A review of work reported in the literature was used to present quantitative descriptions of protein use in the growing pig. These are detailed in the text, which also points to preferred values, and to anomalies and lacunae. The review was prepared with the objective of allowing from its content the inclusive and quantitative modelling of amino acid requirement. Requirement was approached as the sum of the component factors: maintenance and protein retention. Ileal true digestible protein and amino acid requirements are presented in a form consistent with that forwarded for energy. Thus both energy and protein elements can be conceptualized within a single coherent framework. Priority uses for absorbed amino acids were assumed to be (a) to support endogenous protein losses resultant from the passage of food and incomplete re-absorption prior to the terminal ileum, (b) to replace lost hair and skin, and (c) to cover the basic maintenance losses which will occur as a result of minimal protein turn-over even when protein retention is zero. The bulk of the protein requirement was directly linked to the daily rate of protein retention, for which the linear-plateau response was accepted. For determination of the maximum rate of protein retention the Gompertz function was proposed, although the use of a single value throughout the growth period was not dismissed. The balance of amino acids for protein retention is specified as different from that for maintenance. Central to the approach was the proposal that the inefficiency of use of ileal digested ideal protein, even when not supplied in excess, was an expression of protein losses occurring as a result of protein turn-over. The requirement for the satisfaction of the losses from protein turn-over occurring as a consequence of protein retention, and therefore additional to the requirements for maintenance, was identified. Quantification was attempted with sufficient success to warrant its inclusion into requirement estimation. It was concluded that this element addressed previously inadequately explained protein utilization inefficiencies. Algorithms are presented based upon protein turn-over which appear to be consistent with empirical findings.

The objective of this study was to test that genetic variation for resistance to clinical and subclinical diseases exists in growing pigs. A total of 13 551 male growing pigs were assessed for resistance to five categories of clinical and subclinical disease: (i) any clinical or subclinical disease, (ii) lameness, (iii) respiratory diseases, (iv) diarrhoea, and (v) other diseases (i.e. any clinical or subclinical disease with the exception of (ii), (iii), and (iv)). Additive genetic variation for resistance to each disease category was estimated by fitting a Weibull, sire-dam frailty model to time until the pigs were first diagnosed with a disease from that category. Genetic correlations among the resistances to each disease category were approximated as product-moment correlations among predicted breeding values of the sires. Additive genetic variation was detected for resistance to (i) any clinical or subclinical disease (additive genetic variance for log-frailty (± s.e.) = 0·18 ± 0·05, heritability on the logarithmic-time scale = 0·10), (ii) lameness (0·29 ± 0·11, 0·16), (iii) respiratory diseases (0·24 ± 0·16, 0·12), (iv) diarrhoea (0·30 ± 0·27, 0·16), and (v) the other diseases (0·34 ± 0·15, 0·19) and there were generally positive and low-to-moderate correlations among the predicted breeding values (-0·03 to + 0·65). These results demonstrate that additive genetic variation for resistance to clinical and subclinical diseases does exist in growing pigs, and suggests that selective breeding for resistance could be successful.

This paper presents an analysis of nematode faecal egg counts from Scottish Blackface ewes facing mixed, natural nematode infections (predominantly Teladorsagia circumcincta). The data set comprised 1445 measurements on 421 ewes taken at 4 and 6 weeks post-lambing, over a 4-year period. The ewes, themselves, were the progeny of 73 sires and 285 dams. Only Strongyle eggs were consistently present, and faecal egg counts from this genera ranged from zero (0·4 of all measurements) to 3388 eggs per g. Faecal egg counts were significantly affected by the number of lambs reared and suckled (increasing reproductive burden led to higher counts) by ewe age (older ewes had lower counts) and by previous selection history (ewes from a line previously selected for increased carcass fatness had lower faecal egg counts than ewes from a conversely selected lean line). The heritability of log-transformed faecal egg counts was 0·23 (s.e. 005) and the repeatability, including both within- and between-year permanent environmental effects, was 0·25 (s.e. 004). The apparent presence or absence of infection had a heritability of 015 (s.e. 007) on the observed scale and 0·39 (s.e. 016) when analysed as a binomial threshold trait. The genetic correlation between average 4-week weight of lamb suckled by the ewe and faecal egg counts was 0·24 (s.e. 010). The results suggest that faecal egg counts during early lactation are heritable and influenced by the reproductive performance of the ewe. Selection to reduce nematode faecal egg output from ewes during this period should be successful in reducing pasture larval contamination.

One hundred and eight Holstein-Friesian cows in six herds were run on six separate farmlets over a 5-year period from 1995 to 1999 at Wollongbar Agricultural Institute, on the subtropical north coast of New South Wales, Australia. Three of the herds comprised high genetic merit (HGM) cows — Australian breeding value (ABV) of +49·1 kg for milk fat (F) plus protein (Pr) and three herds comprised low genetic merit (LGM) cows-ABV of 2·3 kg. Within genetic merit groupings, one herd was given 0·34 t (l), one herd was given 0·84 t (m) and one herd 1·71 t (h), of concentrate per cow per lactation. Within each genetic merit group, cows were matched for milk yield and live weight, and over all groups for time of calving and age at the commencement of the study. The 30 paddocks within each farmlet were matched between farmlets for pasture type and pasture growth rate and soil fertility. Half the cows within each herd calved over a 3-month period in spring and the other half in autumn. Strict management criteria ensured that there was no bias towards particular treatment groups.

HGM cows were ‘open’ (days from calving to conception) for 8 days longer than the LGM cows (99 v. 91 days). The lHGM cows took 11 days longer to commence luteal phase activity and 21 days longer to first observed oestrus post calving than hLGM cows (P < 0·001), with the other groups being intermediate.

After 24 days of mating, 22% of lHGM cows were pregnant, and this was less than half of the rate of the best herd-mLGM. After 9 weeks of mating, the chances of an LGM cow being pregnant was 87% greater than an HGM cow. After 12 weeks of mating, 70% of lHGM cows were pregnant compared with a mean pregnancy rate of 87% for the LGM cows.

The number of cows treated for abnormal ovarian activity (anoestrus, cystic) was highest (P < 0·001) in the HGM herds given ‘l’ and ‘m’ levels of concentrate compared with the remaining herds (0·24 v. 0·12 treatments per cow mated, respectively).

There was a significant positive relationship between live-weight change from 4 weeks before, to the start of, the mating period and the chances of a cow being pregnant at 24 days (P < 0·05) and at 6 and 9 weeks after the commencement of mating.

There was a significant negative relationship (P < 0·001) between the change in daily F plus Pr yield, from the start to 4 weeks after mating began, and pregnancy rate at 9 weeks. The change in F plus Pr yield was +63 g/day for cows pregnant at nine weeks as opposed to +154 g/day for cows not pregnant.

The results of the present study indicate that the reproductive performance of HGM cows, with a mean of 61% North American (NA) genes, is lower than LGM cows (22% NA genes) under a predominantly pasture-based system of farming. The influence on reproduction was possibly due to genes favouring partitioning of energy to milk yield rather than body-condition maintenance in the HGM cows and when food intake was inadequate, then being more willing to use body reserves.

These reproductive problems may be reduced by more intensive reproductive management. However, such practices are costly and time consuming. Another approach may be to ensure that live-weight loss over the mating period is minimized by strategic supplementary feeding.

A total of 7444 lactation records which include milk, fat and protein yields (MY, FY, PY) and fat and protein content (F%, P%) from 6429 Black-Faced Latxa ewes were employed to estimate genetic parameters for milk traits. Traits were standardized to 120 days of lactation. For the calculation of composition traits, not all test-days had their composition measured and therefore a correction taking this into account was included in the analysis. A first-derivative restricted maximum likelihood algorithm was used on an animal model with repeatability analysis, using models including fixed effects (flock-year-season of lambing, age-parity at lambing, number of lambs, interval between lambing and first milk recording and the combination of sampled test-days) and random effects (the additive genetic effect and the permanent environmental effect). The resulting heritabilities were 0·20, 0·16, 0·18, 0·14 and 0·38 for MY, FY, PY, F% and P% respectively. Heritability of F% was much lower than expected, probably due to problems derived from the recording method. Genetic correlations were high and positive between yields and moderately positive between F% and P%, and negative or null between yields and composition, as has been reported for other European dairy sheep breeds. As most of the milk produced by Latxa dairy sheep is processed into cheese, the inclusion of milk sampling in official milk recording and a change in the selection criterion are recommended to avoid a long-term worsening in milk composition.

Three selection indexes for the UK hill sheep sector are derived to suit the extremes of hill production systems. These are: (i) intensive, where all surplus lambs not required for breeding are finished for slaughter, (ii) extensive, where all surplus ‘store’ lambs are sold to other farmers for finishing, and (iii) semi-intensive, which is intermediate between the two extremes, i.e. farms finish some lambs for slaughter and sell others as store lambs. Parameters for 12 breeding goal and index traits were estimated using a total of 3962 lamb records and 5944 ewe lambing records from Scottish Blackface sheep on two Scottish Agricultural College experimental hill farms. The breeding goal comprised carcass, maternal and survival traits. The evaluation of these indexes showed that improvements in maternal traits are possible, along with more modest improvements in carcass quality traits. Responses to selection are expected to be lower for the extensive farm in general, compared with the intensive farm. Evaluations of alternative indexes show that an index using measurements of fat and muscle on ewes rather than on lambs may be more cost-effective to implement in practice, compared with the original index, although this change results in a higher (i.e. undesirable) gain in mature size. Sensitivity analyses showed that in general, the indexes are robust to changes in economic values and to changes in heritability estimates.

Japanese Black cattle (Wagyu), deposit much higher amounts of intramuscular fat, known as marbling, than other breeds of cattle. To determine whether this unique fat deposition is attributable to the somatotropic axis, we compared pulsatile growth hormone (GH) secretion, plasma levels of insulin-like growth factor-1 (IGF-1) and cellular density of somatotrophs (GH-expressing cells) in the anterior pituitary glands of Japanese Black and Holstein steers. Blood samples were withdrawn every 15 min for 6 h from 14 Japanese Black and 12 Holstein steers at about 17 months of age, and GH and IGF-1 concentrations were determined. The distribution and proportion of GH-expressing cells were analysed by immunohistochemistry combined with point-count morphometry in pituitaries from six steers from each breed aged about 18 to 21 months. Overall mean and baseline plasma GH concentrations were lower (P < 0·001) in Japanese Black than Holstein steers. In addition, Japanese Black had smaller (P < 0·05) amplitudes of GH secretory pulses than Holstein steers, whereas the GH pulse frequency did not differ between the breeds. Japanese Black steers also had lower (P < 0·001) plasma levels of IGF-1 than Holstein steers. The marbling score of Japanese Black steers was higher (P < 0·001) than that of Holsteins at the same carcass weight. The proportion of GH-expressing cells was smaller (P < 0·05) in Japanese Black than Holstein steers at the hind dorsal and hind ventral regions of the adenohypophysis. Thus, in Japanese Black and Holstein steers, the breed difference in the relative density of GH-expressing cells corresponded to that in profiles of pulsatile GH secretion. These results suggest that the features of the somatotropic axis intrinsically differ between Japanese Black and Holstein cattle and that these features may be partly responsible for the genetic ability of the former to deposit greater amounts of marbling fat and for the smaller frame of Wagyu cattle.

The objective of this study was to examine the effect of dietary vitamin A (retinol) on leptin in cattle. The relationship between plasma leptin and insulin was also examined. The experiment studies 16 9-month-old steers over the following 20-month fattening period. Four treatment diets were given to four steers in each of four groups. Cattle in treatment A were given a diet high in vitamin A (9000 to 10500 µg/day) throughout the experiment. Cattle in treatment B were given a diet low in vitamin A (300 to 4500 µg/day) for 0 to 10 months, after that they were given the high vitamin A diet during the period 10 to 20 months. Cattle in treatment C were given the low vitamin A diet for 0 to 14 months, after that they were given the high vitamin A diet for the period 14 to 20 months. Cattle in treatment D were given the low vitamin A diet throughout the experiment. Plasma samples were collected at 2-month intervals during the experiment to determine the plasma leptin, insulin and vitamin A concentrations. Plasma leptin concentration significantly increased over the fattening period (P < 0·001) but did not differ between the treatments (P > 0·05). Plasma leptin concentration was positively correlated with insulin concentration (r = 0·44, P < 0·001), although it was not correlated with plasma vitamin A concentration (r = –0·01, P > 0·05). It was concluded that dietary vitamin A in cattle does not affect plasma leptin concentration.

This study was designed to explore the effect of protein source on muscle susceptibility to lipid peroxidation in two representative species of fish farmed for human consumption: the freshwater rainbow trout and the seawater European sea bass. Four isoproteic diets (digestible protein in the range 366 to 392 for rainbow trout and 391 to 415 g/kg for European sea bass) were formulated to contain one of the following as the main protein source: fish meal, warm water alcohol-extracted or toasted soya protein concentrates or maize gluten meal. Highest daily growth indices were always achieved using the diets based on fish meal as the main source of protein (P < 0·05). Fish of both species given diets containing maize gluten and the toasted soya protein concentrate showed slowest growth. The depressant growth effect of the vegetable protein concentrates was greater in sea bass than in rainbow trout. Dietary treatment was not correlated with any significant effect on whole-body composition or intramuscular fat content except for ash concentration in European sea bass. Under conditions of forced peroxidation in vitro for 240 min, muscle specimens of trout and sea bass given diets containing fish protein as the main source of protein showed the highest peroxidation levels (P < 0·05); while the lowest peroxidation values were found in fish given maize gluten-containing diets (P < 0·05). In the present case, the partial substitution of fish meal with vegetable proteins in diets led to a lower susceptibility of fish flesh to peroxidation. This finding may have applications in the production of fish of improved quality and longer shelf life.

The research was carried out to evaluate the effect of different dietary α-tocopheryl acetate (DTA) concentrations in light-weight lambs on muscle α-tocopherol accumulation and on quality characteristics of stored meats. Thirty-two Manchego lambs were randomly distributed to four groups and given diets containing four levels of DTA (20, 270, 520 and 1020 mg/kg diet) for 6 weeks. Lambs were slaughtered at live weights ranging from 23·5 to 26·4 kg. A linear (P < 0·001) and quadratic (P < 0·001) effect of dietary supplementation level was observed on muscular α-tocopherol concentration, which fitted the following equation: mg muscle α-tocopherol per kg muscle = 1·78(s.e. 0·18) + 7·08 (s.e.0·89)(1 - e00012DTA)) (P < 0·001, R2 = 0·99). There was a linear effect (P < 0·001) of muscle vitamin E concentration on thiobarbituric acid reactive substance on day 0 of storage, but a linear plus quadratic effect (P < 0·001) on days 3, 6 and 9. Broken line analysis of data at day 9 of storage indicated a target muscle α-tocopherol concentration of 5·4 mg/kg. Evolution of surface redness of lamb chops also showed a linear and quadratic effect of dietary treatment on days 3 and 6 of storage, but only a linear effect on day 9. Broken line analysis of data at 3 and 6 days indicated a target α-tocopherol concentration in the range 5·3 to 5·6 mg/kg muscle for optimum red colour stability. Surface luminosity showed no effect of dietary treatment at days 0, 3 and 6 of storage but a linear (P < 0·01) plus quadratic (P < 0·05) effect on day 9 of storage. Broken line analysis at this point indicated a target muscle α-tocopherol concentration of 3·2 mg/kg. It is concluded that the effectiveness of dietary α-tocopheryl acetate supplementation depends on the meat quality attribute assessed. A significant positive effect for lipid oxidation can be reached even at the lower supplementation level utilized in this experiment (270 mg/kg diet). However, considering the protecting effect at different storage times and particularly the effect on meat surface redness, the optimum level would be in the range 5·3 to 5·6 mg/kg muscle, which correspond to a dietary inclusion of 550 to 625 mg α-tocopheryl acetate/kg diet.

An experiment was conducted to measure the effects of stocking density (increased number of pigs per pen) on lysine requirements of pigs grown from 25 to 60 kg live weight. Two hundred and sixty-four female Large White ✕ Landrace pigs were assigned at 25 kg to one of four dietary lysine treatments (13·3 (L1); 11·4 (L2); 9·5 (L3) and 7·6 (L4) g/kg) and either seven or 13 pigs per pen (or 1 0 and 0·5 m2 per pig, respectively). An additional treatment of one pig per pen (20 m2 per pig) was included to compare the responses of solitary- versus group-penned pigs. Animals were given ad libitum access to dietary treatments from a mean pen starting weight of 261 (s.e. 0·35) kg to a mean pen finishing weight of 63·4 (s.e. 0·61) kg live weight. There were no significant interactions between dietary lysine content and floor space per pig on food intake (FI), average daily growth rate (ADG), the amount of food per unit of gain (FCR) and the rate of protein retention (PR). Significant interactions were evident for body composition and the rate of lipid retention (LR). Over the weight range 25 to 40 kg there were significant differences in FI (P < 0·05) and FCR (P < 0·001) between dietary lysine treatments but most of these differences had disappeared over the 40 to 60 kg live weight. Individually penned animals had significantly higher (P < 0·05) FI and ADG than group-penned animals. However, there were no differences between seven and 13 pig per pen treatments. Stocking density had no effect on LR or body protein content but did cause a significant reduction in PR (P < 0·001) and an increase in body lipid content (P < 0·05) as the number of pigs per pen increased from seven to 13. Lysine requirements (expressed in g/day) therefore could be seen to be reduced with increasing stocking density. However, as lysine intake was reduced in group-penned animals, the reduced daily requirement does not necessarily warrant a reduction in the lysine content of the food. Feeding according to the requirements for maximum PR will still produce the best carcass and growth performance irrespective of the group size. The improvement in PR associated with higher dietary nutrient levels did not completely offset the adverse physiological effects of higher stocking density but may partly counteract the effect of reduced lysine intake. However, there were indications that feeding crowded pigs a lower dietary lysine concentration may not further reduce the already diminished protein (lysine) growth rate. An additional experiment was performed to test whether the number of feeder bins may have constrained food intake and therefore growth in group-penned animals. The results of this experiment showed that the number of bins had no significant effect on FI, ADG and FCR in group-penned pigs, and therefore a single feeder bin was not considered a constraining factor in pigs housed with limited floor space.

When weaned early, piglets commonly take some time to accept solid food, resulting in a growth check and reduced welfare. The transmission of information about food between animals has been demonstrated in other species and it would be advantageous if this occurred in piglets. This experiment investigated the effects of pairing piglets that were consuming solid food with newly weaned piglets. Six litters of piglets did not receive solid food until weaning. In each litter four piglets (3 plus 1 spare) were weaned at 21 days of age and housed together for 7 days and offered one of two foods (3 litters per food). At 28 days of age the remaining piglets were weaned and four pairs of piglets were formed, such that there were three experienced animals paired with three inexperienced observers, each pair having visual contact and varying degrees of physical contact (1: none, 2: through wire mesh, 3: housed together), and a pair of inexperienced piglets (4: housed together) to act as controls. Food intake and weight gain were recorded over a period of 7 days. There was no effect of food type on food intake or live-weight gain of the pairs but the inexperienced pigs had higher gains on food 1 than food 2. The inexperienced pairs ate less food than the other pairs and the experienced/observer pairs that were housed together had the greatest weight gain. The level of variation between piglets was such that there were no significant effects of pairing treatment on the weight gain of the inexperienced animals. Total time spent feeding increased with time from pair formation. The number of simultaneous feeding events was higher for the experienced/observer pairs housed together than for the inexperienced pairs. This experiment has indicated that food intake is stimulated when an inexperienced piglet is housed with an experienced piglet and, with further work, this could be exploited to alleviate the weaning check.

Seventy-two entire male pigs (initially 28 kg body weight) were used to study the effects of by-product (pollard, rapeseed meal, peas and copra meal combined) inclusion level with or without expander processing, on growth performance and nutrient digestibility in a 3 ✕ 2 factorial arrangement of treatments. Productive performance and nutrient digestibility coefficients (no. = 6) were determined in individually fed pigs offered pelleted diets ad libitum containing a low by-product diet (350 g/kg), medium by-product diet (520 g/kg) and high by-product diet (752 g/ kg). The expanded diets were processed at 105ºC for 5 s at 35 bar pressure having been previously conditioned at 85ºC for 5 s. All diets were formulated using standard values for ingredients to have similar concentrations of digestible energy (DE) and ideal protein. Starch contents of 437, 401 and 314 g/kg and crude fibre contents of 48, 58 and 74 g/kg were recorded for the low, medium and high by-product diets respectively. No by-product level ✕ expander processing interactions (P > 0·05) were observed in growth criteria, carcass characteristics or nutrient digestibility. Expander processing decreased (P < 0·05) the apparent organic matter (OM), ash and energy digestibility of the diets, as well as the digestible energy content of the diets. The level of by-product in the diet had no statistically significant effect on the OM, protein and energy digestibility or the DE content of the diets. The increase in by-product inclusion levels decreased (P < 0·05) average daily gain (ADG) (0·899 v. 0·888 v. 0·854 (s.e. 0·014) kg/day) from 28 kg to slaughter and food intake (1·62 v 1·48 v 1·48 (s.e. 0·028) kg/day) in the 28 to 55 kg weight range. Expander processing had no effect on ADG, food intake or food conversion ratio. The increase in byproduct level decreased (P < 0·01) killing-out proportion (723 v 705 v 710 (s.e. 3·94) g/kg) and carcass ADG (0·684 v 0·651 v. 0·635 (s.e. 0·012) kg/day) (P < 0·05). Expander processing decreased (P < 0·05) killing out proportion (707 v. 718 (s.e. 3·22) g/kg). In conclusion, increasing the by-product content of the diet decreased ADG while expander processing had no effect on growth performance.

Salmon oil (16·5 kg /t), a source of long-chain polyunsaturated n-3 fatty acids, was included in diets offered to multiparous sows during pregnancy and lactation to measure responses in pre-weaning mortality and performance of piglets in two studies. The first study, carried out under commercial conditions, included 196 sows which were offered salmon oil and control diets from immediately post service until weaning. The same diets were also offered to 10 sows per treatment from day 58 of pregnancy in a controlled nutritional study which measured the effects of salmon oil on piglet tissue fatty acid composition. Offering salmon oil to the sow significantly increased gestation length and decreased individual piglet birth weight but had no effect on litter size at birth. Overall, salmon oil reduced pre-weaning mortality from 11·7% to 10·2% mainly by reducing the incidence of deaths from crushing by the sow. More detailed analysis of mortality using a general linear mixed model and 2294 piglet records, demonstrated that the incidence of pre-weaning mortality was significantly decreased with increasing individual piglet birth weight and by inclusion of salmon oil in the diet; the incidence of mortality increased with average piglet birth weight in a litter. Salmon oil inclusion had no effect on weight of litter weaned, sow lactation food intake or subsequent reproductive performance. In both studies, dietary salmon oil increased the proportions of long-chain n-3 polyunsaturated fatty acids in colostrum to a similar extent. In the nutritional study, inclusion of salmon oil reduced the proportions of 20: 4 n-6 in piglet liver and brain at birth and increased the proportions of long-chain n-3 polyunsaturated fatty acids. Therefore, despite reducing piglet birth weight, offering sows salmon oil reduced pre-weaning mortality of piglets. The nutritional study showed that the amount and type of marine oil used may not have been optimal.

Seasonal milk production systems rely on heavy inputs of nitrogenous fertilizer, which typically generate pastures with a high crude protein (CP) and low fermentable energy concentration. High intake of CP, particularly in association with low rumen fermentable energy, increases systemic ammonia and urea and has been associated with reduced fertility in cattle. The objective of this study was to examine the relationship between pasture protein intake and fermentable energy supplementation on a range of blood metabolites and on embryo survival and development in cattle.

Oestrous synchronized, nulliparous beef heifers (no. = 175) were randomly assigned to one of four pasture-based dietary treatments in a 2 ✕ 2 factorial study carried out over 2 years. Animals were randomly allocated to either high (85 kg nitrogen (N) per ha; HN) or low (0·0 kg N per ha; LN) N fertilized pastures and within pasture treatment were randomly allocated to receive either zero or three (+3P) kg dry matter (DM) of molassed sugar-beet pulp (MSBP) per head per day as follows: (1) HN (no. = 44), (2) HN + 3P, (no. = 43), (3) LN (no. = 44), (4) LN + 3P (no. = 44). Blood samples were collected to measure systemic concentrations of ammonia, urea, insulin, glucose and progesterone. Heifers were artificially inseminated (AI) and pregnancy diagnosis was carried out by ultrasonography 30 days after AI. Subgroups of pregnant animals across treatments were slaughtered 40 days after AI to estimate conceptus development.

The HN pasture had a higher CP (P < 0·001) and lower water-soluble carbohydrate (P < 0·01) concentration. Plasma concentrations of ammonia (P < 0·05) and urea (P < 0·001) were higher in the animals on the HN pastures and were reduced (P < 0·05) by MSBP supplementation, but only in animals on the HN pastures. Embryo survival rate across treatments was high overall (71%) and not related to pasture CP concentration, fermentable energy supplementation or systemic concentrations of ammonia, urea, glucose or insulin. There was no relationship between dietary treatment or systemic metabolites and any of the estimates of conceptus development. Systemic insulin was not affected by pasture N treatment or MSBP supplementation (P > 0·05). Systemic concentrations of glucose were not affected by pasture N treatment (P > 0·05) but were increased by MSBP supplementation (P < 0·05). Systemic progesterone was not affected by pasture CP or MSBP supplementation (P > 0·05) but at day 7 after AI was positively related (P < 0·05) to embryo survival. Intake of high CP herbage elevated systemic ammonia and urea but there was no association with embryo survival rate or embryo development in heifers.

Two trials were conducted to study the effect of the stage of maturity of fresh herbage on its digestibility by two breeds of sheep (Churra v. Merino). The sward consisted of a mixture of grasses and clover, and was harvested either in late May (early cut, EC) or in late July (late cut, LC). In each trial, 12 mature sheep of each breed were used. Each animal received a different amount of fresh herbage, so that levels of food intake ranged between 8·1 and 24·7 g dry matter (DM) per kg body weight per day. EC herbage showed higher crude protein content (116 v. 67 g/kg DM), lower neutral-detergent fibre concentration (494 v. 664 g/kg DM) and higher DM digestibility (0·687 (s.e. 0·005) v. 0·463 (s.e. 0·007)) than the LC herbage. DM digestibility coefficients observed in Churra (0·694 (s.e. 0·028) for EC and 0·476 (s.e.0·028) for LC herbage) tended to be greater than those observed in Merino sheep (0·680 (s.e. 0·021) for EC and 0·452 (s.e. 0·040) for LC herbage). With the EC herbage DM digestibility tended to decrease as the level of intake increased. Samples of dried herbage were incubated in the rumen of Churra and Merino sheep to determine the DM degradability by the in situ technique. Fractional degradation rates (c values) were significantly faster in the rumen of Churra than in Merino (0·046 (s.e. 0·003) v. 0·031 (s.e. 0·002)), with large differences between breeds in the DM disappearance rates at intermediate incubation times, and no significant differences between Churra and Merino sheep in the mean a + b values. Microbial N supply, calculated from the urinary excretion of purine derivatives, was significantly affected by the herbage maturity stage and by the level of DM intake, but not by the breed of sheep. It is suggested that differences between breeds of sheep in food digestibility may be related to their ability to digest fibrous diets.

Eight mid-lactation Holstein-Friesian dairy cows were used in an experiment to investigate whether poor transfer to milk of (n-3) long chain (≥C20) poly-unsaturated fatty acids (n-3 LCPUFA), from diets containing fish oil, is related to their mode of transport in plasma lipoproteins. The cows were split into two groups of four, each of which was housed with 24 other cows which did not provide blood data in this experiment. All cows received a basal diet ad libitum consisting of (kg/t dry matter) silage (539), grain distillers’ grains (148), rolled barley (248) and soya (65). All cows also received a mid-day meal of 2·76 kg per cow per day of molassed sugar-beet shreds. The control group (C) received no oil supplement but those in the treatment group (F) received 300 g per cow per day of fish oil absorbed onto the sugar-beet shreds. Fish oil inclusion progressively depressed milk fat concentration of the four cows from each group over the 3 weeks of the experiment so that levels were approximately 20 g/kg lower for cows in treatment F than for those in C (P < 0·05). Mean concentrations over all cows of the long-chain (≥C20, n-3) poly-unsaturated fatty acids in milk fat (g/100 g) were 0·12 and 0·54 for treatments C and F respectively, whilst corresponding output in milk (g/day) increased from 116 to 3·91, an average efficiency of transfer of 4·6%. The fatty acid compositions of the lipoproteins were measured in plasma samples from the four cows from each group after 3 weeks on the experimental diets The proportions (g/100 g fatty acids) of C20: 5 (n-3) in cholesteryl (CE) and phospholipid (PL) of high-density lipoprotein (HDL) in the plasma were respectively increased from 0·97 to 4·39 (P < 0·05) and from 1·15 to 4·74 (P < 0·01) by the fish-oil supplementation. For C22: 6 (n-3), the proportions in CE and PL of HDL respectively increased (P < 0·001) from 0·02 to 0·23 and from 0·16 to 2·18 as a result of the supplementation. The mean proportions (g/100 g fatty acids) of C20: 5 (n-3) and C22: 6 (n-3) in the triglyceride fraction of very low-density lipoprotein were 1·05 and 2·3 respectively and were not significantly altered by fish-oil supplementation (P > 0·05). It is suggested that the low transfer efficiency of (n-3) LCPUFA to the milk is partly due to their transport in the plasma largely as components of HDL lipids which are unavailable to the mammary gland.

Sixteen Holstein Friesian cows were offered ad libitum a forage mixture of three parts (dry-matter (DM) basis) maize silage (starch and neutral-detergent fibre (NDF) 324 and 395 g/kg DM) and one part grass silage (NDF 518 g/kg DM) in a 4 ✕ 4 Latin-square change-over design experiment using four periods each of 4 weeks. Cows were housed in a cubicle house, bedded on sand and given food through Calan gates. The four supplement treatments were control (no oil supplement, C); 1·5 kg/day processed crushed linseed (PL); 1·5 kg/day crushed linseed (L) and 0·6 kg/day marine algae (A) providing 0, 440, 423 and 109 g/day of oil respectively. Cows also received a pelleted concentrate in three equal meals (12·0, 10·5, 10·5 and 11·2 kg/day for C, PL, L and A respectively) containing (g/kg DM) 260, 203, 288 and 74 of crude protein, NDF, starch and water-soluble carbohydrate respectively. Oil supplementation depressed (P < 0·05) forage intake (11·2, 10·3, 10·1 and 10·1 kg DM per day) but milk yield was unaffected (P > 0·05) by treatment (mean 35·9 kg/day). Milk fat concentrations were low and further depressed (P < 0·05) by algal supplementation (33·5, 32·3, 32·3 and 25·6 g/kg). Algal supplementation caused a three-fold increase in the concentrations of (n-3) long chain (>C20) polyunsaturated fatty acids in milk fat (to 0·51 g/100 g fat) representing a transfer efficiency from diet to milk of ca. 5%. Oil supplementation increased levels of all trans monoenes in milk but the effect was much greater for treatment A (P < 0·05) and for trans-10 C18: 1 (1·52, 1·94, 1·72 and 6·12 g/100 g milk fat for C, PL, L and A respectively). Trans-10 C18: 1 was the predominant trans monoene in milk fat for all treatments (47·7, 45·2, 45·6 and 67·4% of total). Treatment A also caused the greatest increases (P < 0·05) in conjugated linoleic acid (CLA to 0·54, 0·69, 0·65 and 0·97 g/100 g milk fat). Although mainly cis-9, trans-11, a small proportion (4·8 to 5·5%) of the CLA was identified as the trans-10, cis-12 isomer for all treatments. This pattern of isomers of trans monoenes and CLA, which may have implications for the health properties of the milk, may be related to effects on rumen function caused by the high starch intakes (5·75, 5·09, 5·11 and 5·27 kg/day).

Sixteen Finnish Ayrshire dairy cows were used in a cyclic change-over experiment with four 28-day experimental periods and a 4 ✕ 2 factorial arrangement of treatments to evaluate the effects of dietary nitrogen (N) source on dry-matter (DM) intake, diet digestibility, milk production, blood metabolite concentrations and N utilization. Experimental treatments consisted of two silages prepared from timothy and meadow fescue swards fertilized with either 52 or 104 kg N per ha (SL and SH, respectively) offered ad libitum supplemented with one of four concentrate supplements offered at 10 kg/day. A basal concentrate (control) was formulated from (g/kg on an air-dry basis) barley (307), oats (460), molassed sugar-beet pulp (200) and vitamins and minerals (33). Three isonitrogenous concentrates were prepared by replacement of basal concentrate ingredients (g/kg) with urea (14·4), wheat-gluten meal (WGM; 57·2) and heat-moisture treated mechanically expelled rapeseed cake (RSC; 188), respectively. Harvesting of secondary growths receiving higher applications of fertilizer N increased silage N content (19·2 and 23·6 g/kg DM, for SL and SH, respectively) but decreased water-soluble carbohydrate concentrations (respective values 149 and 93 g/kg DM). Increases in N fertilizer had no effect on silage DM intake, output of energy-corrected milk, milk fat or milk protein secretion, while provision of additional N in concentrate supplements improved all of these parameters. However, the magnitude of silage DM intake responses to additional N in concentrates was higher (P < 0·05) for SL than SH silage-based diets. Increases in dietary N content derived from silage or inclusion of urea, WGM or RSC in concentrate supplements led to a decline in the proportion of N intake secreted in milk. Relative to N derived from silage or urea, WGM and RSC supplements had beneficial effects on milk production. Both the quantity and quality of dietary N sources should be considered in future attempts to improve the efficiency of on-farm N utilization.

The live-weight gain (LWG) of young male red deer in New Zealand naturally slows during winter and feeding diets of mainly silage appears to exacerbate this effect. We aimed to quantify the effect of feeding silage on intake and LWG during winter and the ability to improve LWG by feeding supplements, mainly in the form of barley. Seven groups of eight deer were maintained outside in gravelled enclosures and offered silage ad libitum for 94 days during winter. Six groups were given supplements (950 g barley with 50 g rapeseed meal per kg to make all diets isonitrogenous) at rates of proportionately 0·2, 0·4, 0·5, 0·6, 0·7 and 0·9 of the metabolizable energy (ME) intake of the group given only silage (0). The study also examined the effect of the winter treatments on subsequent LWG to slaughter weight whilst grazing on pasture during spring and into summer (102 days).

Increasing supplement intake resulted in a decrease in silage dry matter (DM) and ME intake (P < 0·001) and an increase in total ME intake (P < 0·01). The substitution rate for silage DM was 0·84 (s.e. 0·079). LWG during silage feeding was positively related (P < 0·01) to supplement intake with an increase of 6·21 g/day per MJ per day. LWG on pasture was not related to either supplement feeding rate or LWG during winter. LWG over the entire experiment was related (P < 0·01) to supplement feeding rate, with a final difference in live weight of 6 kg between 0 and 0·9 groups.

This study has confirmed that the LWG of young male deer is low during winter when given only silage and that feeding supplements increases total ME intake and LWG. The reduced LWG due to silage feeding was not compensated for on pasture during spring and summer, thus delaying the time to reach slaughter weight by approximately 1 month. High proportions of silage in the diet appear unsuitable for young male deer if the aim is to achieve rapid LWG during winter.