Showing papers in "Annales De Zootechnie in 2000"

Methane production by ruminants: its contribution to global warming

Abstract: The aim of this paper is to review the role of methane in the global warming scenario and to examine the contribution to atmospheric methane made by enteric fermentation, mainly by ruminants. Agricultural emissions of methane in the EU-15 have recently been estimated at 10.2 million tonnes per year and represent the greatest source. Of these, approximately two-thirds come from enteric fermentation and one-third from livestock manure. Fermentation of feeds in the rumen is the largest source of methane from enteric fermentation and this paper considers in detail the reasons for, and the consequences of, the fact that the molar percentage of the different volatile fatty acids produced during fermentation influences the production of methane in the rumen. Acetate and butyrate promote methane production while propionate formation can be considered as a competitive pathway for hydrogen use in the rumen. The many alternative approaches to reducing methane are considered, both in terms of reduction per animal and reduction per unit of animal product. It was concluded that the most promising areas for future research for reducing methanogenesis are the development of new products/delivery systems for anti-methanogenic compounds or alternative electron acceptors in the rumen and reduction in protozoal numbers in the rumen. It is also stressed that the reason ruminants are so important to mankind is that much of the world's biomass is rich in fibre. They can convert this into high quality protein sources (i.e. meat and milk) for human consumption and this will need to be balanced against the concomitant production of methane.

Ruminant milk fat plasticity: nutritional control of saturated, polyunsaturated, trans and conjugated fatty acids

Abstract: After a brief survey of metabolic pathways and nutrient fluxes involved in mammary lipogenesis, this review summarises the known effects of diet on ruminant milk fat composition. Special attention is given to fatty acids that could play a positive role for human health, such as butyric acid, oleic acid, C18 to C22 polyunsaturated fatty acids and conjugated linoleic acid (CLA). The efficiency of the transfer of C18:2, C18:3, C20:5, C22:5 and C22:6, from the duodenum to the milk, is reviewed. The main dietary factors taken into account are the nature of forages, including pasture, and the supplementation of dairy rations with protected or unprotected vegetable or fish oils. Dose-response curves of milk CLA are reviewed for different fat supplements, as well as the non-linear relationship between milk CLA and trans C18:1. The potential of dietary factors to increase the mean CLA content in cow milk fat is about 300% above basal values. There is, however, a need to evaluate how the different feeding strategies could change the other aspects of milk fat quality.

Dietary fatty acids and human health

Abstract: A considerable amount of evidence has accumulated to support the view that the very long chain omega 3 fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) have beneficial cardiovascular and anti-inflammatory properties and that levels of their consumption are insufficient in most Western diets. More recently, attention has been given to the possibility that the precursor omega-3 PUFA, alpha linolenic acid (ALNA), may share some of the beneficial actions of EPA/DHA on human health. Further research into the metabolism and physiological actions of ALNA, and comparisons with EPA/DHA, is needed before conclusions regarding the optimal amounts and types of omega-3 PUFA for human health can be defined. Conjugated linoleic acid (CLA), which arises as a metabolic by-product of rumen hydrogenation and which is found in foods of animal origin, has been proposed to possess potent health promoting properties, but much of this research has been conducted in experimental animals. There is an urgent need for complementary studies in human volunteers, to confirm the putative anti-carcinogenic, anti-atherogenic, anti-lipogenic and immuno-suppressive properties of CLA.

The relationship between farmers' attitude and behaviour towards calves, and productivity of veal units

Abstract: Although veal production is highly standardised, there still remains variability in pro- ductivity between farms, which might be due to the farmers' behaviour towards their animals, which in turn depends on their attitude towards animals. Fifty farms affiliated with the same veal company were studied. The farmers' behaviour with the calves was observed during one morning meal. The farmers were then asked to fill in questionnaires designed to measure their attitude towards calves, and to obtain information about their background (e.g. age, gender, level of education). The pro- ductivity results (daily weight gain, feed conversion, and mortality rates) were obtained from the veal company. The frequency of gentle contacts was positively correlated with the description the farm- ers made of their behaviour with the calves and their beliefs about the sensitivity of calves. Female farmers showed a more positive behaviour towards the calves, had more positive beliefs about the importance of contacts with calves, and made a more positive description of their own behaviour. Pos- itive behaviour was associated with better productivity. Furthermore, bigger units had lower mortality rates. It is concluded that for veal farmers, a positive attitude towards calves, a positive behaviour towards them, and good production results are linked. veal calves / human-animal relationship / handling / behaviour / attitude

The accuracy of intake estimation based on the use of alkane controlled-release capsules and faeces grab sampling in cows

Abstract: Alkanes are digesta markers for use as a research tool giving the opportunity to estimate feed intake and digestibility in vivo. The development of intra-ruminal controlled-release capsules (CRC) offers a practical method of dosing even-chain alkanes and may give less diurnal variability of marker excretion improving the validity of grab-faecal sampling. This was tested in the present study by total faeces collection in four cows for 7 days. Dry matter intake was 10.4 kg forages and 10.4 kg concentrate (diet 1) and 15.1 kg forage (diet 2). The recovery (proportion of dosed or dietary alkane intake found in faeces) of C 31 was lower than that of C 32 and consequently underestimated intake. C 33 and C 32 had similar recoveries giving accurate intake estimates from pooled samples from total daily faecal collections and also from grab samples taken at 6.30 a.m. The study confirms that a single injec- tion for gas chromatography is sufficient. Alkane CRC are concluded to be an accurate method for estimating forage intake of cows consuming diets with or without concentrate when spot sampling of faeces is conducted over 7 days and only moderately less precise when sampling over 5 days.

Effect of health disorders on culling in dairy cows: a review and a critical discussion

Abstract: La revue porte sur le risque de reforme consecutif a la survenue des principaux troubles de sante dans les systemes de production actuels. Pour estimer ce risque, les modeles d'analyse de survie dans lesquels les troubles de sante sont definis en tant que variables dependantes du temps apparaissent les plus appropries car ils permettent de tenir compte des variations de leurs effets au cours de la carriere des animaux. Pour decider la reforme, les eleveurs tiennent compte preferentiellement des evenements de sante survenant dans la lactation en cours et/ou en debut de lactation. Dans l'ensemble des etudes, le risque de reforme apres survenue d'une dystocie et/ou d'un trouble de la mamelle (mammites, blessures du trayon) est augmente, alors que les travaux divergent quant aux effets des troubles metaboliques et de la reproduction. Les differences de populations d'etude, variables d'etude et methodes utilisees peuvent expliquer ces differences de resultats. Les consequences, en terme d'effets estimes, des choix methodologiques effectues (par exemple, le choix d'inclure ou non dans les modeles des descripteurs des performances de production et de reproduction dans la lactation de reforme) sont discutees. L'effet des troubles metaboliques et de la reproduction sur le risque de reforme serait plutot indirect, via la diminution des performances qu'ils peuvent induire. L'effet des troubles de sante est en moyenne plus faible que celui de faibles performances de production et de reproduction. Pour une vache donnee, le risque de reforme consecutif a la survenue d'un trouble de sante depend fortement des caracteristiques de l'elevage (disponibilite en genisses de remplacement, situation par rapport au quota, …) L'interet de nouveaux travaux (1) pour preciser le sens et analyser la fiabilite de l'information relative aux motifs de reforme, (2) pour evaluer l'impact relatif des troubles de sante et des performances sur la reforme dans les differentes parites, (3) pour identifier et quantifier le role des facteurs d'elevage sur le risque de reforme est souligne.

Ruminants et environnement: la methanogenese

Abstract: Ruminants and environment: methanogenesis. Methane, the most important green- house gas after carbon dioxyde, contributes for 16% to the greenhouse effect. Only 30% of total methane emission originates from natural sources, whereas 70% is linked to human activities, includ- ing livestock production. Rumen methanogenesis can be incorporated into models of different lev- els of complexity, based on stoichiometry and kinetics of fermentation and estimation of energy content of nutrients. Nevertheless, recent efforts in estimating ruminant methanogenesis remain sub- ject to important variability, both on the animal and population level. In general, methane production in the digestive tract of production animals is estimated to be responsible for 22% of the anthro- pogenic sources. Attempts have been made to decrease this contribution, using methane inhibitors such as long chain fatty acids, halogenated methane analogues, antibiotics and biotechnological inter- ventions such as defaunation or reductive acetogenesis. However, none of the proposed methods for methane inhibition is acceptable nor applicable today due to the interaction of inhibitors with different rations or individual animal characteristics and series of interrelated effects associated with consumer scepticism towards certain additives. methanogenesis / rumen / greenhouse gas / environment

Relation between nutrition, performances and nitrogen excretion in dairy cows

Abstract: Reducing N excretion from individual cows is one way among others to better cope with the problem of the negative contribution of the dairy herd to the "Nitrogen cycle" on the farm. The objectives of this paper are first to quantify the effects of the main forage systems and protein feed- ing level on the amount of N excreted in relationship to their simultaneous effects on animal per- formances and efficiencies and then to examine the particularities of the grazing situation. N excre- tion depends primarily on the level of N intake i.e. on forage species, fertilisation, growth stage and protein supplementation and therefore varies between the main usual forage systems from 90 to 150 kg N per cow per year (i.e. 12 to 20 kg N per ton of milk). A simple method is proposed to cal- culate the load of excreta N from a dairy herd according to the specific pattern of feeding practices over the year. The effects of the level of metabolic protein supply over a wide range of dietary con- centrations (80-125 g PDI per UFL) were analysed from a set of 5 feeding trials. Through that range, excreta N were largely increased and productive responses were also important (but without any residual effect), not only for milk yield (+15 to +30%) but also for milk protein concentration (+2 g.kg -1 ) and feed efficiency (+10%). The simultaneous increase observed in feed intake (+1 to +3 kg DM) accounted for half of the productive responses and could explain why the nutritive bal- ance was hardly affected by protein levels, even in early lactation. Most of the productive parameters responded to increasing PDI levels according to laws of decreasing return that are given in the text. On the contrary, the relative N losses (excreta N per milk N) decreased curvilinearly with decreasing PDI levels reaching a minimal plateau. The concentration of 100 g PDI per UFL appears as a com- mon key value for both phenomena: higher PDI levels results only in small increases in productive performances whereas N losses increase sharply, and the reverse occurs with lower PDI levels. At graz- ing, the level of N fertilisation, through the increase in sward yield and N content, is the main deter- minant of productive performances and losses of excreta N per ha. The other factors of sward val- orisation such as stocking rate only have a moderate effect whereas the effect of concentrate supply could be low or high according to protein content. Total grazing days per ha is an integrative param- eter that accounts quite well for all these factors since it reflects both sward yield and herd valorisa- tion conditions. Roughly, each extra 100 grazing days induced by higher fertilisation increases N flows by 10-15 kg.ha -1 as milk and by 70-80 kg.ha -1 as excreta.

Replacement of digestible fibre by starch in the diet of the growing rabbit. II. Effects on performances and mortality by diarrhoea.

Abstract: Au total, 2 328 lapins en croissance ont ete mis en experience dans six stations experimentales, afin d'etudier les effets d'un apport croissant d'amidon en substitution de fibres digestibles, sur les performances de croissance et la mortalite au cours de la periode d'engraissement. Quatre aliments (A12, A16, A20, A24) renfermant de 12 a 24 % d'amidon (12 a 24 %) ont ete compares. L'amidon remplacait des fibres digestibles (hemicelluloses et pectines) sans variation concomitante des teneurs en proteines et en lignocellulose. Les aliments ont ete distribues a volonte depuis le sevrage (entre 28 et 35 j d'âge selon le site) jusqu'a l'abattage (entre 68 et 71 j d'âge). L'accroissement de 12 points du taux d'amidon entre les regimes extremes (A1 2 vs. A24) entraine un doublement de la mortalite par troubles digestifs sur la periode totale d'engraissement (respectivement 4,6 et 10,1 %). Parallelement l'indice de consommation s'abaisse faiblement (mais significativement) de 0,15 point entre ces memes regimes (respectivement 3,16 et 3,01 kg d'aliment par kg de gain). Entre les regimes extremes (A12 vs. A24) et sur la periode totale (28 a 71 j d'âge), l'ingestion d'aliment et d'energie digestible baisse faiblement (resp. -4,5 % et -1,5 %; P < 0,01) tandis que la vitesse de croissance ne varie pas significativement (42,5 g.j -1 en moyenne). Pour assurer la securite digestive du lapin en croissance, il est donc recommande de limiter le taux d'amidon a 14 %, en periode pose-sevrage; alors qu'en fin d'engraissement le taux d'amidon alimentaire peut atteindre 18 %.

Replacement of digestible fibre by starch in the diet of the growing rabbit. I. Effects on digestion, rate of passage and retention of nutrients.

Abstract: The effects of digestible fibre replacement (25 to 15% ) by starch (12 to 23% ), were studied on rabbit digestion with four diets (A12 to A24) having a similar level of lignocellulose (ADF, 18% ). Faecal digestibility, retention of nutrients and rate of passage were measured on four groups of 12 young rabbits fed the four diets ad libitum from weaning to slaughter (72 d). Intake, weight gain, and feed conversion were not significantly different among the 4 treatments (mean 102.4 g.d$^{-1}$, 34.0 g.d$^{-1}$, 3.02 respectively). Despite a 100% increase in the starch level between A12 and A24, the digestibility of organic matter and energy were similar (mean 65.5 and 63.7% respectively). Energy or protein retention were not significantly affected by treatments (mean 28.4 and 13.6% respectively). With a reduction of the supply in digestible fibre, overall fibre digestibility (NDF) was logically reduced (-10 units), particularly for the uronic acid fractions (71 to 44% respectively for A12 and A24). Consequently the quantity of degraded NDF (period 28-72 d) decreased from 13.7 to 8.1 g.d$^{-1}$ for the A12 to A24 diets, while it doubled for starch (12.5 vs. 23.1 g.d$^{-1}$). Whole tract mean retention time for the particulate phase increased by 2 h ($ P$ = 0.06) for the A12 to A24 diets, while it increased by 4 h ($ P$ $< $ 0.01) for the liquid phase. Caecal retention time of fine particles was more affected (+6 h) than that of large particles (+2 h). In conclusion, digestible fibre replacement by starch did not change the digestive efficiency of the rabbit, but slowered the passage rate.

The effects of size of suckled litter on intake behaviour, performance and health status of young and reproducing rabbits

Abstract: We compared feed intake, performance and health status of females and their young reared in litters of 4 (group L4; $n$ = 18) or 10 kits (group L10; $n$ = 20) between 16 and 32 days of age. Between days 16 and 25, the individual milk intake was lower (-15.7% ; $P = 0.08$) and the solid feed intake per kit was higher (+117% ; $P < 0.01$) for the L10 than for the L4 litters. Between days 26 and 32 (weaning), milk and solid feed intake were similar among groups. Live weight of the young was 10% lower in the L10 than in the L4 group at weaning ($P < 0.05$) but was similar in both groups at 70 days of age. Mortality rate around weaning (16-42 days) was higher in the L10 than in the L4 group (29% vs. 17% ; $P < 0.05$). Thirty-five days after parturition (day of slaughter), females showed a body condition and reproductive performance (conception rate, ovulation rate and litter size) which were similar in both groups, except for the weight of adipose tissues which was 35.8% lower in the L10 females ($P < 0.01$). These results suggest that the growth and survival of young rabbits are weaker if the rabbits are reared in large-sized litters in spite of an earlier and higher solid food ingestion which only partially compensates for the low milk availability.

Sources of shared variability among body shape characters at marketing age in New Zealand White and Egyptian rabbit breeds

Abstract: Body measurements (body length, thigh circumference, shank length and chest width) of 311 rabbits representing three breeds, New Zealand White (NZW), Red Baladi (RB) and Black Baladi (BB) purebreds were subject to factor analysis. The objectives of this study were (a) to disclose the main sources of shared variability among body shape characters, (b) deduce the factors that describe these traits, (c) quantify the breed differences in size and shape and (d) predict live weight at marketing age from orthogonal body shape characters. Body conformation 'shape' appeared to be controlled by common and unique factors. The communalities ranged from 0.80 for chest width to 0.99 for thigh circumference and uniqueness (special factors) made the balance. Compared with local breeds (RB and BB), NZW had higher communality (proportion of variance for a variable that is shared in common by other variables) for chest width and lower communality for thigh circumference and body length. Our findings indicated that most of the common variability in NZW body dimensions could be accounted for by factors representing general size and chest width. Corresponding factors in RB were general size and shank length and those in BB were general size and thigh circumference. Independent body shape characters derived from factor analysis accounted for 83.4%, 87.9% and 90.8% of the variation in live body weight in New Zealand White, Red Baladi and Black Baladi, respec- tively. New Zealand White rabbits / Egyptian rabbits / body dimensions / multicollinearity / factor analysis / shared variability

Nitrates in the human diet - good or bad?

Abstract: Although the nitrate and nitrite have been used for centuries, it has only recently been discovered that nitrate is manufactured in mammals by the oxidation of nitric oxide and that the nitrate formed also has the potential for disinfecting the food we eat. The mechanisms by which nitric oxide and other nitrogen oxides provide selective toxicity towards pathogens is not yet completely understood, and it is likely that the mechanisms will be different with different organisms. Whereas it is clear that acidified nitrite is produced on mucosal surfaces, and that this combination is effective in killing a variety of human gut and skin pathogens, there is no definite evidence as yet that this mech- anism is truly protective in humans exposed to a contaminated environment. Further understanding of the complex chemistry of nitrogen oxides may also help develop new antimicrobial therapies based on augmenting what seems to be a simple and effective host defence system. nitrates / nitrites / human diet / health

Measuring and managing genetic variability in small populations

Abstract: Genetic variability in small populations is affected by specific phenomena. The joint effects of genetic drift and selection, in addition to the decrease in genetic variance due to the mere selection (Bulmer effect), enhance the risk of losing alleles at selected or unselected genes and increase the inbreeding in the population by changing the family structure. Criteria for measuring this change in genetic variability are derived from the three approaches to describe the genetic variabil- ity. At the genealogical level, the kinship and inbreeding coefficients, or the effective population size, can be used. At the trait level, the estimation of its heritability is a good measure of remaining genetic variance. At the genome level, studying the polymorphism of known genetic markers can inform on the degree of genetic diversity. These criteria are to be integrated in specific tools for the management of the genetic variability. After a short introduction on the basic concepts needed for the study of genetic variability in small populations, the main criteria available to measure its change in populations is exposed and their relative efficiencies discussed. The strategies for monitoring genetic variability, deriving from the previous criteria, are illustrated through different examples. small population / genetic variability / genetic drift / genetic management / conservation programme

Effect of dexamethasone on milk yield and composition in dairy cows

Abstract: Dexamethasone was injected in dairy cows in order to get a better insight into the effects of corticosteroids on milk secretion and composition. A single intramuscular dose of 40 mg dexamethasone caused a 45% reduction in milk yield after 24 h; full recovery took 5 d. The secretion of fat, casein and magnesium was not affected by the treatment. Consequently, the concentration of fat, total protein, total casein, magnesium and phosphorus increased then decreased in direct proportion to the changes in milk yield. The secretion of total protein, calcium and phosphorus decreased as a result of the treatment. The concentration of lactose and the monovalent ions (sodium, potassium, and chlorine) was unaffected, and as a result their secretion decreased and returned to pretreatment level in direct inverse proportion to the changes in milk yield. Whey protein secretion decreased for 48 h and was responsible for the decrease in total protein secretion for 48 h. The most profound effect of dexamethasone is the reduction in the secretion of the osmotic components. milk yield / dairy cows / stress / corticosteroids

Rearing density effect on the production performance of the edible snail Helix aspersa Müller in indoor rearing

Abstract: Six different indoor rearing densities (250 to 500 animals per m 2 ) were tested. Three repeats were carried out for each density. The following were recorded: feed intake, weight and number of adult individuals (animals with a reflected peristome), non-adult weight at the end of the experiment, and mortality. A simplified calculation of gross margin is also presented. It was observed that, at low densities, the animals consumed more, were bigger and more of them became adults. How- ever, the total amount of biomass produced is greater at higher densities. If the breeder merely fattens the snails, then the gross margin is maximal at a density of 250 animals per m 2 . If the breeder fattens and cooks his own produce, then the gross margin is maximal at high densities. Compared to the mixed rearing method currently used, the performances observed in this indoor rearing experiment could be improved further (particularly in terms of the percentage of adult animals obtained).

Degradation in the rumen of proteins from fresh lucerne forage in various stages of growth and conserved as silage or hay

Abstract: The extent to which rumen soluble nitrogen can contribute to the intestinal flow is unknown. Therefore a study was carried out to simultaneously assess the dynamics of protein dis- appearance from dacron bags placed in the rumen and the amount of various N products (total nitro- gen (tN), ammonia nitrogen (NH3-N), non-ammonia nitrogen (NAN). Measurements were carried out on 4 sheep fed various lucerne forages. These forages included fresh lucerne cut at the vegetative or bud stage, fresh lucerne cut at the 6-week second growth stage and at stemmy regrowth stage. In addi- tion two silages made from lucerne at the bud stage, with or without formic acid were also given. The hay was dried on the ground in good weather. The effective degradability of nitrogen (DegN) estimated from the nylon bag procedure was lower (p < 0.05) with the latter vegetation stage (0.80 for vegeta- tive stage vs. 0.76 for bud stage). This value was 0.81 for the regrowth stage. The DegN of the silages was higher (p < 0.05) without additive (0.84) than with formic acid (0.80) and the DegN of the hay was markedly lower (0.66, p < 0.05) than with the original fresh forage. Whatever the forage studied, tN and NAN rumen fluid contents were high at 1 h or 2 h after feeding (from 0.458 mg .g -1 for hay to 0.813 mg.g -1 for fresh forage at the vegetative stage) and diminished rapidly up to 7 h after feeding except for the silages, for which the minimum content was observed 4 h after feeding. A part of the solubilised nitrogen remained as proteins at 1 h and 2 h after feeding for fresh lucerne at var- ious stages of harvesting (from 0.187 mg.g -1 to 0.221 mg.g -1 at 1 h) while no protein could be seen in the rumen fluid after feeding of sheep fed silage (with or without preservative) or hay. The part of NAN escaping rumen degradation and transiting with the rumen fluid represented 7 to 11% of the nitro- gen disappearing from the nylon bags placed in the rumen. There was little difference linked to the veg- etation stage of the forage or its mode of conservation in particular. This content remained high for hay while its effective degradability (0.66) was much lower than for other forages (from 0.76 to 0.84). lucerne / green forage / silages / hay / vegetation stage / protein degradation / rumen fluid composition

Chemical composition and coagulation properties of Modicana and Holstein cows' milk.

Abstract: The chemical composition and clotting properties of milk from 45 Modicana (Mo) and Holstein (Ho) cows were assessed over the winter (December and January) and spring periods (March-April). The cows came from 4 farms of the Ragusa region (Italy). Considerable differences in milk yield, milk composition and clotting properties were noted between breeds. During the win- ter and spring periods, Mo and Ho produced an average 15.4 and 35.8 kg .day -1 of milk, respec- tively. The Mo milk contained significantly more fat (+5.8 g .kg -1 ), nitrogen (+5.9 g.kg -1 ) and lactose (+1.9 g.kg -1 ). The casein/true protein ratio was also higher in Mo milk (+3.5%) and the plasmin content was 87% lower. The fatty acid composition was the same in both breeds. The pH of the Mo milk was lower (-0.07), coagulation time and curd firming rate were quicker (32 and 53% respectively) and the curd was firmer (+50%). The results obtained during the spring period were very close to those of the winter period. For a same nitrogen content, the Mo milk produced a 16% firmer curd than the Ho milk, probably due to its higher casein/protein ratio and its higher content of casein κ variant B (75 and 28% for Mo and Ho cows respectively). milk / Holstein and Modicana breeds / chemical composition/ clotting properties

Genetically modified organisms: consequences for ruminant health and nutrition

Abstract: Many of the plants eaten by farmed ruminants are capable of being genetically modified, and may in the future be modified for nutritional, agronomic or industrial purposes. Techniques are also becoming available for genetic modification of silage and ruminal bacteria. Those working in agri- cultural biotechnology have a clear responsibility to detect and avoid any unintended or undesir- able consequences of such modifications, whether direct or indirect, upon the animal, the consumer and the environment. One of the most general concerns that has been expressed is the possibility for onward transfer of modified gene sequences to gut microorganisms or host cells. Rare acquisition of diet-derived DNA fragments cannot be ruled out, but if this occurs, it must have also occurred throughout mammalian history. The possible impact of genes not normally present in ruminant diets must, however, be considered. Discussion of the use of antibiotic resistance markers in transgene con- structs must take into account the wider debate on the likely impact of antibiotic use in animal agri- culture on the spread of antibiotic resistant bacteria. There is increasing evidence that overuse of antibiotics has lead to extensive transfer of antibiotic resistance genes between bacteria from the human and animal gut. In general this is likely to have a far greater impact than any rare transfer events involving resistance genes passing from transgenic plants to microbes. Our rapidly improving abil- ity to use sophisticated molecular approaches to predict and track the consequences of genetic mod- ification will help to ensure safe application of GM technology in agriculture in the future. GMO / rumen / ruminant nutrition / gene transfer

Nutritive value of on-farm common vetch-oat hays. II. Ruminal degradability of dry matter and crude protein

Abstract: Les caracteristiques de degradation et la degradabilite theorique (DT) dans le rumen de la matiere seche (MS) et des matieres azotees totales (MAT) de 11 foins de vesce-avoine ont ete mesurees avec des sachets de nylon sur trois moutons munis d'une canule du rumen. Les animaux ont ete nourris avec une ration composee de foin de vesce-avoine et d'aliment concentre dans des proportions 2:1 (sur MS) a un niveau de 40 g MS.kg -1 .P 0,75 . Les valeurs de DT, calculees avec des taux de sortie des particules du rumen mesures pour chaque animal, ont ete peu variables tant pour la MS (moyenne = 65,8 %; CV = 7,9 %) que pour les MAT (moyenne = 79,3 %; CV = 4,7 %). La proportion de vesce du foin a ete positivement reliee avec la DT de la MS (r = 0,412; P < 0,05) et des MAT (r = 0,583; P < 0,001). Des equations de prediction de la DT a partir de la composition chimique ont ete obtenues. Dans le cas de la MS, les teneurs en parois cellulaires et en lignocellulose expliquent 79,4 % de la variation totale observee pour la DT. En revanche, la meilleure prediction de la DT des MAT a ete obtenue avec la teneur en cellulose comme variable independante (r 2 = 0,839). Les etudes de degradation ont aussi montre que ces foins ont une faible teneur en proteine non degradee dans le rumen et potentiellement digestible dans l'intestin. De cette facon, la plus grande partie de l'azote disponible pour l'animal est fournie par la synthese microbienne dans le rumen.

Evolution of milk somatic cell count of cows grazing an alpine pasture according to the infection of udder by pathogens

Abstract: The infection of udder by a pathogen and milk somatic cell count (SCC) of 220 quarters from 55 Abondance and Tarentaise cows coming from three Northern Alps herds were analysed three times: in June when cows use a valley pasture before turning to highland pasture and in July and September, respectively at the beginning and the end of highland pasture grazing period. During the three periods, 31% of the experimental quarters were free or infection, 61% were infected by a minor pathogen and 8% were infected by a major pathogen. In quarters infected by a major pathogen, SCC was constantly high (> 1 600 000 cells/ml in the three periods). SCC of uninfected quarters remained below 60 000 cells/ml in the three periods whereas SCC of quarters infected by a minor pathogen averaged 89 000 cells/ml in June and 512 000 cells/ml in September. For the latter, SCC was all the higher as the infection was older. Results are discussed according to the highland grazing conditions that may have had an impact on SCC.

Chemical composition, digestibility and in situ degradability of narbon vetch grain and straw grown in a Mediterranean region

Abstract: Apparent digestibility of narbon vetch ( Vicia narbonensis)grain and straw were mea- sured using four Chios wether sheep per foodstuff. In another trial, the in situ degradation of narbon vetch grain and straw in the rumen of three Chios ewes were measured. The crude protein (CP) and in vitro organic matter digestibility values were 23.4 and 87.6 for narbon vetch grain and 7.4 and 44.8% for narbon vetch straw. In vivo apparent digestion coefficients of dry matter (DM), organic matter (OM) and CP were for narbon vetch grain 78, 80 and 75% and for narbon vetch straw 44, 42 and 47%, respec- tively. The effective degradability (outflow rate 0.05 .h -1 ) for narbon vetch grain and straw were for CP 74 and 31% (corrected for microbial contamination) and for DM 64 and 36%, respectively.

Ileal true digestibility of amino acids in wheat milling by-products for pigs

Abstract: Ten batches of wheat milling by-products - 3 of wheat middlings (WM), 4 of wheat feed (WF), 3 of wheat bran (WB) - were analysed and studied for their protein and amino acid ileal true digestibility (ITD). Each batch was tested on four castrated male pigs weighing between 35 and 95 kg, and fitted with an end-to-end ileo-rectal anastomosis. In all types of by-products, lysine and threonine were among the least digestible amino acids, whereas methionine was among the most digestible ones. N and all amino acids ITD decreased significantly ( P < 0.05) from WM to WF and to WB. In WM, the average N, lysine, threonine and methionine ITD values were 93.6, 90.8, 90.4 and 95.1%, respectively. They decreased to 85.5, 86.6, 83.3 and 91.5%, respectively in WF and down to 70.1, 68.3, 68.4 and 78.9%, respectively in WB. N and all amino acids ITD was predicted according to either the ratio of the feedstuff fibre to amino acid concentrations, or the proportion of total N bound to the NDF (neutral detergent fibre) residue, or both. For most amino acids, the use of CF (crude fibre), ADF (acid detergent fibre) or ADL (acid detergent lignin) as fibre criteria provided accurate equations with coefficient of determination higher than 90%.

Influence of genotype on contractile protein differentiation in different bovine muscles during foetal life

Abstract: The purpose of this work was to compare muscle fibre differentiation in two genetic types: "normal Charolais" and double-muscled (DM) "INRA 95" cattles displaying muscle hypertrophy. Six muscles with different contractile and metabolic characteristics in adult animal: Masseter, Diaphragma (Di), Biceps femoris (BF), Longissimus thoracis, Semitendinosus and Cutaneus trunci (CT) were excised from 60 to 260-day-old foetuses of both genotypes. These muscles present different degrees of hypertrophy in DM animals. Fibre types were characterised by immunohistochemistry using mon- oclonal antibodies raised against different myosin heavy chain isoforms. They were also studied by SDS-PAGE electrophoresis, immunoblotting and ELISA methods. In both genotypes, foetal muscle development involved at least two generations of fibres but their contractile differentiation was more or less delayed in double-muscled animals according to the muscle type. CT muscle, the most hyper- trophied in adults DM, showed the most important differences in the appearance of the primary and secondary fibres in DM foetuses. It showed a delay of differentiation which was made up during the last third of foetal life. Other muscles did not differ in the speed of appearance of the two gener- ations of fibres. They were originated from a higher proliferation of secondary fibres. Moreover, all DM muscles presented similar characteristics at 210 days of foetal life. These characteristics seem to be genetically determined. Just before birth, muscles of double-muscled foetuses were composed of a greater proportion of fast type II fibres than normal animals. The most important differences between genotypes were observed in BF and Di muscles. muscle / foetus / differentiation / cattle / double-muscled

The effect of feed enzymes on nutrient and energy retention in young racing pigeons

Abstract: Eight nests of two squabs were weaned at 24 days then housed in individual cages. A squab of each nest received a commercial feed for racing pigeons, the other group received the same feed but supplemented with xylanase, β-glucanase, pectinase and hemicellulase. No difference in body weight was observed between groups. Despite feed restriction, intake was higher for enzyme-sup- plemented diet. When related to feed intake, excreta were lower by 11% for enzyme-supplemented diet. Enzyme addition improved dry matter, organic matter, protein, energy and fibre retention. These results may show that pigeons are more sensitive to enzymes than common poultry. pigeon / enzymes / growth / metabolizable energy

Variation in gestation length as breeding season advances in Bruna dels Pirineus beef cattle breed

Abstract: The variation in gestation length according to the time lapse from the onset of the breeding season until the day of mating was investigated in the Bruna dels Pirineus beef cattle breed. A total of 359 gestations belonging to five breeding seasons were analysed. Average gestation length under natural service was 288.6. Gestation length tended to increase significantly (p $< $ 0.05) to about 1.5 days in cows that were mounted in the two last thirds of the breeding season. The effects of domestication on birth synchrony are discussed.

Effect of turning out dairy cows to pasture on milk somatic cell count

Abstract: An increase in milk somatic cell count is often observed in commercial herds when cows are on pasture during summer. The objective of this study was to check, in experimental con- ditions, if this effect is due to the turning out to pasture. Three groups of cows were observed for five weeks: 10 cows with low somatic cell count ( 300 000 cells/ml) went to pasture after two weeks in the cow-shed. The measurements were: milk production, chemical composition, somatic cell count, pathogens in the milk and plasma markers. Milk production and fat content were higher in cows turned out to pasture than in cows staying in the cow-shed (+1.4 kg and +3.4 g/kg). No effect of turning out to pasture on milk protein content, milk somatic cell count and plasma markers level was noticed. In conclusion, the increase in milk somatic cell count observed in summer seems not to be due to the environmental change when cows turned out to pasture. Alternative explanations are suggested. dairy cow / milk / somatic cell count / pasture

Consumer concerns about industrialized agriculture and food safety: importance, origin and possible solutions.

Abstract: Modern agriculture and the food industry throughout western Europe, especially in France, have become the subject of consumer criticism. The concern is focussed mainly on product quality and safety, and on environmental impact. It has therefore appeared interesting to analyse the concern along with the answers offered by the various actors concerned. First, a global review of the good and bad points of the techno-economic development of agriculture over the past few decades is presented. Then, referring to survey results, an evaluation is made of the risks as perceived by consumers. The underlying explanatory factors motivating consumer concern and the lack of confi- dence in agriculture are studied in order to see if the answers proposed are appropriate to the prob- lems. In fact, the answers often appear to be relatively technical (for example of a biochemical nature), whereas the points of concern are not limited to technical matters. Several wider range, more prospective ideas are discussed in conclusion, notably the world-wide situation and the over- all question of biotechnology. consumer / food safety / industrialized agriculture / risk / evolution of agriculture

Sources of shared variability of the carcass and non-carcass components in pekin ducklings

Abstract: A factor analysis with a vari max rotation was applied to 5 highly intercorrelated slaughter traits on 430 Pekin ducks to disclose the main sources of shared variability and deduce the factors that describe carcass and edible offal 'non-carcass' traits. Carcass and edible offal traits appeared to be controlled by common and unique factors. The communalities ranged from 0.57 (gizzard) to 0.92 (abdominal fat) and the uniqueness (special size factors) complement to 1. Findings indicated the most of the common variability (72.9% ) in slaughter traits could be accounted for by factors representing general size and abdominal fat factors. Independent slaughter traits 'general size and abdominal fat' derived from factor analysis accounted for 77.8% of the variation in live body weight.

Effects of within-group homogeneity of physiological state on individual feeding behaviour of loose-housed Charolais cows

Abstract: The criteria used by farmers to assign animals to the different groups do not only con- cern nutritional aspects, implying that each group is not homogeneous with regards to nutrient requirements. The food intake and feeding behaviour of 12 loose-housed Charolais cows (6 dry and 6 lactating), given hay ad libitum were compared in homogeneous (Hom) and heterogeneous (Het) groups according to their physiological states: Hom groups were comprised of cows in similar phys- iological states (dry or lactating) and Het groups were comprised of cows in different physiological states (dry + lactating). No difference was detected in daily intake level in Hom and Het groups: 14.8 and 14.5 kg DM for dry cows, 15.4 and 15.3 for lactating cows, respectively, nor for daily time of eating: 4 h 53 and 4 h 44 for dry cows, 5 h 50 and 5 h 34 for lactating cows. In Het groups, lactating cows ate more at night: from midnight to 10.00 hours, they had already spent 2 h eating vs. 1 h 30 in Hom groups. Cows had significantly more short meals (< 1 h) in Het groups: 11.1 vs. 9.0 for dry cows and 12.4 vs. 10.6 for lactating cows in Het and Hom groups, respectively. This fractionising of the eat- ing activity concerned particularly submissive dry cows and high producing lactating cows.