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.     

The effects of allowance and frequency of allocation of deferred herbage, and grass silage feed value, when offered to ewes in mid-gestation on ewe and lamb performance and subsequent herbage yield

The effects of (i) herbage allowance, (ii) frequency of allocation and (iii) grass silage feed value on ewe and lamb performance were studied in mid-gestation ewes. Furthermore, the effects of (i) herbage allowance, (ii) frequency of allocation and (iii) grazing date and their interactions on subsequent herbage yield and feed value were also evaluated. Swards, which had a cut of silage removed on 6 September, received fertiliser nitrogen (34 kg/ha) for extended (deferred) grazing between 6 December and 1 February. Two grass silages differing in feed value were ensiled either precision chopped or in big bales from predominantly perennial ryegrass swards, respectively. In experiment 1, a completely randomised study involving 120 crossbred mid-gestation ewes (Belclare × Scottish Blackface) that had been mated in October was undertaken to evaluate the effects of extended grazed herbage allowance (1.0 and 1.8 kg dry matter (DM)/day), frequency of herbage allocation (daily and twice weekly) and grass silage feed value (low and medium) on ewe and subsequent lamb performance. The six diets were offered from days 63 to 120 of gestation. From day 120 of gestation to parturition all ewes were housed and offered the medium feed value silage ad libitum. All ewes received 19 kg concentrate prior to lambing. Increasing herbage allowance increased forage intake (P < 0.05), lamb birth weight (P < 0.01), weaning weight (P < 0.05) and growth rate from birth to weaning (P < 0.05), decreased herbage utilisation (P < 0.05) and tended to increase ewe condition score at lambing (P = 0.06). Frequency of herbage allocation or grass silage feed value did not alter (P > 0.05) ewe or subsequent lamb performance. In experiment 2, the effect of extended grazed herbage allowance (1.0 and 1.8 kg DM/ewe daily), frequency of allocation (daily and twice weekly) and grazing date (6 to 12 December, 27 December to 3 January and 17 to 23 January) on herbage yield at two harvest dates (27 April and 25 May) was examined in a split plot design study consisting of 72 plots. Delaying grazing date decreased herbage yield (P < 0.01) whilst delaying harvest date increased herbage yield (P < 0.05). Frequency of herbage allocation did not alter (P > 0.05) subsequent herbage yield. It is concluded that for ewes in mid-gestation 1.0 kg of low feed value silage DM had the same feed value, as determined by weaned lamb weight, as 1.3 kg herbage DM allowance. Each 1-day delay in grazing date reduced herbage DM yield by 54.2 kg/ha.     

Effects of exogenous progesterone on gestation length, foetal survival and colostrum yield in ewes

Twin bearing mature ewes (n=40) were treated with exogenous progesterone (100mg daily in oil) or vehicle (oil control) from Day 143 of gestation until lambing to investigate the effects on gestation length, foetal survival and colostrum yield and composition. Compared to control ewes, progesterone treated ewes had increased (P<0.05) serum progesterone concentrations (by 4.3 ng/ml) before lambing and in the first day post-partum (by 10 ng/ml). Progesterone treatment increased gestation length (150.4+/-0.6 days versus 147.8+/-0.6 days, P<0.05) and colostrum yield at 1h after lambing (P<0.05) but the colostrum had a lower concentration of IgG (P=0.02). In the first 24h after lambing, total colostrum and IgG yields were not different between groups. Four (20%) of the progesterone treated ewes produced either one or two dead lambs, while one ewe died on day 155 without initiating the birth process. We conclude that the daily administration of 100mg progesterone resulted in extended gestation length and reduced lamb survival but did not lower colostrum yield.     

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 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.     

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.     

The effect of late pregnancy supplementation of ewes with vitamin E on lamb vigour

The experiment measured lamb responses to supplementation of the pregnant ewe diet with vitamin E above requirement. Crossbred ewes were mated with either Suffolk or Texel rams. Twin-bearing ewes were randomly allocated (approximately 21 months of age at allocation) to one of four treatment groups (20 ewes per group, 10 mated with Suffolk and 10 with Texel rams). Treatments imposed were 50, 100, 150 or 250 IU supplementary vitamin E per ewe per day to give a four treatment by two sire-type factorial experimental design. Ewes were fed concentrates to meet energy requirements for stage of pregnancy and hay ad libitum. Diets were introduced approximately 6 weeks before lambing. Blood samples were obtained prior to introduction of diets, 17 days after introduction of diets and within 24 h of lambing from a subset of eight ewes per treatment (32 total). Colostrum samples were obtained from 10 ewes per treatment, 12 h after birth of the first lamb. All births were observed and a lamb vigour score was assigned to each lamb 5 min after birth. At 1 and 12 h after birth, rectal temperature, and at 12 h after birth, sex, crown-rump length and BW of each lamb were recorded. Mean ewe plasma α-tocopherol concentration prior to introduction of the diets was 1.5 μg/ml (s.e.m. 0.09) and did not differ between groups. There were positive linear (P < 0.001) effects of dietary vitamin E on plasma (17 days after introduction of diets) and colostrum (12 h after birth) α-tocopherol concentrations. Lamb vigour scores were superior (P < 0.001) for lambs sired by Texel rather than Suffolk rams but there were no differences as a result of vitamin E supplementation. Lamb mortality was low and unrelated to either sire or supplementary vitamin E. Lamb birth and weaning weights were also unaffected by vitamin E supplementation. Supplementing the ewe with vitamin E therefore had no effect on any lamb measurements.     

The effects of cobalt and iodine supplementation of the pregnant ewe diet on immunoglobulin G, vitamin E, T3 and T4 levels in the progeny

Sixty twin-bearing ewes were allocated to one of four dietary treatments investigating the effects of supplementary iodine or cobalt during late pregnancy on lamb serum immunoglobulin G (IgG), triiodothyronine (T3), thyroxine (T4) and vitamin E concentrations, and lamb IgG absorption efficiency. Ewes were offered grass silage ad libitum supplemented with 800 g per ewe per day of a 190 g/kg crude protein (CP) concentrate from day 126 of gestation until parturition plus one of the following supplements (n = 15 per treatment); no supplement (C); 26.6 mg iodine per day for final 3 weeks pre partum (I-3); 26.6 mg iodine/day for final week pre partum (I-1); 20 mg cobalt/day for final 3 weeks pre partum (Co-3). Lambs were blood sampled at 24 and 72 h post partum for serum IgG and vitamin E concentrations. Ten lambs from C and I-3 were blood sampled at 1 h post partum for serum IgG, vitamin E, T3 and T4 concentrations. There were no differences in serum IgG, vitamin E or T4 values (P > 0.05) at 1 h post partum between lambs born to the C and I-3 ewes. T3 levels were lower in I-3 compared with C progeny (P < 0.05). Supplemental iodine reduced colostral IgG absorption efficiency (P < 0.001) and lamb serum IgG concentrations at 24 and 72 h post partum (P < 0.001). Serum vitamin E concentration in I-3 and I-1 lambs was lower than in Co-3 lambs at 24 h post partum, while at 72 h post partum I-3, I-1 and Co-3 lambs had significantly lower concentrations than C lambs (P < 0.001). Supplementing the ewe's diet with 26.6 mg/day of iodine for the final week of pregnancy reduced lamb serum IgG concentration at 24 and 72 h post partum. The lower total and free T3 values in the progeny of I-3-treated ewes suggest interference in the synthesis and metabolism of thyroid hormones when ewes receive excessive dietary iodine for 3 weeks immediately pre partum. Based on these findings, the indications are that the toxicity level for iodine in the diet of the pregnant ewe should be lowered to 20 mg per ewe per day, equivalent to 40% of its current level. The finding that high-level cobalt supplementation during the final 3 weeks of pregnancy will have a negative effect on serum vitamin E concentration at 72 h post partum is a new and significant finding and previously has not been reported in the literature.     

A pre-partum lift in ewe nutrition from a high-energy lick or maize or by grazing Lotus uliginosus pasture, increases colostrum production and lamb survival

This experiment tested the hypothesis that a lift in the nutrition of ewes, before lambing, to increase colostrum production would enhance lamb survival. In all, 261 mature Corriedale ewes, each with a single fetus from a synchronised mating, grazed native pasture to day 130 after mating; at which point they were weighed, condition scored and allocated to graze either native pasture or a pasture dominant with Lotus uliginosus. Five days later (14 days before the expected start of lambing) the ewes were allocated to one of four treatments and fed: (i) native pasture alone, (ii) native pasture plus a commercial high-energy lick, (iii) L. uliginosus pasture alone or (iv) L. uliginosus pasture plus whole maize. The weight, viscosity and concentration of components and immunoglobulin G in the colostrum that had accumulated at parturition, were measured for 10 ewes in each treatment. The lambs that survived to 20 days of age from the 221 ewes that were not milked, were recorded. The ewes supplemented with the lick or maize grain and those that grazed the L. uliginosus pasture alone accumulated two to three times more colostrum at birth than the ewes that grazed native pasture alone (396, 635 and 662 g v. 206 g; P < 0.01). The colostrum from the ewes that grazed only native pasture was more viscous (lower score) than that from the ewes supplemented with the lick or maize grain or the ewes that grazed the L. uliginosus pasture alone (scores of 4.1 v. 6.2, 6.5 and 6.4, P < 0.001) and, not surprisingly, the concentration of lactose in the colostrum of the ewes fed only native pasture was also much lower (1.1% v. 3.0%, 2.8% and 2.6%; P < 0.001)he survival of lambs from the ewes fed only native pasture was less than that of the lambs from ewes fed native pasture plus the commercial lick (81.8% v. 95.5%; P < 0.05) or the L. uliginosus pasture alone (92.4%, P < 0.05), and also tended to be lower than that for lambs born to ewes fed L. uliginosus pasture plus maize (91.8%, P = 0.08). The concentration of glucose in the blood of the lambs from the ewes that grazed only native pasture was lower than that of the other lambs (42.1 v. 60.2 ng/ml, P = 0.012). We conclude that the marked increase in colostrum production associated with the lift in ewe nutrition, just prior to lambing, enhanced lamb survival.     

The effect of fish oil supplementation of pregnant and lactating ewes on milk production and lamb performance

Supplementation of pregnant ewes with long-chain n-3 polyunsaturated fatty acids (PUFA) demonstrably improves indicators of neonatal lamb vigour, potentially improving the number of lambs reared per ewe. The present study investigated the effect of supplementing ewes with fish oil and vitamin E (α-tocopherol acetate) throughout both pregnancy and lactation on the performance of lactating ewes and sucking lambs. Forty-eight ewes were supplemented with one of four concentrates containing either Megalac or fish oil plus a basal (50 mg/kg) or supranutritional (500 mg/kg) concentration of vitamin E from 6 weeks pre-partum until 4 weeks post partum in a two-by-two factorial randomised-block design. All concentrates were formulated to contain approximately 60 g/kg supplemental fatty acids. Ewes were housed, penned on sawdust and offered straw ad libitum. Blood samples were taken from ewes and lambs at intervals throughout the experiment and milk samples were obtained at 21 days into lactation. There was no notable effect of dietary vitamin E concentration upon ewe or lamb performance. Ewe dry-matter (DM) intake and yield were unaffected by dietary treatment, although ewes fed fish oil lost less weight during lactation (-1.88 kg compared with -3.97 kg for Megalac-supplemented ewes; P < 0.01). Milk fat concentrations (67.3 g/kg compared with 91.8 g/kg; P < 0.01) and yields (6.65 g/h v. 9.26 g/h; P < 0.01) were reduced in ewes fed fish oil and these decreases were associated with lower litter-growth rates (0.49 g/day compared with 0.54 g/day; P < 0.05). Milk protein yield was increased by fish oil supplementation (3.82 g/h) compared with Megalac supplementation (3.28 g/h; P < 0.05); moreover, there was an interaction between fat source and vitamin E concentration in that both protein concentration and yield were significantly lower in milk from ewes fed treatment with Megalac + basal vitamin E (MB) compared with the other three treatments. Fish oil supplementation increased the concentrations of C18:1 trans-, cis-9, trans-11 conjugated linoleic acid (CLA), C20:5 (n-3) and C22:6 (n-3) within ewe plasma, milk and lamb plasma. The mechanisms by which fish oil supplementation affects milk composition warrants further investigation.     

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.     

The effect of photoperiod and melatonin feeding on reproduction in the ewe

Sixty anestrous ewes were used to determine the effects of artificial photoperiod and/or melatonin feeding on seasonality of reproduction. Treatments included natural daylight (ND), 8 h of light, 16 h of darkness (8L: 16D), natural daylight plus 3.5 mg melatonin fed per ewe daily (ND + MEL), and 8L: 16D plus 3.5 mg melatonin fed per ewe daily (8L: 16D + MEL). The percentage of ewes lambing was lower (P < 0.05) for ND treated ewes (40%) than for ewes in 8L: 16D (100%), ND + MEL (91.7%), or 8L: 16D + MEL (93.3%). The earliest mean conception date was for ewes in the 8L: 16D + MEL treatment. This was 10 days earlier than for ewes in the ND treatment (P < 0.05). ND and ND + MEL treated ewes had fewer lambs (P < 0.05) and lighter litter weight (P < 0.05) per ewe lambing than did 8L: 16D and 8L: 16D + MEL treated ewes. Serum progesterone levels above 1.0 ng/ml were reached and maintained approximately 3 wk earlier in the 8L: 16D, 8L: 16D + MEL, and ND + MEL treated ewes than in the ND treated ewes (P < 0.05). Ewes in ND treatment had higher overall serum prolactin levels (P < 0.05) than did ewes in all other treatments. Results indicate that the 8L: 16D treatment and/or feeding melatonin can hasten cyclicity in ewes and increase the number of ewes conceiving.     

Artificial insemination of ewes with frozen-thawed semen at a synchronized oestrus. 1. Effect of time of onset of oestrus, ovulation and insemination on fertility

In three experiments, the onset of oestrus, time of ovulation and lambing after intrauterine insemination with frozen-thawed semen were examined following synchronisation of oestrus using intravaginal progestagen-impregnated sponges (inserted for 12 days) and an injection of PMSG at sponge removal.

The number (and percentage) of ewes detected in oestrus 12, 24, 36, 48, 60 and 72 h after sponge removal was 1 (0.3), 2 (0.6), 17 (5.2), 120 (36.7), 65 (20.0) and 10 (3.1) respectively. One hundred and twelve ewes (34.3%) remained unmarked. Egg fertilisation rates were not different between ewes irrespective of time of onset of oestrus or whether or not ewes were marked.

The median time of ovulation with respect to sponge removal (with 95% fiducial limits) for ewes joined with vasectomised rams (10:1) at spronge removal (teased ewes) was 55.8 h (54.61–57.09) and for unteased ewes 59.7 h (58.27–61.12).

In the third experiment, a total of 394 ewes were inseminated by laparoscopy with frozen-thawed semen. The percentage of ewes lambing and lambs born per ewe inseminated, and number of lambs born per ewe lambing for inseminations 48, 60, 72 and 78 h after sponge removal were 45.9, 57.7 and 1.25; 55.1, 72.0 and 1.31; 57.4, 80.9 and 1.41; and 39.3, 60.7 and 1.54, and for 59 control ewes receiving fresh semen by cervical insemination 47.5, 69.5 and 1.46 respectively. The lambing data after insemination with frozen semen was not different to that of the controls. The percentage of ewes lambing and lambs born per ewe inseminated increased with time of insemination at 48, 60 and 72 h (linear, P < 0.01) but was lower for inseminations at 78 h after sponge removal. Number of lambs born per ewe lambing increased with time of insemination after sponge removal (linear, P < 0.05).     

A new approach to enhance reproductive performance in sheep using royal jelly in comparison with equine chorionic gonadotropin

The objective was to compare the effects of royal jelly (RJ) and eCG treatments on reproductive performance of ewes synchronized using intravaginal progesterone-releasing devices. Forty-two cycling Awassi ewes were treated intramuscularly (i.m.) with 15 mg PGF2alpha. On the following day, all ewes were administered with CIDR-G for 12 days and were randomly allocated to three (RJ, eCG and control) groups of 14 ewes each. Ewes in the RJ-treated group received daily i.m. treatments of 400mg RJ during the period of CIDR-treatment. Each ewe in the eCG-treated group received an i.m. treatment of 500 IU eCG at the time of CIDR-G removal (day 0) and no further treatment was given to ewes in the control group. Ewes were exposed to four fertile rams for 72 h, from the time of CIDR-G removal, and checked for breeding marks at 6-h intervals. Blood samples were collected from day -13 until day 0 and thereafter until day 19 for progesterone analysis. Royal jelly treatment resulted in a greater rate of decline and lower (P<0.02) progesterone concentrations between days -10 and 0 than eCG-treated and control ewes. Expression of estrus was similar among the three groups and intervals to onset of estrus were shorter (P<0.01) in RJ-treated (31.3h) and eCG-treated (29.8h) than control (41.3h) ewes. First-cycle pregnancy and lambing rates were greater (P<0.05) in RJ-treated (71.4 and 71.4%) and eCG-treated (85.7 and 78.6%) than in control (42.9 and 35.7%) ewes, respectively. Results demonstrate that the treatments of RJ and eCG in conjunction with CIDR-G were similarly effective in induction of estrus and improvement of pregnancy and lambing rates.     

Effects of pressed beet pulp silage inclusion in maize-based rations on performance of high-yielding dairy cows and parameters of rumen fermentation

Beet pulp contains high amounts of pectins that can reduce the risk of rumen disorders compared to using feedstuffs high in starch. The objective was to study the effects of inclusion of ensiled pressed beet pulp in total mixed rations (TMR) for high-yielding dairy cows. Two TMR containing no or about 20% (on dry matter (DM) basis) beet pulp silage were used. The beet pulp silage mainly replaced maize silage and corn cob silage. The TMR were intentionally equal in the concentrations of energy and utilisable crude protein (CP) at the duodenum. TMR were fed to 39 and 40 dairy cows, respectively, for 118 days. The average daily milk yield was about 43 kg/day. No significant differences in milk yield and milk fat or milk protein content were detected. DM intake of cows was significantly reduced by the inclusion of beet pulp silage (23.0 v. 24.5 kg/day). However, a digestibility study, separately conducted with sheep, showed a significantly higher organic matter digestibility and metabolisable energy concentration for the TMR that contained beet pulp silage. In vitro gas production kinetics indicated that the intensity of fermentation was lower in the TMR that contained beet pulp silage. In vitro production of short-chain fatty acids, studied using a Rusitec, did not differ between the TMR. However, the inclusion of beet pulp silage in the ration caused a significant reduction in the efficiency of microbial CP synthesis in vitro. The amino acid profile of microbial protein remained unchanged. It was concluded that beet pulp silage has specific effects on ruminal fermentation that may depress feed intake of cows but improve digestibility. An inclusion of beet pulp silage of up to 20% of DM in rations for high-yielding dairy cows is possible without significant effects on milk yield and milk protein or milk fat.     

Comparison of two progestogens during out-of-season breeding in a commercial ewe flock

A comparison was made of the relative effectiveness of subcutaneous ear implants containing 2 mg Norgestomet or vagnial pessaries containing 60 mg medroxyprogesterone acetate (MAP) to induce estrus and conception in dry anestrous ewes. Groups of ewes were treated with one of the two progestogens for 14 d, and 500 IU pregnant mare serum gonadotropin (PMSG) was administered intramuscularly at the time of progestogen withdrawal. No significant differences in estrus induction, pregnancy rate or number of lambs born per ewe lambing were observed. Ewes treated with Norgestomet had 96% estrus, 60% pregnancy rate and 1.4 lambs per ewe lambing. Comparably, ewes treated with MAP had 94% estrus, 65% pregnancy rate and 1.7 lambs per ewe lambing. Norgestomet implants compared favorably with MAP pessaries for estrus induction and breeding of commercial, dry anestrous ewes.     

Sexual maturation of ewes raised without ram exposure in a controlled lighting environment

Finn x Dorset ewe lambs (n = 70) born in the spring (March 28 to April 6) from two successive lambing seasons were evaluated for age at first ovulation in the absence of mature rams. Ewe lambs were born in a controlled, short light (8L:16D) photoperiod or in ambient light (13L:11D). At about 10 to 11 wk of age, ewe lambs were allocated to a short (8L:16D) or long (16L:8D) light environment. Plasma progesterone (P(4)) concentrations were measured as an index of first ovulation. First exposure of ewes to sexually mature rams was in November. Most ewe lambs (77%) ovulated before ram exposure. More lambs (P < 0.025) born in ambient light and raised in short light reached puberty with typical cycles of plasma progesterone compared to other treatments. Long days tended to retard the onset of puberty. Although pregnancy rate did not differ across light treatments, more ewes became pregnant from the ambient-light born and short-light raised treatment. Photoperiod is an important factor affecting the onset of sexual maturation and genesis of normal luteal progesterone secretion in the ewe lamb.     

Mob size of single-bearing or twin-bearing Merino ewes at lambing may not influence lamb survival when feed-on-offer is high

Limited research has suggested that higher lambing densities increase interference from foreign ewes at lambing which disrupts the ewe-lamb bond and compromises lamb survival. This may be particularly evident in mobs of twin-bearing ewes compared to single-bearing ewes because a greater number of lambs are born per day. Therefore, we hypothesised that; (i) decreasing the mob size of ewes at lambing has a greater impact on the survival of twin-born lambs than single-born lambs; (ii) the relationship between mob size and lamb survival can be explained by differences in the rate of interaction with foreign ewes and lambs at lambing; and (iii) ewes will utilise a limited area of the paddock at lambing and thus lambing density will be defined by the distribution of ewes in the paddock rather than the paddock area. Merino ewes were allocated into a 2×2 factorial combination of ewe pregnancy status (single- or twin-bearing) and mob size (high (n=130 ewes) or low (n=50 ewes)) on day 140 from the start of joining. Each treatment had two replicates excepting the low mob size for twins which had a third replicate. Ewes lambed at a stocking rate of 11 ewes/ha. Feed-on-offer during lambing exceeded 2400 kg dry matter (DM)/ha. Ewe-lamb behaviour was observed and dead lambs were autopsied over 11 days during the peak of lambing. The distribution of ewes in each paddock was recorded every 2 h during daylight hours by counting the number of ewes occupying 2500 m² grids. The proportion of ewes and their newborn progeny which interacted with foreign ewes at lambing did not differ between the high and low mob sizes for single- (24.9% v. 20.8%) or twin-bearing ewes (14.3% v. 19.6%; P=0.74). Similarly, interaction with foreign lambs did not differ between the high and low mob sizes for single- (14.5% v. 25.2%) and twin-bearing ewes (34.5% v. 26.4%; P=0.44). The distribution of ewes within the paddock did not differ between treatments (P=0.95). On average, single-bearing ewes which lambed at the high and low mob sizes occupied 34% and 36% of the paddock during daylight hours, and the corresponding values for twin-bearing ewes were 40% and 43%. Survival of twin-born lambs was lower than single-born lambs (75.3% v. 87.9%; P<0.01), however, lamb survival was not influenced by mob size regardless of birth type. These results suggest that higher mob sizes may not compromise lamb survival when feed-on-offer during lambing exceeds 2400 kg DM/ha.     

Effect of eCG on the pregnancy rate of ewes transcervically inseminated with frozen-thawed semen outside the breeding season

An experiment was conducted to determine whether factors affecting pregnancy rate out-of-season are associated more with transcervical artificial insemination (T-AI) procedures or with the reproductive state of the ewe. Twenty Finncross ewes were treated with progesterone sponges, and at sponge removal (0 h) 10 ewes were treated with eCG. Blood samples were collected for LH and progesterone analyses, and follicular development was monitored using ultrasonography. Ewes were inseminated from 48 to 52 h with 200 million motile frozen-thawed spermatozoa. The incidence of estrus, LH surges and ovulation was greater (P < 0.01) and intervals to these responses were shorter (P < 0.01) in the eCG-treated ewes. The number of follicles > 5 mm was higher (P < 0.05) in eCG-treated than control ewes. Progesterone concentrations increased and remained elevated through Day 19 in 7 eCG-treated and in 1 control ewe, and these ewes were pregnant based upon ultrasonographic examination. The results demonstrate that the T-AI technique using frozen-thawed semen produces a relatively high (70%) pregnancy rate out-of-season. The pregnancy rate was found to reflect primarily the reproductive condition of the ewe.     

Effect of plane of nutrition of 1- and 2-year-old ewes in early and mid-pregnancy on ewe reproduction and offspring performance up to weaning

The objective of the present study was to determine the effect of plane of nutrition in early pregnancy (EP) and mid-pregnancy (MP), on the productive performance of 1- and 2-year-old ewes and their offspring. Over 2 successive years, between days 0 and 39 after synchronized mating (EP), 1- (n = 117) and 2- (n = 52) year-old ewes were allowed 60% (low, L-EP), 100% (medium, M-EP) or 200% (high, H-EP) of requirements for maintenance (M). Between days 40 and 90 (MP), 1-year-old ewes were allowed 140% (M-MP) or 200% (H-MP), while 2-year-old ewes were allowed 80% (M-MP) or 140% (H-MP) of their M requirement. After day 90, all ewes were fed to meet requirements for late pregnancy. Increasing the plane of nutrition between days 0 and 39 resulted in increases in live weight (LW) (P < 0.001) and body condition score (BCS) (P < 0.001) during the EP period (H-EP > M-EP > L-EP), differences that in 1-year-old ewes were sustained to lambing (P < 0.05). On day 42 of gestation H-EP ewes had lower plasma progesterone concentrations than L-EP or M-EP ewes in 1- (P < 0.01) and 2- (P < 0.001) year olds. This was concomitant with diet H-EP tending to reduce the number of lambs born per ewe in both age groups (P = 0.06 and 0.07, respectively). Foetuses from 1-year-old L-EP ewes had smaller cranial (P < 0.01) and abdominal (P < 0.05) diameters at day 53 of gestation, with H-EP lambs tending to be heaviest at birth (P = 0.07). Similar findings were recorded for 2-year-old ewes. One-year-old ewes offered diet L-EP presented negative maternal behaviours more frequently (P < 0.05), while the incidence of lamb mortality at 6 weeks tended to be greater for L-EP lambs (P = 0.07). In MP, 1-year-old ewes offered diet M-MP were associated with foetuses with bigger abdominal diameters at day 78 (P < 0.05). However, there were no differences in lamb weight or size at term (P > 0.05). These ewes exhibited more positive maternal behaviours (e.g. increased grooming frequency and duration; P < 0.05) than ewes offered diet H-MP, and their offspring were more successful in suckling (P < 0.05). Results suggest that in young ewes, a temporary nutrient restriction in EP resulted in increased prolificacy. However, ewes and their offspring were lighter at birth and ewe maternal behaviour was poorer, resulting in increased lamb mortality. In MP, a medium plane of nutrition offered to 1-year-old ewes led to improved maternal and offspring behaviour.