effect on carcass composition. The proportion of propionate in rumen fluid was greater in lambs offered diets FS and FA than in those offered diets SS and SA (222 v. 168 mmol/mol respectively; P < 0·01). Plasma urea concentrations exhibited a cyclical trend throughout the day with highest concentrations occurring 2 h after fresh food was offered. Lambs offered diet FS had lower plasma urea concentrations at 6, 10 and 14 h after feeding. Plasma concentrations of ß-hydroxybutyrate were lower throughout the day in lambs offered diet FS. The current findings are consistent with the view that a rapid release of OM and synchronizing hourly N: OM release in the rumen can improve the efficiency of growth through improvements in protein and/or energy metabolism.

Rate of passage of digesta out of the rumen is generally assumed to follow first order kinetics but this assumption may not hold within 24-h feeding cycles. Four lactating cows offered a mixed forage/concentrate diet ad libitum from 08.00 h to 00.00 h and a protein-rich meal at either 08.30 or 00.30 h were used to investigate diurnal patterns in rumen volume and composition of digesta flowing into the duodenum. Cows were fitted with large rumen cannulae to permit complete emptying of rumen digesta and T-piece duodenal cannulae with inserts to enable collection of representative samples of digesta. Chromium-mordanted lucerne hay manually dosed to the rumen at 2-h intervals and a continuous infusion of cobalt-EDTA were used as digesta flow markers. Duodenal digesta was sampled over three alternate days to obtain samples representing every hour of the 24-h day, which were analysed individually. Use of either of the two markers gave similar results for mean daily flow but not for hourly flow and thus hourly flow data were not considered reliable. The content of crude protein in duodenal digesta varied within one feeding cycle from 200 to 320 g/kg in cows offered protein at 08.30 (‘day’) and from 240 to 300 in cows offered protein at 00.30 h (‘night’). On a daily basis, fractional passage rates (calculated from duodenal flow divided by rumen pool size) were significantly (P = 0·016) lower for protein for ‘night’ (0·0750 per h) versus ‘day’ (0·0824 per h) cows. The observation that marked diurnal patterns in the composition of protein flowing into the duodenum can apparently be ‘smoothed’ simply by altering feeding sequence, which was correlated with an increased milk fat yield, suggests there is potential for improving production through manipulating the way in which dietary components are offered within a day.

Rate of passage of digesta out of the rumen is generally assumed to follow first order kinetics but this assumption may not hold within 24-h feeding cycles. Four lactating cows offered a mixed forage/concentrate diet ad libitum from 08.00 h to 00.00 h and a protein-rich meal at either 08.30 or 00.30 h were used to investigate diurnal patterns in rumen volume and composition of digesta flowing into the duodenum. Cows were fitted with large rumen cannulae to permit complete emptying of rumen digesta and T-piece duodenal cannulae with inserts to enable collection of representative samples of digesta. Chromium-mordanted lucerne hay manually dosed to the rumen at 2-h intervals and a continuous infusion of cobalt-EDTA were used as digesta flow markers. Duodenal digesta was sampled over three alternate days to obtain samples representing every hour of the 24-h day, which were analysed individually. Use of either of the two markers gave similar results for mean daily flow but not f or hourly flow and thus hourly flow data were not considered reliable. The content of crude protein in duodenal digesta varied within one feeding cycle from 200 to 320 glkg in cows offered protein at 08.30 day’) and from 240 to 300 in cows offered protein at 00.30 h (‘night’). On a daily basis, fractional passage rates (calculated from duodenal flow divided by rumen pool size) were significantly (? = 0·016) lower for protein for ‘night’ (0·0750 per h) versus ‘day’ (0·0824 per h) cows. The observation that marked diurnal patterns in the composition of protein flowing into the duodenum can apparently be ‘smoothed’ simply by altering feeding sequence, which was correlated with an increased milk fat yield, suggests there is potential for improving production through manipulating the way in which dietary components are offered within a day.

Four silages were prepared at 1-week intervals from a primary growth of timothy-meadow fescue sward. They were offered to 32 Finnish Ayrshire cows and supplemented with 7 or 10 kg of concentrate containing 0 or 1·15 kg rapeseed meal (RSM). The basal concentrate consisted of barley, oats and molassed sugar-beet pulp (2: 2: 1) and minerals. Diets were arranged 4 × 2 × 2 factorially in a cyclic change-over experiment with four periods of 21 days each.

Silages contained 739, 730, 707 and 639 g digestible organic matter (D value) per kg dry matter (DM) for harvests I, II, III and IV, respectively. All dietary factors had marked effects on the performance of the cows but generally interactions between treatments could not be detected. A decrease of 10 g/kg in silage D value decreased energy-corrected milk (ECM) production of the cows by 0·50 kg/day and silage DM intake by 0·162 kg/day. An increment of 1 kg concentrate DM decreased silage DM intake by 0·61 kg and yielded 0·55 kg more ECM per day. Inclusion of RSM into the concentrate increased daily ECM production by 1·7 kg and silage DM intake by 0·60 kg/kg RSM when substituting the basal concentrate. Milk yield and yields of milk constituents decreased curvilinearly with delayed date of harvest the difference being greatest between the last two cuts and thus closely reflected the changes in silage D value. Milk protein concentration increased as apparent digestibility (P < 0.001) and concentrate level in the diet increased (P < 0.001). Milk fat concentration was not affected by the dietary treatments.

Marginal ECM production responses to estimated metabolizable energy (ME) intake were higher when intake was manipulated with the date of silage harvest (0·138 kg ECM per MJ additional ME) compared with increased concentrate feeding (0·103); highest response was achieved by RSM feeding (0·244). Additional intake of calculated amino acids absorbed from the small intestine (AAT) manipulated by silage harvest time resulted in the highest marginal response (0·59 g milk protein per g additional AAT), while increased concentrate feeding and inclusion of RSM were equal (0·50 v. 0·49, respectively). Improving silage quality by earlier harvest resulted in higher milk yield, and in greater efficiency in the use of increments of estimated ME and AAT than was seen with increased concentrate feeding. Protein supplementation improved milk production irrespective of silage harvest date.

The effect of quebracho tannin (QT) on the activities of rumen microbes was studied both in vivo and in vitro. The in vivo study was carried out in four rumen environments created by feeding four fistulated sheep a basal diet of chopped grass hay, grass cubes and whole barley (control) with or without the addition of QT and the dietary modifier Browse Plus (BP). The active ingredients in BP are polyethylene glycol (PEG, more than 0·95 of the dry material), polyvinyI pyrrolidone (PVP) and calcium hydroxide. The diets offered were control, control plus 50 g QT per kg diet (CQT), control plus 50 g QT per kg and 0·1 (CQT+ 0·1) or 1.0 g BP per kg (CQT + 1·0). The experiment was a 4 X 4 Latin-square design with periods of 4 weeks. Rumen liquor samples were collected at 0, 2, and 8 h after feeding, 18 and 25 days after commencement of each period. Changes in free and bound proanthocyanidin (PA) concentrations, rumen pH, ammonia, volatile fatty acids (VFA), soluble protein concentrations, particle-bound cellulase and xylanase activities and rumen protozoal counts were used as indices of microbial activities. The same diets were incubated with rumen contents in vitro, except that the 0.1 g/kg level of BP was replaced by a fourth treatment made up of control plus 1·0 g BP per kg DM of hay (CBP). In vivo, bound PA concentrations in the rumen liquor of all the sheep given QT-containing diets were higher than those of the free PAs. The bound PA was higher (V < 0·05) in the rumen liquor of sheep given CQT in comparison with those containing BP. There were reductions in ammonia (P > 0·05), soluble protein (P < 0·05) and total VFA (P > 0·05) concentrations in the rumen liquor of sheep given CQT in comparison with those given the control and BP-containing diets. Reductions (P > 0·05) were also observed in the cellulase and xylanase activities of the rumen microbes and in protozoal counts (P < 0·05) in the presence of QT in the diet. In vitro, QT reduced (P > 0·05) the viable bacterial counts, gas production and the total VFA concentrations after incubation. In both the in vivo and in vitro experiments, BP was able to alleviate some but not all of the depression in microbial activities. The main constituent (PEG) in BP binds to some of the tannins in solution and may displace tannins from tannin-protein complexes.

To optimize performance and carcass quality of Belgian Blue double-muscled bulls four phased feeding regimens were evaluated. All diets were offered ad libitum and consisted of 650 g concentrates and 350 g maize silage per kg dry matter (DM). Total period was divided into three phases (ca. 360 to 460, 460 to 570 and 570 to 680 kg). All four groups received the same maize silage but the different energy and protein densities were applied using different concentrates. During the three phases, the negative control (NC) group constantly received a diet with a low protein and a moderate energy density; the second group (DP) received with each phase diets with decreasing protein density while the energy density remained moderate; the third group (IE) received diets with increasing energy density at a constantly high protein density and the last group (DPIE) received diets which decreased in protein and increased in energy density.

The NC group grew significantly slower during the first interval (1·37 v. 1·62 kg/day for the other groups), resulting in a significantly longer total finishing period. During the third period IE had the slowest growth. The NC group needed 21 and 20 days more than the DP and DPIE groups, respectively, to reach the same slaughter weight. The NC group had the lowest DM intake during the first interval, the IE group during the third interval. No significant differences (P > 0·05) were found for food conversion, when expressed as DM or NEF (net energy for fattening). IE had the worst protein conversion while NC had the best, with the two other groups being intermediate.

The only important significant difference concerning carcass quality was the improved dressing proportion of the IE and DP groups. Although significant, differences in the fat content of the m. longissimus thoracis are of minor importance. These results proved that for Belgian Blue double-muscled bulls, protein density of the diet can be decreased with increasing live weight, while energy should be increased to give optimal performance.