Effects of shearing at housing, grass silage feed value and extended grazing herbage allowance on ewe and subsequent lamb performance

The study involved 120 crossbred ewes (sixty 1.5 years old animals and sixty 2.5 years old animals; initial liveweight 67.6 kg, condition score 3.7), that were mated in October. They were assigned to six treatments (two shearing treatments (shorn and unshorn) × two silage feed values (low and medium) and two extended grazed herbage allowances (1.0 and 1.8 kg dry matter (DM)/day)) designed to evaluate the effects of shearing at housing, grass silage feed value and extended-grazed herbage allowance on their performance and the performance of their progeny. Swards, which had silage harvested on 6 September, received fertiliser N (34 kg/ha) for extended (deferred) grazing between 19 December and lambing in mid-March. The herbage was allocated at DM allowances of 1.0 or 1.8 kg/ewe daily until 1 February. For the final 6 weeks of pregnancy, daily herbage DM allowances were 1.5, 1.6, 2.0, 2.0 and 2.0 kg for weeks 6, 5, 4, 3 and 2 to parturition, respectively. Two grass silages (low and medium feed value) were offered from housing on 19 December to lambing in mid-March. At housing, half the ewes were shorn whilst the remainder remained unshorn. Each ewe received 23.4 kg concentrate prior to lambing. For the extended-grazed herbage and the low and medium feed-value silages, DM concentrations were 132, 225 and 265 g/kg, and metabolisable energy (ME) concentrations were 10.0, 10.0 and 10.7 MJ/kg DM, respectively. Treatment did not alter (P > 0.05) litter size or number reared. Grass silage feed value did not significantly alter silage DM intake, or ewe and subsequent lamb performance. Increasing herbage allowance in mid-pregnancy decreased herbage utilisation (P < 0.05) and increased herbage intake (P < 0.05). Shearing increased silage intake (P < 0.05), lamb birth weight (P < 0.01) and tended to increase lamb weaning weight (P = 0.07). Relative to the housed shorn ewes, extended grazing did not alter (P > 0.05) ewe or subsequent lamb performance. It is concluded that shearing ewes at housing increased lamb birth weight due to increased silage intake probably associated with cold stress immediately post shearing and reduced heat stress in late pregnancy. Based on differences in lamb weight at weaning 0.8 kg of grass silage DM intake had the same feed value as a daily extended herbage DM allowance of 1.8 kg per ewe throughout the study. Neither silage feed value nor herbage allowance in mid-pregnancy affected lamb birth weight or subsequent growth rate.     

Shearing during late pregnancy increases size at birth but does not alter placental endocrine responses in sheep

Shearing during the latter half of pregnancy is a common practice to improve flock health and productivity. Previous studies have demonstrated that shearing pregnant ewes at mid or late pregnancy is associated with an increase in lamb birth weight. In the present study, we used singleton Polypay × Dorset pregnant sheep, to investigate the potential roles of placental function and changes in maternal metabolism in underlying this increased birth weight response. Two groups were randomly established and blocked at enrollment by animal BW, body condition score and subcutaneous adipose tissue depth. The groups were shorn (SH; n = 18) or not (C; n = 20) at gestational day (GD) 107 ± 1 (mean ± SEM). Weekly maternal plasma samples were collected between shearing and birth, but only six samples were assayed for progesterone, pregnancy-associated glycoproteins (PAG1), glucose and non-esterified fatty acids (NEFAs). At birth, sex, birth weight, and newborn body mass index (BMI) were recorded. Maternal BW during mid- to late-pregnancy was similar between groups. Shearing resulted in increased lamb birth weight and BMI (P < 0.05) regardless of fetal sex but did not affect the maternal concentration of PAG1 or progesterone from GDs 100 to 142. After shearing (GD100) and up to lambing, shorn females had higher circulating glucose concentrations (P < 0.05), but not NEFA, compared to the control group. Maternal circulating PAG1, progesterone, glucose or NEFA concentration across pregnancy did not differ according to lamb sex. Across pregnancy, birth weight was positively associated with PAG1 (P < 0.001), but not with progesterone concentrations. In conclusion, weight and BMI at birth were higher in both sexes upon shearing in singleton pregnancies. Despite PAG1 being associated with birth weight, late-pregnancy shearing did not alter the placental endocrine response. Whether other placental factors are altered upon shearing and may influence the increase in birth weight and BMI remain to be investigated.     

Early prepartum shearing increases milk production of wool sheep and the weight of the lambs at birth and weaning

The use of mid prepartum shearing has been described as a possible tool to increase the weight of the lambs at birth and at weaning. The effect of prepartum shearing (53 days of gestation) on production and chemical composition of milk, weight of the lambs at birth and weaning and growth rate were evaluated in this trial. Twenty Polwarth ewes were inseminated with rams of the same breed in May (autumn), 2009. All ewes bore singletons and were maintained together under cultivated grazing conditions, during the experimental period. The ewes were allocated to two treatments groups, based on expected day of parturition, body weight and BCS of the dams. Ten ewes were shorn at 53 days of gestation (S53) and 10 ewes were kept unshorn during gestation (US). Milking of the ewes was recorded 7 days after parturition, and this was repeated weekly for 15 weeks. Milk production of the S53 ewes was 22.2% higher (P < 0.05), when compared to US control ewes - with no change in the milk composition. At lambing, the lambs born to the S53 ewes were 1.41 kg (P < 0.05), and at weaning 4.5 kg heavier (P < 0.05), than lambs born to US ewes. In conclusion, it can be said that the higher weaning weight of the S53 lambs was the result of both a higher birth weight and an increased growth rate up to weaning in part, due to an improved milk production of the ewes.     

Fluctuations in energy-related metabolites during the peri-parturition period in Lori-Bakhtiari ewes

This study describes the fluctuations in serum energy-related metabolites during a period of 2 weeks before, to 2 weeks after parturition in Lori-Bakhtiari ewes. The effect of parity was also studied. Blood profiles were determined in 60 healthy pregnant ewes with single (n = 30) and twin (n = 30) lambings. Blood was collected from each ewe on days 14 and 7 prepartum, and days 7 and 14 postpartum to determine the serum non-esterified fatty acid (NEFA), β-hydroxybutyrate (BHBA), glucose, cholesterol, blood urea nitrogen (BUN) and calcium (Ca) levels. The age of the ewes had no significant effect on the energy metabolism indicators. Serum NEFA, BHBA, glucose, BUN and calcium concentrations recorded peak levels 7 days before parturition. However, NEFA and BHBA recorded significant changes (P < 0.05) during the peri-parturition period. All metabolites changed significantly in ewes carrying twin-bearing ewes, compared to single-bearing ewes. Serum BHBA concentrations recorded positive correlations with the serum NEFA (P < 0.01) and cholesterol (P < 0.05), while blood glucose had negative correlations (P < 0.01) with NEFA, BHBA and Ca. Blood NEFA and BHBA recorded positive correlations (P < 0.05) with the BUN levels and negative correlations (P < 0.05) with Ca. The results showed that blood NEFA and BHBA levels are sensitive indicators of the energy balance during the peri-parturition period in ewes.     

Effect of early shearing during gestation on the productive and reproductive behavior of female sheep offspring in their first 18 months of age

The research has shown the interesting contributions of shearing in mid-gestation on the performance of lambs from birth to weaning. Other studies have reported that shearing at early pregnancy influences the development of the placenta and lamb live weight at birth. However, there was a lack of information on the effect of early-prepartum shearing on the behavior of the offspring from weaning onward. This study evaluated the effect of shearing ewes at 50 days of gestation on the growth, reproductive behavior and response to a gastrointestinal parasite challenge in the female offspring from weaning to 18 months old. Fifty-seven Polwarth female lambs were used, 22 being singles and 35 twins born to ewes either shorn at 50 days of pregnancy (PS, n = 23) or shorn at 62 days postpartum (U, control, n = 34) resulting in four subgroups: single lambs born to PS ewes (n = 8), born to U ewes (n = 14), twin lambs born to PS ewes (n = 15) or born to U ewes (n = 20). All progeny were managed together under improved pasture with a minimum forage allowance of 6% live weight on dry basis. Body weight, body condition score and fecal eggs count were recorded every 14 days from weaning to 18 months of age. Concentrations of progesterone were measured weekly (from 4 to 10 months of age and from 14 to 18 months of age) to establish the onset of puberty. Ovulation rate at an induced and a natural heat (545 ± 1.0 and 562 ± 1.0 day old) was recorded. Prepartum shearing did not affect the age at puberty or the ovulation rate of female offspring, but those born as singles were more precocious ( P = 0.03) and heavier ( P = 0.02) at puberty than twin born lambs. Both the average value of parasite egg count ( P = 0.0 7) and the Famacha index ( P = 0.02) for the entire study period were lower in lambs born to prepartum shorn ewes than those born to postpartum shorn ewes. In conclusion, shearing at 50 days of gestation did not affect the growth or the reproductive behavior of female offspring. However, female lambs born from ewe shorn during gestation showed a better response to the parasitic challenge, and further research is required to confirm this.     

Low pasture allowance until late gestation in ewes: behavioural and physiological changes in ewes and lambs from lambing to weaning

Low pasture allowance during gestation affects ewes’ BW at parturition, the bond with their lamb, lamb development, and thus also may affect their responses to weaning. The objectives were to determine if native pasture allowance from before conception until late pregnancy affects ewe–lamb behaviours at lambing, ewes’ milk yield, lambs’ BW, and the behavioural and physiological changes of ewes and lambs at weaning. From 23 days before conception until 122 days of pregnancy, 24 ewes grazed on two different native pasture allowances: high (10 to 12 kg of dry matter (DM)/100 kg of BW per day; HPA treatment; n=12) or low (5 to 8 kg of DM/100 kg of BW per day; LPA treatment; n=12). Thereafter, all ewes grazed on Festuca arundinacea and received rice bran and crude glycerine. Ewes’ body condition score (BCS) and BW were recorded during pregnancy and postpartum periods. Milk yield was determined on days 32, 41 and 54 after lambing. Lambs’ BW was recorded from birth until 72 days after lambing. Latency from parturition until the ewe licked her lamb, maternal behaviour score (a test that evaluates maternal attachment to the lamb) and latency for lamb to stand up and suckle were determined. The behaviour of the lambs and ewes was recorded before and after weaning (at 65 days). The ewes’ serum total protein, albumin and globulin concentrations were measured before and after weaning. The HPA ewes presented greater BW (P<0.005) and BCS (P<0.005) than the LPA ewes during pregnancy and postpartum (P<0.04), and had a greater milk yield than the LPA ewes (P<0.03). Treatments did not influence any behaviour at lambing, lambs’ BW, neither the ewes’ behavioural and physiological changes at weaning. HPA lambs paced and vocalized more than LPA lambs (P<0.0001). The variation of albumin concentration before and after weaning was greater in the HPA lambs than in the LPA lambs (P<0.0001). In conclusion, although ewes’ BW, BCS and milk production were affected by pasture allowance until late pregnancy, this did not affect the behaviours that lead to the establishment of the mother–young bond, nor the ewes’ behavioural responses at weaning. Lambs reared by ewes that grazed on low pasture allowance during pregnancy presented fewer behavioural changes and a lower decrease of albumin concentration after weaning. Lambs’ BW was not affected by the feeding received by their mothers.     

Influence of hot environments on some blood variables of sheep

Thirty-two Polwarth sheep of ages up to 1 year were observed under temperatures varying from 10.5 to 46.5°C. The following blood cell counts were made: erythrocyte (RBC), leucocyte (WBC), eosinophil (EOS), neutrophil (NEU), lymphocyte (LYM) and monocyte (MON). Other traits measured were: haemoglobin (HB), haematocrit (HT), blood glucose (GLU) and serum protein (PROT). Multivariate analysis of variance was used and the results showed a significant (P<0.001) effect for the interaction of shearing and temperature treatment. Under temperatures >25°C, sheep presented a decrease of RBC, WBC, HB and HT, these differences being greater in the shorn than in the unshorn animals. Unshorn animals presented higher variations in EOS, NEU, LYM, MON and GLU. Blood glucose increased under high temperatures in the shorn animals (from 56.36±0.65 mg/100 ml to 60.52±0.69 mg/100 ml) as in the unshorn animals (from 54.72±0.74 mg/100 ml to 57.56±0.77 mg/100 ml).     

The effect of different types of stressors during mid- and late pregnancy on lamb weight and body size at birth

Mid-pregnancy shearing has consistently been shown to increase lamb birth weight, which can lead to an increase in lamb survival rates. However, shearing ewes during the winter months and under outdoor pastoral farming conditions can expose the recently shorn ewe to a greater risk of hypothermia. The aim of this study was to determine if exposure of ewes to repeated stressors, in mid- and late pregnancy, would result in an increase in lamb birth weight. This information may assist in the elucidation of the mechanism for the birth weight response to mid-pregnancy shearing, which in turn could assist in the design of management options to increase lamb birth weight without placing the ewe at risk. One hundred and forty-four twin-bearing Romney ewes were allocated to one of six mid-pregnancy treatments: control, isolation on 2 or 10 occasions, sham-shearing on 10 occasions, intramuscular cortisol injection on 10 occasions or shearing. Isolation, sham-shearing and cortisol treatments were conducted twice a week beginning, on average, day 74 of pregnancy and shearing occurred on day 76. During pregnancy, ewe treatment had no effect on ewe live weight. However, average ewe body condition scores were higher in the shorn group than in the sham-shorn or cortisol groups (P < 0.05). Intramuscular injections of cortisol had a greater effect on ewe plasma cortisol concentrations than all other treatments (P < 0.05). Shearing produced a greater plasma cortisol response than isolation × 10 and sham-shearing (P < 0.05). Ewe plasma cortisol responses decreased during the 5 weeks of isolation and sham-shearing but cortisol injections produced a greater response during the fifth treatment than the first or ninth treatments (P < 0.05). Lambs born to shorn ewes were heavier and had a longer crown rump, forelimb and hind limb lengths than all other lambs (P < 0.05). In addition, lambs born to ewes in the cortisol treatment were lighter than lambs born to control, isolation × 2, isolation × 10 and shorn ewes (P < 0.05). The plasma cortisol concentrations observed for ewes injected with cortisol were far greater than those observed in all other groups, which is likely to explain the low birth weights of lambs born to ewes in that group. These results indicate that the mechanism by which mid-pregnancy shearing increases lamb birth weight is unlikely to be repeated stressors.     

Effects of grass and maize silage feed value,offering soybean meal with maize silage,and concentrate feed level in late pregnancy,on ewe and lamb performance

In many countries, daily herbage accumulation on pasture declines towards zero during the winter period; thus, many pregnant ewes are housed and offered conserved forages supplemented with concentrate prior to parturition. The effects of forage type and feed value (FV), offering soybean meal with maize silage during mid and late pregnancy, and concentrate feed level in late pregnancy on the performance of ewes and their progeny (to slaughter) were evaluated. Ewes (n = 151) were assigned to one of nine treatments from mid-pregnancy until lambing. Medium FV and high FV grass silages (metabolisable energy concentrations of 10.7 and 12.0 MJ/kg DM) were offered ad libitum supplemented with either 15 or 25 kg concentrate/ewe during late pregnancy. Low and high DM maize silages (starch concentrations of 80 and 315 g/kg DM) were offered ad libitum either alone or with soybean meal (200 g/d) and supplemented with 15 kg concentrate during late pregnancy. A final treatment consisted of high FV grass silage supplemented with 5 kg soybean/ewe over the final 4 weeks of pregnancy. Ewes and lambs were put to pasture in a rotational-grazing system within 3 days of lambing. There were no interactions (P > 0.05) between grass silage FV and concentrate feed level for ewe or lamb traits. Increasing grass silage FV increased food intake (P < 0.001) during late pregnancy, ewe BW and body condition score (BCS) at lambing (P < 0.001), lamb BW at birth (P < 0.001) and weaning (P < 0.05), and reduced age at slaughter (P = 0.06). Increasing concentrate feed level increased metabolisable energy (P < 0.05) intake during late pregnancy but had no effect (P > 0.05) on ewe or lamb performance. Increasing maize DM at harvest and offering soybean meal with maize silage increased food intake (P < 0.001) and ewe BW and BCS at lambing (P < 0.05 or P < 0.01). Offering soybean meal with maize silage increased lamb BW at birth (P < 0.01) and reduced age at slaughter (P < 0.05). Reducing supplementation of high FV grass silage to 5 kg of soybean meal had no effect (P > 0.05) on animal performance. Replacing grass silage with maize silage did not affect (P > 0.05) BW gain of lambs. It is concluded that increasing the FV of the grass silage offered during pregnancy had the greatest positive impact on ewe and lamb performance.     

Effects of nutritional level during late pregnancy on colostral production and blood immunoglobulin levels of Karakul ewes and their lambs

An experiment was conducted to examine the changes in colostral production and composition in Karakul ewes fed at different nutritional levels. Pregnant ewes were randomly allotted to one of four groups (n = 20 per group) 90 days after artificial insemination. Three groups were fed with total mixed rations supplying 90, 100 and 110% of the NRC requirements, respectively, and the last group served as the control feeding on natural vegetations until parturition. Blood samples were taken from the jugular vein during late pregnancy, and soon after lambing. Fifteen singleton ewes from each group were hand-milked completely at 1, 12 and 24 h post-lambing. Samples of colostrum were obtained and the lambs were fed with their ewe's colostrum (30 g/kg BW) at each milking. Blood samples were taken from the lambs before receiving their first colostrum, and again at 24 and 48 h post-lambing. Ewes on 110% NRC diet produced significantly (P < 0.01) more colostrum than did the ewes in other groups. Feeding level did not have a significant effect on the IgG level of the colostrums and blood sera of ewes and lambs. Mean IgG concentration in the ewe serum was greatest during late gestation (1–2 months before lambing) and were significantly reduced at 1 h post-lambing. Non-immunoglobulin composition of colostrum was not significantly affected by the treatment. There was a significant correlation between IgG levels of the ewe serum and colostrum (r = 0.64, P < 0.0001). Mean weight of the ewes on the control ration at lambing and the mean birth weight of their lambs were significantly lower as compared with other dietary groups. The results suggested that hand-feeding of Karakul ewes on poor rangeland vegetation with 110% NRC for 2 months before parturition increased colostral production, decreased the ewe loss and increased lamb birth weight which is beneficial to lamb survival.     

Effects of joining at 7 months,and ewe genotype,on the performance of ewes to 19 months of age and that of their progeny to slaughter

Two ways of reducing the cost of replacements are increasing litter size and number of litters produced; thus, the total weight of lamb carcass output per ewe lifetime. The effects of ewe genotype on the performance of ewes lambing at 1 year and of their progeny to slaughter, and the effect of age at first joining (7 or 19 months) on BW at ~19 months and survival to joining at 19 months were evaluated over two consecutive years, using 460 ewe lambs from three genotypes: Belclare (Bel), Suffolk × Belclare (Suf × Bel) and ≥ 75% Suffolk ancestry (Suf75). Lambs from the three genotypes were at a similar proportion of mature BW and half of the lambs, within genotype, were allocated to be joined for the first time at 7 or 19 months. The ewe lambs were managed in a grass-based rotational-grazing system, except when housed from December to March on a grass silage-based diet. Belclare ewes had larger litters (P < 0.001), reared more lambs per ewe joined (P < 0.01), were lighter at lambing and at 19 months (P < 0.01), were of smaller body size at 19 months (P < 0.001) and their progeny were lighter at weaning (P < 0.05) relative to Suf75 genotype; the Suf × Bel ewes were intermediate for most traits but had a significantly lower litter size (P < 0.05) than Bel ewes. Progeny from Suf × Bel ewes were 17 days younger at slaughter (P < 0.01) relative to those from Bel ewes. Ewe genotype had no effect (P > 0.05) on lamb mortality (born dead, total mortality to weaning), lambing assistance, number of ewes that failed to lamb, or on ewe survival to 19 months of age. Increasing ewe BW at joining increased the probability (P < 0.001) of rearing at least one lamb and this effect was consistent across genotypes. There were significant relationships (P < 0.001) between ewe BW at lambing and lamb BW at birth and at weaning of 0.053 (SE 0.0089) kg and 0.29 (SE 0.049) kg, respectively. Ewes that lambed at 1 year were 2 kg lighter (P < 0.001) at 19 months of age and had a smaller body size (P < 0.01) relative to those not joined. It is concluded that ewe genotype had a significant effect on number of lambs reared, and thus lamb carcass output. Whilst lambing at 1 year reduced BW by 2 kg when joined at 19 months, it did not affect ewe survival to that stage.     

An assessment of Walk-over-Weighing to estimate short-term individual forage intake in sheep

The main limitation for determining feed efficiency of freely grazing ruminants is measurement of daily individual feed intake. This paper describes an investigation that assessed a method for estimating intake of forage based on changes in BW of ewes. A total of 24 dry and non-pregnant Romane ewes (12 hoggets, HOG; mean±SD 51.8±2.8 kg BW; body condition score (BCS) 2.6±0.2; and 12 adults, ADU; 60.4±8.5 kg BW; BCS 2.7±0.8) were selected for the study and moved from their rangeland system to a confined pen with controlled conditions and equipped with individual automatic feeders. The experiment lasted for 28 days (21 days adaptation and 7 days feed intake measurement). Ewes were fed hay and trained to use the electronic feeders (one feeding station per ewe) in which actual daily intake (H_intake24) was measured. The pens were designed to maximize movement of trained ewes through an automated Walk-over-Weighing device, by using water and mineral salts as attractants. Total individual intake of hay measured in the automatic feeder at each meal (H_intake) was compared with indirect estimates of feed intake determined using differences in the BW of the ewes (∆BW) before and 1 h following morning and afternoon feeding at fixed times. The BW, BCS, H_intake, H_intake24, as well as plasma non-esterified fatty acids (NEFA), glucose and insulin profiles were determined. The BW was higher in ADU v. HOG but BCS was not affected by parity. The H_intake24 was affected by day of experiment as a consequence of reduced availability and intake of water on one day. Plasma glucose, NEFA and insulin were not affected by parity or day of experiment. The H_Intake was and ∆BW tended to be higher in the morning in HOG, whereas H_intake was and ∆BW tended to be higher in ADU at the afternoon meal. Irrespective of parity or feeding time, there was very strong correlation (r²=0.93) between H_intake and ∆BW. This relationship confirms that our indirect method of estimating individual forage intake was reliable within the strictly controlled conditions of the present experiment. The method appears suitable for use in short-term intensive group feeding situations, and has potential to be further developed for longer-term forage intake studies, with a view to developing a method for freely grazing ruminants.     

Reproductive performance and milk yield in Awassi ewes following crossbreeding

The objective of this study was to evaluate the effect of crossbreeding Awassi ewes with either Charollais or Romanov sires, on pre-weaning lamb production as reflected by reproductive performance and milk production in the ewes. Two hundred and five, 3- to 6-year-old multiparous ewes of three breeds were allocated to three groups [Awassi (A; n = 56), F₁ Romanov × Awassi (RA; n = 78) and F₁ Charollais × Awassi (CA; n = 71)]. Upon lambing, ewes and their offspring were placed in a large pen in which they remained until the end of the trial. Body weight (BW) and body condition score (BCS) of the ewes and the BW of the lambs were recorded weekly from birth to weaning at 70 days of age. Milk production was recorded weekly from parturition to weaning. Pregnancy rates were not influenced by breed-type. Multiple births and the fecundity of ewes were greater (P < 0.05) in the RA group, compared to the A and CA groups—while the weaning percentage was similar between the breeds. Lamb birth and weaning weights were similar, while the kg lamb born per kg ewe lambed was greater (P < 0.05) in the RA group, compared to the CA group. The CA ewes recorded a higher BW (P < 0.01) and BCS (P < 0.01) than the other breed groups. Awassi ewes produced more milk (P < 0.01) throughout the observation period. Milk ash percentage was higher (P < 0.05) in the CA group, while the percentage of crude protein and dry matter was similar for the different groups. Results of the present study indicate that crossbreeding of Awassi ewes with Charollais and Romanov breeds decreased milk production in the progeny, without affecting lamb growth. The crossbreeding of Awassi with Charollais resulted in improved BW and BCS, while the crossbreeding of Awassi ewes with Romanov resulted in improved reproductive performance of the crossbreds. Crossbreeding Awassi ewes with exotic rams can thus be conducted to increase the number of lambs produced per ewe.     

Associations between minerals and metabolic indicators in maternal blood pre- and postpartum with ewe body condition,methane emissions,and lamb body weight development

In sheep production, economic efficiency strongly depends on the maternal health and feed efficiency status and on weaning performances of their offspring. Accordingly, an optimal level for the supply with macro- and microelements and the ewe energy status has impact on the fetal development during gestation and on maternal milk production during lactation. Furthermore, this study addressed intergenerational aspects, i.e., on associations between maternal energy metabolism profiles considering the macro- and microelement status, metabolic indicators (e.g. β-hydroxybutyrate (BHB)), body condition and methane (CH4) emissions with lamb BW (LBW) in two sheep breeds. Traits were recorded at the beginning of gestation (ewe traits), at lambing, three weeks postpartum, and at weaning (ewe and lamb traits). Trait recording included CH4 emissions (recorded via laser methane detector (LMD)), ewe BW (EBW), backfat thickness (BFT), and body condition score (BCS) from 46 ewes (24 Merinoland- (ML), 22 Rhönsheep (RH)), and LBW of their 87 (35 ML, 52 RH) purebred lambs. Serum levels of the following ewe blood parameters were determined: calcium (Ca), sodium (Na), potassium (K), phosphate (P), nonesterified fatty acids (NEFA), BHB, glutamate dehydrogenase (GLDH), selenium (Se), copper (Cu), iron (Fe), zinc (Zn), and magnesium (Mg). Mixed models were applied to infer associations between ewe blood parameters with EBW, BFT, BCS, and CH4 and with LBW recorded in offspring. At weaning, a maternal serum Mg level > 1.0 mmol/L was significantly associated with an increase of 13% in LBW in ML, compared to offspring from ML ewes with a serum Mg concentration within the lower reference range (0.8 mmol/L). Furthermore, higher Cu levels were favorably associated with ewe BCS and BFT at weaning in both breeds. In RH ewes, a Se level > 2.4 μmol/l was significantly associated with increased BCS. In the ML breed, high Zn levels during lactation were associated with reduced CH4 emissions. Ewe EBW was significantly larger for ML ewes representing low Ca levels. A low BHB level was associated with decreasing CH4 emissions in RH and ML. Serum levels for Na, K, P, GLDH, and Fe did not significantly affect the traits of interest. Trait associations from the present study indicate the importance of the mineral supply and metabolic status of the ewe with regard to body condition, CH4 emissions, and LBW development, but depending on the breed. Identified associations might contribute to energy efficiency in sheep production systems.     

Effects of replacing grass silage with either maize silage or concentrates during late pregnancy on the performance of breeding ewes fed isonitrogenous diets

A study was undertaken to investigate the performance of breeding ewes fed a range of forage and concentrate-based diets in late pregnancy, balanced for supply of metabolizable protein (MP). For the final 6 weeks before lambing, 104 twin-bearing multiparous ewes were offered one of four diets: ad libitum precision-chop grass silage + 0.55 kg/day concentrates (GS); ad libitum maize silage + 0.55 kg/day concentrates (MS); a 1 : 1 mixture (on a dry matter (DM) basis) of grass silage and maize silage fed ad libitum + 0.55 kg/day (GSMS); or 1.55 kg/day concentrates + 50 g/day chopped barley straw (C). The CP content of the concentrates was varied between treatments (157 to 296 g/kg DM) with the aim of achieving a daily intake of 130 g/day MP across all treatments. Compared with ewes fed GS, forage DM intake was higher (P < 0.05) in ewes fed MS (+0.21 kg/day) and GSMS (+0.16 kg/day), resulting in higher (P < 0.001) total DM intakes with these treatments. C ewes had the lowest total DM intake of all the treatments examined (P < 0.001). C ewes lost more live weight (LW; P < 0.001) and body condition score (BCS; P < 0.05) during the first 3 weeks of the study but there were no dietary effects on ewe LW or BCS thereafter. The incidence of dystocia was lower (P < 0.01) in C ewes compared with those offered silage-based diets (7.5% v. 37.4% ewes), and was higher (P < 0.01) in ewes fed MS compared with GS or GSMS (50.7%, 34.7% and 26.9%, respectively). There were no significant dietary effects on the plasma metabolite concentrations of ewes in late pregnancy, pre-weaning lamb mortality, weaned lamb output per ewe or on lamb growth rate. The results of this study demonstrate that both maize silage and all-concentrate diets can replace grass silage in pregnant ewe rations without impacting on performance, provided the supply of MP is non-limiting. The higher incidence of dystocia in ewes fed maize silage as the sole forage is a concern.     

Polyethylene glycol marker measured with NIRS gives a reliable estimate of the rangeland intake of grazing sheep

Polyethylene glycol (PEG) measured with NIRS is known to be a valuable faecal marker when used in indoor experiments. In order to verify whether it can be used at pasture, an experiment was conducted with two trials. In trial 1, six Romane breed adult dry ewes placed in metabolism cages were fed daily with natural, freshly cut rangeland from a fertilised or unfertilised paddock for 6 weeks. Three ewes did not receive PEG and the three others were dosed with 10 g of PEG in solution form once daily until the end of the experiment to measure in vivo dry matter digestibility and PEG recovery rate for each forage quality. At the same time (trial 2), 15 ewe lambs and 14 lactating adult ewes suckling one or two lambs were allowed to graze together on the same herbage as that cut for indoor ewes. All animals were initially equipped with faecal bags emptied twice daily for collecting total faeces, and eight ewe lambs and seven adults were dosed once daily with 10 g of PEG. Faecal grab samples were collected for 4 to 5 days for each forage quality grazed. Indoor trial 1 showed that PEG had no effect on dry matter intake (DMI) or on digestibility. PEG recovery rates measured on fertilised (77.7%) and unfertilised (82.1%) forage were not different (P>0.05). PEG recovery rates measured at pasture did not differ (P>0.05) between pasture quality and animal type with an average value of 68.9%. Faecal output measured with bags or estimated with PEG and calculated DMI were not different (P>0.05) when PEG recovery rate measured at pasture was used. Conversely, using indoor PEG recovery values, significantly (P<0.05) or tended to overestimate faecal output. In conclusion, PEG could be used as a faecal marker administered at a minimal dose of 1% of DMI with a recovery rate measured under pasture conditions for pasture intake measurements on a group of animals at the same physiological stage but not for individual measurements.     

Metabolic and biochemical changes in plasma of the periparturient rabbit does with different litter size

The aim of this study was to investigate the metabolic and biochemical changes in plasma that occur in the reproductive rabbit doe close to the parturition, as well as if the number of offspring affects the metabolism and the health status of the doe. At −3, 4 and 12 days from parturition (–D3, D4, and D12, respectively) nine rabbit does at their third parity from a commercial hybrid line (HYPLUS PS 19) selected for high prolificacy were weighted and blood was collected for a wide inflammometabolic profile. According to the number of offspring the does were retrospectively divided in two groups: high litter size group (HI; n=5) and low litter size group (LO; n=4). BW was higher (P<0.01) at –D3 and had the lowest values at D4. At D12, the BW was lower (P<0.05) in LO compared with HI. Several metabolites significantly changed from dry to lactation period. Glucose and cholesterol had the lowest levels at –D3; non-esterified fatty acid (NEFA) and aspartate aminotransferase had the highest values before parturition (P<0.05); creatinine and β-hydroxybutyrate (BHBA) were higher at –D3 with respect to D4 (P<0.05). The lowest value of paraoxonase was observed in does at –D3 (P<0.05), whereas at this time ceruloplasmin and total bilirubin had the highest concentration (P<0.05). The differences for blood profile parameters between does grouped according to litter size were mainly evident before parturition (–D3). In particular, BHBA, NEFA and total bilirubin had higher concentrations (P<0.05) in HI v. LO group, whereas albumin and PON were lower in HI group (P<0.01). After parturition there were no significant differences for the metabolic parameters between the two groups. The results show that for reproductive rabbit doe the last days of gestation are very stressful from a metabolic and inflammatory point of view. The genetic selection of does for higher litter size has increased their ability to mobilize body reserves in order to guarantee the nutrients to a high number of kits. This exposes them to a more severe metabolic and inflammatory challenge during the transition period. Consequently, feeding and managerial strategies for high prolificacy periparturient rabbit does should be revised.     

Plane of nutrition during the rearing phase for replacement ewes of four genotypes: II - effects on performance during first pregnancy and to weaning,and of their progeny

Plane of nutrition (PN) offered to ewe replacements during the rearing phase (8 to 17 months) and first pregnancy may affect reproductive and progeny performance when replacements are joined at ~19 months. The effects of PN offered to spring-born ewe replacements during their first winter (winter_1), second summer (summer_2) and subsequent winter (mid and late pregnancy; winter_2) were evaluated, over 3 consecutive years, using 287 ewe lambs of four genotypes: Charmoise×Scottish Blackface (C×SBF), Belclare×SBF (Bel×SBF), Belclare (Bel) and Belclare×SBF (heterozygous for a gene, either FecG^H or FecX^G mutations, that increases ovulation rate: BelMG×SBF). Ewe lambs were offered, daily, a deferred-grazed herbage allowance (HA) of either 0.75 or 1.75 kg dry matter during winter_1. During summer_2 the replacements were set-stocked to maintain sward heights of 4 or 6 cm. Ewes were housed during mid and late pregnancy (winter_2) and offered either medium or high-feed-value grass silage, thus yielding a 2×2×2 factorial design. Increasing HA during winter_1 and residual sward height during summer_2 increased ewe BW post joining (P<0.001) and at lambing (P<0.01), but had no effect (P>0.05) on number of lambs reared. Increasing HA during winter_1 increased lamb BW at birth (P<0.05) and reduced carcass fat score (P<0.05). There was a significant interaction between PN offered during winter_1 and summer_2 for average daily gain (ADG) from birth to 5 weeks (P<0.01) and from 5 to 10 weeks (P<0.05): progeny of replacements that experienced either a high or low PN throughout the rearing phase had lower ADG than lambs born to the replacements that experienced a low PN only during winter_1 or summer_2. Increasing PN during winter_2 increased ewe BW (P<0.001), lamb BW at birth (P<0.001) and weaning (P<0.05) and reduced the proportion of ewes that failed to lamb (P<0.01). Ewe genotype had a significant (P<0.001) effect on litter size (1.48 to 2.45), number of lambs reared, lamb BW at birth and weaning, lamb ADG and age at slaughter. It is concluded that, among the nutrition treatments examined, increasing PN during mid and late pregnancy had the greatest effect on ewe and progeny performance. Although increasing PN offered during winter_1 increased lamb birth BW, PN offered during summer_2 had no effect on lamb performance. There were no significant interactions between PN and ewe genotype.     

Cereals level and source effects on rumen fermentation,colostrum and milk properties,and blood metabolites in periparturient ewes

Optimal type and dietary inclusion rates of cereal grains for periparturient sheep are unknown. The objective was to determine effects of feeding diets with high (H) v. low (L) levels of ground corn grain (CN) v. combined ground wheat and barley grains (WB) on intake, rumen fermentation, colostrum and milk properties, and blood metabolites of periparturient sheep. Twenty Afshari×Merino ewes were used in a completely randomized design study from 24 days prepartum through 21 days postpartum. Ewes were kept indoors in individual boxes and received once daily at 0900 h total mixed rations. Treatments were mixed rations containing either (1) H or (2) L concentrate based on either (1) 100% CN or (2) 50 : 50 ratio of ground wheat : ground barley grains in a 2×2 factorial arrangement. Each treatment group had five ewes including two twin-lamb ewes and three single-lamb ewes. Postpartal dry matter intake (DMI) increased by feeding high CN v. high and low WB, while high v. low CN improved postpartum DMI. The DMI during lambing tended to increase with the high v. low WB. Feeding CN v. WB, and feeding both CN and WB at L v. H level increased fecal pH. Postpartal rumen pH was lower with the high v. low WB (5.7 v. 6.2). Rumen concentrations of propionate were lower and of acetate were higher with L v. H grain levels. Increased dietary grain reduced urine pH for WB (7.24 v. 7.83) but not for CN (7.63 v. 7.52) prepartum. Colostrum properties, postpartal urine pH, lamb weight at birth and 21 days of age, and placental weight and expulsion time were unaffected. Milk yield increased and milk fat yield tended to increase by H v. L grain diets. Plasma glucose was increased by feeding high v. low WB, whereas CN v. WB tended to reduce peripartal plasma non-esterified fatty acids (NEFA) and increased insulin to NEFA ratio. In conclusion, more cereal grains can be included in periparturient sheep diets and CN instead of WB may be fed to periparturient sheep to improve energy status. Findings suggest opportunities to optimize periparturient ewe physiology and performance through feeding certain cereals and avoiding high levels of WB.     

Selenium-methionine and chromium-methionine supplementation of sheep around parturition: impacts on dam and offspring performance

To examine the effects of maternal energy restriction along with selenium-methionine (Se-Met) and chromium-methionine (Cr-Met) supplementation on performance of pregnant sheep and their offspring, the following treatments were allotted randomly to 40 multiparous Baluchi ewes (53.9 ± 1.15 kg of body weight [BW]) from 5 weeks prior to 5 weeks after parturition: (1) Control diet (60% and 100% of NRC energy requirements in pre- and post-partum, respectively); (2) Control diet plus 5 mg Se-Met/kg dry matter (DM); (3) Control diet plus 3 mg Cr-Met/kg DM and (4) Control diet plus 5 mg Se-Met and 3 mg Cr-Met/kg DM (Se–Cr-Met) of concentrate diet. The results indicated that Cr-Met alone or in combination with Se-Met increased average DM intake of ewes. In addition, Group Cr-Met had higher average BW than the Control (p < 0.05). Se-Met and/or Cr-Met supplementation led to decreased average serum cholesterol of the ewes (p < 0.05). Groups Cr-Met and Se–Cr-Met displayed decreased average serum malondialdehyde compared to the Control (p < 0.05). At 24 h post-partum, Group Se–Cr-Met had a greater serum Se content than the Control (p = 0.006). Compared with the Control, the Se concentration in milk was significantly increased from 30 to 138 µg/l and 197 µg/l in Groups Se-Met and Se–Cr-Met, respectively (p < 0.01), which proved that Se-Met supplementation can increase the Se concentration of ewe milk. Furthermore, feeding Cr-Met may attenuate BW loss post-partum and Se-Met and/or Cr-Met supplements may ameliorate oxidative stress condition in ewes around parturition.