Methodology can play a critical rôle in the measurement of digestion kinetics, especially when the objective is to define kinetic parameters for use in formulating rations or modelling animal responses. Measurement of gas production kinetics provides the opportunity to evaluate the rate of digestion of the soluble, more rapidly fermenting fractions of foods but has the potential for being more sensitive to the in vitro procedure used. Differences among procedures that have little impact on digestion of dry matter after 48 h of incubation, may have dramatic effects on fermentation of soluble matter during the first 20 h. Our objective was to develop a method for measuring the kinetics of gas production that would minimize any detrimental effects associated with the in vitro system and provide estimates of digestion kinetics that can be used to both describe foods for ration formulation systems and provide parameters for models of ruminal digestion.

The feeding of high fibre diets to sows prior to ovulation has been shown to have beneficial effects on embryo viability, leading to a possible increase in piglet litter size. This trial was conducted to look at the effect of feeding sows a high fibre diet from mid lactation until breeding on subsequent litter size on a commercially run farm. The sows used were either Large White or Large White x Landrace in genotype and ranged from parity 1 to 7. The sows were allocated to receive either a cereal-based control diet (C), or a high fibre diet (HF) of similar specification but containing unmolassed sugar beet pulp (USBP) at a 20% inclusion rate during lactation and 40% from weaning to oestrus. The diets were fed from day 11 of lactation until oestrus. The sows were inseminated at oestrus and then fed a standard gestation diet until farrowing. The trial was conducted over a 3-month period and in total 198 sows received the HF diet with the rest of the sows over the 3-month period acting as controls (496) on the cereal-based diet. The effect of the diet on total litter size and the number of piglets born alive per sow was analysed in a general linear model (Minitab release 12.1). The combined results for both breed types showed that sows fed the HF diet had a significantly higher number of piglets born (12.37 ± 0.27 versus 11.41 ± 0.26, P<0.01) and a higher number of piglets born alive (11.47 ± 0.26 versus 10.85± 0.26, P<0.01) compared to 130 control fed sows matched for farrowing week. The difference in piglet litter size was still apparent when all the control sows farrowing over the 3 month trial period were included in the statistical analysis, with values of 12.47 ± 0.27 versus 11.79 ± 0.15 (P<0.05) for total number of piglets born and 11.77 ± 0.26 versus 11.16 ± 0.14 (P<0.05) for the number of piglets born alive for the HF and control diet respectively. Based on the results from this trial and previous studies, feeding a diet with a high content of USBP during late lactation and prior to insemination can increase the total number of piglets in the litter and the number of piglets born alive. This effect is less marked in crossbred sows with high baseline performance.

Two studies (expt. 1, 185 cows in 1996/97; expt. 2, 168 cows in 1997/98) were conducted with Prim ‘Holstein dairy cows in the Mayenne region (France) to investigate suboestrus. Cows which had not been observed in oestrus since calving were allocated alternately to treatment groups between 60 and 90 days post partum. Expt. 1. Group 1: GnRH (Day 0, 100 μg im), PGF2α (Day 7, 25 mg im), GnRH (Day 9, 100 μg im) with artificial insemination (AI) Day 10. Group 2 : PGF2α (Day 0, 25 mg im), AI at oestrus or if oestrus not observed a second PGF2α injection was given (Day 13) with AI on Day 16 and Day 17. Expt. 2. Group 1 : GnRH (Day 0, 100 /μg im), PGF2α (Day 7, 25 mg im), GnRH (Day 9, 100 μg im) with AI at observed oestrus after Day 0 or at Day 10 if oestrus not observed. Group 2 : PGF2α (Day 0, 25 mg im), AI at oestrus, or if oestrus was not observed a second PGF2α injection was given (Day 13) and AI at observed oestrus. Progesterone was measured in serum at Day 0 and in milk at AI. Pregnancy diagnosis was performed by measuring bovine Pregnancy Specific Protein B (bPSPB) (Day 50 + 3) and confirmed by ultrasonography when the result was doubtful.

In expt. 1, farmers observed 47/101 (46.9 %) of group 1 cows in oestrus, 33/91 on Day 10 and 10 before Day 10. The progesterone concentrations were compatible with oestrus in 69/86 (80%) of cows on Day 10. In group 2, 36/83 (43.4 %) of cows were inseminated after the first PGF2α injection. After the second PGF2 α, only 29/43 (67 %) of cows had a low progesterone concentration at AI. The pregnancy rates were 36.1% and 32.5 % for groups 1 and 2, respectively. In expt. 2, oestrus was observed in 31/93 (33.7 %) of group 1 cows. In group 2, 51/75 (66 %) of cows were inseminated after the first injection of PGF2α, 13/75 (17.3 %) after the second and 11/75 (14.7 %) were not seen in oestrus. Pregnancy rates were 53.7% and 53.3% in groups 1 and 2, respectively. In conclusion, it is recommended that suboestrus be treated with PGF2α followed by AI at observed oestrus when oestrus detection is good while, the use of GnRH + PGF2α + GnRH is recommended when oestrus detection is poor.

Rapid predicted worldwide growth in demand for animal products to 2020, the so-called “next food revolution” in animal agriculture, portends complex interactions among people, biological and geophysical resources, and economic objectives. Consumer demand for beef and pork is expected to increase by 2.8% per year, somewhat slower than demand growth for poultry meat (3.1%/yr). Demand for dairy products is predicted to grow fastest, at 3.3%/yr (Delgado et al., 1999).

Milk yield is ultimately constrained by the number of mammary secretory cells and the amount produced by each cell; increasing yield during early lactation is associated with increased output per cell, whilst decreasing yield during declining lactation correlates with reduced number of cells. Overall, yield is highly correlated with mass of secretory tissue but strategic control of lactation involves a galactopoietic complex of hormones including GH, prolactin and oxytocin acting to ensure efficient milk ejection and maintenance of secretion. Fine control, on the other hand, is achieved locally within the mammary gland by an autocrine mechanism which matches supply of milk to demand. The feedback inhibitor of lactation (FIL) is a milk protein which is inhibitory to secretion, so as milk accumulates between milkings, secretion rate gradually falls. The more frequently FIL is removed by milking, the greater the overall secretion rate. Storage of milk occurs within secretory tissue (alveolar milk) but also in the cistern (cisternal milk); FIL is effective in alveolar milk but not in cisternal milk, because it is then remote from its site of action. Therefore predictions would be that for a given mass of secretory tissue, large-cisterned cows should produce more milk, be more tolerant of infrequent milking but be less responsive to frequent milking. Methods developed by us for determining cisternal and alveolar milk storage spaces have obtained statistically proven support for the latter two predictions in dairy cows; the first prediction has been proven in goats. It has been shown that cisternal milk fraction increases during the course of lactation and with increasing parity. It is now intended to investigate the feasibility of incorporating storage characteristics into future selection strategies.

In horses, forages account for the greatest proportion of the diet (Micol and Martin-Rosset, 1995). As a result, the energy value of forages has to be determined very accurately to meet the horse requirements. In the UFC system (Horse Feed Unit) proposed by INRA (Martin-Rosset et al., 1994), the energy value of forages is closely related to organic matter digestibility (OMD).

In ruminants, OMD has been related to the in vitro gas production after 24 h of fermentation of foodstuffs with rumen fluid (Menke et al., 1979). The prediction of OMD with the gas test method is less accurate than with the nylon bag method but better than prediction performed with in vitro method or from chemical composition of foods (Khazaal et al., 1993 and 1995).

In the UFC system, three routine methods have been performed by our laboratory and proposed by INRA to predict routinely OMD of foodstuffs. OMD can be predicted either from chemical composition (Martin-Rosset et al., 1996a), by a pepsin cellulase method (Aufrère, 1982; Martin-Rosset et al., 1996b) or by near infra-red spectrometry (NIRS) (Andrieu et al., 1996).

The gas test method was subjected to be adapted in horses for predicting OMD. The accuracy of the prediction with the gas test method was compared with the other routine methods.

Crude protein concentration and energy value of cereal crop residues and poor quality grasses are below animal requirements during much of the year and browses have been incorporated in the feeding systems to improve the nutritional status of ruminants. Leaves and fruits of leguminous browses can be used as protein supplements for ruminants and are commonly used as foods in many agricultural systems. The new systems of protein evaluation (Agricultural and Food Research Council, 1992; Tamminga et al., 1994) partition food nitrogen into the amount degraded in the rumen and that which escapes ruminal degradation. Protein available for absorption post-ruminally is influenced by the amount of food nitrogen that is resistant to ruminal degradation plus microbial protein (Brown and Pitman, 1991). Several studies have been carried out to assess the digestibility of ruminal escape protein (Hvelplund, 1985; Frydrych, 1992), and the digestibility varies considerably across foods (Krishnamoorthy et al., 1982). Values between 0·80 and 0·85 are adopted for the true digestibility of protein from temperate foods and from microbial amino acids (van Bruchem et ah, 1989). However, no data are available on intestinal digestibility of browses although they have been recognized as good protein supplements. The mobile nylon bag (MNB) method is useful for assessing the digestibility of rumen undegradable food protein in the intestine (de Boer et ah, 1987). Since the MNB is labourious, it was desirable to assess the accuracy with which an in vitro (pepsin/pancreatin) procedure could predict results from the former. Therefore, the objective of this study was to determine apparent digestibility of browse rumen undegradable protein using MNB method and pepsin/pancreatin in vitro technique.

In nutritional terms productivity in dairy cows is best expressed in multiples of their energy requirements for maintenance, which is directly related to Metabolic Body Weight (MBW). Energy requirements can further be specified as those for free energy (fME), ketogenic energy (kME), glucogenic energy (gME) and aminogenic energy (aME). For maintenance, energy is required in an approximate ratio fME:gME:aME of 85:5:10.For a production level of 6x maintenance the required ratio of fME:kME:gME:aME is approximately 18:31:29:22, hence 70% of the required ME has to be delivered as specific nutrients.

During their productive life, dairy cattle alternate periods with high and periods with low risk of an inadequate nutrient supply. A period of high risk is between 10 days pre-partum and 90 days postpartum. High risk in this period means a high susceptibility for metabolic and reproductive disorders, many of which are interrelated. Negative Energy Balance (NEB) in early lactation is a metabolic status that is almost inevitable in high yielding dairy cows. In severe cases this is an important predisposing factor for metabolic disorders (paturient paresis, fatty liver, ketosis, displaced abomasum) and reproductive disorders (undetected heat, delayed ovarian cycle, reduced fertility, increased between calving interval).

Adequate nutrient supply is required from 2 weeks pre-partum onwards. Critical issues are energy density, distribution between structural and non-structural carbohydrates and distribution between fME, kME, gME and aME. Practical solutions, which can help alleviate the metabolic and reproductive problems, could be a nutrient based feed evaluation system, a lower peak yield combined with an improved persistence and maybe a deliberately increased calving interval.

Management control of a herd of animals is undertaken even at the most primitive level by recording data and subsequently recalling the information to effect decisions. This was true of the shepherd and goatherd of antiquity and the techniques used then were not much improved until the 1930's when an impetus for change came from setting up such bodies as the Milk Marketing Board. With dairy cattle, the major emphasis is now on herd control using methods equivalent to management control in industry. In management control, an aggregate of data, retrieved by suitable analysis, is used to effect a policy decision.

Cost–price models were developed to describe milk collection, manufacture and marketing of standardised fluid milk, butter, cheese, casein, and milk powders. Market constraints were modelled by fixing fluid milk demand to 10% or 70% of milk production. Milks representative of New Zealand Holstein-Friesian (HF) and Jersey (J) breeds, and novel technologies were considered. The true value of each milk was assessed from its own processing performance on the basis of fat, protein, lactose and volume considerations. Average milk was worth £0.193/kg when a significant fluid market exists, reducing to £0.112/kg when most milk was manufactured into concentrated dairy products for sale on the world market. Milk from different breeds varied in true value. On a per kilogram basis, HF milk was less valuable than J milk.

Single and multiple component payment systems were quantified for various subsets of milk components and used to obtain predicted values of a range of milks for comparison to their true values. Values of milks that differ in composition from average milk tend to have predicted values that deviate from their true value. The extent of such bias varies depending upon the payment system considered. For example, volume-based payment over-valued HF milk and penalised J milk. Other payment systems undervalued HF milk and over–valued J milk.

Payment systems should be fair, discourage unfavourable changes in composition and provide opportunities for shifts towards the production of more valuable milk. The marketing mix and the choice of payment system have major impact on the potential for economic benefits to the producer from modifying the composition of milk. Payment systems need careful, thorough investigation in concert with market research and studies into breeding and other management opportunities for modifying milk composition.

A value-based payment system can encourage producers to alter the composition of their milk in order to increase revenue.

The symptoms of trace element deficiency arise from the combined effects of the different lesions provoked within the animal body. Since a variety of different lesions have been described, many of which affect inter-related systems, it is not surprising that diverse symptoms may arise even from the one trace element deficiency; nor that similar symptoms may be caused by deficiencies of different trace elements. The major effects of trace element deficiencies on body functions have been outlined in Table 3.2.1 (from Underwood, 1980).

Despite the extensive knowledge of animals' dietary requirements for trace elements and detailed research into the uptake by plants of nutrients from the soil, it is surprising that the production of animal feedstuffs, having an appropriate trace-element content, still presents a considerable challenge to the agronomist. The present paper draws attention to some of the problems involved, using data from the many years of field-experiment research at the Macaulay Institute for Soil Research. These experiments have been largely restricted to the system of intensive agriculture prevailing in north-east Scotland, where heavily-grazed pasture and conserved herbage are the principal components of animal diets. The 6-7 year crop rotation most commonly practised includes a 3-4 year period of grass ley. The factors discussed have a wider relevance although their relative significance under conditions of low stocking rates, for instance on the rough or natural grazing on hill-land in the U.K. and other countries, will clearly be different.

There is no information on the metabolism of the cattle embryo during the period from day 8 to 16 a period of greatest embryonic loss. In this study the rate of protein synthesis and phosphorylation was measured in 13 to 15 day old cattle embryos. The rate of glucose utilisation and amino acid uptake/efflux by day 14 to 16 embryos was also measured. Protein synthesis and phosphorylation activity when expressed per unit of protein decreased with increasing embryo size and age. Similarly the rate of glucose utilisation was greatest for the earlier day 14 embryos. Embryos differed in their requirement for different amino acids. The pattern of uptake/efflux was similar to that of the earlier day 7 embryo. This study suggests that the metabolic rate of cattle embryos expressed per unit of protein content tends to decrease with increasing age and size from the initial burst of activity at day 13 around the time that expansion of the embryo begins.

The economic implications of sub-standard performance in animal production which result from the increased incidence of metabolic disorders such as bovine ketosis and ovine pregnancy toxaemia, and accompanying reduced reproductive performance, plus the detrimental effects of undernutrition, are well known. Together they pinpoint the desirability of being able to assess the adequacy of rations in supplying nutrients, particularly energy, to provide an appropriate diet. The assessment of nutritional status is becoming increasingly important as farmers attempt to maintain enterprise profitability by either reducing feed costs and maintaining production, or by maintaining feed costs and increasing overall production, or by a combination of these two procedures.

Cloning mammals from somatic cells by nuclear transfer has the potential to assist with the preservation of genetic diversity. An increasing number of species have been successfully cloned by this approach; however, present methods are inefficient with few cloned embryos resulting in healthy offspring. In those livestock species that have already been cloned, it is clearly feasible to use cloning to preserve endangered breeds (e.g. the last surviving Enderby Island cow). The opportunity exists to recover oocytes from these cloned heifers and use frozen Enderby Island sperm from deceased bulls for in vitro fertilisation and thus, expand the genetic diversity of this breed. Where there exists an adequate understanding of the reproductive biology and embryology of the species concerned and adequate sources of females to supply both recipient oocytes and surrogates to gestate the pregnancies, intra-specific nuclear transfer and embryo transfer can be utilised. However, when these requirements cannot be met, as is common for most endangered species, cloning technology invariably involves the use of inter-species nuclear transfer and embryo transfer. Even in intra-specific cloning the source of oocyte for nuclear transfer is an important consideration. Typically, cloned animals are only genomic copies of the founder if they possess mitochondrial DNA which differs from the original animal. Different maternal lineages of oocytes both within and between breeds significantly affect cloning efficiency and livestock production characteristics. Cloning should not distract conservation efforts from encouraging the use of indigenous livestock breeds with traits of adaptation to local environments, the preservation of wildlife habitats or the use of other forms of assisted reproduction. Whilst it is often difficult to justify cloning in animal conservation at present, the appropriate cryo-preservation of tissues and cells from a wide selection of biodiversity is of paramount importance. This provides an insurance against further losses of genetic variation from dwindling populations, disease epidemics or even possible extinction. It would also complement the gene banking of gametes or embryos and can be performed more easily and cheaply. Future cloning from preserved somatic cells can reintroduce lost genes back into the breeding pool. With greater appreciation of the heritable attributes of traditional livestock breeds there is the desire to identify superior animals within these local populations and the genetic loci involved. Through clonal family performance testing, nuclear transfer can aid the selection of desirable genotypes and then the production of larger numbers of embryos or animals for natural breeding to more widely disseminate the desirable traits. With the identification of alleles conferring desirable attributes, transgenesis could be utilised to both improve traditional and industrial livestock breeds. This further emphasizes the importance of preserving global farm animal genetic resources.

Leg weakness reduces the amount of time broilers spend on their feet (Weeks and Kestin, 1994). It has been shown for wild birds that the frequency of visits to a food source relate to the cost of reaching it (Kacelnik, 1984). We recently reported (Weeks and Davies, 1996) that this appeared to apply to lame broilers which fed for approximately twice as long but half as frequently as their mobile contemporaries.

Energy balance is a function of dry-matter intake (DMI), live weight and milk yield over a certain time period. To investigate potential strategies to use genetic selection for the improvement of the negative energy balance, genetic co-variances were estimated among DMI, live weight and milk yield during the first 15 weeks of lactation (no.=628). Rather than estimating the full 45 by 45 matrix a random regression model was used to estimate a second order covariance functions for the additive genetic and permanent environmental effects. Fixed effects were test-day, a group effect and week in lactation. Estimates for the genetic covariance function demonstrated that a high level of milk yield is only moderately correlated with a high level of DMI (0.21) but very strongly correlated to an increase of intake (0.97) and a loss of live weight (-0.46) during the first 15 weeks of lactation. Levels of weight and intake were correlated strongly (0.81). Estimates for the genetic correlations between weeks 1 and 15 were 0.79, 0.34 and 0.83 for milk yield, DMI and live weight respectively. DMI during early lactation was negatively correlated with milk yield but DMI during the later weeks was positively correlated with milk yield. The implication is that when selection is for a linear combination of milk yield, DMI and live weight (i.e. energy balance or efficiency) the moment in lactation of measuring each trait on the cow is of importance