Effects of restricted feeding of prepubertal ewe lambs on growth performance and mammary gland development

The aim of this study was to determine the effects of restricted feeding before puberty on growth performance and mammary gland development in replacement ewe lambs. At weaning, 72 Dorset ewe lambs were assigned to one of the three diets: an ad libitum control diet with medium-quality forage (MQF; diet A-MQF); a restricted diet with the same forage as A, but less feed concentrate (diet R-MQF); or a high-quality forage (HQF) diet (diet F-HQF). The quantity of concentrate offered to the group R-MQF and F-HQF ewe lambs was adjusted to obtain 70% of the control ewe lambs' growth rate. The diets were offered for 75 days after weaning to cover the allometric phase of mammary gland development. During this period, average daily gain (ADG) was 223 and 229 g/day for groups R-MQF and F-HQF, respectively, compared to 305 g/day for group A-MQF (P < 0.0001). At the end of this period, 28 ewe lambs were slaughtered and their mammary gland was collected. Parenchymal fresh tissue weight tended to be higher for groups R-MQF and F-HQF compared to group A-MQF (P = 0.09). Stroma weight was greater (P < 0.05) for the group A-MQF ewe lambs than for those in the other treatments. Total DNA and total protein in parenchymal tissue tended to be greater for groups R-MQF and F-HQF (P = 0.09 and P = 0.07, respectively). Dry fat-free tissue was greater for groups R-MQF and F-HQF (P < 0.05). The remaining ewe lambs were fed the same haylage and barley diet until their first lambing. During this period, compensatory growth was observed. ADG was greater (P < 0.01) for groups R-MQF and F-HQF than for group A-MQF, and feed conversion was improved (P < 0.01) for groups R-MQF and F-HQF compared with the control, whereas the dry matter intake was similar for all groups. Live body weight, loin eye depth and backfat depth at breeding and around lambing were similar for all groups. The results of this study suggest that restricted feeding before puberty improves mammary gland development without compromising growth performance in ewe lambs.     

Effects of dietary sewage solids on second-generation ewes fed an experimental diet from weaning through two reproductive cycles

Eighteen fine-wool ewe lambs produced by mature, conventionally fed dams and 21 similar offspring from sewage-fed ewes were randomly allotted at weaning to one of two groups. Half of the lambs from each maternal diet group received a conventional (18% protein) diet during the growing phase while the remainder was fed the conventional diet plus 7% undigested, irradiated sewage solids (18% protein). At the end of the 147-day growing period and just before a fall breeding season, conventionally fed ewe lambs were switched to a control diet (12% protein) suitable for mature ewes and sewage-fed ewe lambs began receiving the control diet plus 7% sewage solids. Animals received these diets for two years. Maternal sewage consumption did not influence performance of F₁ ewe lambs. By the beginning of the first breeding season, controls were heavier (P<0.01) than were animals receiving sewage solids (51.7 and 44.5 kg, respectively). Similarly, only 75% of sewage-fed ewe lambs exhibited estrus during their first breeding season compared with 94.7% of controls (P<0.10). Conception rate (40.0 and 84.2%, respectively) and lambs born per ewe exposed (0.4 and 0.89, respectively) were also lower (P<0.05) in animals receiving sewage solids than in controls. During the second reproductive cycle, conception rate as well as lambs born per ewe exposed was comparable (P>0.10) between the two groups. Offspring from the sewage-fed ewe lambs, however, weighed less (P<0.05) at weaning than did lambs produced by control animals. Results indicate that a diet containing 7% sewage solids may not be suitable for preparing ewe lambs to go into the breeding flock; once mature size is attained, however, reproductive performance is not hampered by sewage feeding.     

Effects of rapid weight gain to puberty on reproduction, mammary development and lactation in ewe lambs

The effects of rapid weight gain to puberty on reproduction, mammary development and milk production in ewes lambing at 13 mo of age were investigated on three trials. A total of 64 Dorset and 93 Suffolk ewe lambs were weaned at 42 d of age and their mean weight was 16 kg. These ewes were assigned, within breed groups, to either a finishing diet or a growing diet. Onset of puberty was determined by daily checks for estrus and ewes were bred beginning at 7 mo of age. In Trial 2, mammary gland development was determined in eight Suffolk ewes from each diet. Ewes on the finishing diet were younger at puberty than those on the growing diet (199 vs 206 d, P<0.05) but required more services per conception (1.3 vs 1.1, P<0.05). Dietary conception rate and lambing rate means were similar. Mean 4-h milk yield was lower (P<0.10) for ewes on the finishing diet (283 g) than for those on the growing diet (310 g). Mammary gland fat pad area was higher (P<0.05) for ewes on the finishing diet compared with those fed for growth. Gross and adjusted duct areas were higher in ewes on the growing diet, but differences were not significant. At puberty, negative correlation coefficients for milk yield with performance traits were as follows: daily weight gain, -0.184 (P<0.08); weight-to-height ratio -0.262 (P<0.01); body condition score, -0.189 (P<0.07); and body weight, -0.212 (P<0.05). Results of this study indicate that rapid weight gain to puberty impairs mammary gland development and milk production in ewe lambs.     

Maternal versus artificial rearing shapes the rumen microbiome having minor long-term physiological implications

Increasing productivity is a key target in ruminant science which requires better understanding of the rumen microbiota. This study investigated how maternal versus artificial rearing shapes the rumen microbiota using 24 sets of triplet lambs. Lambs within each sibling set were randomly assigned to natural rearing on the ewe (NN); ewe colostrum for 24 h followed by artificial milk feeding (NA); and colostrum alternative and artificial milk feeding (AA). Maternal colostrum feeding enhanced VFA production at weaning but not thereafter. At weaning, lambs reared on milk replacer had no rumen protozoa and lower microbial diversity, whereas natural rearing accelerated the rumen microbial development and facilitated the transition to solid diet. Differences in the rumen prokaryotic communities disappear later in life when all lambs were grouped on the same pasture up to 23 weeks of age. However, NN animals retained higher fungal diversity and abundances of Piromyces, Feramyces and Diplodiniinae protozoa as well as higher feed digestibility (+4%) and animal growth (+6.5%) during the grazing period. Nevertheless, no correlations were found between rumen microbiota and productive outcomes. These findings suggest that the early life nutritional intervention determine the initial rumen microbial community, but the persistence of these effects later in life is weak.     

Dietary protein or energy restriction influences age and weight at puberty in ewe lambs

The working hypothesis was that restricted protein content in diets of prepubertal ewe lambs would delay time of onset of puberty to a greater extent than restricted energy content. Restriction of dietary protein (metabolizable protein, MP) or energy (ME) intake on age and weight at puberty was studied in ewe lambs in two experiments. In Experiment 1, 85 crossbred ewe lambs were assigned by weight to one of five dietary treatment groups: control (CTL; 18 mg ME day⁻¹ and 173 g MP day⁻¹); energy restricted (ER; 10.2 mg ME day⁻¹ and 96 g MP day⁻¹); protein restricted (PR; 11 mg ME day⁻¹ and 66 g MP day⁻¹); ER for 9 weeks then switched to CTL (ER/CTL); PR for 9 weeks then switched to CTL (PR/CTL). Ewe lambs were weighed biweekly, bled weekly, and serum was assayed for progesterone to determine time of puberty. Average age at puberty differed among lambs fed the various diets (P < 0.01). Ewe lambs in the CTL group were younger and weighed more at puberty. Lambs fed diets restricted in protein or energy content were similar in age at puberty. Dietary switching, ER/CTL and PR/CTL, affected body weight and gain (P < 0.05), but did not result in changed age at puberty compared with lambs fed ER or PR diets. In Experiment 2, two breed types (maternal type and meat type) were used to compare responses of dietary protein restriction to dietary energy restriction. In Experiment 2, lambs (n = 60) were assigned to either the CTL, PR or ER diets. Lambs in the CTL group gained more weight than lambs fed the PR diet and lambs fed the PR diet gained more weight than lambs fed the ER diet (P < 0.05). Diet affected age (P < 0.001), but not weight at puberty (P = 0.13). Dietary energy and protein restriction influenced age at puberty in ewe lambs with energy restriction having a greater influence on delaying onset of puberty than protein restriction. Realimentation did not overcome effects of previous feed restriction by inducing an earlier age at puberty than ewe lambs fed the ER or PR diet throughout the experimental period. Body weight gain prepuberty is more important than type of dietary restriction (protein or energy) with regard to impacting age at puberty. We, therefore, reject the working hypothesis that dietary protein restriction prepuberty would have a greater impact in delaying onset of puberty than dietary energy restriction.     

Growth response, reproductive activity, and serum growth hormone in fine-wool ewe lambs treated with triiodothyronine

Forty-four 6-mo-old, fine-wool ewe lambs were randomly allotted to one of three triiodothyronine (T(3)) treatment groups (14 or 15 ewe lambs/group). Treatments (0, 200, and 400 mug T(3)) were administered daily by subcutaneous injection during a 30-d treatment period in September. Following the treatments, ewe lambs were allowed to mate with Debouillet rams during a 34-d breeding season. Animal weights did not differ (P > 0.10) among treatment groups throughout the study. However, ewe lambs receiving 400 mug T(3)/d gained less (P < 0.05) during the treatment period than did those receiving 200 mug T(3)/d or controls. Grease fleece weights (6-mo clip) were similar (P > 0.10) among treatment groups. Serum growth hormone (GH) values in blood samples collected on Days 7 and 28 of the 30-d treatment were similar (P > 0.10) before treatments were administered and on Day 7 after treatments were administered. However, on Day 28 after treatments were administered, serum GH was lower (P < 0.01) in ewe lambs receiving 400 mug T(3)/d (1.5 ng/ml) than in those receiving 200 mug/d (2.1 ng/ml) or controls (2.2 ng/ml). Ovarian cyclicity was determined by monitoring serum progesterone. Forty percent of control ewe lambs were determined to have cycled during treatment compared with 20% of those receiving 200 mug T(3)/day and none of those receiving 400 mug T(3)/d (P < 0.10). Pregnancy rates were lower (P < 0.10) in ewe lambs receiving 400 mug T(3)/d (29%) compared with those receiving 200 mug T(3)/d (60%) or controls (66.7%). Day of conception, lambs born/ewe exposed, lambs born/ewe lambing, and lambs weaned/ewe lambing did not differ (P > 0.10) among treatments. Preweaning performance of offspring was not altered by maternal treatment with 200 or 400 mug T(3)/d (P > 0.10). These data indicate that 200 and 400 mug T(3)/d will not enhance GH production or improve reproductive performance of ewe lambs.     

Oocyte pick-up in juvenile lambs affects neither onset of puberty nor their future fertility

A study was designed to evaluate whether the time of onset of puberty and fertility of young ewe lambs would be affected by oocyte pick-up conducted in single or repeated sessions during the first months of lambs' live. Five groups of lambs from the Karagouniko breed were used (A-E each n=12). In group A no treatments were applied (control group) while, laparoscopical follicular aspiration (OPU) was performed early in the third, fourth and fifth month of lambs age (groups C-E, respectively). From the second to fifth month of their age, group B lambs were aspirated four times in monthly intervals. All lambs were weighed at birth, weaning, at second month and monthly thereafter until the eighth month of age. Progesterone priming and ovarian stimulation by serial FSH administrations proceeded each OPU session. To determine onset of puberty blood progesterone concentration was assayed in samples collected initially every week and after the seventh month of age twice weekly. From the seventh month a fertile ram was introduced in each group and oestrous behavior/mating was daily monitored and recorded. Pregnancy diagnosis was carried out by transabdominal ultrasound scanning 55 days after rams' removal. At the fourth and fifth month of age group B lambs were lighter (p<0.05) than controls, but this difference was later equalized. The time of onset of puberty did not differ between groups (p=0.069) and ranged between 224 and 270 days. Some animals (n=15) entered puberty with a full-length luteal phase having progesterone concentration greater than 1ng/ml, while others (n=32) exhibited one or two short luteal phases before luteal length restoration. During the first breeding season 41 animals were fertilized and maintained pregnancy to term, without noticeable differences between groups (p=0.555). During the second breeding season, all ewes were naturally served and lambed at the expected time. It is concluded that OPU in young dairy lambs does not affect the time of onset of puberty, the endocrine profile of the lambs and it does not compromise their future fertility even if it is applied at four successive months.     

The effect of exposure to oestrous ewes on rams' sexual behaviour, plasma testosterone concentration and ability to stimulate ovulation in seasonally anoestrous ewes

Ruminants eat a variety of foods from different locations in the environment. While water, cover, social interactions, and predators are all likely to influence choice of foraging location, differences in macronutrient content among forages may also cause ruminants to forage in different locations even during a meal. We hypothesized that lambs forage at locations containing foods that complement their basal diet and meet their nutritional needs. Based on this hypothesis, we predicted that lambs (n=12) fed a basal diet low in protein and high in energy would forage where a high-protein food (Food P) was located, and that lambs (n=12) fed a basal diet low in energy and high in protein would forage where a high-energy food (Food E) was located. Food P was a ground mixture of blood meal (50%), grape pomace (30%), and alfalfa (20%) that contained 47% crude protein (CP) and 2.211 Mcal/kg digestible energy (DE). Food E was a ground mixture of cornstarch (50%), grape pomace (30%), and rolled barley (20%) that contained 6% CP and 3.07 Mcal/kg DE. Food P provided 212 g CP/Mcal DE, whereas Food E provided 20 g CP/Mcal DE. Lambs growing at a moderate rate require 179 g CP and 3.95 Mcal DE. During Trial 1, we determined if lambs foraged to correct a nutrient imbalance, and if they preferred a variety of foods (Foods P and E) to only one food at a location (Food P or E). During Trial 2, we determined if nutrient-imbalanced lambs foraged in the location with the food that corrected the imbalance when the location of the foods changed daily. During Trial 3, lambs were offered familiar foods (Foods P and E) at the location furthest - and novel foods (wheat and soybean meal) at the location nearest - the shelter of their pen. During all three trials, lambs foraged most at the location with the food that contained the highest concentration of the macronutrient lacking in their basal diet, but they always ate some of both foods. Lambs did not feed exclusively at the location with a variety of foods (P and E). Rather, they fed at the location nearest the shelter that contained the macronutrient lacking in their diet. As availability of the food with the needed macronutrient declined in one location, lambs moved to the nearest location that had food with the needed macronutrient. When food that complemented their basal diet was moved to a different location, lambs foraged in the new location. Collectively, these results show that lambs challenged by imbalances in energy or protein selected foods and foraging locations that complemented the nutrient content of their macronutrient imbalanced basal diets.     

Effect of nutrition and endoparasitic treatment on growth, onset of puberty and reproductive activity in Menz ewe lambs

Ewe lambs of the Ethiopian Menz breed were assigned at weaning (90+/-3 days) to four levels of nutrition (poor, low, medium and high) to achieve different premating growth rates with or without treatment for endoparasites. A concentrate mixture providing 2.5 Mcal/kg dry matter (DM) metabolizable energy and 15.2 g/kg DM digestible protein was used. Improved nutrition increased lamb postweaning average daily weight gain up to puberty by 6 to 26 g/day and the conception rate to first estrus by 9 to 16% while it reduced the mortality rate by 24 to 31% and age at first lambing by 2 to 5 months. Lambs reached puberty (age at first estrus) at 16.9+/-0.1 kg (+/-SEM) or 60% of mature body weight and 350+/-12 days of age. The onset of puberty was advanced by weaning weight (P<0.05), itself being well correlated with birth weight (r = 0.51, P<0.001), and by level of nutrition (high=299+/-19, medium=301+/-18, low=383+/-23 and poor=454+/-31 days, P<0.001) through enhanced growth rate (r = -0.82, P<0.001). No independent effect of drenching for endoparasites on pubertal development was observed (P>0.05), but its interaction with season-of-birth improved the growth of lambs born during the period of short rains (P<0.05). Overall mean litter size at first lambing was 1.07; the twinning rate was 6.5% and the birth weight was 1.9+/-0.1 kg. Up to 13.4% of newborn lambs, averaging 1.3+/-0.6 kg, died on the day of parturition. The results indicate that improved growth rate and body weight, resulting from better postweaning nutrition, affects the attainment of puberty in Menz ewe lambs. Mitigation of nutrition stress and endoparasitic infection depending on season-of-birth would thus increase the annual reproductive rate of breeding ewes and flock productivity.     

Effect of milk replacer and rumen inert fat on growth and reproduction of Malpura ram lambs

The objective of this study was to assess the effects of milk replacer and rumen inert fat on growth, testicular development, puberty, semen production and sperm motion characteristics of ram lambs reared under intensive management in semi-arid climatic conditions. Seven-day-old male lambs of Malpura breed (n=20) were divided equally into two groups. Up to weaning, the lambs in G1 group (control) were fed concentrate, green khejri (Prosopis cineraria) leaves and cowpea (Vigna unguiculata) hay along with suckling of dams, whereas lambs in G2 group were fed reconstituted milk at 17 g/lamb per day for the 1st week and at 34 g/lamb per day from 2nd week in addition to the feed inputs given in G1. During post weaning, lambs in the G1 group were given control concentrate, whereas in G2 the control concentrate supplemented with 40 g rumen inert fat per kg of feed was offered along with dry pala (Zizyphus nummularia) and ardu (Ailanthus excelsa) leaves. BWs of lambs were recorded weekly up to 6 months of age. Ram lambs of both the groups were trained for semen collection at a weekly interval from the age of 5 months and simultaneously testicular measurements were recorded fortnightly. The feeding of milk replacer and rumen inert fat had positive (P<0.05) effects on BW, testicular length, testicular volume, semen volume, sperm concentration, mass motility, % motility, % rapid, medium or slow motile spermatozoa. However, no significant effect was observed on testicular breadth, scrotal circumference, age of puberty, sperm velocities and other CASA-derived parameters. The results of this study indicate that higher plane of nutrition in the form of milk-replacer feeding during preweaning and rumen inert fat-supplemented feed during the postweaning period to growing ram lambs enhances their growth, testicular development and semen quality.     

The effects of zearalenone on reproduction in swine. II. The effect on puberty attainment and postweaning rebreeding performance

Eighty-five prepuberal, crossbred gilts received, ad libitum, a diet containing 0 or 10 ppm purified zearalenone for 30 d beginning at 145 to 193 d of age. At the end of this period all gilts were placed on the control diet and exposed daily to a mature boar for 60 d. Within 3 to 5 d of zearalenone ingestion, gilts showed marked vulval swelling and reddening, which continued for the 30-d feeding period. Thereafter symptoms slowly subsided. Zearalenone treated gilts showed first estrus significantly later than controls (P < 0.05), but the proportion of gilts showing estrus within 60 d of boar exposure was similar (P > 0.05). The length of the first estrous cycle was not affected by the ingestion of zearalenone before puberty (P > 0.05). In a second study, 65 multiparous, crossbred sows were full-fed twice daily a ration containing 0 or 10 ppm of purified zearalenone beginning 14 d before weaning. Postweaning, all sows were fed the control diet, were checked for estrus daily, and inseminated at the first postweaning estrus. Neither sows nor gilts from their litters exhibited signs of hyperestrogenism during treatment. Weaning to estrus interval was significantly extended in zearalenone treated sows (P < 0.05), but all other variables of fertility assessed were similar. These data suggest that zearalenone ingestion before puberty delays the stimulation of puberty associated with boar exposure, but does not affect subsequent cyclicity if zearalenone is removed from the ration. Similarly, zearalenone ingestion during lactation delays the return to estrus after weaning, but does not affect subsequent fertility when removed from the ration at weaning.     

Effect of maternal exposure to the environmental estrogen,octylphenol, during fetal and/or postnatal life on onset of puberty,endocrine status,and ovarian follicular dynamics in ewe lambs

Octylphenol (OP) is one of a number of compounds found in the environment that has estrogen-mimicking actions in vivo. Our objective was to determine if maternal exposure to octylphenol during fetal and/or postnatal life would affect the onset of puberty, endocrine status, and subsequent ovarian follicular dynamics of ewe lambs. Lambs were born in March to ewes that received twice weekly s.c. injections of octylphenol (1000 micro g/kg/day) from Day 70 of gestation to weaning (n = 6); Day 70 of gestation to birth (n = 3); birth to weaning (n = 5; gestation = 145 days); or corn oil from Day 70 of gestation to weaning (control; n = 5). Blood samples were collected twice weekly to determine progesterone and FSH concentrations from 20 wk of age throughout the first breeding season. Onset of puberty and interestrous intervals were determined from 20 wk of age by twice daily observation for estrus in the presence of a vasectomized ram. During January the ovaries of each lamb were examined using transrectal ultrasonography from the day of estrus for 15 days. Blood samples were collected every 8 h to examine FSH concentrations and every 2 h to detect the preovulatory gonadotropin surge throughout this estrous cycle. The onset of puberty and first progesterone rise was advanced and the FSH preovulatory surge was elevated for longer in the OP-treated lambs compared with the control lambs (P < 0.05). Interestrous intervals, FSH profiles, and ovarian follicular dynamics were not affected (P > 0.05) by exposure to octylphenol. In conclusion, octylphenol exposure advanced the onset of puberty but it did not disrupt FSH concentrations or the dynamics of ovarian follicular growth.     

Effect of dry-matter concentration of milk substitute and method of feeding on intake and performance by lambs

Forty-eight lambs were artificially reared from 1 day old and offered milk substitute reconstituted to give diets containing 10, 16, 22 and 28% dry matter (DM). Three feeding methods were used for each diet: milk substitute available ad libitum (AL); restricted to a mean daily intake of 1300 g liquid milk substitute (RLQ); and restricted to a mean daily intake of 247 g milk substitute DM (RDM).Solid food intake and lamb growth rate were measured both before and after weaning at 28 days.For method AL, decreasing DM concentration in the milk substitute increased intake of the liquid but decreased that of DM. When DM intakes were held constant, neither method of feeding nor DM concentration had an effect on lamb growth, and level of reconstitution of the milk substitute had no effect on its digestibility. Differences in growth rate before weaning were due entirely to differences in intake of milk substitute DM.After weaning, lambs which had received the diet containing 10% DM tended to perform less well than those that had received the other diets.The lambs were slaughtered at 35 kg live weight. There were no effects of treatment on gains of water, fat and protein.     

Reproductive, hormonal and milk characteristics in ewe lambs treated with ovine growth hormone before breeding

One month before a fall breeding season, 30 6-mo-old fine-wool ewe lambs were allotted to one of three treatment groups consisting of either 0, 2.5 or 5 mg ovine growth hormone (oGH) daily for 10 d and then, on alternate days, for an additional 20 d. Five ewes from each treatment group were bled at hourly intervals for 8 h on Days 0 (first day of treatment), 9, 19 and 29. Milk yield and composition were examined on Day 21 post partum. Neither feed intake nor ewe weights differed (P > 0.20) among treatments. Serum insulin did not differ (P > 0.20) among treatments before or during the 5 h following treatment on Day 0 or 29; however, 6, 7 and 8 h after oGH administration, a linear, dose-dependent increase (P < 0.10) in serum insulin was noted. On Day 9, serum insulin differed linearly (P < 0.10) before and after treatment. On Day 19, serum insulin differed (P < 0.10) among the groups 2, 3, 6, 7 and 8 h following oGH treatment. One hour after treatment on Day 0, serum GH increased linearly (P < 0.01) among groups. Serum GH continued to rise 3 h after treatment and remained elevated through Hour 8 in ewes receiving oGH. Serum GH was increased (P < 0.01) before and after oGH administration on Days 9, 19 and 29 in GH-treated ewes. Percentage of ewes that cycled during treatment or breeding as determined by serum progesterone was similar (P > 0.20) among groups. Pregnancy rates did not differ (P > 0.20) in ewe lambs receiving 0 (70%), 2.5 (80%) and 5 (60%) mg oGH. No differences were detected (P > 0.40) in milk yield or composition among treatments. In fine-wool ewe lambs treated with 2.5 or 5 mg of exogenous oGH for 30 d before breeding, neither reproductive performance nor subsequent milk production were enhanced; however, these treatments increased serum GH and insulin.     

Short- and long-term effects of conventional and artificial rearing strategies on the health and performance of growing lambs

Artificial rearing of young animals represents a challenge in modern ruminant production systems. This work aims to evaluate the short- and long-term effects of the type of rearing on the animal’s health, growth, feed utilization and carcass performance. A total of 24 pregnant ewes carrying triplets were used. Within each triplet set, lambs were randomly allocated to one experimental treatment: natural rearing on the ewe (NN); ewe colostrum for 24 h followed by artificial rearing with milk replacer (NA) and 50 g of colostrum alternative supplementation followed by artificial rearing (AA). Milk replacer, ryegrass hay and creep feed were offered ad libitum, and each experimental group was kept in independent pens until weaning at 45 days of age. After weaning all lambs were placed together on the same pasture for fattening for 4 months. Blood samples were taken at 24 h after birth, at weaning and at the end of the fattening period (23 weeks). Results showed that no failure in the passive immune transfer was detected across treatments. Although artificially reared lambs at weaning had lower plasma levels of β-hydroxy-butyrate (−62%), high-density lipoproteins (−13%) and amylase (−25%), and higher levels of low-density lipoproteins (+38%) and alkaline phosphatase (+30%), these differences disappeared during the fattening period. Only the greater levels of calcium and the lower levels of haemoglobin and white blood cells detected at weaning in artificially reared lambs (+7.2%, −2.8% and −17.8%) persisted by the end of the fattening period (+4.3%, −3.3% and −9.5%, respectively). Minor diarrheal events from weeks 2 to 5 were recorded with artificial rearing, leading to lower growth rates during the 1^st month. However, these artificially reared lambs caught up towards the end of the milk feeding period and reached similar weaning weights to NN lambs. During the fattening period NN lambs had a greater growth rate (+16%) possibly as a result of their greater early rumen development, which allowed a higher feed digestibility during the fattening period in comparison to NA lambs (+5.9%). As a result, NN lambs had heavier final BWs (+7.0%), but tended to have lower dressing percentage (−5.7%) than artificially reared lambs, thus no differences were noted in either carcass weight or in carcass conformation across treatments. In conclusion, the use of a colostrum alternative and milk replacer facilitated the successful rearing of lambs, reaching similar productive parameters; however, special care must be taken to maximize the rumen development before weaning.     

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.     

Serum luteinizing hormone, growth hormone and insulin-like growth factor-I after releasing hormone challenge in prepubertal ewe lambs selected for twinning

Two studies evaluated hormonal markers as indicators of the onset of puberty in Debouillet sheep selected for twinning. In Trial 1, 29 ewe lambs (50 +/- 0.5 kg, 159 to 187 d of age) were given 10 microg GnRH (i.v.) on September 15 and blood was collected at 30 min intervals after the injection for 2 h. Additional samples were taken twice weekly and progesterone (P4) was measured. The day that serum P4 was greater than 1 ng/mL for 2 consecutive sampling days was classified as the day of puberty. Average day of puberty was October 12 (average age at puberty was 199 d) and ewes with values less or greater than the average were classified as early or late, respectively. Average weight at GnRH challenge was 50 kg and ewes weighing less or more were classified as light or heavy, respectively. Early ewes weighed more (P = 0.01) and reached puberty sooner (P = 0.01) than late ewes. Heavy lambs reached puberty earlier, weighed more at GnRH challenge, and had more LH area under the curve (AUC, P < 0.05) than light ewes. In Trial 2, we gave 27 ewe lambs (54 +/- 0.9 kg, 173 to 189 d of age) a single i.v. injection of 10 microg GnRH and 10 microg GHRH on September 17. Average day of puberty was October 13, average weight was 54 kg, and average age at puberty was 208 d. Categories were designated as described for Trial 1. Early lambs reached puberty sooner (P = 0.01) and weighed more (P = 0.01) than late lambs, but the puberty groups had similar LH AUC (P = 0.64) and GH AUC (P = 0.75), whereas IGF-I was greater (P = 0.01) in early puberty ewes than in late puberty ewes. Heavy lambs reached puberty earlier (P = 0.06), weighed more (P = 0.01), and tended (P = 0.11) to have more GH AUC than light ewes. No difference was observed in LH AUC or IGF-I between weight groups (P > 0.15). Results suggest that serum LH after GnRH is not a reliable indicator of the onset of puberty in ewe lambs selected for twinning, but heavier ewes tended to produce more GH after a GHRH challenge and reach puberty earlier than lighter ewe lambs.     

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.     

Tropical tannin-rich fodder intake modifies saliva-binding capacity in growing sheep

We evaluated the effect of feeding dietary tannins from Lysiloma latisiliquum fresh forage on the saliva tannin-binding capacity of hair sheep lambs without previous exposure to tannin-rich (TR) fodder. Twenty-four hair sheep lambs (13.6±3.04 kg LW) were fed a tannin-free diet at the beginning of the experimental period (from day 10 to 13). On day 14, lambs were distributed into three groups (n=8): control group (CG), fed with the tannin-free diet (from D10 to D112); tannin short-term group (TST), fed the basal diet and 650 g of L. latisiliquum forage (from D14 to D55); tannin long-term group (TLT), fed the basal diet and 650 g of L. latisiliquum forage (from D14 to D112). Saliva samples were collected from the mouth of each lamb in the morning before feeding time on D10 and D14 (baseline period), on D49 and D56 (period 1) and on D97 and D112 (period 2). The tannin binding response of salivary protein (∆% turbidity) was determined with the haze development test (HDT) using either tannic acid or L. latisiliquum forage acetone extract. A turbidity protein index (TPI) was calculated as (∆% turbidity/[salivary protein (mg)]). Differences in HDT and TPI in the different groups were compared by repeated measures ANOVA using Proc Mixed. All groups had similar ∆% turbidity throughout the experiment (P>0.05). At baseline and period 1, the TPI of the different groups was similar (P>0.05). On period 2 the TLT group showed higher TPI compared with CG (P<0.05). Meanwhile, CG and TST showed similar salivary TPI. The saliva of hair sheep lambs consuming TR L. latisiliquum fresh fodder (TLT group) increased their TPI compared with control lambs not exposed to tannins.     

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.