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Two randomized-block experiments were carried out to examine the relative value of wheat and barley as supplements to grass silage for finishing beef cattle. In each experiment unwilted, formic acid-treated silage was offered ad libitum and supplemented with 500 g soya-bean meal and 50 g minerals and vitamins to 44 12-month-old bulls for 157 and 172 days in experiments 1 and 2 respectively. Twelve of the animals also received 2·5 kg rolled spring barley (LB), 12 received 4·0 kg barley (HB) and 20 received 3·25 kg rolled wheat (W). For experiments 1 and 2 respectively the barley contained 796 and 787 g dry matter (DM) per kg; 118 and 105 g crude protein (CP) per kg DM; 47 and 57 g crude fibre per kg DM; the wheat contained 845 and 800 g DM per kg; 112 and 116 g CP per kg DM; 23 and 25 g crude fibre per kg DM; and the silages contained 190 and 177 g DM per kg; 153 and 176 g CP per kg DM; 80 and 104 g ammonia-nitrogen per kg total nitrogen. On average over the two experiments, for treatments LB, HB and W respectively, silage DM intakes were 5·4, 4·7 (s.e. 0·14) and 4·9 (s.e. 0·11) kg/day; total DM intakes 7·9, 8·3 (s.e. 0·14) and 8·1 (s.e. 0·11) kg/day; metabolizable energy intakes 91·4, 97·8 and 94·2 MJ/day; live-weight gains 1·04,1·19 (s.e. 0·029) and 1·10 (s.e. 0·023) kg/day and carcass gams 0·65, 0·77 (s.e. 0·017) and 0·70 (s.e. 0·013) kg/day. It is concluded that the feeding value of wheat was proportionately 0·98 of that of barley for finishing beef cattle when given as a supplement to grass silage, and that the type of cereal offered did not affect silage intake or carcass composition.

In two experiments, the first with 96 pigs from 5 weeks of age and the second with 384 pigs from 3 weeks of age, high nutrient dense diets (HND) or conventional diets (CONV) were given with (50 g/kg diet) or without fish meal, up to slaughter at 90 kg live weight. Diets were unmedicated. In both experiments pigs were given food according to scales which equalized digestible energy intakes for the HND and the CONV diets. In experiment 1 pigs were individually fed; in experiment 2 group feeding was practised with pens of 16 pigs either floor or trough fed.There was no mortality in experiment 1, but the mortality was high in experiment 2, particularly amongst those pigs receiving the CONV diet without fish meal. In experiment 1, in the first 56 days, inclusion of fish meal in the CONV and HND diets significantly improved growth rate but food conversion efficiency was significantly improved in the CONV diet only. Overall, up to slaughter, growth rate and food conversion efficiency were significantly poorer in pigs given the CONV diet without fish meal (cf. the three other diets) but the HND diets were significantly better than the CONV diet with fish meal. In experiment 2, overall there were no significant differences in performance between floor- and trough- feeding methods, CONV diets without fish meal gave significantly poorer growth rates in the first 56 days and overall than the other three diets, between which there were no significant differences. In both periods, for food conversion efficiency, fish meal inclusion was without significant effect in the HND diets but significantly improved the CONV diets, both of which were significantly inferior to the HND diets.

Energy intake was recorded for two batches of 12 individually-penned piglets weaned at 5 kg live weight and fed milk-based diets of 18·7 MJ metabolizable energy (ME) per kg up to 8 kg live weight and 15.4 MJ ME per kg thereafter. The piglets were kept within their thermoneutral zone throughout the experiments. Regression equations describing the relationship between energy intake and days after weaning were developed for each piglet and the means of the regression coefficients and constants were incorporated in an equation for estimating energy intakes for piglets of 5 to 15 kg live weight. The lower and upper critical temperatures were calculated for each piglet on every day of the trial. These values were extrapolated to give temperature recommendations for piglets of 5 to 15 kg live weight kept in groups of 20. The temperatures ranged from 30°C at weaning to 19°C, 23 days after weaning. This represented a reduction in temperature equivalent to 0·5°C per day.

The influence of season and management system on the productivity of Friesian cows in a Mediterranean climate was assessed. Intakes of food and water and milk yields were measured in 154 cows over 2·5 years while intensively managed in yards giving access to shelter (free stalls) or that were fully exposed to solar radiation (open lots). Food quality was also monitored to permit estimates of the efficiency of utilization of metabolizable energy for milk production over fortnightly periods.The highest milk yields and energetic efficiencies were recorded during spring. Energy intakes were highest but energetic efficiencies were lowest during winter. Cows consumed the least food during summer and autumn and drank the most water during summer. The only significant effect of management system was for water intake, which was higher in the open lots than in the free stalls. There was evidence of heat stress in summer and cold stress in winter, but there appeared to be little benefit with milk yields through the provision of shelter.

Individual dry matter intakes were measured using four groups of 16 ewes, indoors or at sparse winter grazing. In periods of varying duration (14 to 35 days) the ewe groups received 14 feedblock supplements competitively, eight trough supplements competitively or two feedblock supplements individually. In each period hay was available ad libitum. All supplements contained chromic oxide and individual supplement intakes were estimated by total faecal collection. Individual hay and total dry-matter intakes were estimated by faecal apportionment according to indigestibility of dietary components.Metabolizable energy content (0·81 × digestible energy) of the feedblocks ranged from 7·9 to 9·2 MJ/kg dry matter compared with a value of 13·0 MJ metabolizable energy/kg dry matter for concentrates. The variation in individual supplement intake was large, irrespective of type of supplement. However the mean coefficient of intake variation for 14 feedblock supplements (0·56) significantly (P < 0·05) exceeded that (0·39) for eight trough supplements at equivalent mean dry-matter intakes.Thus, ‘free-access’ feedblocks did not allow a more uniform supplementation than trough supplements. Supplement intake variation was higher outdoors and increased as total feedblock intake reduced.The variation in individual hay and total dry-matter intake was lower, and generally independent of that for the supplements. Mean coefficient of variation of 0·24 and 0·22 were obtained for hay and total dry matter, respectively, based on 22 collections with competitively fed sheep.Total daily metabolizable energy intakes of individual ewes outdoors ranged from 5 to 22 MJ per collection.

1. Eighteen New Zealand White × Califomian young female rabbits (does) were paired by weight and age and, at 800 g live weight, placed on a restricted intake based on the mean body weight of each pair. On attaining 1 kg one of each pair was then given 10 mg trenbolone acetate by injection on days 1, 3 and 5 of each week. This continued until the animals reached 2·3 to 2·4 kg (5 to 6 weeks).2. There were no differences in digestible or metabolizable energy intakes between treated and untreated rabbits. However, the treated animals showed small but significant increases in rates of gain for live and empty body weight compared with control does. Treated animals also had significantly more nitrogen (P < 0·001) and less energy (P < 0·05) per unit empty body weight than controls. Although the proportion of total nitrogen retention was 0·19 greater (P < 0·001) in treated does, total energy retention was only slightly less. Treated animals had approximately 40 g (200 g/kg) less fat and 50 g more protein (N × 6·25) than control does at the end of the trial.3. Increases in liver weight and clitoral size were observed in treated animals.

Thirty-two Friesian cows in early lactation were divided into four treatment groups to receive ad libitum a mixed diet consisting of silage (0·70) and grain-based concentrate (0·30). Fish meal was subsequently mixed into the diet at levels of 0, 40, 80 and 120 g/kg to provide crude protein concentration (g/kg dry matter) in the complete diets of 156, 181, 200 and 212 respectively. In the 2nd week after calving the yields of fat-corrected milk (FCM) were 28·5, 29·2, 32·0 and 34·9 kg/day for the four levels respectively; at this time, food intake was sufficient only to meet the calculated energy requirement for 15 kg FCM per day. Due to recurring problems with ketosis on the diet containing 120 g fish meal per kg, this treatment was terminated and the experiment continued for 15 weeks with the groups receiving 0, 40 and 80 g/kg fish meal supplements. During this time average yields of FCM were 23·5, 25·6 and 28-0 kg FCM per day respectively and energy intakes were calculated to be sufficient to meet the requirement for 18 kg FCM per day.It appeared possible to increase milk yield by stimulating fat mobilization through giving undegraded protein supplements to underfed cows in early lactation. However, when an excessive mobilization occurred with a high supplement, and when the animals were yielding 15 to 20 kg FCM more than their metabolizable energy intake was calculated to sustain, some cows became ketotic.

Forty-five Large White × Landrace gilts were given food to realize energy intakes recommended by the Agricultural Research Council (1981) to attain maternal weight gains in pregnancy of either 40, 20 or 10 kg using a diet containing 125 g crude protein and 12·5 MJ digestible energy (DE) per kg over three parities. During a 3-week lactation period all animals were given a standard level of feeding. Maternal weight gains in pregnancy were much greater than those anticipated, for all treatments during each parity. The relationship between the actual and the predicted weight gains (kg) was the same for all three parities, actual AW = 22·62 + 0·71 predicted AW (R = 0·69). There was a large range of weight gains within treatments which was related to backfat thickness (P2 measurement (mm)) at conception in the second and third pregnancies, AW = 10·52 + 0·62 P2 measurement (R = 0·63) and to the change in P2 measurement, AW = 38·37 + 1·68 AP2 (R = 0·38) in the first pregnancy. The daily gain per MJ DE intake decreased wth parity and with decreasing energy intake. Numbers of piglets born and weaned were similar for all treatments; birth weights were also similar but there was an unexplained significant difference in piglet weaning weight in parity 2. There were no significant differences among treatments for either the total number or weights of piglets produced over the three parities.

A group of 16 Romney wether sheep fitted with rumen and abomasal cannulae and aged 11 to 12 months was allocated to either high or low crude protein (CP) pelleted diets (220 (HP) and 120 (LP) g CP per kg) to give four daily intakes of dry matter (356, 711, 1067 and 1422 g) within each diet, giving two sheep per treatment. Diets were given hourly for 40 days during which time growth rates, plasma concentrations of insulin (I) and growth hormone (GH) were determined, a glucose tolerance test was performed and relative rates of fatty acid (FA) synthesis were determined.Live-weight changes ranged from –46 to 215 g/day and wool growth ranged from 86 to 210 mg per 100 cm2daily.Plasma GH concentrations were significantly higher (P< 0·001) in sheep given LP diets (21·2 (s.e. 4·2) μg/1) than in those given HP diets (10·1 (s.e. 1·8) μg/1) and negatively correlated with both energy (E) (r= –0·62;P< 0·01) and nitrogen (N) (r= –0·63;P< 0·01) intakes which proportionately accounted for 0·47 of the variance in plasma GH concentration (P< 0·01). Plasma I concentrations were higher (P< 0·05) in sheep given HP diets (2·77 (s.e. 0·34) μg/1) than in sheep given LP diets (1·86 (s.e. 0·23) μg/1). Intakes of E and N proportionately accounted for 0·38 of variance in I concentration which was primarily determined by N intake.After intravenous infusion of glucose (150 mg/min) for 30 min, significant differences in the rate at which plasma glucose and I concentrations declined to pre-infusion levels were evident with different daily intakes of the pelleted diets.Synthesis of FA in adipose tissue was on average 1·7 times more rapid in sheep given HP than in sheep given LP diets (P< 0·05) and increased approximately three-fold with increasing intake. Partial correlations showed differences in E and N intakes were able to account for 0·73 (P< 0·01) of the variance in FA synthesis rates, with N intake having a greater influence than E intake (partial correlations:r= 0·53;P< 0·05 andr= 0·35;P> 0·05 respectively).

In three experiments the effects of giving Hereford × Friesian cows 61 to 64 MJ/day of metabolizable energy in the last 8 weeks of pregnancy, followed by either 49 to 56 (L) or 85 to 100 (H) MJ/day for the first 8 weeks of lactation, were determined. A further comparison was made in experiment 3, in which energy intakes were restricted to 46 and 64 MJ/day (M) in the two periods respectively. The L and M groups had a similar average weight loss of approximately 55 kg over winter whereas the H groups maintained their weight. The L and M treatments had a negligible effect on milk production at 3 weeks post calving but they caused a significant depression at 6 weeks in experiments 2 and 3. Milk energy and protein concentrations were reduced in all three experiments. Calf growth was similar on both treatments in experiment 1 but was 9 to 13% lower in experiments 2 and 3 for the L and M groups compared with the H group. Reproductive performance was not significantly affected. There was a substantial increase in milk production for all groups on turnout to grazing. This was greater for the L and M groups so that their summer milk production was almost equal to that of the H group. Cows from L and M groups gained more weight at pasture. By the end of the trials cows and calves from all treatments had similar weights except in experiment 3, when cows from the L and M treatments were still lighter than those from the H treatment.

SUMMARYThree diets were given separately, each at four levels of digestible energy (DE) intake, to gilts, castrates and boars growing from 21 to 92 kg live weight. The energy levels were those suggested by the Agricultural Research Council, compared with a 5% increase or 10% or 20% decreases in daily allowance. One diet (ME 18) had 3·0 Meal DE/kg and 18·2% crude protein; the other two (HE 16 and HE 19) had 3·26 Meal DE/kg and 16·1% or 19·3% crude protein.They were given unchanged throughout the experiment. Responses to change in daily DE intake were not affected by sex or diet, except in shoulder fat thickness. Feed eaten per kg gain did not vary by more than 4% over the intake levels investigated, and no difference was significant. On average, each reduction in daily intake below the ARC+5% allowance led to an increase of 1·2 percentage units of carcass lean and a decrease of 1·3 percentage units of carcass fat.In comparison with HE 16, the higher protein diet HE 19 gave improved feed conversion efficiency and growth rate, particularly in gilts. It did not cause significant changes in carcass measurements. In comparison with ME 18, HE 19 gave more efficient conversion of DE to weight gain, and faster growth.Boars required less feed per kg gain and had faster growth rates and leaner carcasses than gilts, which were superior to castrates. There was a high incidence of unpleasant odour in fat from boars, but some was also detected in that from gilts and castrates.

SUMMARYSixty Scottish Blackface ewes were used in a 2 × 2 factorial experiment in which two levels of metabolizable energy (ME) were given during the final 6 weeks of pregnancy. In two treatments 1600 and 2000 kcal M E were given daily over the total period while in the remaining treatments daily ME intakes were 1200 and 1600 kcal ME during the first 3 weeks of the feeding period and 2000 and 2400 kcal ME during the last 3 weeks. Digestible crude protein (DCP) intakes were constant at approximately 30 g per head daily in the constant energy treatments and 15 and 45 g per head daily in the first and second periods respectively for the low-high energy treatments.Energy intake had no statistically significant effect on lamb birth weight nor on ewe net body-weight change (change from the start of the experimental feeding period to immediately post partum). Ewes on low-high energy intakes had a significantly lower net body-weight loss than did ewes on constant energy intakes. Pattern of feeding had no significant effect on lamb birth weights. Negative nitrogen balances were found during the first feeding period where the daily DCP intake was approximately 15 g per head.

1. The voluntary feed intakes of pigs fed on diets having calculated digestible energy contents of 2,970, 3,356, 3,630 and 3,910 kcal/kg. dry matter were measured over four periods from 38 to 105 kg. live-weight.2. The pigs achieved similar daily digestible energy intakes regardless of the digestible energy content of the diet.3. When housed in metabolism crates pigs ate less than when housed in holding pens and the difference was greater than would be expected solely from the reduced exercise of the pigs in crates.4. Daily digestible energy intake was 575 kcal/kg. live-weight 0.675 when the pigs were in holding pens. The daily digestible energy intake of pigs in metabolism crates increased less with live-weight.5. The use of metabolism crates to obtain digestibility coefficients and values for nitrogen retention to be applied to animals housed under other conditions is discussed in relation to the differences found in apparent digestibility coefficients, feed intake and growth rates between pigs in crates and in holding pens.

SUMMARYAllowances of about 1·4M, 1·8M, 2·2M, 2·6M, 3·OM, and 3·4M (M = feed required for maintenance) were compared for pigs growing over the live-weight ranges 20·40, 40·60, 60·80, and 80·100 kg, with feed conversion efficiency (FCE) as the main response criterion.Response to increased digestible energy (DE) allowance was curvilinear; FCE improved rapidly up to 2·2M-2·6M, and changed much less with intakes above 2·6M. It is concluded that optimum FCE occurs at about 2·7M for pigs of 30 kg and at about 3·OM for pigs of 50, 70 and 90 kg.Allowances of dietary DE suggested by the Agricultural Research Council correspond to 2·56M, 2·95M, 3·04M and 3·08M for pigs of 30, 50, 70 and 90 kg live weight, respectively. It appears that these are near to the optima in promoting the best FCE.Changes of −25%, −15%, −5%, +5% and +15% in daily intake around the optimum levels caused FCE to deteriorate by averages of about 13%, 4·5%

SUMMARYFour levels of a proprietary concentrate (0, 100, 200 and 400 g/day) were offered to Welsh Mountain ewe lambs receiving hay or straw ad libitum for 14 weeks. The apparent digestibility of the energy and nitrogen in the various diets was determined in a concurrent digestibility trial.The voluntary intakes of the straw and hay dry matter when given alone were 242 and 451 g/day respectively (28·4 and 49·2 g/kg W0·73 per day). Straw intake increased with an increase in concentrate feeding up to a level of 25% concentrate in the total dry matter and then declined. Hay intake declined linearly with increasing concentrate level (3 g/day decline per unit increase in the percentage of concentrate). In each case the total intake of dry matter and digestible energy increased with an increase in concentrate level.There was a positive within-treatment relationship between initial live weight and voluntary intake, an additional 0·019 Meal ME/day being consumed per kg increase in live weight. Within treatment groups lambs consuming relatively more food also made relatively higher weight gains. Estimates based on published standards of the metabolizable energy intakes required to produce the live weight changes observed on each treatment were considerably higher than the intakes recorded in the trial.