A total of 166 crossbred does were used to study the possible long term effect of two types of crossbred does (H1 v. H2, old and current generations, respectively) from the cross of different generations of lines selected for litter size, the use of a feeding programme based on a low-energy diet during the rearing and the administration of a high-energy diet during reproductive life, on the performance and body condition of multiparous pregnant does. Selection did not affect the live weight (LW) of does at the effective artificial insemination (AI; 4257 g), the LW change (+12·3 g/day) and food intake (172 g dry matter (DM) per day) until the 28th day of pregnancy. However, H2 does showed greater LW losses during the pre-partum period than H1 does (120+g; P<0·05), perhaps related to their higher prolificacy (+1·1 total pups born; P<0·05). H2 does showed a higher perirenal fat thickness (PFT) at first AI (+0·12 mm; P<0·05) than H1 does, these differences disappearing at effective AI. Females given a high-energy reproduction diet showed a lower LW at effective AI than those receiving a medium-energy diet (4210, 4305 g, respectively; P<0·05). However, type of reproduction diet did not affect the LW and PFT changes of pregnancy does, reaching partum with a similar PFT (8·83 v. 8·93 mm) and maintaining the differences in LW. Pregnant does given high-energy diet consumed 20 g DM and 1·4 g digestible protein per day less than does receiving medium-energy diet until the 28th day of pregnancy, but their digestible energy (DE) intake was significantly higher (+78 kJ DE per day; P<0·05). Does given high-energy diet showed a significantly lower litter size at birth (−0·7 pups; P<0·05), although there were no significant differences in the number of pups born alive (9·54 and 9·76 pups for high and medium-energy diets, respectively). Pups from does given high-energy diet were slightly weightier than those from medium-energy diet (+5·4 g; P<0·05). Multiparous pregnant does that received a low-energy diet ad libitum during the rearing period and first pregnancy showed a higher LW at effective AI (+137 g LW; P<0·05) but a lower PFT (−0·26 mm; P<0·05) than those females that received a medium-energy diet restricted during this same period. These differences were maintained at parturition (+142 g LW and −0·20 mm; P<0·05). Feeding programme during rearing affected neither the food intake of multiparous pregnant does until the 28th day of pregnancy, nor the litter size and weight at birth. The interval between parturitions was not affected by the selection for litter size or the reproduction diet received, but was longer for does that received the low-energy diet ad libitum during the rearing period (+2·9 days; P<0·05). In conclusion, rabbit selection programmes by litter size seem to be working well, but high energy reproduction diets, frequently used to cover their higher energy requirements, must be used carefully out of lactation in the long term to avoid a reduction in litter size.

In an experiment which showed that the results of a genotype comparison are influenced by the design of the test, 16 castrated male and 16 female pigs of each of Large White (LW) and Gloucester Old Spot (GOS) breeds were allocated equally among four treat- ments: WW—rationed by weight and slaughtered by weight; A A—rationed by age and slaughtered by age; AW—rationed by age and slaughtered by weight; and WF—rationed by weight and slaughtered after a common total feed intake. The experiment was designed so that performance of LW would be similar on all treatments, and the degree to which the GOS differed from the LW on each of these treatments was then evaluated. All pigs started on the experiment at 12 weeks of age, at which time mean weight of the LW was 14% greater than the mean for the GOS. The only between- breed difference that was statistically significant (P<0·05) on all treatments was weight of lean. Average daily gain and efficiency of feed conversion were significantly different between breeds only on the WW treatment. Weight of fat was significantly different on WW and AW but not on AA or WF.

Lameness in dairy cows is an important welfare issue. As part of a welfare assessment, herd level lameness prevalence can be estimated from scoring a sample of animals, where higher levels of accuracy are associated with larger sample sizes. As the financial cost is related to the number of cows sampled, smaller samples are preferred. Sequential sampling schemes have been used for informing decision making in clinical trials. Sequential sampling involves taking samples in stages, where sampling can stop early depending on the estimated lameness prevalence. When welfare assessment is used for a pass/fail decision, a similar approach could be applied to reduce the overall sample size. The sampling schemes proposed here apply the principles of sequential sampling within a diagnostic testing framework. This study develops three sequential sampling schemes of increasing complexity to classify 80 fully assessed UK dairy farms, each with known lameness prevalence. Using the Welfare Quality herd-size-based sampling scheme, the first ‘basic’ scheme involves two sampling events. At the first sampling event half the Welfare Quality sample size is drawn, and then depending on the outcome, sampling either stops or is continued and the same number of animals is sampled again. In the second ‘cautious’ scheme, an adaptation is made to ensure that correctly classifying a farm as ‘bad’ is done with greater certainty. The third scheme is the only scheme to go beyond lameness as a binary measure and investigates the potential for increasing accuracy by incorporating the number of severely lame cows into the decision. The three schemes are evaluated with respect to accuracy and average sample size by running 100 000 simulations for each scheme, and a comparison is made with the fixed size Welfare Quality herd-size-based sampling scheme. All three schemes performed almost as well as the fixed size scheme but with much smaller average sample sizes. For the third scheme, an overall association between lameness prevalence and the proportion of lame cows that were severely lame on a farm was found. However, as this association was found to not be consistent across all farms, the sampling scheme did not prove to be as useful as expected. The preferred scheme was therefore the ‘cautious’ scheme for which a sampling protocol has also been developed.

The absence of a simple, accurate method of lamb carcass composition assessment presents difficulties in satisfying an increasing consumer demand for leaner meat. Present carcass classification methods, depending on visual appraisal by trained personnel, may be perceived as subjective and consequently little support for the scheme is found within the industry. Ten carcasses of varying weight (19·9 (s.d. 5·9) kg) and side concentration of fat (303·61 (s.d. 102·70) g/kg) were assessed for impedance to the flow of an alternating current (800μΛ at 50Hz) by use of an impedance analyser. Impedance measurements were highly repeatable (> 0·90) and prediction equations for side concentration of fat and lean produced residual s.d.s of 23·25 to 18·80 g/kg and 37·10 to 18·55 g/kg respectively. Impedance measurements may provide an inexpensive, accurate and simple means of assessing lamb carcass composition

Since comparison of live-weight change of breeding cows is complicated by pregnancy and reproductive synchrony, possible analytical methods for overcoming these problems were reviewed. It was concluded that correction of cow live-weight by subtracting the weight of the gravid uterus and products of conception was biologically and practically meaningful. Two exponential models using polynomial coefficients were derived from published data to predict the fresh weights, at any time during gestation, of the foetus (calculated from calf birth weight) and the gravid uterus and foetal membranes and fluids.

Several in situ studies have been conducted on maize silages to determine the effect of individual factors such as maturity stage, chop length and ensiling of maize crop on the rumen degradation but the information on the relationship between chemical composition and in situ rumen degradation characteristics remains scarce. The objectives of this study were to determine and describe relationships between the chemical composition and the rumen degradation characteristics of dry matter (DM), organic matter (OM), CP, starch and aNDFom (NDF assayed with a heat stable amylase and expressed exclusive of residual ash) of maize silages. In all, 75 maize silage samples were selected, with a broad range in chemical composition and quality parameters. The samples were incubated in the rumen for 2, 4, 8, 16, 32, 72 and 336 h, using the nylon bag technique. Large range was found in the rumen degradable fractions of DM, OM, CP, starch and aNDFom because of the broad range in chemical composition and quality parameters. The new database with in situ rumen degradation characteristics of DM, OM, CP, starch and aNDFom of the maize silages was obtained under uniform experimental conditions; same cows, same incubation protocol and same chemical analysis procedures. Regression equations were developed with significant predictors (P<0.05) describing moderate and weak relationships between the chemical composition and the washout fraction, rumen undegradable fraction, potentially rumen degradable fraction, fractional degradation rate and effective rumen degradable fraction of DM, OM, CP, starch and aNDFom.

Complete C, N and energy balances were carried out on two mature sheep receiving a basal diet of pelleted hay plus continuous intraruminal infusions of either water or 400 kcal/day of propionic acid, butyric acid or a mixture of acetic acid and sodium acetate, for periods of 1 to 5 weeks. The efficiency of utilization for maintenance plus fattening of the basal diet and the basal diet supplemented with acetate, propionate or butyrate was 20·7 ± 1·0%, 28·3 ± 1·5%, 30·2 ± 0·5% and 31·3 ± 0·2%, respectively. The calculated efficiency of utilization for fattening (kf) of the infused energy sources was 69·9 ± 8·4%, 84·0 ± 3·4% and 86·0±2·0% for acetate, propionate and butyrate, respectively. In most instances kf did not vary with the length of the period of infusion but in one sheep there was an adverse response to the infusion of the acetate mixture, and during the first week of infusion kt was only 29·3%. During the third and fifth weeks of the infusion the corresponding values were 76±3% and 72±5%.

Repeated cloning of bovine embryos by nuclear transfer, producing large clones of monozygous animals, may be possible in the future. Initially, clones could be tested and the best one selected and spread over the commercial population by embryo transfer. Further genetic improvement could be obtained by rebreeding a number of the best clones to produce a new set of clones. However, the testing and selection systems to pick the best clone (for short-term clonal response) and to pick clones with the best breeding values (for long-term genetic response) are different. The objective of this study was to derive a system which achieves both high clonal and high genetic responses. An adult MOET (multiple ovulation and embryo transfer) scheme with 40 breeding males and 40 breeding females per generation (cycle) was used to maintain adequate genetic variation for continued genetic response. For a fixed set of testing facilities and a given family structure initial clonal response is maximized by testing several members per clone. Long-term genetic response is usually greatest when testing one member per clone. Compromises to obtain both high clonal response and high genetic responses were from 95 to 100% efficient.

1. A comparison has been made of 305-day lactation milk yields and butterfat percentages of twin and single-born cattle under experimental and field conditions. Experimental two-egg twins, as judged from within-pair variances, were four times as variable as one-egg twins. Two-egg twins in the experimental herd were more alike than twins in dairy herds in fat percentage due to more frequent butterfat testing. Variance of milk yield within pairs was the same in both experimental and farm twins.

2. Twins and half sisters in dairy herds had similar within-pair variances for milk yield and fat percentage. Full sisters, of necessity non-contemporary, differed more in yield than twins and half sisters; significantly so in the latter comparison.

3. The between-pair variance components for experimental twins were high, relative to twins in herds. In experimental twins, breed differences, lack of culling and uniform treatment were probably contributing causes, and also more frequent observation of fat percentage during lactation. Twins n i dairy herds had greater between-pair variances than full sisters.

4. Experimental MZ twins had an intra-class correlation for milk yield of 0·88 and DZ twins of 0·67 which was much higher than for twins on farms. Farm twins and half sisters had correlations for milk yield of 0·37 and 0·31, to be compared with 0·20 in full sisters. Corresponding values for fat percentage were 0·40, 0·35 and 0·25 on farms as against 0·88 and 0·65 for MZ and DZ twins at the experiment station. These differences between experimental and commercial pairs were largely attributable to differences in between-pair variance.

5. There is no evidence from experimental or commercial data that twins produce less milk than single-born cows.

6. Differences between farms increased the within-pair variance in yield and decreased the intra-class correlation of twins and half sisters but had less effect on full sisters.

Productive and metabolic responses were determined in ewes given diets containing calcium soaps of fatty acids for a period of 90 days after lambing as compared with ewes given a control diet.

Yield of milk and milk fat, milk protein and milk lactose were increased over the experimental period by feeding calcium soaps. Live-weight changes after lambing were not different in the two experimental treatments. No changes in rumen metabolism were observed when calcium soaps were offered whereas plasma concentrations of protein, glucose, triglycerides, phospholipids and cholesterol were enhanced.

It is concluded that calcium soaps of fatty acids can be included in diets of ewes to increase production of milk and milk solids.

Inert fibre particles were used in a series of experiments in order to quantify the effects of some physical characteristics of dietary long fibre on rumination. Removal of hay from the diet of hay I concentrate-fed sheep reduced true rumination to zero after a period of 8 days, although pseudorumination, much reduced in duration, persisted. Then by introducing loose, chopped, inert polyethylene particles through a rumen cannula, rumination was restored. When different masses of loose inert polyethylene particles chopped into 10-mm lengths were placed in the rumen, the time spent ruminating was found to be directly proportional to mass of fibre placed in the rumen (P < 0·001). By inserting a fixed mass of particles of different lengths, the optimum length of inert fibre for rumination to occur was found to lie between 7 and 30 mm. Finally, when, in place of loose fibre, a polyethylene fibre ‘pompom’, fixed on a rod, was introduced via the cannula and placed so as to brush different areas of the retkulorumen, it was found that the greatest rumination response was evoked when the pompom was allowed to stimulate mechanically the cranial regions of the retkulorumen (P < 0·05). It is concluded that inert polyethylene fibre mimicked the peripheral excitatory effects of dietary fibre by stimulating mechanoreceptors (epithelial receptors) located in the cranial portions of the retkulorumen. Adding about 50 g of 7 to 30 mm inert fibre caused sheep on low-fibre diets to ruminate normally for over 3 h.

Two groups of 14 intact male weanling beef breed calves were each fed 1·45 kg oat hay daily and concentrates ad libitum, in a 158-day feeding trial. Group ‘a’ received 35 p.p.m. monensin in the concentrate. Group ‘b’ served as a control.

Average daily gain was 1·28 and 1·27 kg, dressing percentage was 58·1 and 58·0, daily intake of concentrate was 8·10 and 8·79 kg and conversion ratio of metabolizable energy into live weight was 74·53 and 81·30 MJ/kg for the monensin and the control group respectively. The percentage of acetic acid in rumen liquor was reduced and that of propionic acid increased very markedly. As a result the acetic acid: propionic acid ratio was reduced from 3·2 in the control group to 1·8 in the monensin group. No peculiarity in the response of intact male cattle to monensin was observed.

Chlormequat is a commonly used plant growth regulator in agriculture. Defined levels of chlormequat residue are allowed in food and an acceptable daily intake is defined for humans. However, there are results in the literature suggesting that a daily intake below the acceptable level for human is detrimental for mammalian reproduction. In the present experiment we investigated the effect of chlormequat at levels up to that acceptable for humans on reproduction in male pigs. Chlormequat (also known as chlorocholine chloride (CCC)) was mixed into the diet and given to the experimental animals at three levels (three treatment groups), i.e. 0 mg CCC/kg BW per day (Control), 0.025 mg CCC/kg BW per day and 0.05 mg CCC/kg BW per day. Eight mother sows per treatment group were used in the experiment. From the day of insemination, the mother sows received the experimental diets. The piglets were weaned at 4 weeks of age and two boar littermates continued on the same treatment as the dam until maturity and delivery of semen for in vitro fertilization (IVF) and in vivo fertilization. Semen volume, sperm concentration and fraction of live sperms were not (P ⩾ 0.46) detrimentally affected by chlormequat intake. The fraction of oocytes developing to more than the one-cell stage at day 5 after IVF was not (P = 0.88) detrimentally affected by chlormequat intake. Chlormequat intake did not detrimentally affect the fraction of gilts being pregnant after one insemination (P = 0.65) or the number of embryos in the pregnant gilts (P = 0.36). Serum chlormequat concentration was 0.9 μg/kg in the 0.025 mg CCC/kg BW per day group and 1.8 μg/kg in the 0.05 mg CCC/kg BW per day group, but was below the detection limit in control animals. In conclusion, the plant growth regulator chlormequat could not be proven to be detrimental to the selected reproduction traits in male pigs. This is in contrast to existing results from the male mouse.

Southdown and Welsh Mountain female sheep, equal numbers on high and low plane nutrition, were shorn and subjected to two acute cold exposures (−20°C, 4 mph wind) in climate chambers. Before the first exposure the sheep were kept in either a cool (+8°C) or a thermoneutral (+30°C) environment for two weeks. Between exposures these environmental temperatures were reversed within groups. Blood samples were withdrawn at the beginning and end of the two week exposures and on three occasions during acute cold exposure. Plasma analyses of Ca, P, Mg, Na and K were carried out. Exposure to +8°C caused a 12% reduction in plasma Mg levels of all sheep, but had no effect on Ca, Na or K levels. There were breed × temperature interactions with respect to plasma P levels. Acute cold exposure caused reductions in plasma Mg and Ca levels and an increase in plasma P levels of all groups of sheep. Changes in plasma Na and K levels could have been caused by plasma concentration.

Electrolyte levels initially displaced by exposure to +8°C showed no evidence of a return to normality two weeks later. Only for Ca was there evidence that prior exposure to +8°C modified the response to acute cold exposure.

Our laboratory recently reported that the ratio of a piglet’s weight to that of its placenta (RATIO) varies approximately three-fold within a litter, due predominantly to variation in placental size which is known to be a limiting factor in litter size. It was further determined that selection of boars and gilts with a higher than average RATIO for breeding resulted in an increased litter size and reduced placental weights. The objective of this experiment was to examine the effects of RATIO on economically important production traits (piglet survival to weaning, 21-day weights, days to 105 kg, backfat depth and loin muscle area at 105 kg) in a purebred breeding stock herd of Finnish Yorkshire and Landrace pigs. Sows were monitored throughout farrowing and each piglet was matched to its placenta. Each piglet and its placenta were individually weighed and a RATIO determined. Placental weight but not piglet birth weight exhibited a strong (P < 0·001) negative correlation with RATIO (r = -073). Up to three-fold differences in RATIO were observed within a single litter. These differences were much greater than the variation noted between litters and litter mean RATIO was not significantly associated with litter size. The distribution of individual piglet RATIOS across the entire group of pigs ranged from 2·8 to 11·4 suggesting a marked difference in placental efficiencies. No significant association was seen between RATIO and 21-day weight, days to 105 kg, backfat depth or loin muscle area. Thus, an above average ratio of a piglet’s weight to that of its placenta is indicative of a smaller more efficient placenta and appears to have no subsequent detrimental effects on growth efficiency.

Most farms that were feeding complete diets to dairy cows in the east midlands lost barley to starlings during the 1978/79 winter and more outdoor than indoor feeding sites were infested. The maximum total loss recorded on any one farm was 11 -881, this being 9% of the 1321 of barley presented to the cattle. The presentation of ground barley, rather than rolled barley, reduced the quantity of grain removed by starlings but the proofing of buildings i n which cattle are fed complete diets is suggested as the most effective means of preventing this food loss.

The present study aimed to evaluate the mechanisms modulated by dietary arginine supplementation to sows during lactation regarding antioxidant capacity and vascularization of mammary glands. At 109 days of gestation, animals were transferred to individual farrowing crates equipped with manual feeders and automatic drinker bowls. Environmental temperature and humidity inside the farrowing rooms were registered every 15 min. At farrowing, sows were assigned in a completely randomized design to a control diet (CON) or the CON diet supplemented with 1.0% L-arginine (ARG). A total of three gilts and two sows were fed the CON diet, whereas three gilts and three sows were fed ARG diets. Sows were fed a fixed amount of 6.0 kg/day, subdivided equally in four delivery times (0700, 1000, 1300 and 1600 h) for 21 days. At weaning, sows were slaughtered and mammary tissue samples and blood from the pudendal vein were collected. Data were analyzed considering each sow as an experimental unit. Differences were considered at P<0.05. L-arginine fed sows presented lower messenger RNA (mRNA) expression for prolactin receptor (P=0.002), angiopoietin1 (P=0.03) and receptor tyrosine kinase (P=0.01); higher mRNA expression for prostaglandin synthase 1 (P=0.01); a trend of decrease for glucocorticoid receptor (P=0.06) and IGF receptor 1 (P=0.07); and a trend (P=0.05) for an increased glutathione peroxidase mRNA expression. The angiopoietin2:angiopoietin1 mRNA ratio tended to increase (P=0.07) in ARG fed sows. L-arginine fed sows had greater (P=0.04) volumetric proportion of blood vessels and a trend of enhance (P=0.07) in the number of blood vessels per mm2. These findings show that 1.0% ARG supplementation to sows activates proliferative mechanisms, may improve mammary tissues’ angiogenesis and tended to increase mRNA expression of genes that encode antioxidant enzymes in mammary gland of sows.

An experiment was carried out with mice over 24 generations to measure the response obtained to selection for litter size and litter weight at weaning on two dietary regimes designated normal and diluted. In addition, control groups bred by random mating were maintained on each diet. The stock were maintained on the diets from generation 0–3 after which time selection for the traits started and continued up to generation 17. After generation 17 for a further 6 generations, all selection stopped and half of each group was switched on to the other diet, while the remaining half continued as before.

No significant response was obtained to selection for either litter size or litter weight at weaning.

The diets provided did not bring about a differential response to selection for the traits, and the response to the dietary switch was small and temporary in its effect.

Due to strong maternal effects and low heritability, little genetic improvement was obtained by selection for litter size and litter weight at weaning in these mice.

Two experiments have been conducted to compare wilted, formic acid-treated red clover and unwilted, formic acid-treated grass silages for beef production, and to examine the effects of digestibility of red clover and level of concentrate supplementation on food intake and animal performance.

In experiment 1, 12 groups of four British Friesian steers (initial live weight 229 kg) were given red clover silages of high and low dry-matter digestibility (0·70 and 0·60 respectively) and grass silage (0·71) ad libitum for a period of 11 weeks. Silage dry-matter intake and live-weight gain for the steers given red clover of high digestibility, red clover of low digestibility and grass silages were 7·75, 0·89; 6·91, 0·69; and 5·59, 0·59 kg/day respectively.

In experiment 2, 12 groups of four British Friesian steers (initial live weight 332 kg) were given red clover silage with a dry-matter digestibility of 0·63 and grass silage with a value of 0·76 ad libitum, either unsupplemented or supplemented, with 2 kg/day of fortified barley per head for a period of 19 weeks. Silage dry-matter intake, live-weight gain and carcass gain were 8·52, 0·63, 0·32 and 6·98, 0·78, 0·43 kg/day for the unsupplemented and supplemented red clover silage treatments, and 6·82, 0·59, 0·31 and 5·75, 0·75, 0·44 kg/day for the unsupplemented and supplemented grass silage treatments respectively. The performance of the cattle offered red clover silage was similar to that of cattle offered grass silage of 0·12 higher digestibility, largely as the result of higher dry matter intakes achieved on red clover silage.

Milk production and reproductive performance of pluriparous dairy cows was compared for cows whose lactations were induced by hormonal treatment or followed natural calving. The study was conducted on 179 high-yielding dairy cows in a large dairy operation in a hot arid environment of northern Mexico, where bovine somatotropin (bST) was routinely used in all cows. To induce lactation, 98 cows that had previously failed to become pregnant were treated with 500 mg bST on days 1, 8 and 21. From days 2 to 8, cows were treated with oestradiol cypionate (0·30 mg/kg live weight (LW) per day) and progesterone (0·28 mg/kg LW per day). From days 9 to 15, oestradiol cypionate alone was given. PGF2α was given on day 16. Nothing was administered on days 17 and 18, and 15 mg flumetasone was administered from days 19 to 21. Lactation was induced successfully in all 98 cows subjected to the hormone treatment. All cows received 500 mg bST every 14 days throughout lactation from 63±7 days after lactation had started. Cows with induced lactations produced less (P<0·01) milk per 305-day lactation (9599±1387 kg) than controls (12 302±1245 kg). Proportion of cows pregnant was similar in induced cows and non-treated cows (71 v. 75%). Induction of lactation was associated with increased numbers of services per pregnancy (5·8±4·0 v. 4·22±2·98; P<0·01) compared with controls; however, impaired reproduction might not necessarily have been related to the hormonal treatment to induce lactation, but due to the nature of the cows utilized for this treatment group. This protocol can be used on dairy farms where bST treatment and prolonged steroid administration of dairy cows is legally permitted.