Forty crossbred heifers, mated to one sire, that calved in a 20-day period were used to study the effect of varying time and level of post-partum nutrition on productivity. Heifers were individually fed for 90 days post partum beginning at parturition: (1) proportionately 1·3 National Research Council (NRC) 1984 recommendations for 45 days followed by 0·7 NRC for 45 days (130·70); (2) 1·0 NRC for 90 days (100·100); and (3) 0·7 NRC for 45 days followed by 1·3 NRC for 45 days (70·130). Milk production, growth and body condition were estimated periodically during the lactation. The 130·70 heifers maintained their weight during the first 45 days of lactation, while the 100·100 and the 70·130 heifers lost weight (−0·33 and 0·60 kg/day, respectively). During the second 45-day period, the 100·100 and 70·130 heifers gained weight (0·24 and 0·72 kg/day, respectively) while the 130·70 heifers lost weight (−0·39 kg/day). Visual condition scores paralleled weight changes during both phases of the feeding period. Milk production varied according to nutrient intake and treatment differences were greatest at 45 days post partum (8·1, 7·3 and 6·1 kg/day for 130·70, 100·100 and 70·130, respectively). Calf weight gains were unaffected by dam nutrition. Days to first oestrus, days to conception or services per conception were not significantly different (P > 0·05) among treatment groups. Based on this experiment, neither of the alternate feeding systems resulted in decreased performance when compared with feeding at a constant level. Therefore, it appears that latitude exists in the way heifers can be fed early in their first lactation, without adversely affecting production.

Results are reported of an experiment with 60 pigs (12 pigs/treatment) covering the growing period between 22 and 87·5 kg live weight in which the growth-stimulating properties of sodium salicylate were examined either as a single additive or with copper sulphate. The pigs were individually fed a wet diet ‘to appetite’ and the quality of the carcasses was assessed at slaughter.

No significant improvement in live-weight gain or feed: gain ratio was obtained when either 200 or 700 mg of sodium salicylate/kg was added to the diet. When 700 mg of salicylate was given together with 250 mg Cu/kg diet, the response in growth rate was significantly higher than that obtained from the addition of copper alone.

There was no significant treatment effect on carcass quality as assessed by linear measurements, nor on the dry matter, nitrogen or ash contents of the gluteus medius muscle.

A genetic algorithm (GA) was used to find optimal male and female age distributions in a natural mating system that maximizes cumulative response to mass selection over a 20-year time horizon for the case where inbreeding affects reproduction at 0·0 (F-0) and 0·1 (F-10) per 0·1 inbreeding coefficient. Twenty breeding female population sizes were considered ranging from 25 to 500 breeding females distributed across five age groups. Loss of response due to inbreeding effects on reproduction ranged from 19.4% and 15.5% in small breeding female populations to 2.5% and 5.2% in large breeding female populations when number of males was fixed (FX) or optimized (OP), respectively. OP resulted in an increase in response over FX ranging from 0·0 % to 69.3% for F-0 and 0·0 % to 77.6% for F-10. The potential loss of genetic gain that resulted from ignoring the inbreeding effects upon reproduction when they really existed ranged from 0·1 % to 44.6%. The potential loss of genetic gain that resulted from including inbreeding effects upon reproduction when they did not exist ranged from 0·1% to 3.9%. Optimal male and female age structures depended upon breeding female population size, the number of breeding males and inbreeding effects. Ignoring inbreeding effects upon reproduction may result in over estimation of response to selection. Use of a GA allowed accounting for complex relationships in the optimization.

Imported semen from 10 Italian Chianina bulls was used to inseminate beef and dairy cattle throughout England and Southern Scotland. A total of 2134 records of calving performance were subjected to least squares analyses. Dystocia score was significantly affected by county of birth, parity of dam, sire, type of birth, birth weight (P < 0·001), season of birth and sex of calf (P < 0·01). There were no significant effects of breed or size of cow. Serious dystocia was encountered in 3% of calvings, with the incidence for individual sires ranging from 1·7% to 6·7%. Arithmetic mean gestation length was 284·2 days and it was significantly affected by county, sire (P < 0·05), sex of calf (P < 0·01), and type of birth (P < 0·001). Arithmetic mean birth weight of the calves was 41·2 kg and this was significantly affected by all main effects studied except season of birth and type of herd.

H2A histone family, member Z (H2A.Z) is required for early mammalian development. In the present study, the 932 bp of full-length cDNA encoding a 128 amino-acid protein and the sequences of intron 2 to 4 of the porcine H2A histone family, member Z (pH2AFZ) gene were obtained. By comparative sequencing of pH2AFZ gene in Large White and Meishan pigs, a 4 bp deletion/insertion in intron 2 was detected and a PCR-Bsu15I-RFLP was established to detect this variation. In DIV (4th Dam line of Chinese lean-type new lines) pigs, the first-parity females with AA genotype had fewer piglets born alive (−2.64 and −1.83 piglets per litter) than those with AB (P < 0.01) and BB (P < 0.05) genotype. The additive allelic and dominance effect were estimated to be 0.92 (P < 0.05) and −0.87 piglets per litter (P < 0.01) for number of piglets born alive, respectively. This result suggests that the pH2AFZ gene might be a good candidate gene of litter-size trait and provides some marker information for marker-assisted selection.

In populations where generations overlap and initial genetic differences between age groups differ from steady-state values, genetic responses fluctuate in the early years of a selection programme. The degree of deviation of these selection responses from steady-state responses indicates the usefulness of estimates of economic returns calculated more simply using the steady-state value. Here these deviations and their effect on sums of discounted returns are first defined and the models derived then used in numerical analysis. Some problems of definition of these deviations are discussed.

The results showed that deviations from sums of discounted returns calculated using steady-state responses varied from about −1% when starting conditions were similar to steady-state conditions to more than 20% when initial genetic differences between age groups were taken as zero. Increases in discount rate increased the effect of the deviations from uniform response while the effect of changing age structure was unpredictable. As initial genetic differences between age groups increased, deviations were increasingly positive among selection methods which made better use of those differences.

A molassed sugar-beet product with added urea and dicalcium phosphate was evaluated as an energy and protein source for housed lactating ewes. Comparisons were made with a barley-vegetable protein and a barley-urea concentrate each formulated to supply approximately the same amount of crude protein. The overall performance of ewes and lambs given barley and vegetable protein was very significantly superior to that of ewes receiving the sugar-beet product. At 6 weeks after lambing the ewes given barley and vegetable protein had lost 57% (with singles) and 23% (with twins) less weight and their lambs had grown 28% (singles) and 48% (twins) more quickly than for ewes receiving the sugar-beet product. The intermediate performance of the ewes receiving barley and urea illustrated that the difference between the barley-vegetable protein concentrate and the sugar-beet product was both an energy and a protein effect.

The paper reports the results of experiments to study the effects of different levels of dietary protein on the performance and carcass quality of bacon pigs fed on a high-energy diet: (a) to make similar rates of live-weight gain on all treatments, (b) to make similar rates of live-weight gain but with the level of protein on some treatments being reduced at 130 lb., (c) to allow ad libitum feed intake on all treatments, (d) to obtain two distinct

patterns of growth (fast-fast and slow-fast) on each of two levels of dietary protein.

In the comparison of the two contrasting patterns of growth there was no significant interaction between rate of gain during the period 40–125 lb. live-weight and level of dietary protein. Differences in carcass density and linear measurements were significant and the results suggest that irrespective of growth pattern there was a carcass response to level of protein.

Where diets of different protein content were given ad libitum or to obtain a uniform growth pattern on all treatments, growth rates were generally good, with little difference in feed intake between the treatments within each experiment; variations in level of protein therefore had little effect on growth rate. In some of the comparisons, significant carcass differences were found in terms of density, dissection data and linear measurements; in others only the density differences were significant.

The results suggest that with each of the feeding systems a level of about 17% crude protein, associated with 12% fish meal, is more likely than lower levels to give lean bacon carcasses. In the one experiment in which the protein level was reduced at 130 lb. live-weight there was no marked effect on carcass composition.

A dynamic simulation model was used to predict the long-term effects of published heat stress-associated fluctuations in conception rate (CR) and milk production (MP) on the monthly MP pattern in Israel. The model results showed that the pattern of seasonal decline and rise in CR, and hence conception occurrences, produces a similar pattern of MP. This pattern closely resembles that of actual MP in Israel in 1987 and in 1988. On the other hand, seasonal correction factors for MP have no marked effect on the shape of the MP curve. These results show that in order to stabilize MP throughout the year, the prevention of seasonal (summer) decline in CR would be more effective than direct efforts to prevent seasonal MP decline.

The efficacy of feed additives in enhancing the performance of growing pigs, together with the effect of different protein levels (18 v. 16% from 13 to 18 kg body weight and 16 v. 14% from 18 to 39 kg body-weight), were evaluated in three experiments with 412 pigs. In Experiment 1, from 13 to 39 kg body weight, pigs receiving 55 p.p.m. carbadox (C) produced a greater (P<0·05) average daily live-weight gain than did the non-medicated (NM) pigs and those receiving 275 p.p.m. chlortetracycline-sulphamethazine-penicillin (ASP) with a similar but non-significant (P>0·05) trend n i daily feed intake and gain/feed ratio. The ASP pigs also produced a greater (P<0·05) weight gain than the NM pigs. The higher dietary protein level sequence produced a greater (JP<0·05) weight gain and gain/feed ratio.

In Experiment 2, from 16 to 39 kg body weight, NM control pigs achieved high weight gains, and all the feed additive treatments studied [C+106 p.p.m. of the worming agent pyrantel tartrate (C+P); ASP+8 mg of the worming agent levamisole-HCl per kg body weight fed once on day 7 of the experiment (ASP+L); and 113 p.p.m. tylosin+13 p.p.m. of the worming agent hygromycin B] were similar to the NM controls in daily feed intake, weight gain and gain/feed ratio. However, in Experiment 3, the C+P and ASP+L treatments resulted in a greater (P<0·05) weight gain with a trend toward greater daily feed intake than did the NM control treatment from 17 to 35 kg. The weight gain of the ASP+L pigs was also greater (P<0·05) than that of 165 p.p.m. oxytetracycline and NM pigs from 35 to 57 kg. From 57 to 96 kg all the pigs received the same NM control diet and their weight gains were similar. The gain/feed ratio was similar among the treatments within each of the weight periods in Experiment 3. Pigs slaughtered at the beginning and at various stages during Experiments 2 and 3 were free of internal parasites and migration damage.

One hundred and twenty-five boars were given diets containing five levels of methionine: 1·5, 1·7, 1·9, 2·1 and 2·3 g methionine per kg diet, from 21 to 49 days of age. The mean weight gain of the pigs given the diet containing 1·5 g methionine per kg was 71 g/day and this increased linearly to 346 g/day for the pigs given the diets containing 2·3 g methionine per kg.

From 49 to 97 days of age all pigs were given a commercial pig grower diet containing 160 g protein per kg. Live-weight gains over this period increased linearly from 477 to 689 g/day with increasing methionine content of the starter diets. There was no compensatory weight gain.

The growth rate and body composition of lambs depend on their rate of feed intake and the composition of the feed given. The purpose of the experiment described here was to test predictions of the growth and composition of lambs given feeds of two protein contents at three levels of feeding.

73 Scottish Blackface wethers were abruptly weaned at 49 days of age and an average live weight (LW) of 18 (sd 2.2) kg. Six, chosen to cover the range in initial liveweight, were killed and those remaining were put into individual pens and fed in one of six ways. Two feeds with 140g CP/kg fresh weight (FW), called LP, and 220 g CP/kg FW, called HP, were used. They were formulated using barley, maize and soyabean meal, and hay at 150g/kg FW, and were calculated to yield 11.8 MJ ME/kg FW. Each feed was given ad libitum (AL) and at daily rates of 1.2 or 0.8 kg FW. The numbers of sheepstarted were: ALHP, n = 8; ALLP, n = 8; 1.2 HP, n = 12, 1.2 LP, n = 13, 0.8 HP, n = 14, 0.8 LP, n = 12. Sheep were killed from each treatment at 5 kg LW intervals from 25 to 50 kg. After slaughter the weights of gut-fill and organs were taken and the carcase physically dissected into lean, bone and fat. The chemical composition - dry matter and the ash, N, lipid and gross energy contents of the dry matter - of the whole empty body, excluding wool, was measured. Wool weights were determined. The intakes and weights of each sheep were measured twice weekly.

The effects on reproductive performance offeeding supplements to ewes grazing predominantly perennial ryegrass swards before and during mating which started in mid November were examined with approximately 200 Scottish Blackface ewes in each of three experiments. In two experiments, ewes were offered no supplement (C), 600 g barley (S(B)) or 500 g barley + 100 g white-fish meal (S(B + FM)) per head per day from 3 weeks before until 3 weeks after the start of the mating period. Ewes in experiment 1 were grazed on different areas and in experiment 2 were rotated around these areas on a 12-day cycle. Initial herbage allowance in both experiments was 40 to 50 kg organic matter per ewe and stocking rates ranged from 10 to 14 ewes per ha. Ewes in experiment 3 were rotated around the same areas on a 10-day cycle at a stocking rate of 18 ewes per ha and offered either no supplement (C) or 600 g barley (S(B)) per head per day when live weight started to decrease or sward height declined to 3·5 cm, whichever occurred first. Both of these occurred shortly after the start of mating. Sward height fell from mid October and throughout November and was between 3 and 4 cm at the start of mating in all experiments.

There were no differences in response to the (S(B)) and (S(B + FM)) treatments in live weight, body condition or reproductive performance in experiments 1 and 2 and the effects of supplementation were examined with these treatments pooled.

Supplementation had very little effect on live weight, resulting in higher values only in experiment 1 but did produce higher body condition in all experiments. This occurred by the start of mating in experiment 1 but not until mid December in experiment 3 and early January in experiment 2.

A significant increase in the number of lambs born per ewe lambing was obtained from supplementation when the data from experiments 1 and 2 were combined (P < 0·05). There was no response in reproductive performance to supplementation in experiment 3. It was concluded that supplementation in the pre-mating period can improve reproductive performance when sward height declines from 6 to 3·5 cm but that supplementation in the post-mating period may not, even when the sward height is below 3·5 cm.

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.

Random regression (RR) analysis has been recommended to estimate the genetic parameters of longitudinal data. The objective of this study was to evaluate the growth of turkeys using RR models. Data were collected from 957 turkeys and included 15 478 individual body weight recorded during the first week of life and between weeks 2 and 32 by 2-week intervals. To take into account the repeated measurements of weight for each animal, a specific overall growth curve was modelled using a cubic smoothing spline. Animal deviation to this curve was also modelled using an RR function. All data were analysed with the ASReml package. The results showed an increase in heritability estimates over the trajectory and peaked at 0.60 around 20 to 32 weeks of age. Genetic correlations showed that turkeys could be selected at earlier time points, at 12 weeks of age, in order to increase the growth rate. In general, genetic correlation estimates were higher among adjacent ages, decreasing markedly with the increase of distance between ages. Negative genetic correlations were observed between ages.

In two experiments 480 and 360 pigs were housed in groups of 10 and given diets containing different proportions of cassava between 35 and 87 kg live weight. The cassava contained 672, 34, 57 and 39 g/kg air dry matter of starch, crude fibre, total ash and insoluble ash respectively. The diets in the first experiment contained 0, 238, 475 or 713 kg cassava per t. In the second experiment the different levels of dietary cassava (0, 150, 300 or 450 kg cassava per t) were combined in a factorial design with different levels of tallow (0, 50 or 100 kg tallow per t). The pigs were given quantities of food calculated to give isoenergy intakes on the assumption that air-dry cassava contained 14·2 MJ digestible energy (DE) per kg. The feeding scale increased with time to give a maximum daily allowance of DE of 31·8 MJ per pig. Relative to each MJ of DE the calculated levels of lysine and of methionine plus cystine in the diets were 0·64 g and 0·39 g respectively.

In both experiments, increasing levels of cassava resulted in significant reductions in growth rate but had no effect on the conversion of food to live weight or on carcass weight. In both experiments, the diets with the highest inclusions of cassava produced pigs with the thickest backfat. The effect was not significant in the second experiment but in the first experiment the differences were significant between diets with the highest and intermediate levels of cassava. There was a significant interaction between cassava and tallow on growth rate with the depression due to high levels of cassava being reduced when 100 kg tallow per t was included in the diet.

The results of these growth experiments suggested that cassava of the type used here was of similar value to barley on an energy basis when used in diets based on barley and soya bean meals.

A molassed sugar beet product with 32% crude protein and containing added urea (8%), dicalcium phosphate, trace elements and vitamins was evaluated in two experiments as a protein source for intensively-fed 100 kg British Friesian steers. Comparison was made with an equal amount of crude protein supplied as a mixture of decorticated groundnut and cottonseed meals.

Both forms of supplementation equally and significantly increased live-weight gains and improved food conversion ratios compared with those recorded when the basal diet consisted of barley with no protein supplement.

The performance of Hereford × Friesian calves sired by Hereford bulls selected for either lean growth rate (LGR) or lean food conversion ratio (LFCR), or by unselected Hereford bulls, was evaluated on 327 calves on three farms over 2 years. Animals started test at 130 days of age on average and remained on test for approximately 300 days, whereupon all animals were slaughtered and carcass dissections were undertaken. Individual food intake was measured on tioo of the farms (189 animals), but only intake per pen of animals was measured on the third farm and individual food intake had to be estimated. LGR, LFCR and other traits describing performance were calculated from the growth, food intake and carcass composition data.

If no breed or environment interactions exist it is expected that proportionately 0-5 of the genetic differences between selected and control line bulls would be transmitted to their offspring. For the LGR and LFCR line bulls these values were 0·38 and 0·44, respectively, however the LGR value had a much smaller confidence interval. Genetic correlations derived from regressing breeding values predicted from offspring performance on breeding values predicted from the bulk's own performance in the selection experiment were 0·62 (s.e. 0·28) and 0·96 (s.e. 0·28) for LGR and LFCR, respectively. Heritabilities were: live-weight gain on test, 0·27; daily gain, 0·48; food intake, 0·06; food conversion ratio, 0·46; predicted carcass lean content, 0·10; killing-out proportion, 0·10; LGR, 0·36 and LFCR, 0·48.

Data from 726 male and 765 female pigs (364 litters) from 28 threebreed crosses obtained from mating Poland China boars to gilts and sows from different two-breed-crosses were analysed. The 28 two-breed-crosses were obtained from mating Yorkshire (Y), Landrace (Ld), Lacombe (Lc), Hampshire (H), Duroc (D), Berkshire (B) and Large Black (LB) sows to Ld, Lc, H, D, B, LB and Tamworth (T) boars in an incomplete diallel mating design. The traits studied were age at slaughter (72 kg carcass weight), carcass backfat measurement and an index combining both traits.

The youngest pigs to reach slaughter weight were those from LB x D sows (191·3 days) while the oldest were from T x D sows (211·6 days). The pigs with the least depth of backfat were those involving the Hampshire breed (mean 7·28 cm) while those involving the Large Black had the thickest backfat (mean 7·81 cm). In descending order, the five highest ranking crosses based on the index were those from H x Ld, H x Lc, LB x D, Lc x Ld and H x Y sows.

An initial experiment was conducted to investigate the variability of selected metabolites in the plasma from guanacos. A second experiment directly compared plasma biochemical values for guanacos with those for sheep. During the first experiment, jugular blood samples were collected from five mature castrated guanacos using an embedded experimental design. Weekly blood samples were collected at the same time (09.00 h) on the same day each week for 7 weeks. Daily blood samples were collected at the same time each day (09.00 h) during week 5. On day 2 of week 5, blood samples were collected every 3 h from 09.00 h for a 24-h period. No evidence of a cyclical pattern of plasma parameters was observed on a weekly, daily or 3-h basis. During the second experiment, the metabolic profiles of 11 mature castrated guanacos and 11 mature barren ewes (Merino × Welsh Mountain) were compared. Significant differences in plasma concentrations of all metabolites except urea-nitrogen (guanacos -15·42 mmolll, sheep - 15·60 (s.e.d. 1·506) mmolll) were found with values for guanacos v. sheep as follows: glucose (7·63 v. 3·63 (s.e.d. 0·268) mmolll); acetate (0·26 v. 0·48 (s.e.d. 0·035) mmol/l); β hydroxybutyrate (0·06 v. 0·50 (s.e.d. 0·019) mmol/l); albumin (33·4 v. 29·5 (s.e.d. 0·93) g/l); and total protein (53·8 v. 65·6 (s.e.d. 2·12) g/l); (P < 0·001 for all previous variables); non-esterified fatty acids (0·48 v. 0·29 (s.e.d. 0·048) meq per 1; P < 0·01) and a-amino N (2·44 v. 2·66 (s.e.d. 0·088) mmolll; P < 0·05). This study indicates that the reference plasma metabolite concentrations of sheep are not suitable alternatives for use for nutritional or veterinary purposes with guanacos, but those of llamas or alpacas are. The results also suggest that energy capture and transport in camelids may be markedly different from that in conventional ruminants.