Data for individually recorded silage dry-matter intake (SDMI), concentrate dry-matter intake (CDMI), live weight, milk yield and milk composition of lactating dairy cows offered silage ad libitum and concentrates on a flat-rate basis, together with data for silage composition from experiments conducted at four sites, were used to obtain simple and multiple regressions of SDMI on other variables.

Simple regressions showed that the most important variables affecting SDMI were, in order of importance: silage ammonia nitrogen, fat yield, CDMI, silage digestible organic matter concentration (DOMD) and live weight. The best multiple regression for the mean SDMI over weeks 4 to 13 of lactation accounted for proportionately 0·649 of the variation. Examination of week by week data for weeks 3 to 20 of lactation showed that two models for early and mid lactation were required to give a reasonable pattern of residual variances. These models accounted for 0·627 and 0·581 of the variation respectively. It was necessary to fit time effects explicitly in early lactation. Live weight was best represented by fitting post-calving live weight and deviations from post-calving live weight separately. A number of models requiring fewer input variables were also obtained to allow for use in situations where the full range of measurements is not made.

The new models were tested using independent data from three sites. They performed better than a number of previously published models but the best model still gave a prediction error of proportionately 0·17 about the mean actual silage intake in early lactation and 015 in late lactation.

The results suggest that there is little to be gained from further refinement of the functional form of the models and that the construction of a number of models for specific food and management situations is preferable to the use of global models.

Nucleus breeding schemes for dairy cattle give opportunities for selection on characteristics other than milk production, such as food intake or efficiency, and for the application of reproductive technologies such as embryo transfer. The emphasis in such schemes involving embryo transfer will be on early lactation measurements of production and food intake, to minimize generation intervals. The aim of this study was to examine the value of early lactation measurements of food intake and other characteristics in predicting longer-term food intake. Intakes of a complete diet, offered ad libitum, were available for 101 heifers up to week 38 of lactation, from the Edinburgh School of Agriculture's Langhill herd. Partial correlations between weekly dry-matter (DM) or metabolizable energy (ME) intakes in early lactation and cumulated intakes to week 38 of lactation, after fitting year and month of calving as fixed effects, and proportion of Holstein blood as a covariate, ranged from 0·27 for week 1, to 0·70 for week 12. Cumulated ME intakes, up to week 38, were regressed on shorter measures of ME intake, together with fat plus protein yield in weeks 1 to 10 of lactation. Other independent variables, such as point estimates of, or changes in, live weight, condition score and backfat depth did not further increase the precision of prediction. The means and standard deviations for milk yield, DM intake and ME intake up to week 38 of lactation were 5877 (s.d. 1087) kg, 4070 (s.d. 400) kg and 51579 (s.d. 4614) MJ respectively. For a fixed duration of intake recording, measurements taken later in lactation gave the most precise prediction of 38-week ME intake (e.g. residual s.d.s from models including 4-week cumulated ME intakes in weeks 1 to 4, 3 to 6 and 5 to 8 of lactation were 2865, 2636 and 2501 MJ respectively, with R2 values of 0·62, 0·67 and 0·71). Shorter periods of intake recording started in week 5 of lactation gave slightly more precise prediction than longer periods of recording started in weeks 1 to 4 (e.g. residual s.d.s from models including cumulative ME intakes in weeks 1 to 10, 3 to 10 and 5 to 10 were 2391, 2298 and 2277 respectively, with R2 values of 0·69, 0·75 and 0·76). These results have implications for the cost: benefit of food intake recording in breeding schemes.

Records on milk yield, fat plus protein yield, food intake, food efficiency, calving live weight and mean live weight, up to 26 and 38 weeks of lactation, were obtained from dairy cows, fed ad libitum, in the Edinburgh School of Agriculture's Langhill herd. The data were divided into first and later lactations and restricted maximum likelihood analyses carried out on heifer, cow and pooled data, fitting an animal model, with repeat lactations as an additional random effect. Univariate analyses were done after canonical transformation of heifer data and approximate canonical transformation of cow and pooled data. Heritability estimates for food efficiency and food intake, from pooled data, were 0·13 (s.e. 0·09) and 0·37 (s.e. 0·11) for 26-week and 0·13 (s.e. 0·12) and 0·52 (s.e. 0·14) for 38-week lactation periods, respectively. Over the same periods, estimates for milk yield were 0·20 (s.e. 0·08) and 0·20 (s.e. 0·11), respectively. Estimates from the analyses of cow and heifer data separately were higher, as were their standard errors. Genetic correlations between milk production traits and efficiency, from the pooled data analysis, ranged from 0·44 to 0·61 and those between milk production traits and food intake from 0·32 to 0·74. Genetic correlations between live-weight traits and efficiency ranged from −0·81 to −;0·99, and those between food intake and live-weight traits from 0·28 to 0·46. The results indicate that when selection is on yield, the correlated responses in efficiency may be smaller under ad libitum feeding, compared with published values where cows were given food according to yield. Including live weight in the selection criterion may give higher responses in efficiency compared with selection on yield alone. In MOET nucleus schemes it may be worthwhile to include food intake or efficiency directly in the selection criteria.

Records on fat plus protein yield, food intake and food efficiency up to 26 and 38 weeks of lactation, were obtained from dairy cows fed ad libitum in the Edinburgh School of Agriculture's Langhill herd. After discarding the first 2 weeks data, the records were divided into successive 6-week periods. Restricted maximum likelihood analyses were carried out on each period for each trait, fitting an animal model, with repeat lactations as an additional random effect. Univariate analyses were done after approximate canonical transformation of the data. Heritability estimates for 6-week fat plus protein yield, food intake and efficiency, from the 38-week lactation data, ranged from 0·08 (s.e. 0·10) to 0·17 (s.e. 0·12), 0·15 (s.e. 0·09) to 0·49 (s.e. 0·15) and 0·08 (s.e. 0·14) to 0·25 (s.e. 0·11), respectively. Generally, lower heritabilities were obtained for earlier part measures of fat plus protein yield and efficiency and for later part measures of food intake. Genetic correlations between part measures and ‘total’ lactation fat plus protein yield, food intake, and efficiency ranged from 0·82 to 100, 0·85 to 0·98, and 0·60 to 1·00, respectively. Corresponding phenotypic correlations ranged from 0·76 to 0·94, 0·68 to 0·87, and 0·73 to 0·89, respectively. The correlations were lowest for the first 6-week period then gradually increased up to a maximum in the third or fourth periods and declined thereafter. The results indicate that selection on a part measure of food intake or efficiency, taken between 15 to 20 weeks of lactation, will be equally effective in improving intake and efficiency compared with selection on total lactation measures. Other 6-week measures taken between weeks 9 to 14 and 21 to 26 will also give good prediction of total lactation intake and efficiency.

The mineral balance of male calves given neutralized (with HC1) and unneutralized 35 g NaOH per kg treated wheat straw (WS), was determined in a digestibility trial in which WS was offered at inclusion levels of 300, 500 and 700 g/kg diet. The ratio of apparently retained sodium (Na) and potassium (K) increased with increasing proportion of straw in the diet and was lower on neutralized straw diets.

The effect of supplementation with 3 and 6 g K per kg diet dry matter in a diet comprising approximately 500 g/kg of 35 g NaOH per kg treated WS, on performance, mineral status and acidbase balance was examined in a growth trial with 56 Israeli-Friesian male calves. The animals on the untreated WS diet had significantly (P < 0·05) less fat in the large depots and lower fat trim of carcass than did animals on the treated WS diets. No other differences in performance were significant. Ammonia concentration in rumen liquor and urea in blood were lower in the animals given alkali-treated WS. The concentrations of Na, K and chlorine in blood serum of the experimental animals were not affected by the treatment. The data on Na, K and magnesium (Mg) in muscle show depletion of Na and K and a trend towards a decrease in Mg concentration. K supplementation reduced the extent of depletion of Na and K. In bone, only Na was affected by the feeding of alkali-treated WS, the pattern being the same as in the muscle. The blood acid-base balance of the experimental animals was not significantly affected by treatments. The values of pH, actual bicarbonate and pCO2 of the animals given 35 g/kg alkali-treated WS indicate mild alkalosis in those animals. This alkalotic state did not affect performance. It appears that there is no Na loading problem which might interfere with growth.

Three types of straw were used, a spring barley (variety Corgi) untreated (UC), ammonia-treated Corgi (AC) and an ammonia-treated winter wheat (variety Longbow) (AW). Each straw was included in a complete diet containing either 350 (L), 450 (M) or 550 (H) g/kg straw. The other principal ingredients were rolled barley, molassed sugar-beet pulp and fish meal. Hereford cross steers approximately 16 months old and weighing 350 kg live weight were given the diets ad libitum in both a main trial lasting 80 days, to assess intakes, live-weight gains and food efficiency, and in a subsidiary trial to measure in vivo apparent digestibility.

The live-weight gains during 80 days for steers given the UC diet at L, M and H inclusion were 117, 102 and 0·70 kg/day respectively. The respective live-weight gains for AC were 1·32, 1·27 and 1 02 kg/day and for AW 1 ·26, 1 ·20 and 0·95 kg/day.

While experimental comparisons were terminated at 80 days when the first steers were slaughtered, all except five with the lowest growth rate reached the target fat class for slaughter before 6 months on the diets. While differences in intake and performance between steers given the straws closely reflected differences in degradation characteristics determined by in sacco measurements, the increase in in vivo apparent digestibility between untreated (0·510) and treated (0·545) was small. It is concluded that a large proportion of high quality or treated straw can be incorporated and utilized in diets for finishing cattle.

Two experiments have been carried out to examine the effects of the level of protein supplementation given with grass silage-based diets on the performance and carcass composition of bulls, and to compare diets based on silage and dried forage. The five treatments used consisted of grass silage offered ad libitum and supplemented with 2·5 kg dry matter (DM) of barley-based concentrates containing (1) zero (2) 200 (3) 400 and (4) 600 g soya-bean meal per kg and (5) artificially dried grass and hay supplemented with 3·2 kg concentrate DM. The silages used in both experiments were well preserved, containing on average 200 g DM per kg; 140 g crude protein (CP) per kg DM; 63 g ammonia-nitrogen per kg total N and 731 g digestible organic matter per kg DM. The bulls were of late-maturing breed type and were initially 12 months old and 412 and 405 kg live weight in experiments 1 and 2 respectively. For treatments 1, 2, 4 and 5 in experiment 1 respectively (treatment 3 was not used) total DM intakes were 8·3, 8·3, 81 and 110 (s.e. 0·21) kg/day; CP intakes 1063, 1271, 1664 and 1539g/day; metabolizable energy intakes (MEI) 98, 99, 96 and 87 MJ/day; carcass weights 317, 316, 317 and 316 (s.e. 3·2) kg; carcass saleable meat concentrations 714, 712, 718 and 716 (s.e. 5·8) g/kg and carcass fat trims 73, 81, 73 and 68 (s.e. 3·9) g/kg. In experiment 2 for treatments 1 to 5 respectively total DM intakes were 8·3, 8·5, 8·3, 8·4 and 11·2 (s.e. 0·26) kg/day; CP intakes were 1090, 1329, 1504, 1720 and 1561 g/day; MEI 102, 106, 103, 103 and 94 MJ/day; carcass weights 318, 331, 330, 327 and 321 (s.e. 3·3) kg; carcass saleable meat concentrations 726, 721, 725, 721 and 732 (s.e. 60) g/kg and fat trims 71, 77, 78, 80 and 64 (s.e. 4·5) g/kg. It is concluded that protein supplementation of a silage-based diet did not affect performance or carcass fatness in experiment 1 or carcass fatness in experiment 2, but including 200 or 400 g soya-bean meal per kg concentrate increased performance in experiment 2. Animals given silage produced fatter carcasses than those given dried forage in experiment 2 but not in experiment 1.

Two divergent lines of sheep were produced by selection on an index of testis diameter adjusted for body weight at 6, 10 and 14 weeks of age. There were correlated changes in growth patterns, such that animals in the high and low lines were of a similar weight at birth, but thereafter, the low line became progressively heavier than the high line. After 11 years of selection there was a 7-kg difference between the mean body weight of females in the two lines at 1·5 years of age and a 12-kg difference at 2·5 years. There was little evidence of any accompanying changes in body shape or in carcass composition. High-line females of all reproductive ages had a significantly higher fertility. High-line lambs had a significantly lower mortality and, at the end of selection, had an estimated probability of survival to 210 days of 0·25, 013 and 003 higher than in lambs from the low line, in lambs from 1-, 2- and 3-year-old dams respectively. The estimated number of lambs alive at 210 days per ewe mated was 0·30, 0·38 and 0·34 higher in the high line for ewes of 1, 2 and 3 years of age, but low-line lambs were 3 kg heavier on average at 210 days. The combined impact of improved ewe performance and changes in growth patterns led to a predicted greater production efficiency in the high line. It was estimated that, after 11 years of selection on the index of weight adjusted testis diameter, 0·62, 0·71 and 0·74 kg of high-line ewe at 1, 2 and 3 years of age, respectively, would be needed to produce the same weight of lamb at 210 days as 1 kg of low-line ewe. Improved ewe performance had a much larger impact on the changes in comparative efficiency than changes in growth patterns, but the contribution of the latter increased with age of ewe. Further experimental verification of the line differences in reproduction and lamb survival and study of their causes are needed. Nevertheless, these results indicate the promise of using indices of body weight and testis size to increase the efficiency of lamb production.

Various types of constant-release melatonin implants were designed and administered to adult ewes during seasonal anoestrus. Implants were given between May and July in a series of four experiments. Treatment of ewes with melatonin implants resulted in advancement of the onset of oestrous activity. Melatonin treatment also resulted in improved reproductive performance, increased numbers of lambs born per ewe bred and caused more multiple births. Results from this study show, therefore, that constant-release melatonin implants administered during late spring or early summer advance the onset of the breeding season and improve reproductive performance in ewes.

Two experiments were conducted each using one batch of six Landrace littermate, entire male, pedigree pigs in a Latin-square change-over study of the effects of energy intake on nitrogen and energy metabolism over the range 33 to 88 kg live weight. One animal from each litter was slaughtered at 33 kg body weight to obtain initial body composition data. Five feeding levels (80, 100, 120, 140 and 160g/kg M0·63) were used during five consecutive metabolism trials each of 11-days duration, excreta being collected during the last 7 days. The pigs were housed in individual metabolism cages and the diets were offered in liquid form (approx. 300 g dry matter (DM) per kg) twice daily at 09.00 and 16.00 h. Heat production was measured for 1 day during each balance period in an open-circuit respiration chamber. The average daily gain, nitrogen retention, heat production and energy retention increased linearly (P < 0·001) with increasing metabolizable energy (ME) intake. The relationship between energy intake and protein deposition was linear up to levels above the normal ad libitum consumption of energy. Protein deposition potential of these high genetic potential pigs was at least 200 g/day, and tended to be constant between 35 and 85 kg live weight. From the combined results of experiments 1 and 2, the energy requirement for maintenance was 0·982 MJ ME per kg M0·63 per day and the decrease in protein deposition was approximately 6 g/MJ reduction in ME within the range of practical energy intakes.

Ground full-fat rapeseed (FFRS) and the resulting extracted oil (RSO), meal (RSM) and recombined RSO and RSM (ORSM) from a triple-low cultivar containing low levels of erucic acid, glucosinolates and tannins were evaluated. RSO, FFRS and ORSM were included into a basal diet to give levels of added oil of 40, 80 and 120g/kg. RSM was also incorporated into the basal diet at the same rates as in ORSM. The 12 experimental diets together with the basal diet were given to 13 gilts in a metabolism trial conducted over four time periods. A 10-day acclimatization in holding pens preceded a 5-day total collection of faeces and urine in metabolism crates. Rapeseed products, diets, faeces and urine were analysed for gross energy (GE) and all, except urine, for oil content measured by two methods (petroleum ether and acid hydrolysis prior to ether extraction). Apparent digestible energy (DE) and metabolizable energy (ME) of rapeseed products were determined by single-level assay and by regression. Oil DE was also derived indirectly as a product of apparent oil digestibility (AOD) and oil GE. Apparent nitrogen digestibility was estimated for diets and rapeseed products. The response of dietary DE, ME and AOD to rates of test material inclusion was linear (P < 0·001) in all cases except for ORSM and RSM the DE and ME of which, in addition, showed evidence of curvilinearity. Age of pig had no significant effect on dietary AOD and energy values. Linear regression techniques were better than single level assays (particularly at low rates of inclusion) in determining energy values and gave DE values of 42·4, 190, 14·6 and 25·8 MJ/kg dry matter for RSO, FFRS, RSM and ORSM respectively. Oil DE and AOD were not influenced by method of evaluation. The results of this study indicated improved energy values for FFRS and RSM of a triple-low cultivar over published data for high-glucosinolate varieties but not over data for double-low varieties. In addition it appears that AOD is the main factor determining dietary utilization of FFRS and would need to be considered in order to optimize the nutritive value of FFRS in diets for growing pigs.

Genotype × environment interaction for age at puberty was evaluated using gilts from the Nebraska Gene Pool population derived from lines selected randomly (RS; no. = 48) or for seven generations for decreased age at puberty (AP; no. = 73). Age at puberty was evaluated in two environments: boar exposure for 15 min daily (BE) or no boar exposure (NBE). Pigs were randomly assigned to treatment and mixed into groups of 20 in pasture lots. Oestrous detection was initiated when the oldest gilt in a pen was 125 days of age. Blood samples were taken weekly and assayed for progesterone. Gilts were considered to have expressed oestrus if they exhibited lordosis or had consecutive weekly blood samples with progesterone values above 6·4 × 109 mol/1 (2 μ, g/l). Gilts were removed from the pen upon confirmation of puberty or at 250 days of age. Two gilts failed to reach puberty by 250 days so this value was assigned as their age at puberty. Least-squares analyses of variance were used to analyse the data. A model including line, sire within line, farrowing group, treatment and line × treatment interaction was fitted to the dependent variables age at puberty and percentage cycling by 185 days. Line and treatment each affected age at puberty (P < 0·05) but did not interact. Least-square mean ages at puberty were 154 (s.e. 4·5), 164 (s.e. 4·7), 164 (s.e. 6·1) and 179 (s.e. 5·9) days for AP-BE, AP-NBE, RS-BE and RS-NBE, respectively. Treatment affected percentage of gilts cycling by 185 days (P < 0·05). Least-square percentages were 91 (s.e. 6·9), 76 (s.e. 71), 84 (s.e. 9·2) and 65 (s.e. 8·9) % for AP-BE, AP-NBE, RS-BE and RS-NBE, respectively. These results indicate that expression of response to selection for decreased age at puberty in the gilt is not dependent on stimuli from the boar.

A study of the determinants of inter- and intra-litter variation in muscle fibre number was carried out on five litters of Large White piglets. Fresh frozen, whole mid-belly sections of m. semitendinosus were stained to demonstrate acid-stable myosin adenosine triphosphatase activity. From these sections it was possible to identify which fibres had developed as primary and which as secondary fibres. Estimations of total muscle fibre number, total primary fibre number and ratio of secondary fibres to primary fibres were made for each animal. Results demonstrated that primary fibre number varied between litters (P<0·01) and was responsible for the variation in total muscle fibre number (P < 005) between litters since there was no significant variation in secondary: primary ratio. Within-litter differences in total fibre number could be attributed to both the secondary: primary ratio and primary fibre number, in almost equal contributions. However, when only the largest and smallest extremes of the litters were compared, variation in fibre number was due to the significant difference in the secondary: primary ratio (P<0·01). Taken as a whole, the results appear to show that primary fibre number is responsible for all the variation in muscle fibre number between litters, and also makes a significant contribution, with secondary: primary fibre ratio, to the variation present within a litter. The factors responsible for variations in primary and secondary fibre numbers are discussed.

An experiment was conducted to determine the effect of sucrose as an energy source on energy utilization and protein retention by growing pigs. Growing pigs (20 to 50 kg live weight) were restrictively fed (three times maintenance) either a control wheat-based diet (14 MJ digestible energy (DE) per kg), a sucrose-based diet (15 MJ DE per kg) or a wheat-based diet made i so-energetic with the sucrose diet by the addition of oil. Net energy (NE) content of the diet, energy utilization, protein and fat deposition were measured.

Both the sucrose- and the iso-energetic wheat-based diets improved energy utilization and increased NE retention. They also increased fat deposition (P < 0·05) but had no effect on protein deposition (P > 0·05) compared with the wheat-based control. Increased DE utilization in the sucrose-based diet appeared due to (i) lower dietary fibre, (ii) a better balance of amino acids, or possibly due to (iii) increased fat synthesis due to sucrose metabolism. The lack of effect of sucrose on protein deposition appeared due to either (i) an increased amino acid requirement as a result of the higher NE content of the diet or (ii) preferential use of sucrose for fat deposition.

The variation of protein fractions in the milk of indigenous Greek goats fCapra prisca) during the milking period was studied. Total nitrogen (TN), non-casein or soluble nitrogen (SN), rennet whey nitrogen (WN), non-protein nitrogen (NPN) were determined and from these analyses crude protein (CP), true protein (TP), casein (Cas) rennet casein or coagulable protein (Coag P) were calculated. The NPN component is lost during the cheese process whereas Cas and Coag P are important constituents of the cheese itself. The ratios NPNICP, CaslTP and Coag PITP throughout milking, were for the groups A and B 0·0646 and 0·0648 (s.e.d. = 0·00025), 0·846 and 0·845 (s.e.d. = 0·0141) and 0·916 and 0·904 (s.e.d. = 0·0112), respectively, suggesting a high level of suitability for conversion of milk into cheese.

Continuously grazed rye grassl clover swards with surface heights of 8 to 10 cm at 5 weeks before a synchronized mating and 7·5 cm at mating were grazed by 151 Greyface ewes stocked at 12 per ha until mating. The effects of two stocking rates (eight and 16 ewes per ha) for 6 weeks over the mating and post-mating period were then studied on live weight, body condition and reproductive peformance. Sward height fell more rapidly post mating when stocked at 16 ewes per ha than at eight ewes per ha, but remained above 3·5 cm until 4 weeks after first mating under both rates. Ewes stocked at 16 per ha became significantly lighter and leaner than ewes stocked at eight per ha. There was no significant effect of post-mating stocking rate on reproductive performance in terms of conception rate and lambing rate to first mating or lambing rate to all matings. Reproductive performance of Greyface ewes is therefore unlikely to be adversely affected by post-mating stocking rate on swards of 7 to 8 cm which do not fall below 3·5 to 4·0 cm until 3 to 4 weeks after mating.

Thirty-nine Charolais × (Hereford × Friesian) autumn-born calves, whose dams had been given either 92 or 63 MJ metabolizable energy per day during winter and subsequently grazed at two sward heights, either 4-8 (short) or 7·6 (tall) cm from 6 May until weaning on 3 July in a factorially designed experiment, were used to examine the effect of pre-weaning performance on post-weaning growth rates. Following weaning the calves grazed as one group for a period of 76 days. There was no effect of winter treatment on postweaning performance. From weaning until 76 days later there was a significant (P < 0·01) effect of pre-weaning sward height on live-weight gain (0·94 and 0·69 kg/day for the calves from the short and tall swards respectively), so that the 41 kg liveweight difference at weaning was reduced to 22 kg (P > 0·05) with compensatory growth occurring independently of the height of the sward grazed.

Fresh sperm motility declined from 79·2 (s.e. 0·9)% to 55·8 (s.e. 1·7)% while occurrence of normal acrosomes declined from 82·9 (s.e. 1·3)% to 71·3 (s.e. 1·2) % from the day of collection to 7 days after collection, and conception rate declined from 47·6% using 3-day-old semen to less than 30% from using 5· or 7-day-old semen. Neither the number of embryos nor embryo survival from pregnant sows were affected by the age of semen. Boar effects were evident but they did not interact with the effects of age of semen, indicating that semen quality after storage was proportional to initial semen quality.