Dry Ewes Research Articles

A mechanistic model of intake and grazing behaviour in sheep integrating sward architecture and animal decisions

The grazing process determines not only the nutrient intake of ruminants at pasture but also the intensity of their impact on vegetation. Grazing dynamics are the result of complex interactions between animal and sward characteristics. While sward is being depleted, a decline in intake rate is partly offset by longer grazing time. This behaviour may be controlled by nutritional feedback from digestion and nutrient absorption as the quality of the ingested herbage decreases. To simulate the dynamics of feeding behaviour and intake during sward exploitation, we developed a mechanistic model of intake rate that combines sward architecture and foraging decisions, and we linked this model with another focusing on control of intake. The sward was divided into horizons characterised by bulk density and nutritive value (NDF content and digestibility), enabling prediction of bite mass and potential intake rate for each grazed horizon. Animal decisions were simulated at two levels: (i) animal activity (eating, ruminating or resting) was self-regulated every minute by comparing a motivation-to-eat function with a satiation function based on a digestion and metabolic sub-model; (ii) while eating, the horizon to be grazed was decided through a choice function taking into account the relative availabilities and potential intake rates of the two upper horizons. The model simulates the animal–sward interactions from elementary parameters (bite mass, intake rate, etc.) to integrated outputs (sward height, daily intake, etc.). Hence, the interplay between characteristics of the vegetation and the internal state of the animal is dynamic taken from the level of a few bites to several successive days. Satisfactory validations were obtained on experimental data sets obtained in both rotational grazing with dry ewes and continuous grazing with lactating ewes. The sensitivity analysis highlights the balance between factors that control bite mass and intake rate and factors that control grazing time. Combining both series of factors in the same model represents significant progress in predicting intake at grazing in a mechanistic way. The model makes it possible to explore the balance between intake regulation by nutritional variables (animal needs and sward quality) and by the availability and structure of the sward. Finally, it is a promising tool to explore the sensitivity of the grazing process to characteristics of both sward (height, bulk density, nutritive value) and animals (weight, nutritional requirements, behavioural traits), and to management practices (stocking rate, rotational versus continuous grazing).

A mechanistic model of intake and grazing behaviour in sheep integrating sward architecture and animal decisions

The grazing process determines not only the nutrient intake of ruminants at pasture but also the intensity of their impact on vegetation. Grazing dynamics are the result of complex interactions between animal and sward characteristics. While sward is being depleted, a decline in intake rate is partly offset by longer grazing time. This behaviour may be controlled by nutritional feedback from digestion and nutrient absorption as the quality of the ingested herbage decreases. To simulate the dynamics of feeding behaviour and intake during sward exploitation, we developed a mechanistic model of intake rate that combines sward architecture and foraging decisions, and we linked this model with another focusing on control of intake. The sward was divided into horizons characterised by bulk density and nutritive value (NDF content and digestibility), enabling prediction of bite mass and potential intake rate for each grazed horizon. Animal decisions were simulated at two levels: (i) animal activity (eating, ruminating or resting) was self-regulated every minute by comparing a motivation-to-eat function with a satiation function based on a digestion and metabolic sub-model; (ii) while eating, the horizon to be grazed was decided through a choice function taking into account the relative availabilities and potential intake rates of the two upper horizons. The model simulates the animal–sward interactions from elementary parameters (bite mass, intake rate, etc.) to integrated outputs (sward height, daily intake, etc.). Hence, the interplay between characteristics of the vegetation and the internal state of the animal is dynamic taken from the level of a few bites to several successive days. Satisfactory validations were obtained on experimental data sets obtained in both rotational grazing with dry ewes and continuous grazing with lactating ewes. The sensitivity analysis highlights the balance between factors that control bite mass and intake rate and factors that control grazing time. Combining both series of factors in the same model represents significant progress in predicting intake at grazing in a mechanistic way. The model makes it possible to explore the balance between intake regulation by nutritional variables (animal needs and sward quality) and by the availability and structure of the sward. Finally, it is a promising tool to explore the sensitivity of the grazing process to characteristics of both sward (height, bulk density, nutritive value) and animals (weight, nutritional requirements, behavioural traits), and to management practices (stocking rate, rotational versus continuous grazing).

The effects of previous grazing experience and ewe presence on the response to novel grass species by weaned lambs

AbstractForty single lambs were either artificially reared indoors or were at pasture with their mothers until weaning at 3 months of age, after which one half of each group were joined by five adult, dry ewes, to examine the effects of grazing experience and presence of adult ewes on the response to the introduction of novel grass species. Lamb groups sequentially grazed paddocks with one, two, three and then four grass species in four 1-week periods, and grazing and ruminating times and pasture biting rates were recorded during daylight hours. In the first period the lambs grazed only perennial ryegrass, then timothy, cocksfoot and finally red fescue were introduced in periods 2 to 4 respectively. The total time that lambs spent grazing and ruminating were both increased (P < 0·001) by grazing experience and to a lesser extent by the presence of adult ewes. Pasture biting rate was considerably increased by experience, and to a lesser extent adult presence, with a synergistic effect between these two factors (P < 0·001). Timothy and to a lesser extent perennial ryegrass were the most preferred species, and lambs spent less time grazing cocksfoot than either of these two, and even less time grazing red fescue (P < 0·001). Experience of grazing particularly increased the time spent grazing cocksfoot and red fescue (P < 0·001), but the presence of adult ewes did not increase the time lambs spent grazing novel species (P = 0·59). The pasture biting rate was greater on species that the lambs preferred grazing (P < 0·001), but neither experience nor ewe presence increased the biting rate on novel species in the period of their introduction. It is concluded that although both grazing experience and, to a lesser extent adult presence, increased the total time spent grazing and the pasture biting rate, only grazing experience increased the acceptability of novel species.

The ability of sheep at different stocking rates to maintain the quality and quantity of their diet during the grazing season

The degree to which grazers maintain the amount (organic matter intake) or the quality (organic matter digestibility) of their diet without adversely affecting the other component was addressed by investigating how sheep managed trade-offs between quantity and quality throughout the grazing season in an upland area of central France. Two groups of five dry ewes, grazing two plots of contrasting areas from April to the end of September 2000, were studied. On the smaller plot (1500 m2), the application of a high stocking rate (HSR) produced a resource of good quality but in low quantity; and on the larger plot (3000 m2), a low stocking rate (LSR) created a sward of low quality but in good quantity. In spring, in both conditions, the sheep maintained their intake of digestible organic matter (OM) at between 1000 and 1250 g/day. Both organic matter intake and digestibility remained high at both stocking rates. In summer, the intake of digestible OM decreased to between 750 and 1000 g/day. On HSR, this was mainly due to a decline of intake in relation to the decrease of intake rate and bite weight. On LSR a decrease in digestibility and to a lesser extent in intake was involved. At both stocking rates, the sheep maximized the digestibility of their diet by selecting the green laminae throughout the grazing season. In spring, the sheep modulated their daily grazing time to compensate the decrease in intake rate and maintained a high daily intake. In summer and autumn, the sheep failed to maintain their daily intake at the same level as previously observed. On both plots they modulated their daily grazing time to cover their needs (730 g/day), but they did not increase it further to maximize daily intake. This may be attributable to the costs involved in selecting (LSR) or taking (HSR) the best components from the sward.

A review of the biology linking fibre diameter with fleece weight, liveweight, and reproduction in Merino sheep

There is increasing economic pressure on the Merino industry to grow finer wool and at the same time to turn off more sheep meat. Fleece weight generally decreases with finer fibre diameters, so theoretically, finer wool sheep should be able to partition more nutrients to reproduction and muscle growth. However, complex and often indirect mechanisms appear to prevent this in practice. This review summarises the available data on genetic and phenotypic relationships between wool fibre diameter and fleece weight, liveweight, fatness, and reproductive performance, and develops mechanistic hypotheses for these relationships that could be tested experimentally.Selection for reduced fibre diameter may decrease liveweight, fatness, and reproductive performance. These characteristics are also affected by the availability of nutrients, and finer fibre diameter may affect nutrient metabolism through 2 adaptations that tend to maintain fleece weight: an increase in follicle density and/or an increase in relative fibre length. These act in different ways. Follicle density may affect final body size through linkages established during fetal development. Increased fibre growth rate requires an increase in protein synthesis rate in the skin, which in turn may affect whole-body protein turnover rate and the sensitivity of tissues to insulin. Other pathways potentially affected by fibre diameter include the control of feed intake, prenatal programming of insulin sensitivity, and a reduced responsiveness of tissues to nutrient supply. However, none of these mechanisms accounts for the reports of an increased proportion of dry ewes in fine wool sheep, particularly if run in environments that experience periods of low quality pasture.Although associations between fibre diameter and growth rate, fatness, and reproduction rate are repeatable, there are not yet enough data for such associations to be realistically accounted for in breeding goals. More experimentation and a better knowledge of the causative relationships will facilitate development of finer wool sheep for environments where sheep turnoff normally provides a significant proportion of income from the sheep enterprise. Such mechanistic understanding will facilitate the development of molecular techniques for targetted selection, and the identification of more useful attributes for a quantitative genetics approach to improving simultaneously the profitability from both wool and meat.

Distribuição horizontal e taxas de crescimento, senescência e desfolhação de azevém perene e festuca, puros e em associação

O experimento foi realizado no INRA (Institut National de la Recherche Agronomique) em Theix, França. Duas gramíneas (azevém perene e festuca)foram semeadas em caixas (0,13 m²) usando-se três distribuições horizontais do pasto (pura, linhas alternadas e faixas alternadas) e três intervalos de desfolhações (3,5, 7 e 14 dias), com quatro repetições por tratamento. Quatro meses após a semeadura, a cada data de desfolhação, as caixas foram oferecidas, individualmente, a quatro ovelhas secas e retiradas após a realização de 340 bocados.m-2. Para cada gramínea estudaram-se a densidade populacional e a massa de perfilhos, a altura e a produção de matéria seca, a profundidade e a massa do bocado e as taxas de crescimento, senescência e desfolhação. A maior altura do pasto, gerada por desfolhações menos freqüentes, promoveu a realização de bocados mais profundos e de maior massa. Por outro lado, em desfolhações mais freqüentes a altura do pasto foi mantida mais baixa, e a profundidade e massa do bocado foram menores. A distribuição horizontal das plantas promoveu respostas diferenciadas em relação as taxas de crescimento, senescência e desfolhação. Quando em linhas alternadas a festuca teve a taxa de crescimento limitada, provavelmente desfavorecida pela competição.

Intervalo e intensidade de desfolhação nas taxas de crescimento, senescência e desfolhação e no equilíbrio de gramíneas em associação

O experimento foi realizado no INRA (Institut National de la Recherche Agronomique) em Theix, França. Duas gramíneas (azevém perene e festuca)foram semeadas em caixas (0,13 m²) e submetidas a três intervalos (3,5, 7 e 14 dias) e três intensidades (160, 320 e 640 bocados.m-2 a cada desfolhação) de desfolhação, com quatro repetições por tratamento. Quatro meses após a semeadura, a cada data de desfolhação, as caixas foram oferecidas, individualmente, a quatro ovelhas secas e retiradas após a realização de um determinado número de bocados. Para cada gramínea foram estudadas as taxas de crescimento, senescência e desfolhação. Os resultados mostraram que o intervalo e a intensidade de desfolhação tiveram efeitos diferenciados nas taxas de crescimento, senescência e desfolhação e no equilíbrio da associação.

The value of Kikuyu foggage for overwintering dry ewes

Kikuyu (Pennisetum clandestinum) is a summer growing tropical pasture species well adapted to the Midlands of KwaZulu-Natal. Kikuyu foggage (standing hay) could play an important role in a fodder flow programme to sustain dry ewes during late winter after their lambs have been weaned in mid-winter. The potential of kikuyu foggage to supply in the feed requirements of dry ewes was evaluated over four winter periods. The foggage was obtained by closing off the kikuyu to grazing during either late January or late February. The foggage was grazed for eight weeks, from mid-July to mid-September, using either strip or continuous grazing systems. Closing off date did not significantly influence the chemical composition of the material on offer. The ewes in the different treatments lost between 4.7 and 10.3% of their initial body weight over the grazing period. In vitro digestible organic matter (IVDOM) of the foggage declined as winter progressed and was positively correlated with the body weight loss of the ewes. Foggage utilization varied between 36.7 and 43.5%, indicating a high proportion of fodder wastage. The body weight loss of the dry ewes during the grazing period suggested that kikuyu foggage in the KwaZulu-Natal Midlands was unable to sustain the body weight of the dry ewe. South African Journal of Animal Science Vol.32(1) 2002: 7-13

DINÂMICA DE UMA ASSOCIAÇÃO DE AZEVÉM PERENE E FESTUCA SUBMETIDA A DESFOLHAÇÃO ANIMAL

O experimento foi realizado no INRA (Institut National de la Recherche Agronomique) em Theix, França. Dua gramíneas (azevém perene e festuca) foram semeadas em caixas (0,13 m2) usando-se três distribuições horizontais pastagem (pura, linhas alternadas e faixas alternadas) e três freqüências de desfolhação (3, 5, 7 e 14 dias), com quatro repetições por tratamento. Quatro meses após a semeadura, a cada de desfolhação, as caixas foram oferecidas, individualmente, a quatro ovelhas secas e retiradas após a realização de 340 bocados.m-2. Para cada gramínea estudou-se a densidade e a massa de perfilhos, a altura e a produção de matéria seca, a profundidade e a massa do bocado e os fluxos de crescimento, senescência e desfolhação. A maior altura da pastagem, gerada por desfolhação menos freqüentes, promoveu a realização de bocados mais profundos e de maior massa. Por outro lado, em desfolhações mais freqüentes a altura da pastagem foi mantida mais baixa, e a profundidade e massa do bocado foram menores. A distribuição horizontal das plantas promoveu respostas diferenciadas em relação aos fluxos de crescimento, senescência e desfolhação. Quando em linhas alternadas a festuca teve o fluxo de crescimento limitado, provavelmente desfavorecida pela competição.

Changes in some blood constituents of Barki ewes during pregnancy and lactation under semi arid conditions

A study based on 12 pregnant and six dry Barki ewes was carried out to examine the changes in blood constituents during pregnancy and lactation periods. The blood parameters were blood hemoglobin, packed cell volume percent (PCV%), mean corpuscular hemoglobin concentration (MCHC), glucose, aspartate aminotransaminase (AST or GOT), alanine aminotransaminase (ALT or GPT), total plasma protein, albumin, globulin, albumin to globulin ratio (A/G), urea and creatinine. During pregnancy all these parameters started to increase significantly, but in different stages, reaching maximum values at parturition. In contrast, dry ewes showed almost stable values during the experimental period. From 10th week to parturition, PCV% and MCHC increased ( P<0.01) in pregnant ewes, which resulted in increased ( P<0.01) blood hemoglobin. Blood glucose increased from the 4th week of pregnancy to reach its maximum at parturition (60.15–90.08 mg/dl). The two transaminases increased significantly from the 2nd week (52.23–65.02 IU for AST and 8.02–15.12 IU for ALT). Plasma protein with its two components, albumin and globulin, increased significantly at the 6th week, but dropped throughout the 16–18th week of pregnancy. Urea and creatinine began to increase significantly after 10–12 weeks of pregnancy (from 54.73 to 72.11 mg/dl for urea and from 0.882 to 2.475 mg/dl for creatinine). During the first month of lactation, PCV decreased sharply in lactating ewes and was significantly lower than in dry ewes at the 3rd week of lactation (24.25 versus 27.17%), which resulted in a drop in blood hemoglobin at the 4th week (68.42 versus 74.00 g/l). However, lactating ewes maintained significantly higher values of MCHC (30.01–31.19% for lactating versus 29.87–27.48% for dry). In lactating ewes, levels of glucose, ALT, urea and creatinine returned to levels comparable to those in dry ewes. The same occurred with total plasma proteins, mainly due to a sharp decrease in globulin, while albumin remained higher than in dry ewes with a slow decline, which resulted in higher values of A/G ratio during lactation. Aspartate aminotransferase remained higher than in dry ewes.

Effects of shearing and supplemental level on intake of dry ewes grazing on barley stubble

Twenty-eight Comisana dry ewes were utilised to evaluate the effect of shearing (14 shorn and 14 unshorn ewes) and supplemental level (100 and 300 g of concentrate) on intake of barley stubble. Shorn ewes showed a small increase in dry matter intake (at the end of August: 1.32 vs. 1.10 kg/day; p<0.01). Intake of barley stubble decreased as supplement level increased (mean: 1.18 vs. 1.29; p<0.01). On average, substitution effect was 0.63. Total lamb weight per ewe was greater in the group receiving 300 g of concentrate (7.38 vs. 5.85; p<0.05). Shearing induced a small, but not significant decrease in total lamb weight per ewe (6.18 vs. 7.05 kg/ewe). Results seem to indicate that unshorn ewes react better to environmental stress and that 300 g improve reproductive performance.

In vivo estimation of body composition from the dilution space of deuterium oxide in fat-tailed Barbary ewes

Sixteen dry ewes of the fat-tailed Barbary breed were used to formulate prediction equations of body water, fat, protein and energy content from the live body weight (BW) and the dilution space of deuterium oxide (SD 2O). Ewes were injected with 0.5 g D 2O/kg BW and four blood samples collected after infusion. The D 2O content of blood water was determined by infra-red spectrometry. Ewes were weighed, body condition scored and then slaughtered. The body water, fat, protein, ash and energy were chemically determined. At slaughter, ewes weighed 43.4±7.0 kg, and contained 26.0±2.6 kg of water and 9.3±4.2 kg of fat. A relative lack of variation in the fat-free empty body (FFEB) was confirmed in this particular breed (water percentage, 74.5±1.6). Adiposity (fat as percent empty BW; EBW) varied between 15.1 and 36.9%. There was a close negative relationship ( R 2=0.96; residual standard deviation (R.S.D.)=1.4%) between the fat and the water content of EBW. Body water was significantly correlated with SD 2O. The body fat and energy content prediction equations from SD 2O and BW were similar to those published in a thin-tailed ewe breed ( R 2=0.92; R.S.D.=1.4 kg). The body fat equation prediction from body condition score and/or BW was significant ( R 2=0.81; R.S.D.=1.9 kg) although not as precise as that using D 2O.

Adipose tissue metabolism and its role in adaptations to undernutrition in ruminants.

Changes in the amount and metabolism of adipose tissue (AT) occur in underfed ruminants, and are amplified during lactation, or in fat animals. The fat depot of the tail of some ovine breeds seems to play a particular role in adaptation to undernutrition; this role could be linked to its smaller adipocytes and high sensitivity to the lipolytic effect of catecholamines. Glucocorticoids and growth hormone probably interact to induce teleophoretic changes in the AT responses to adenosine and catecholamines during lactation. Fat mobilization in dry ewes is related both to body fatness and to energy balance. The in vivo beta-adrenergic lipolytic potential is primarily related to energy balance, whereas basal postprandial plasma non-esterified fatty acids (NEFA) are related to body fatness, and preprandial plasma NEFA is the best predictor of the actual body lipid loss. Several mechanisms seem to be aimed at avoiding excessive fat mobilization and/or insuring a return to the body fatness homeostatic set point. As well as providing the underfed animal with fatty acids as oxidative fuels, AT acts as an endocrine gland. The yield of leptin by ruminant AT is positively related to body fatness, decreased by underfeeding, beta-adrenergic stimulation and short day length, and increased by insulin and glucocorticoids. This finding suggests that the leptin chronic (or acute) decrease in lean (or underfed respectively) ruminants is, as in rodents, a signal for endocrine, metabolic and behavioural adaptations aimed at restoring homeostasis.

Reproduction effects on annual fleece production, liveweight and body condition of grazing Merino ewes

This study sought to confirm the long-term consequences of current and previous reproductive cycles on liveweight, body condition and wool growth over the lifetime of Merino ewes (2–6 years of age). Liveweights and body condition scores at 4 stages of the reproductive cycle, and annual fleece weights (greasy and clean), fibre diameter and yield were analysed to determine the effects of the previous and current reproductive performance (birth-type or rearing-type categories) using records from about 3300 Merino ewes collected between 1977 and 1989. The major effect of current reproduction on liveweight and wool production was associated with fertility, although both birth and rearing types also contributed. Ewes that lambed in the current year weighed 5.2 kg less at weaning and grew 0.4 kg less clean wool annually than dry ewes, while ewes that reared a lamb to weaning weighed 4.3 kg less than ewes that lost their lamb(s). The effects on condition score followed those of liveweight. The effects of previous reproduction on liveweights and condition scores were large and, although diminishing with time, lasted for at least 10 months, whereas any effects on annual fleece weight and mean fibre diameter were small. The results suggest that many ewes may enter the next reproductive year before recovering from the reduction in either liveweight or body condition associated with the previous reproductive cycle. Since Merino ewes are required to produce both wool and replacement sheep, the changes in a ewe’s production capacity associated with reproduction are important to Merino wool production enterprises as their profitability may be influenced.

The effect of grazing Lotus corniculatus during late summer - autumn on reproductive efficiency and wool production in ewes

A grazing experiment was conducted at Massey University (Palmerston North, New Zealand) over 80 days in the late summer–autumn of 1998 (9 February–29 April). Reproductive performance and wool growth of ewes grazing on Lotus corniculatus (birdsfoot trefoil) were compared with those of ewes grazing perennial ryegrass–white clover pasture. A rotational grazing system with 210 mixed-age dry ewes (59.80.9 kg/ewe) was used, with 80 ewes grazing pasture [1 g of condensed tannin (CT) per kg dry matter (DM)] and 130 ewes grazing L. corniculatus (24 g CT/kg DM). Half of the ewes grazing L. corniculatus were supplemented orally, twice daily, with polyethylene glycol (PEG; MW, 3500) to inactivate the CTs. The effect of forage species and PEG supplementation on voluntary feed intake (VFI), reproductive performance (as measured by ovulation rate), and wool production was measured during 4 synchronised oestrous cycles. The ewes were restricted to maintenance feeding during the first 10 days of each oestrous cycle and then increased to ad libitum for the 6 days leading up to and including ovulation. In vitro organic matter digestibility in the selected diet was higher for lotus than for pasture (0.80 v. 0.76), with L. corniculatus containing less nitrogen than pasture (36.5 v. 40.8 g/kg organic matter). Ewes grazing on L. corniculatus produced 11% more wool and had an ovulation rate up to 14% higher than ewes grazing pasture, with neither parameter being affected by PEG supplementation. Higher mean ovulation rates of ewes grazing L. corniculatus were due to increases in fecundity (multiple ovulations/ovulating ewe; P &lt; 0.05), with no effect on ewes cycling/ewes mated. Three cycles of grazing on L. corniculatus were required to achieve the maximum response in multiple ovulation, but most of this was achieved after 2 cycles. As the VFI of ewes grazing on L. corniculatus was not greater than that of ewes grazing pasture, the greater wool production and higher ovulation rate of ewes grazing this forage was due to improved efficiency of feed utilisation. It was concluded that feeding ewes L. corniculatus increased the efficiency of both reproduction and wool production without increasing VFI.

Kikuyu (Pennisetum clandestinum) pasture for sheep. 1. Pasture quality and nutrient intake of ewes

Irrigated kikuyu pasture was continuously grazed for 12 months by 30 South African Mutton Merino (SAMM) and 30 Merino ewes at a stocking density of 23 ewes ha−1. Herbage samples for chemical composition were obtained monthly either by quadrat cuts or by oesophageally fistulated (OF) wethers. Intake was determined with controlled chromium release devices on eight dry and eight producing ewes from each breed during the periods of late pregnancy (February) and lactation (March). Significant (P ≤ 0.05) differences in the OM, OMD, CP, ADF, and NDF contents of manually collected and OF‐selected samples occurred between months. The means for CP, OMD, ADF, and NDF of the OF‐samples were, respectively, 18.3%, 62.3%, 37.8%, and 74.1% (expressed on an OM‐basis). During February, SAMM ewes (1184 ± 66 g d−1) consumed 27% (P = 0.01) more OM than Merino ewes (930 ± 66 g d−1), while there was no difference in intake between dry and pregnant ewes. During March, there were no differences in intake between breeds or between dry and producing ewes. When intake was expressed on a metabolic mass basis, there were no significant differences between breeds, while dry ewes tended (P = 0.08) to consume more OM than pregnant ewes during February. During March, there were no significant differences in OMI/kg−1 W0.75 d−1 between SAMM and Merino ewes or between dry and lactating ewes. When intake was compared with the respective requirements for energy and protein, there were no deficiencies during pregnancy, and DOM and CP were inadequate during lactation.

Rate of protein synthesis in the skin and muscle of non-pregnant, pregnant and lactating Merino ewes

Fractional synthesis rates of protein (FSR) in the midside skin and Longissimus dorsi muscle of Merino ewes were measured to assess the partitioning of nutrients during late pregnancy and early lactation in two experiments. Protein synthesis was measured by using a flooding-dose of L −[ 15 N] phenylalanine. The effects of diets (canola meal vs lupin seeds) on nutrient partitioning to skin and muscle in dry, pregnant and lactating ewes were also investigated. The FSR in the skin of non-pregnant ewes ranged between 10.6% d −1 and 12.8% d −1, and in muscle between 1.13% d −1 and 2.06% d −1 at maintenance feed intakes. There were no statistical differences ( P>0.05) in FSR of the skin and muscle between pregnant and non-pregnant ewes though the skin FSR values were slightly lower in pregnant ewes. During lactation, FSR increased in the skin but declined in the muscle in comparison with pregnancy, indicating that muscle protein was being expended while skin and wool follicles continued to use nutrients. The ewes fed a diet containing canola meal, which had a lower degradability of protein in the rumen and a higher content of sulphur-containing amino acids than the lupin seed diet, had a higher rate of protein synthesis in the skin ( P=0.04) but a lower rate of synthesis in the muscle ( P=0.02) than those ewes fed lupins. The differences between the two diets, in skin protein synthesis, were greater in the reproducing than in the dry ewes. In conclusion, FSR in the skin of ewes was not significantly reduced during reproduction but tended to be lower during pregnancy. Reduced wool growth in late pregnancy may be due to a reduction in wool producing tissue alone or to a combination of less tissue and a slightly reduced synthesis rate. Feeding canola meal increased protein synthesis in the skin of reproducing and non-pregnant ewes. Finally FSR in skin and muscle responded differently to pregnancy, lactation and protected protein.

The effect of experimental infectious mastitis on leukocyte subpopulations and cytokine production in non-lactating ewes.

The interactions between leukocytes and cytokines during the acute response to intramammary infections in the dry mammary gland of sheep were studied. Dry ewes were experimentally infected in one udder half with either Staphylococcus aureus or Escherichia coli, or infused with saline as control. Udder secretion samples, blood samples and udder tissue samples were collected before and 4, 8 and 24 h after infections/infusions. Total and differential leukocyte counts were calculated in both blood and mammary secretions, and flow cytometry was used to detect the presence of CD4+, CD8+, WC1+, IL-2R+, CD18+ or L-selectin + lymphocytes, CD18+ or L-selectin + neutrophils, and CD14+ leukocytes. Moreover, the concentrations of interleukin-1 beta (IL-1 beta), interleukin-8 (IL-8) and granulocyte-macrophage colony stimulating factor (GM-CSF) in udder secretions were measured using ELISA, and RT-PCR was used to detect the presence of corresponding cytokine mRNA in udder tissue biopsies. The results suggest an association between the concentrations of IL-1 beta, IL-8 and the intensity of neutrophil infiltration of the infected gland. Immunologically relevant changes in proportions of lymphocyte subpopulations might also occur in the acute phase of the inflammatory reaction of the udder. Greater cellular and cytokine responses to E. coli infection may have contributed to the milder clinical picture and more rapid resolution of infection than that seen for S. aureus. Enhancing the production of pro-inflammatory cytokines may improve defence against bacterial mastitis.

Complémentation d'une paille de blé avec des blocs multinutritionnels : effets sur la digestibilité de la paille et intérêt pour des brebis taries et des agneaux en croissance

Supplementation of wheat straw with multi nutritional blocks: effects on the digestibility of straw and interest for dry ewes and growing lambs. Two blocks characterized by the presence of olive cake in the first block (BMNI) and dropping of poultry in the second block (BMN2) were compared with a classical concentrate (C). The BMN1 or BMN2 blocks were char- acterized by a high mineral matter (26-31 %) and crude protein (21-22 %) level. In vitro digestibil- ity of the two blocks were different, advantaging the BMN2 block. These blocks, fed with straw (P) to adult sheep, dry ewes and growing lambs, improved straw ingestibility in similar quantities com- pared to the concentrate. Straw supplemented with the BMN I block or BMN2 block increased the ad libitum intake by 21 % in contrast to straw without supplement. Straw in vivo digestibility was increased by the supplementation with the blocks. Ration nitrogen balance (P+BMN2) with 30.0 % was higher compared to ration (P+BMN I with 27.0 °Io and similar to the ration (P+C). The (P+BMN2) ration allowed better results with dry ewes (5.9 g per day) and with growing lambs (105 g per day). The (P+BMN I ) ration allowed one weight gain to 83 g per day and reduced the live weight of 8.4 g per day with dry ewes. The ration containing the BMN I block and BMN2 block enabled a saving of, respeclively, 13.6 and 16.7 % on the feeding cost per day with dry ewes and 12 and 23 % on the feed- ing cost per kg of weight gain with growing lambs compared to the ration containing the concentrate. (© Elsevier / Inra)

The intake and nutritional status of sheep grazing wheat stubble

Wheat stubble was grazed continuously during the summer (December–April) for 154 days by producing ewes ( n=12) from mid-pregnancy to early lactation as well as dry ewes ( n=20) at stocking rates of 1 and 2 ewes ha −1. Available material was determined by quadrate ( n=10) during each month, while samples for chemical analysis were also collected monthly by oesophageally fistulated (OF) sheep. Rumen samples were obtained from fistulated wethers. Intake of ewes was estimated monthly by means of controlled chromium release devices. The average available dry matter was 1771 kg ha −1 (1 ewe ha −1) and 1705 kg ha −1 (2 ewes ha −1) during the experimental period. The mean crude protein (CP), digestible organic matter (DOM), acid detergent fibre (ADF) and neutral detergent fibre (NDF) contents of OF samples were respectively 161, 516, 407 and 590 g kg −1 (1 ewe ha −1) and 108, 520, 539 and 721 g kg −1 (2 ewes ha −1) over the experimental period. Dry ewes at the lower stocking rate consumed more ( P≤0.05) CP than at the higher stocking rate in December (195 vs 150 g ewe −1 day −1) and January (213 vs 149 g ewe −1 day −1). Correspondingly the CP intake of ewes at the lower stocking rate was higher ( P≤0.05) during mid-pregnancy (253 vs 142 g ewe −1 day −1), late pregnancy (226 vs 91 g ewe −1 day −1) and lactation (277 vs 84 g ewe −1 day −1). The overall mean DOM intake by dry ewes was 850 g d −1 (1 ewe ha −1) and 675 g d −1 (2 ewes ha −1). For producing ewes DOM intake at the lower stocking rate appeared to increase from mid-pregnancy (922 g d −1) to late pregnancy (1028 g d −1) and lactation (1225 g d −1), with an opposite tendency at the higher stocking rate from mid-pregnancy (820 g d −1) to late pregnancy (661 g d −1) and lactation (658 g d −1). Wethers at the higher stocking rate maintained lower rumen NH 3-N and VFA concentrations which corresponded to the lower CP and DOM intakes of ewes at this stocking level. Results indicated a need for supplementary protein and energy for pregnant and lactating ewes when grazing wheat stubble at a stocking rate of 2 ewes ha −1 for such a long period.