Heat production, energy and nitrogen balances of artificially reared piglets from specific pathogen free sows, housed in a respiratory chamber, were measured over five successive periods of 7 days each from 4 to 39 days of age. The experiment was carried out at an environmental temperature decreasing from 33 to 27°C. The mean weight increased from 1·5 (at day 4) to 11·9 kg (at day 39). Daily rate of gain increased from about 100 g in periods 1 and 2 to 502 g per piglet in the fifth period.

Daily protein deposition, as measured via nitrogen balance, increased from 17 to 96 g; fat deposition increased from about 0 to 100 g. Body composition at the start and end was determined by a comparative slaughter technique. Protein and fat content had a high correlation coefficient with body weight (R2 = 0·69 and 0·89, respectively). At birth these values were much lower, 0·24 and 0·01 for protein and fat, respectively.

Nitrogen balance compared with slaughter technique led to an overestimation for protein deposition of proportionately 0·07. Fat gain measured from slaughter was proportionately 0·08 lower than that calculated from energy balance.

Ratio of gain estimated from protein and fat gain with the balance technique relative to that measured ranged between 0·93 to 1·15 in various periods.

A study of the intake potential of a range of well-preserved silages offered to lambs over several years showed that, of the many parameters considered, those with the greatest positive effect on DM intake were sugars in the grass as ensiled, residual sugars and protein nitrogen in the silage, with ethanol concentration in the silage having a negative effect (Henderson, Anderson and Phillips, 1984). In the experiments reported here ADD-F (85 per cent formic acid) from BP Chemicals International was applied to ryegrass at a rate sufficient to conserve much of the sugar (WSC) in the silage by inhibiting the growth of the micro-organisms on the grass. The initial lowering of the pH should also inhibit the activity of the plant enzymes, conserve protein nitrogen (PN) in the silage and prevent extensive deamination.

In 1986 first-cut perennial ryegrass, and in 1987 Italian/perennial ryegrass, was ensiled direct-cut, untreated or treated with 5 1 ADD-F/t grass in 100t capacity clamp silos. The grass was cut with a mower and lifted with a precision-chop forage harvester. The acid was pumped onto the grass through a dribble bar sited over the pick-up drum.

In an analysis of data from 211 litters in a Pietrain herd, litter size at birth and at weaning was lower than is generally found in indigenous breeds. Mortality in growing and breeding pigs was high with circulatory failure accounting for 23% and 95% of deaths respectively. Pietrains, fed ad libitum over the live-weight range 27 to 87 kg, grew more slowly by 130 g/day than contemporary Large Whites on the same feeding regime, had higher killing-out percentages (by 3 to 4 units) and larger eye muscles in cross-section (by 9·9 cm2) but tended to have higher feed conversion ratios. There was no breed difference in backfat measurements but Pietrain carcasses were shorter by 83 mm and their muscle quality was markedly inferior to that of the Large Whites.

Two experiments were conducted with three types of polyethylene particles to establish their retention time in castrated male cattle (steers) offered diets which contained predominantly cereals ad libitum. The particles were (1) ‘Ruff Tabs’, a corrugated particle of dimension 1·27 × 0·63 × 0·95 cm3 and subsequently referred to as RT and (2) and (3) plain plastic rods of 1·27 cm length and 0·32 cm (BP) or 0·63 cm (RBP) diameter.

In the first experiment with steers weighing 170 or 260 kg, 1 kg of RT particles were excreted in the faeces at a similar rate by the steers of different weights whereas BP particles passed out in the faeces more slowly in the lighter steer.

In the second experiment 30 steers weighing 440 kg were slaughtered at 7, 14, 28 and 42 days after dosing with 1 kg of BP, RT or RBP. The recovery of RT was significantly lower (P < 0·05) than that of BP 7 days after dosing and this difference was also found at 14 and 28 days. RBP behaved like BP up to 14 days but thereafter the rate of passage of RBP was faster than tha t of BP and recovery from the rumen approached that of RT.

Piglet body composition at weaning could be a determinant for pig’s viability and may be influenced by factors such as the nutritional management followed during suckling. An experiment was conducted to study whether intermittent suckling (IS) affects body composition at weaning and nutrient and energy retention during a 34-day lactation period in Iberian piglets. Litters were subjected to conventional suckling (CS) or IS (n=10 litters of six piglets per treatment) in two trials. All piglets had ad libitum access to creep feed from day 15 onwards. In IS, piglets were progressively separated from the sow for 6, 8 and 10 h daily during the last week of lactation, whereas in CS piglets had continuous access to their dams. Creep feed intake in litters and BW development of individual piglets were measured throughout the 34-day lactation. Within each litter, both at birth and at weaning (day 35), one piglet was used to assess nutrient retention and body composition by the comparative slaughter approach. During days 29 to 35 of the experiment, daily creep feed intake was greater in IS piglets (IS 124, CS 67 g/piglet, P=0.040), and average daily gain differed significantly between groups (IS 190, CS 150 g/day, P=0.010). BW at weaning was higher in the IS than in the CS piglets (IS 8.19, CS 7.48 kg, P=0.011). Empty-body fat and energy content at weaning were higher in the IS compared with CS litters, as well as fat content in the carcass (P=0.04). The IS treatment did not affect empty-body protein deposition, but significantly increased daily retention of fat, energy, ash and calcium, compared with CS litters (P<0.05). Thus, IS in Iberian piglets seems to enhance feed intake, growth rate and retention of some body components, which may contribute to a higher body fat content at weaning and facilitate the weaning process.

Dominance allows animals priority of access to resources when these are limited. It is common practice to feed dry sows once or twice daily a relatively small amount of food. This can lead to high competition for food, when there are no provisions for individual feeding of group housed sows. In contrast, competition for food should be low when offered ad libitum. This study was designed to investigate the effect of feeding regime on the measurement of hierarchies in group housed dry sows.

Four groups of 12 multiparous sows were housed in deep straw pens (3.1 m2/sow). Two groups were offered a high fibre diet ad libitum from a three-space hopper (LC) and two groups were floor-fed 3 kg/sow of a standard diet once daily (HC). The diet composition is given in Brouns et al (1992).

Groups were allocated to treatment after service. After two months on treatment, the dominance of every sow in each pen was determined in a feed competition test between all possible dyads of sows. A more detailed description of this test is given in Brouns et al (1992). The results of this test indicated how many pen mates each sow dominated (DR). This was used to calculate an index of linearity for the hierarchy (Appleby, 1983) giving a value between 0 and 1, where 1 indicates a completely linear hierarchy.

There is a considerable literature on the effect of grinding and pelleting roughages on their intake and digestibility by ruminants. It is also well established that intake is correlated with digestibility, which parameters are themselves correlated with the rumen degradability of the roughages concerned (Hovell et al. (1986)). However there is little information in which the effect of processing on the intake and digestibility of roughages of known degradation characteristics has been examined. The objective of the experiment reported here was to examine the effect of grinding and pelleting on the voluntary intake and digestibility of two roughages whose degradation characteristics had been defined.

Four mature 63-69 kg Finn-Dorset ewes fitted with permanent rumen cannulae were used. The roughages were a hay (potential degradability 0.81), and a barley straw (potential degradability 0.57) given coarsely chopped, or ground and pelleted. The composition of the hay and straw is shown in Table 1, and the particle size distribution of the two forms is given in Fig. 1. Urea was added to the straw at 18 g/kg and to the hay at 3.6 g/kg (air dry), with 0.13 g sodium sulphate per g urea. A mineral/vitamin supplement was also given. The experimental design was a latin-square with 21 d periods. Food was offered to 10-15% excess of voluntary intake. Voluntary intakes and digestibility were measured during the last 7 d of each period.

Broilers select an adequate diet when they are given a cycle of 8h free access to whole grain wheat followed by 8h access to a pelleted balancer feed (Foote and Rose 1991). This study had 3 feeding trials. Their objectives were to investigate whether the sequential feeding regimen allowed dietary self-selection by broilers and to compare the productive performance of the broilers with other feeding regimens.

The first trial used 144 broilers in 24 cages. Three balancer feeds were formulated by removing part of the wheat component of a complete feed formulation. Either 35%, 50% or 65% of the wheat was removed from the original formulation. A fourth sequential feeding treatment used the 50% balancer but with another sample of whole wheat as the alternate feed.

A series of metabolism experiments investigated the recovery of continuous-, intravenously infused chromium complexed with ethylenediamine tetra-acetic acid (CrEDTA) and lithium sulphate in the urine of cattle with a view to using the markers to estimate urine and metabolite output in grazing cattle. The recovery of Cr in urine from these infusions was similar (90%) in metabolism trials when cattle consumed three very contrasting diets: high-grain formulated pellet, lucerne hay (Medicago sativa) or low-quality native grass hay (predominantly Heteropogon contortus). By contrast, Li recovery in urine averaged 46.3 ± 0.40% and 72.6 ± 0.43% for native pasture and lucerne hays, respectively, but was not constant across days. There was negligible transfer of Cr from CrEDTA in blood serum to the rumen or faeces, whereas appreciable quantities of infused Li were found in both. The ratio of urine volume estimated by spot samples and marker dilution of Cr, to urine volume measured gravimetrically, was 1.05. In grazing studies using rumen-fistulated (RF) steers grazing seven different tropical and temperate grass and legume pastures, the ratio of concentrations of purine derivatives (PD) to Cr in spot samples of urine was shown to vary diurnally in the range of 49% to 157% of the average 24 h value. This finding indicated the need for regular sampling of urine to achieve an accurate average value for the PD : Cr ratio in urine for use in estimating urinary PD excretion and hence microbial protein production in the rumen. It was concluded that continuous, intravenous infusion of CrEDTA resulted in a constant recovery of Cr in the urine of cattle across diets and, provided an intensive sampling regime was followed to account for diurnal variation, it would be suitable as a marker to estimate urine volume and urinary output of PD in grazing cattle.

This study assessed milk productivity, demographic characteristics and workload distribution on a single high-yield dairy ewe farm in Spain (Avila, Spain; continental climate, latitude of 40.90 N, altitude of 900 m) over a 7-year period considering a transition from a herd management system involving five lambings per year (5LY) to a system involving 10 lambings per year (10LY). The 5LY system was practiced on the farm from 2010 to 2012 and the 10LY system from 2014 to 2015, with 2009 and 2013 being considered transition years. During this period, 27 415 lactations were recorded from an average of 3746 Lacaune sheep/year. Several productivity parameters were higher in 2014 to 2015 than in 2010 to 2012: milk yield/lactation (370±156 v. 349±185 l), lactation length (218±75 v. 192±75 days) and dry period length (53.5±38.3 v. 69.1±34.8 days) (all P<0.0001). During 2014 to 2015, investment in new lambing facilities was possible, workload was distributed more uniformly throughout the year, workload per worker was smaller, rate of ewe culling was lower (35.39±0.53% v. 42.51±7.51%), ewe longevity was greater and higher-order lactations were more numerous (P<0.0001). On the other hand, during 2010 to 2012, daily production was higher (1.73±1.66 v. 1.70±0.62 l/day; P=0.038), the interlambing period was shorter (283±50 v. 302±44 days; P<0.0001) and lambings/ewe per year were greater (1.42±0.01 v. 1.30±0.01; P<0.05). These results suggest that a 10LY herd management system can be compatible with profitability, productivity and good animal and worker’s welfare on a high-yield dairy farm, and may even be associated with better outcomes than a 5LY system.

Milk protein genes are among the most intensively expressed and they are active only in epithelial mammary cells of lactating animals. They code for proteins which represent 30% of the proteins consumed by humans in developed countries. Mammary gland development occurs essentially during each pregnancy. This offers experimenters attractive models to study the expression mechanisms of genes controlled by known hormones and factors (prolactin, glucocorticoids, progesterone, insulin-like growth factor-1 and others) as well as extracellular matrix. In the mid-1970s, it became possible to identify and quantify mRNAs from higher living organisms using translation in reticulocyte lysate. A few years later, the use of radioactive cDNAs as probes made it possible for the quantification of mRNA in various physiological situations using hybridisation in the liquid phase. Gene cloning offered additional tools to measure milk protein mRNAs and also to identify transcription factors. Gene transfer in cultured mammary cells and in animals contributed greatly to these studies. It is now well established that most if not all genes of higher eukaryotes are under the control of multiple distal regulatory elements and that local modifications of the chromatin structure play an essential role in the mechanisms of differentiation from embryos to adults. The technique, known as ChIP (chromatin immunoprecipitation), is being implemented to identify the factors that modify chromatin structure at the milk protein gene level during embryo development, mammogenesis and lactogenesis, including the action of hormones and extracellular matrix. Transgenesis is not just a tool to study gene regulation and function, it is also currently used for various biotechnological applications including the preparation of pharmaceutical proteins in milk. This implies the design of efficient vectors capable of directing the secretion of recombinant proteins in milk at a high concentration. Milk protein gene promoters and long genomic-DNA fragments containing essentially all the regulatory elements of milk protein genes are used to optimise recombinant protein production in milk.

This study examined whether work applied at different stages of lactation had any effect on reproduction of cows under two feeding regimes. Twenty-four F1 crossbred dairy cows (12 Friesian × Boran and 12 Simmental × Boran) were allocated one of two diets (H + 3: natural pasture hay + 3 kg concentrate per day; and H + 5: natural pasture hay + 5 kg concentrate per day) and one of three work treatments — starting 45 days (D45), 90 days (D90) and 135 days (D135) post partum — using a principal component analysis score based on milk yield, live weight, calving interval and parity. Cows pulled sledges for 50 days (pull = 108 N per 100 kg live weight). Over the experimental period of 315 days, cows on diet H + 5 travelled a similar distance and produced amounts of fat-corrected milk (FCM) similar to those of cows on diet H + 3. Total intake of dry matter per kg live weight 0·75 was higher for cows on diet H + 5 than for cows on diet H + 3 and was similar across work times. Hay dry-matter intake was greater for the H + 3 group than for the H + 5 group at 180 days post partum and thereafter. Cows on diet H + 5 lost less weight in early lactation and gained more in mid and late lactation than cows on diet H + 3. During the work period, live-weight change was similar across diets but it was different between work treatments D45 and D135. The interval from calving to conception decreased by 63 and 101 days when start of work was delayed from D45 to D90 and from D45 to D 135, respectively. Output/input ratios of metabolizable energy equivalents were 0·35 for H + 3 and 0·37 for H + 5 diet, and 0·34, 0·37 and 0·40 for work times D45, D90 and D135, respectively. These results indicate that work started in early lactation significantly increased days to conception and decreased overall productivity of lactating working cows. Farmers must weigh the relative importance and cost of delayed ploughing against those of delayed oestrus or against the cost of borrowing draught power.

Previous studies have shown that reciprocal recurrent selection (RRS) would be ineffective in the early cycles of selection if over-dominant loci were at equilibrium gene frequencies in both selected populations. It is shown in the present study that response to RRS may be reduced by this unstable equilibrium even when gene frequencies are as much as 30 % removed from the theoretical equilibrium frequency. Reducing one population to a bottleneck of two individuals for one generation or more before initiating RRS (RRSB) was very effective in overcoming the unstable equilibrium. RRS with recurrent inbreeding, then outcrossing in both populations each cycle of selection (RRSC) was not effective in overcoming the unstable equilibrium, but yielded greater response per cycle after selection response began. The effectiveness of RRSC was inversely proportional to the heritability of the trait. Use of these modifications to increase the effectiveness of RRS in poultry breeding is discussed.

Preweaning mortality generally accounts for 10-20% of all piglets born alive. A better understanding of the reasons for this mortality should help reduce losses.

Data from 493 litters born over a period of 18 months were analysed to investigate the timing, apparent cause and predisposing factors of piglet mortality.

To examine in more detail the way in which deaths occur a continuous video recording was made for the first 48 h. after farrowing for 31 litters. The way in which any deaths happened and the events leading up to them were then examined in detail.

The importance of dietary fibre in rumen buffering has long been overlooked, despite the realisation that the primary mechanism to achieve maximum ruminant production is by the maintenance of a rumen pH suitable for microbial digestion and growth. It has been demonstrated that the rumen pH following cereal based supplementation is depressed to a far greater degree than when the concentrate supplement is non-cereal based (Rymer, 1986).

Two trials are reported, firstly in which silage fed to finishing lambs was supplemented with either dried molassed sugar beet pulp, a source of highly digestible fibre and low in starch; whole barley (55.6% of D.M. content as starch, (British Sugar, 1986)); or a commercial lamb creep pellet and secondly in which silage plus dried molassed sugar beet pulp was supplemented with undegradeable protein or not.

Weaning represents a critical period in the life of a piglet. Although the age at which piglets are weaned is rather variable, it is common practice to wean them at an early age. At weaning the normal pattern of growth and development is interrupted. The extent to which nutritional, climatic, social and managemental practices influences the check in growth rate and change in tissue accretion is not well documented. The present experiments were designed to investigate the influence of some of these factors on the growth and development of the weaned piglet.

A model which was originally developed to derive the probability density of a calving distribution for beef cows under natural breeding has been modified to incorporate the effects of using oestrous synchronization at the beginning of the breeding period.

The model has been used to investigate five oestrous synchronization strategies over four herds, each with differing calving patterns: no synchronization; every cow in the herd is synchronized; every anoestrous cow is synchronized; every cow calving more than 20 days after the date of the planned start of calving is synchronized; every cow calving 30 days after the date of the planned start of calving is synchronized. Two of the herds previously had long calving periods and two previously had short, compact calving periods.

Model results showed that synchronization improved average herd calf live weight by 21 kg in the two herds with long prior calving periods but showed little effect in the two herds with compact prior calving periods. Synchronizing cows which calved more than 20 days after the start of calving in the herd showed similar results to synchronizing every cow in the herd and thus would be more cost effective. Synchronizing cows which calved more than 30 days after the start of calving in the herd showed a smaller advantage but only in the herds with long prior calving periods. The optimal strategy for oestrous synchronization in a herd will depend on the prior calving distribution and the average duration ofanoestrus in that herd as well as the relative costs of the treatment.

A deterministic bio-economic model was used to investigate the impact of different heifer replacement breeding systems for beef suckler cow production in different environments. It was shown that measures of cow efficiency were highly correlated with profitability in suckled calf production. However, where significant genotype differences exist in final output value due to issues of carcass quality, then more complete characterization of system profitability is recommended. In systems utilizing a terminal sire mating policy for all matings in excess of replacement heifer requirements the proportion of terminal sire matings made are affected by female fertility. Reduced cow fertility combined with late attainment of puberty in heifers and low heifer fertility has a substantial negative effect on the proportion of terminal sire matings made. This illustrates an aspect of production that can be improved by the use of crossbreeding to exploit heterosis in reproductive traits. The time frame of impacts of the different systems was seen to vary. Grading up to a pure breed allowed exploitation of heterosis in the early years of the transition leading to a boost in profitability but this boost was lost as the herd became purebred. Composite and rotational crossing systems were seen to create a steady rise in financial margin to the point where they became stable in breed proportion and heterosis. The effect of cow size was evaluated in three different environments, representing UK lowland, upland and hill. It was found that small cows became more profitable in relation to large cows as food resources became more limiting. In a non-limiting environment large cows were more profitable than small cows.