Ewes In Early Lactation Research Articles

Changes in plasma fatty acids profile in hyperketonemic ewes during early lactation: a preliminary study

The transition from late pregnancy to early lactation is characterized by marked changes in energy balance of dairy ruminants. The mobilization of adipose tissue led to an increase in plasma non-esterified fatty acids (NEFA) and β-hydroxybutyrate (BHB). The aim of this study was to analyze the total plasma fatty acids of healthy and hyperketonemic dairy ewes in early lactation through gas chromatography (GC) to evaluate metabolic alterations. An observational study was used with a cross-sectional experimental design. Forty-six Sarda dairy ewes were enrolled in the immediate post-partum (7 ± 3 days in milk) and divided into two groups according to serum BHB concentration: non-hyperketonemic group (n = 28; BHB < 0.86 mmol/L) and hyperketonemic group (n = 18; BHB ≥ 0.86 mmol/L). A two-way ANOVA included the effect of group and parity was used to evaluate differences in fatty acids (FA) concentrations. A total of 34 plasma FA was assessed using GC. 12 out of 34 FA showed a significant different between groups and 3 out of 34 were tended to significance. Only NEFA concentration and stearic acid were influenced by parity. The results may suggest possible links with lipid metabolism, inflammatory and immune responses in hyperketonemic group. In conclusion, GC represents a useful tool in the study of hyperketonemia and primiparous dairy ewes might show a greater risk to develop this condition.

Responses to melatonin of 2 breeds of dairy ewes in early lactation under autumn photoperiod conditions

A total of 72 dairy ewes of 2 breeds (MN, Manchega, 72.4 ± 1.9 kg of body weight, n = 36; LC, Lacaune, 77.7 ± 2.3 kg of body weight; n = 36) were used to evaluate the lactational effects of melatonin implants in early lactation and under the short-day photoperiod conditions of autumn (experiment was centered on the winter solstice). Ewes lambed in autumn and were penned indoors in 12 balanced groups of 6 ewes by breed, body weight, age, and number of lambs, and randomly assigned to a 2 × 2 × 3 factorial design (treatment × breed × replicate). Ewes suckled their lambs for 28 d. Treatments were (1) melatonin (MEL), which received 1 subcutaneous implant of melatonin (18 mg/ewe) in the ear base at 35 ± 1 d (1 wk after lamb weaning), and (2) control, which did not receive any treatment. Ewes were fed ad libitum a total mixed ration (forage:concentrate, 60:40) and machine milked twice daily. Daily milk yield was automatically recorded from d 29 to 105 of lactation and sampled every 2 wk for composition. Jugular blood was sampled for plasma hormone analyses at 30, 50, 80, 110, and 124 d of lactation. Body reserves were assessed every 2 wk. Feed intake was measured by pen during 3 separated periods after the start of the treatments (wk 2 to 3, wk 6 to 7, and wk 10 to 11). Feed intake, and milk yield and composition varied by breed, but no MEL effects were detected on dry matter intake, milk yield, milk composition, or fat and protein standardized milk in either breed. As a result of the unique composition of the implants and the variable body weights of the ewes, the MEL treatment dose (on average, 0.24 mg/kg of body weight) was 6.8% greater in the MN (lighter) than in the LC (heavier) ewes. Plasmatic melatonin markedly increased in the MEL-treated ewes (on average, 111%), but despite the amount of MEL used, the MN responded greatly compared with the LC ewes (150 vs. 63%, respectively). No differences in basal plasmatic melatonin were detected between breeds (6.4 ± 1.1 pg/mL, on average), indicating the greater responsiveness to the implants of the lighter MN ewes. Plasmatic prolactin tended to decrease in the MEL-treated ewes (-35%, on average), but the effect was significant only in the MN ewes (-54%), in agreement with their greater response to MEL. No effects of MEL treatment were detected on plasmatic IGF-I in either breed. Moreover, body reserves did not vary by effect of MEL treatment or breed throughout the experiment. In conclusion, the use of exogenous melatonin as MEL implants, together with the endogenous melatonin naturally produced under short-day photoperiod conditions, had no effects on the early-lactation performances of dairy sheep, despite their breed and level of production.

Somatic cell count–based selection reduces susceptibility to energy shortage during early lactation in a sheep model

During the transition from late gestation to early lactation ruminants experience a negative energy balance (NEB), which is considered to increase susceptibility to mammary infections. Our previous study in 2 divergent lines of sheep selected for high and low somatic cell score (SCS) suggested an association between the response to NEB and genetic susceptibility to mastitis. Forty-eight early-lactation primiparous dairy ewes from the 2 SCS genetic lines were allocated to 2 homogeneous subgroups-an NEB group, which was energy restricted and received 60% of the energy requirements for 15 d, and a control-fed group-to obtain 4 balanced groups of 12 ewes: high-SCS positive energy balance, low-SCS positive energy balance, high-SCS NEB, and low-SCS NEB. High-SCS ewes showed greater weight loss and increased plasmatic concentrations of β-hydroxybutyrate and nonesterified fatty acids than low-SCS ewes when confronted with an induced NEB. The aim of this study was to further characterize this interaction by combining transcriptomic and phenotypic data with a generalized partial least squares discriminant analysis using mixOmics package framework. A preliminary analysis using 3 blocks of phenotypes (fatty acids, weight and production, blood metabolites) revealed a high correlation between fat-to-protein ratio, β-hydroxybutyrate, and nonesterified fatty acids concentrations with milk long-chain fatty acid yields. These phenotypes allowed good discrimination of the energy-restricted high-SCS ewes and confirmed a high level of adipose tissue mobilization in this group. A second analysis, which included RNA-seq data, revealed high correlations between the long-chain fatty acid yields in milk and PDK4, CPT1A, SLC25A20, KLF10, and KLF11 expression, highlighting the relationship between mobilization of body reserves and enhanced fatty acids utilization for energy production in blood cells. Finally, analysis of milk composition measured in 1,025 ewes from the 2 genetic lines over 10 yr confirmed significant higher fat-to-protein ratio in high-SCS ewes in early lactation. Altogether, our results strongly confirmed a genetic link between susceptibility to mastitis and metabolic adaptation to energy shortage. Improving genetic resistance to mastitis using SCS should be accompanied by a favorable effect on the response to metabolic stress, especially in highly stressful early lactation. Moreover, this study suggests that the fat-to-protein ratio could be used as a low-cost tool for monitoring energy balance and ketosis during this critical phase of lactation.

The relation between energy intake and chewing index of diets fed to nursing ewes

The objective of this study was to determine whether a linear relation exists between the metabolizable energy intake (MEI) of nursing ewes in early lactation and the dietary chewing index (CI). This was investigated using five feeding trials with intake data from 108 nursing ewes in the first 4–6 weeks after lambing, giving a total of 528 observations. The ewes were fed grass silage ad libitum separately, supplemented with concentrates or fed a total mixed ration (TMR) ad libitum. The ewes were of different breeds, ranging from 2 to 7 years old, had a mean body weight (BW) in the first week after lambing of 91kg (SD=9.7), and nursed an average of 2.2 lambs (SD=0.37). The average daily MEI was 42.0MJ (SD=8.35). The NorFor CI (min/MJ ME) values of the diets was estimated from the content of neutral detergent fibre (NDF; g/kg DM), indigestible NDF (iNDF; g/kg NDF), and the theoretical chopping length (mm) of the forage. The CI values were adjusted for the BW of the ewes and for NDF intakes higher than 0.7% of BW. The mean corrected CI (CIcor) was 37.3min/MJ ME (SD=6.74). The relation between MEI and CIcor was analyzed using nonlinear mixed-effects modelling, using the equation MEI=ME0−k×ME02×CIcor, where MEI is the daily intake of metabolizable energy, ME0 is the theoretical maximum energy intake capacity of the animal in a situation with no physical constraints on intake, and k represents the decline in MEI with increasing CIcor. The model included random variation of week-within-experiment on the intercept and linear fixed effect of week after lambing on k. The maximum daily chewing time, CTmax, for the ewes was assumed to be 1/(4×k). The MEI declined linearly with increasing dietary CI (P<0.001), with difference within-experiment intercepts in relation to week after lambing (P<0.001), supporting the existence of a linear relation between MEI and CIcor for nursing ewes in early lactation. Despite an overestimated CTmax value, this model has the potential to predict the MEI of nursing ewes in early lactation.

Short communication: Production performance and plasma metabolites of dairy ewes in early lactation as affected by chitosan

The objective of this study was to evaluate the effects of chitosan (CHI) supplementation on production performance and blood parameters in dairy ewes. Twenty-four multiparous Latxa dairy ewes at d 16 of lactation were divided into two groups of 12 ewes each. Ewes were fed one of two experimental concentrates (0.840 kg dry matter/d), control or supplemented with 1.2% CHI, on a dry matter basis. Ewes also had free access to tall fescue hay, water, and mineral salts. The experimental period lasted for 25 d, of which the first 14 d were for treatment adaptation and the last 11 d for measurements and samplings. Supplementation with CHI decreased total (p=0.043) and fescue (p=0.035) dry matter intake (DMI), but did not affect concentrate DMI. Supplementation with CHI, moreover, increased plasma glucose (p=0.013) and BUN concentrations (p=0.035), but did not affect those of non-esterified fatty acids. Dietary supplementation with CHI, however, did not affect milk yield, 6.5% FCM, milk composition, or BW, but it improved dietary apparent efficiency by increasing the milk yield-to-DMI (p=0.055) and 6.5% FCM-to-DMI (p=0.045) ratios. In conclusion, dietary supplementation of chitosan maintained ewe performance while reducing feed intake and improving dietary apparent efficiency.

Thermographic variation of the udder of dairy ewes in early lactation and following an Escherichia coli endotoxin intramammary challenge in late lactation

A total of 83 lactating dairy ewes (Manchega, n=48; Lacaune, n=35) were used in 2 consecutive experiments for assessing the ability of infrared thermography (IRT) to detect intramammary infections (IMI) by measuring udder skin temperatures (UST). In experiment 1, ewes were milked twice daily and IRT pictures of the udder were taken before and after milking at 46 and 56d in milk (DIM). Milk yield was 1.46±0.04L/d, on average. Detection of IMI was done using standard bacterial culture by udder half at 15, 34, and 64 DIM. Twenty-two ewes were classified as having IMI in at least one udder half, the others being healthy (142 healthy and 24 IMI halves, respectively). Four IMI halves had clinical mastitis. No UST differences were detected by IMI and udder side, being 32.94±0.04°C on average. Nevertheless, differences in UST were detected for breed (Lacaune – Manchega=0.35±0.08°C), milking process moment (after – before=0.13±0.11°C), and milking schedule (p.m. – a.m.=0.79±0.07°C). The UST increased linearly with ambient temperature (r=0.88). In experiment 2, the UST response to an Escherichia coli O55:B5 endotoxin challenge (5μg/udder half) was studied in 9 healthy Lacaune ewes milked once daily in late lactation (0.58±0.03L/d; 155±26 DIM). Ewes were allocated into 3 balanced groups of 3 ewes to which treatments were applied by udder half after milking. Treatments were (1) control (C00, both udder halves untreated), (2) half udder treated (T10 and C01, one udder half infused with endotoxin and the other untreated, respectively), and (3) treated udder halves (T11, both udder halves infused with endotoxin). Body (vaginal) temperature and UST, milk yield, and milk composition changes were monitored by udder half at different time intervals (2 to 72h). First local and systemic signs of IMI were observed at 4 and 6h postchallenge, respectively. For all treatments, UST increased after the challenge, peaking at 6h in T 0055 (which differed from that in C00, C01, and T10), and decreased thereafter without differences by treatment. Vaginal temperature and milk somatic cell count increased by 6h postchallenge, whereas lactose content decreased, in the endotoxin-infused udder halves. Effects of endotoxin on lactose and somatic cell count values were detectable in the infused udder halves until 72h. In conclusion, despite the accuracy of the camera (±0.15°C) and the moderate standard errors of the mean obtained for UST measures (±0.05 to 0.24°C), we were unable to discriminate between healthy and infected (subclinically or clinically) udder halves in dairy ewes.

Effect of adding palm oil to the diet of dairy sheep on milk production and composition, function of liver and kidney, and the concentration of cholesterol, triglycerides and progesterone in blood serum

The aim of this study was to evaluate the effect of adding palm oil to the diet of dairy sheep on milk production and composition, function of liver and kidney, and the concentration of cholesterol, triglycerides and progesterone in blood serum. Thirty ewes in early lactation were divided into three groups (n=10) receiving an isoproteic and isoenergetic diet. Palm oil (PALM) was added to the diet at different concentrations: 0% (PALM0), 4.0% (PALM4) and 6.0% (PALM6). Milk production was evaluated on days 0, 60, 120, and blood samples were collected in the same periods. Sera samples were analyzed for aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), urea, creatinine, cholesterol, triglycerides, and progesterone. Changes in the volume of milk produced and milk composition (fat, protein, and lactose) in sheep fed with palm oil were not observed between groups. No significant difference was observed between groups for AST, GGT, and creatinine at day 60. However, an increase was observed in AST and GGT activities in the sera of animals from the group PALM4 compared to the control group (PALM0) at day 120. Urea, cholesterol, triglycerides, and progesterone levels had a significant increase in animals from groups PALM4 and PALM6 when compared to the group PALM0 at days 60 and 120. In summary, the addition of palm oil in the diet of dairy sheep influences the metabolism of lipid and protein and caused an increase on liver enzyme activity in proportion to palm oil concentration. The protected fat increased the levels of progesterone, which may improve reproductive performance.

The effect of palm oil addition to the diet of dairy sheep on the immune response

The aim of this study was to evaluate whether a diet based on palm oil has any influence on the immune response and on the number of eggs per gram of faeces (EPG) of gastrointestinal nematodes (GIN) in dairy sheep. To address this issue, 30 ewes in early lactation were confined and divided into three groups (n = 10) receiving a daily isoproteic and isoenergetic diet. Palm oil was added to the feed at different concentrations: 0% (control; group A), 4% (group B) and 6% (group C). The animals were treated with levamisole 10 days before the beginning of the experiment. Faecal samples were collected and analysed for EPG on day zero of the experiment. On days 60 and 120, individual faecal and blood samples were collected, and the FAMACHA(©) score for assessing clinical anaemia was carried out. The groups receiving palm oil showed a significant reduction in EPG in relation to the control group (A) on day 120. Serum immunoglobulin levels (IgG, IgM and IgE) and proinflammatory cytokine levels (TNF-α, IL-1 and IL-6) were significantly increased on days 60 and 120 (p < 0.05) in groups B and C. Therefore, these results suggest that palm oil stimulates the immune response in sheep, thus reducing EPG of GIN. The hypothesis that palm oil has direct anthelmintic activity should be tested in future studies.

The influence of herbage mass and supplementary feeding on nutrient flows and animal performance in grazing, lactating ewes

SUMMARYThe present paper examines the effect of the type of supplement given to grazing ewes in early lactation on the performance of ewes and lambs on temperate sown pastures. Lactating ewes grazed perennial ryegrass pastures at either low- or high-herbage masses, between days 8 and 96 of lactation. On the low-herbage mass treatments, ewes were either unsupplemented or received either an energy supplement (sugarbeet pulp) or a protein supplement (1:1 sugarbeet pulp:formaldehyde-treated soyabean meal) between days 8 and 50 of lactation. The provision of supplements or the higher herbage mass led to increases in live weight (LW) and body condition score of ewes during days 8–50 of lactation, while unsupplemented ewes on the low-herbage mass treatment lost LW and had lower body condition scores. After supplementation finished, previously supplemented ewes or those grazing the higher herbage mass lost LW and condition, while unsupplemented ewes grazing the low-herbage mass gained both LW and condition. Non-treatment factors such as ewe dentition score significantly affected ewe and lamb LW gains. Regression analyses indicated that lamb LW gains between days 8 and 50 of lactation were 40–60 g/d greater in lambs from supplemented ewes or ewes grazing the higher herbage mass cf. unsupplemented ewes. Overall, there was no difference in the response of ewes or lambs to the type of supplement. Milk yields were estimated in a subset of ewes (replicate 4). Ewes on the high-herbage mass treatment or those supplemented with protein had higher milk yields than those on the low-herbage mass treatment or those given the energy supplement. Supplemented ewes in this replicate had higher metabolizable energy intakes (MEIs). Measurements of digesta flow in a further subset of ewes indicated that both supplements resulted in greater ruminal and post-ruminal supplies of energy and protein than in the unsupplemented ewes at the lower herbage mass, but differences in ruminal and post-ruminal nutrient provision between the supplements were less than had been intended. It is suggested that this is the reason for there being no statistical difference in the performance of ewes and lambs in response to the type of supplement.

Effect of a supplement containing trans-10,cis-12 conjugated linoleic acid on the performance of dairy ewes fed 2 levels of metabolizable protein and at a restricted energy intake

Trans-10,cis-12 conjugated linoleic acid (CLA) inhibits milk fat synthesis in dairy ewes, but the effects under varying dietary metabolizable protein (MP) levels when energy-limited diets are fed have not been examined. The objectives of the study were to evaluate the response of lactating dairy ewes to CLA supplementation when fed diets limited in metabolizable energy (ME) and with either a low or high MP content. Twelve multiparous ewes in early lactation were randomly allocated to 1 of 4 dietary treatments: a high MP (110% of daily MP requirement) or low MP (93% of daily MP requirement) diet unsupplemented or supplemented with a lipid-encapsulated CLA to provide 2.4g/d of trans-10,cis-12 CLA, in each of 4 periods of 25 d each in a 4×4 Latin square design. All diets were restricted to supply each ewe with 4.6 Mcal of ME/d (equivalent to 75% of ME requirement). Supplementation with CLA decreased milk fat percentage and yield by 33% and 24%, respectively, and increased milk, milk protein, and lactose yields by 16, 13, and 17%, respectively. Feeding the high MP diet increased the yields of milk, fat, protein, and lactose by 18, 15, 19, and 16%, respectively. Milk fat content of trans-10,cis-12 CLA (g/100g) was 0.09 and <0.01 for the CLA-supplemented and unsupplemented ewes, respectively. Ewes supplemented with CLA had a reduced yield (mmol/d) of fatty acids of <C16, C16, and >C16, although the effect was greatest for <C16. Feeding a high MP level increased the yield of fatty acids of C16 and >C16. Plasma urea concentrations were lowest in ewes supplemented with CLA compared with those unsupplemented (6.5 vs. 7.4 mmol/L, respectively) and receiving low compared with high MP diets (5.6 vs. 8.3 mmol/L, respectively). In conclusion, dairy ewes fed energy-limited diets and supplemented with CLA repartitioned nutrients to increase yields of milk, protein, and lactose, with the response to CLA supplementation and additional MP intake being additive.

Whole extruded linseed in the diet of dairy ewes during early lactation: effect on the fatty acid composition of milk and cheese

In a long term supplementation trial (10 weeks), the effects of the inclusion of whole extruded linseed in the diet of dairy ewes on milk and cheese fatty acid composition were evaluated. Two groups of 24 Sarda ewes in early lactation were randomly assigned to control concentrate (800 g/d concentrate, C) or whole extruded linseed concentrate (L, 700 g/d, with 30% of extruded linseed, Omega-Lin®). Results showed that, after 2 weeks on the L diet, the milk content of unsaturated fatty acid (UFA), including rumenic acid (RA), vaccenic acid (VA) and alfa-linolenic acid (ALA) increased sharply compared to C group, reaching the highest levels after 7-8 weeks (3.06, 7.31 and 2.31 g/100 g milk fat for RA, VA and ALA, respectively). During the last 2 weeks of the experimental period, when pasture was included in the diet of both groups, the content of the above fatty acids slightly decreased in milk from L group, whereas in milk from C group increased. Nevertheless, the average content of these fatty acids in milk from L group remained significantly higher than that of milk from C group. Compared with the control, the L diet resulted in a significant reduction (-17%) in the concentration of saturated fatty acid in milk. The fatty acid content of the cheese obtained from milk of the two groups reflected the milk fatty acid composition. The inclusion of extruded linseed in the diet of dairy ewes improved the nutraceutical properties of milk and cheese, but further researches are needed in order to better understand the relationship between basal diet and lipid supplementation in dairy ewes.

A Conjugated Linoleic Acid Supplement Containing trans-10, cis-12 Reduces Milk Fat Synthesis in Lactating Sheep

The efficacy of conjugated linoleic acid (CLA) supplements containing trans-10, cis-12 for reducing milk fat synthesis has been well documented in dairy cows, but studies with other ruminant species are less convincing, and there have been no investigations of this in sheep. Therefore, the current study was designed to determine whether trans-10, cis-12 CLA would inhibit milk fat synthesis in sheep. Twenty multiparous ewes in early lactation were paired and randomly allocated to 2 treatments: grass hay plus concentrate either unsupplemented (control) or supplemented with lipid-encapsulated CLA to provide 2.4 g/d of trans-10, cis-12 CLA. The CLA dose was based on published responses of dairy cows extrapolated to ewes on a metabolic body weight basis. The experimental design was a 2-period crossover with 10-d treatment periods separated by a 10-d interval. Compared with the control, CLA supplementation reduced milk fat content from 6.4 to 4.9% and reduced fat yield from 95 to 80 g/d. The CLA treatment also increased milk yield from 1,471 to 1,611 g/d and increased protein yield from 68 to 73 g/d. Milk protein content and DMI were unaffected by treatment. The reduction in milk fat yield was due to decreases in both de novo fatty acid synthesis and uptake of preformed fatty acids. Milk fat content of trans-10, cis-12 CLA was<0.01 and 0.12 g/100g of fatty acids for the control and CLA treatments, respectively. The transfer efficiency of trans-10, cis-12 CLA from the dietary supplement into milk fat was 3.8%. Results of the present study demonstrate that a CLA supplement containing trans-10, cis-12 CLA reduces milk fat synthesis in lactating sheep in a manner similar to dairy cows when fed at an equivalent dose (metabolic body weight basis). Furthermore, the nutrients spared by the reduction in milk fat coincided with an increase in milk and milk protein yield.

Excretion of Aflatoxin M1 in Milk of Dairy Ewes Treated with Different Doses of Aflatoxin B1

Two experiments were conducted to study the amount of aflatoxin M1 (AFM1) in milk in response to feeding aflatoxin B1 (AFB1). In experiment 1, four dairy ewes in early lactation received a single dose of pure AFB1 (2mg). Individual milk samples were collected during the following 5 d to measure AFM1 concentration. The average excretion of AFM1 in milk followed an exponential decreasing pattern, with two intermediate peaks at 24 and 48h. No AFM1 was detected in milk at 96h after dosing. The mean rate of transfer of AFB1 into AFM1 in milk was 0.032%, with a high individual variability (SD = 0.017%).In experiment 2, 16 dairy ewes in midlactation were divided into four groups that received different daily doses of AFB1 (0, 32, 64, and 128μg for control and groups T1, T2, and T3, respectively) for 14 d. Pure AFB1 was administered to each animal divided in two daily doses. Individual milk samples were collected at 12, 24, 36, 48, 72, 96, 144, 216, and 312h after the first AFB1 administration, during the intoxication period, and every 24h for 7 d after the withdrawal of AFB1. AFM1 was detected in the milk of all animals of the treated groups at 12h after the administration of AFB1. In all treated groups, milk AFM1 concentration increased from 12 to 144h after the beginning of administration. It then decreased, reaching a stable concentration at 216 and 312h after the first administration. No AFM1 was detected in milk 3 d after the last administration of AFB1. Milk AFM1 concentration measured at steady-state condition was significantly affected by the AFB1 dose (0.031, 0.095, and 0.166 in T1, T2, and T3 groups, respectively), with a linear relationship between AFB1 dose and milk AFM1 concentration (R2 = 77.2%). The carryover (AFM1/AFB1 ratio) was not significantly affected by treatment, and its mean value was 0.112% (SE = 0.011). The carryover was lower than that reported for dairy cattle and goats, suggesting a better ability of sheep to degrade AFB1.

Induction of breeding in anoestrous crossbred ewes with progestagen and PMSG with or without prior immunisation against an androstenedione-protein conjugate

Results are presented of an investigation into the potential value of immunisation of anoestrous ewes with androstenedione-7-HSA, using a commercial preparation (Fecundin; PitmandashMoore, Australia) prior to treatment with intravaginal sponges impregnated with fluorogestone acetate (Cronolone; Searle) and Pregnant Mare Serum Gonadotrophin (PMSG) for out-of-season breeding. Five experiments, involving treatment of 1292 ewes in various physiological states, were conducted during one anoestrous period of 4 months. Factors introduced were: whether or not immunised; interval from booster dose to mating; and dose of PMSG. The ewes were in three stages of anoestrus, namely early, middle or late. Other associated factors were whether or not they were suckling lambs (lactating) and stage of lactation. In early anoestrus, ewes in early lactation were difficult to impregnate compared with maiden ewes (30.6% vs. 51.9% ewes lambed). In mid-anoestrus, ewes in mid-lactation were comparable with maiden ewes (60.6% lambed). In late anoestrus, by which time most lambs had been weaned, 64.3% lambed. The response to immunisation varied with the time from the booster injection to that of the induced oestrus. A 13–14-day interval was too short and had deleterious effects. At 48 days, there were no deleterious effects and a slight residual beneficial effect on lambing performance. An interval of 21 days was much more effective. It had little effect on the time of onset of oestrus, markedly increased the ovulation rate, did not reduce the percentage ewes that lambed, and resulted in a 47% increase in lambs born to ewes in late lactation or from which lambs had recently been weaned. Immunised ewes consistently shed more ova than did nondashimmunised ewes, and this difference increased with increasing doses of PMSG, raising the question of the potential value of immunised animals as donors in embryo transplant programmes. The use of immunisation in a controlled breeding programme requires evaluation of each particular circumstance. There are potential advantages in terms of increased lambs born but the programme needs to be carefully timed.

The effect of concentrate level on the intakes of silages or hays by ewes in the 1st month of lactation

AbstractIn three experiments, four grass silages and four grass hays were offeredad libitum to a total of 164 Finn Dorset ewes rearing twins in the 1st month of lactation. In addition, one of three constant daily levels (300, 650 or 1000 g fresh weight per ewe) of a barley-based concentrate was offered. In the first experiment, replacement rate of silage with in vitro organic matter digestibility (OMD) of 0·65 was less than for hay (OMD 0·59), at –0·09 v. –0·62 g forage OM per g concentrates OM. Consequently, lamb growth rate was greater and ewe weight loss was less with increased concentrate level for the silage than for the hay. In the second experiment, the replacement rates of three silages (OMD 0·56, 0·60 and 0·67) were not significantly different (mean –0·29) and, once again, increased concentrate level gave significantly better ewe and lamb performance. Finally, the replacement rates for three hays (OMD 0·51, 0·59 and 0·72) were also not significantly different (mean –0·30). Equations are presented to predict the intakes of hays and silages by ewes in early lactation.

Suckling behavior of ewes in early lactation

Previous studies have described the basic suckling behavior of ewe/lamb pairs during daylight hours, but no information is available for the hours of darkness. In this study, the natural pattern of suckling was recorded over a 24-h period once a week for the first 7 weeks of lactation in 7 free-ranging Merino ewes with single lambs. Both the mean suckling frequency per 24 hours and the mean duration of individual suckling bouts declined with increasing age of the lamb. Suckling frequencies fell from 36±5.5 sucks/24 h at 1–2 weeks of age to 14.3±2.78 sucks/24 h at 6–7 weeks of age. Individual suckling bout duration fell from 41.1±9.9 s at 1–2 weeks of age to 11.9±1.2 s by 6–7 weeks. Suckling frequencies per hour were significantly greater during daylight as compared to darkness ( p<0.05). We suggest that the declining frequency and duration of suckling bouts with age probably accounts for the waning influence of lactation on the reproductive state of the ewe, and that the maintenance of a critical interbout interval may first break down at night.

Estimation of the intake of milk by lambs, from the turnover of deuterium- or tritium-labelled water

1. The total water turnovers of grazing ewes and their lambs were estimated on days 9, 23, 44, 69 and 86 of lactation from the dilution of tritiated water injected into the dam and deuterium oxide injected into the offspring. The contribution of milk to the total water turnover of the lambs was estimated at the same times from the accumulation of tritium in their body water. 2. Mean total water turnover in the ewes was 6.5 titres/d over the entire period. In lambs, total turnover rose from 1459 ml/d at 9 d to 2791 ml/d at 86 d, and was closely related to live weight (r2 0.760, P less than 0.001). The corrections to total water turnover, which were required because of the increasing body water pool size of the lambs during each measurement period, fell from + 10.6% at 9 d to + 3.7% at 86 d. All corrections were significant (P less than 0.001). 3. The intake of water as milk fell throughout the study, from 1501 ml/d at 9 d to 471 ml/d at 86 d. Pool-size corrections were significant (P less than 0.001). Milk intakes calculated from these results were 1816, 1054, 862, 742 and 588 ml/d at 9, 23, 44, 69 and 86 d of lactation. The rapid decline in milk intake reflected undernutrition of the ewes in early lactation. 4. The level of live-weight gain in early lactation was closely related to, and at a level expected from, the estimated milk intakes. From comparisons of estimated milk intakes with published estimates, it is concluded that the combined use of deuterium oxide and tritiated water results in accurate estimates of milk intake by the lamb throughout the ewe's lactation.

Voluntary intake, health and performance of lactating ewes fed on turnips with or without straw supplement

ABSTRACTThe effect of cereal straw supplement on turnip diets has been studied in Romanov × Rasa Aragonesa ewes in early lactation. Measurements were made of level of intake, blood characteristics and performance under pen-fed and grazing conditions. Barley straw supplementation resulted in a proportional increase of 0·1 in turnip intake to give daily intakes of 82 and 94 g organic matter per kg M0·75 for pen-fed and grazing ewes respectively.Ewes fed on turnips showed a significant decrease in red blood cell numbers, haemoglobin and packed cell volumes though remaining within the range considered as normal for this species. Heinz bodies were present in proportionately up to 0·25 of erythrocytes and no clinical symptoms were observed.The average weight gain of lambs reared by the grazing ewes was 173 g/day. However, growth rates of lambs and weight losses of ewes on turnip diets were lower than expected from the performance of animals on a control diet based on barley, lucerne and straw.

The effect of physiological state on digestion in the ewe and its influence on the quantity of protein reaching the abomasum

Three experiments were carried out on Finnish Landrace × Dorset Horn ewes in various physiological states and given daily 2 kg of a diet containing equal parts of hay and concentrate. In experiment 1 six ewes, each fitted with cannulae in the rumen and abomasum, gave mean estimates for the proportion of their digestible organic matter intake that was apparently digested in the rumen of 0.50 in late pregnancy, 0.64 in early lactation and 0.65 post-weaning ( P < 0.01). The quantities ( g/d) of non-ammonia nitrogen reaching the abomasum were 46.9 for pregnancy, 36.4 for lactation and 40.4 post weaning ( P < 0.001). In experiment 2 the time required to recover an oral dose of chromic oxide in the faeces was significantly ( P < 0.001) lower for ewes in late pregnancy than for barren ewes and the effect was not influenced significantly by the physical form of the roughage (milled versus chopped). In experiment 3 the fractional outflow rate per hour of a chromium-mordanted fish meal supplement from the rumens of eight ewes in the 18th week of pregnancy was 0.053 compared with 0.044 for the same ewes in early lactation ( P < 0.025). It is suggested that the stimulatory effects of pregnancy on the rate of outflow of material from the rumen and on the quantity of protein reaching the abomasum may play a role in the nitrogen economy of the pregnant ewe.

The effect of stocking rate on a lamb production system with February‐lambing ewes

AbstractMasham ewes were stocked at 12(L), 16(M) or 20 (H) ewes ha−1, with 1·8 lambs per ewe on average, on two blocks (A and B) in both 1976 and 1977. Silage was offered at pasture to the ewes in early lactation and as stocking rate increased from 12 to 16 and then 20 ewes ha−1, 47, 73 and 100 kg DM per ewe was consumed respectively. Silage was cut mainly in the autumn and 179, 100 and 9 kg per ewe was made for L, M and H respectively. More variation between treatments was measured in net herbage accumulation in summer than spring and 11·4, 10·0 and 9·7t DM ha −1 was grown over the whole season for L, M and H respectively as a mean of both years.High intakes of herbage OM were measured with values up to 40 g per kg live weight for BL lambs in 1976. Rapid lamb growth was achieved. There were effects of stocking rate on lamb performance and for L, M and H the respective growth rates to 4 weeks were 266, 248 and 247 g d−1; growth rates to sale were 274, 263 and 252 g d−1; days to sale were 124, 126 and 129; mean carcass weights were 17·7, 17·1 and 16·7 kg. Most ewes lost weight in early lactation, especially AH and BH in 1976, but there were no stocking rate effects on ewe weight change in 1977.