Breed and environmental influences on weaner lamb production in Zimbabwe

Performance of the Dorper and Mutton Merino breeds and their crosses was assessed from 1,305 ewe and 1,453 lamb records from six lambing seasons. Dorper and Mutton Merino were mated in all combinations under an accelerated lambing system and crossbred females were mated to Suffolk rams. The Dorper and Mutton Merino breeds were not significantly different for fertility, pre-weaning lamb growth and survival. Suffolk sired lambs from crossbred ewes grew rapidly and were heaviest at birth and at weaning. They also survived better than lambs from the other breeding groups and this contributed to the higher weaning rate (P less than 0.05) in crossbred ewes. Weight of weaned lambs per ewe exposed to the ram per season was 12% higher (P less than 0.05) in the Dorper than the Mutton Merino ewes. However lifetime production was 28% higher (P less than 0.01) in Mutton Merino ewes due to significantly superior longevity. Crossbred ewes were highly productive. Individual heterosis was not significant but estimates were positive for most traits. Growth rate and survival of lambs increased as age of dam increased to 48 and 40 months respectively. Lambs born to previously non-lactating ewes were heavier and survived better than lambs born to ewes lactating in the previous season. Lambs born and reared as singles were 25% heavier at birth (P less than 0.001) and 52% heavier at weaning (P less than 0.001) than those born and reared as twins. Male lambs grew faster and were 7% heavier at weaning than females (P less than 0.001).     

Effects of maternal selenium supply and plane of nutrition during gestation on passive transfer of immunity and health in neonatal lambs

To investigate the influence of maternal Se supply and plane of nutrition on lamb morbidity, mortality, and passive transfer of IgG, pregnant ewe lambs were used in 2 experiments with 2 × 3 factorial treatment arrangements. Supplementation of Se began at breeding and was either adequate Se (ASe, 9.5 μg/kg of BW) or high Se (HSe, 81.8 μg/kg of BW) in Exp. 1 or ASe (11.5 μg/kg of BW) or HSe (77.0 μg/kg of BW) in Exp. 2. On d 50 or 40 of gestation for Exp. 1 or 2, respectively, ewes were assigned randomly to 1 of 3 nutritional planes: 60% (RES), 100% (control, CON), or 140% (HI) of NRC requirements. This resulted in the following treatments: ASe-RES, ASe-CON, ASe-HI, HSe-RES, HSe-CON, and HSe-HI. Upon parturition, lambs were separated from their dams and serum samples obtained. Lambs were fed artificial colostrum for the first 20 h and then placed on milk replacer and grain pellets until completion of the study (Exp. 1, 57 d; Exp. 2, 21 d). Twenty-four hours after parturition, lamb serum samples were collected for IgG analysis. All lambs were reared similarly and morbidity and mortality assessed. Main effects were considered significant when P ≤ 0.05. In Exp. 1, there was a Se × plane of nutrition interaction (P ≤ 0.01) for lamb morbidity from birth to weaning and for 24-h IgG concentration. Lambs from ASe-RES and HSe-HI ewes were treated more frequently (P < 0.01) for respiratory and gastrointestinal disease, and lambs from HSe-HI ewes had the smallest (P < 0.01) 24-h serum IgG concentration. In Exp. 1, lambs from HI ewes also had the greatest (P < 0.01) mortality rates from birth to weaning compared with lambs from CON and RES ewes. In Exp. 2, there was an effect (P < 0.01) of maternal plane of nutrition with lambs from RES ewes having increased 24-h IgG compared with lambs from CON and HI ewes. There was no effect of maternal Se supplementation on lamb 24-h IgG in Exp. 2; however, there was a Se × plane of nutrition interaction (P < 0.01) for morbidity. From birth to 21 d of age, lambs from ASe-CON ewes had fewer (P < 0.01) treatment days compared with lambs from any of the other treatment groups. There also tended (P = 0.08) to be an effect of maternal Se supplementation on lamb mortality with increased mortality observed in lambs from HSe ewes. Results from the studies show a restricted maternal plane of nutrition can increase lamb serum IgG concentration. Selenium results were not consistent between the 2 experiments and may be due to differences in maternal Se.     

The effect of castration, estradiol and LHRH on LH secretion of lambs fed different levels of dietary energy

To examine the effect of diet on luteinizing hormone (LH) secretion, basal and luteinizing hormone releasing hormone (LHRH)-induced LH release was compared in intact or castrated-estradiol-17 beta implanted Finn-Dorset lambs. Ten to 12 wk old ram (n = 20) and ewe lambs (n = 20) were maintained under a 8L:16D photoperiod and fed for high (HG, 163 to 168 g/d) or low (LG, 76 to 103 g/d) rates of gain. Eight to 10 wk later, baseline LH concentrations were determined in blood samples collected at 20 min intervals for 7 h. The following day, lambs were given an iv injection of 5 micrograms of estradiol-17 beta followed within 4 h by LHRH (.5 or 2.5 micrograms). Baseline concentrations of LH for HG ewes were threefold greater than for LG ewes (4.2 vs 1.4 ng/ml), respectively. Time to peak response was inversely related to dietary energy level (P less than .025). Basal LH levels were similar across diets in rams. Total LH release following LHRH was dose-dependent (P less than .005). Effects of gonadal feedback were tested in a second group (n = 24) of castrated lambs. Changes in LH secretion were not different between diets within 3 to 4 wk after castration. A subcutaneous silastic implant (22 mm) of estradiol-17 beta inhibited (P less than .01) LH concentrations across diets in both ewes and rams. No differences in estradiol feedback on LH secretion (at the dose of steroid tested) were detected between HG and LG lambs. Within 8 d, however, basal LH concentrations were 60% lower (P less than .01) in HG vs LG ewes. Furthermore, peak LHRH-induced LH release was greater (P less than .025) in LG vs HG lambs of both sexes. Estradiol inhibited basal LH secretion in ewes and rams but facilitated LH release in lambs with a reduced rate of gain.     

Effects of supplemental safflower and vitamin E during late gestation on lamb growth, serum metabolites, and thermogenesis

Twin-bearing Targhee ewes (Exp. 1, 1 yr, n = 42) and 1,182 single- and twin-bearing whiteface range ewes (Exp. 2, n = 8 experimental units over 2 yr) were used in a 2 x 2 factorial arrangement of treatments to determine the effect of supplemental energy source and level of vitamin E supplement on lamb serum metabolites and thermogenesis (Exp. 1) and on lamb growth (Exp. 2). During late gestation, ewes were individually fed (Exp. 1) or group-fed (Exp. 2) a daily supplement. Supplements were 226 g/ewe of daily safflower seed (DM basis; SS) with either 350 IU/ewe daily (VE) or no added supplemental (VC) vitamin E; or 340 g/ewe daily of a barley-based grain supplement (DM basis; GC) and either VE or VC. One hour postpartum in Exp. 1, twin-born lambs were placed in a 0 degrees C dry cold chamber for 30 min. Lamb rectal temperature was recorded every 60 s and blood samples were taken immediately before and after cold exposure. In Exp. 2, lambs were weighed at birth, at turnout from confinement to spring range (32 d of age +/- 7; turnout), and at weaning (120 d of age +/- 7). Ewes were weighed at turnout and weaning. In Exp. 1, a level of vitamin E x energy source interaction was detected (P < 0.10) for body temperature and change in NEFA and glucose concentrations. Lambs from SSVC ewes had the lowest (P = 0.01) body temperature and had decreased (P = 0.08) NEFA concentration. The SS lambs tended to have decreased (P < 0.11) concentrations of blood urea N (BUN) and thyroxine at 0 min than did lambs born to GC ewes. After 30 min of cold exposure, SS lambs had increased and GC lambs had decreased BUN, triiodothyronine, and triiodothyronine:thyroxine concentrations (P < 0.10). In Exp. 2, kilograms of lamb per ewe at turnout and weaning and lamb survival at weaning were greater (P < 0.07) for GC than SS lambs. Based on the decreased body temperature in SSVC lambs at birth, the greater change in BUN during the cold exposure for SS than GC lambs, and the decreased survival rate for SS than GC lambs, SSVC-supplemented ewes appeared to give birth to lambs with an apparently decreased energetic capacity. This may compromise the ability of the newborn lamb to adapt to extreme environmental conditions.     

Effects of selenium supply and dietary restriction on maternal and fetal metabolic hormones in pregnant ewe lambs

The objective of these studies was to evaluate the effects of dietary restriction and Se on maternal and fetal metabolic hormones. In Exp. 1, pregnant ewe lambs (n = 32; BW = 45.6 +/- 2.3 kg) were allotted randomly to 1 of 4 treatments. Diets contained (DM basis) either no added Se (control), or supranutritional Se added as high-Se wheat at 3.0 mg/kg (Se-wheat), or sodium selenate at 3 (Se3) and 15 (Se15) mg/kg of Se. Diets (DM basis) were similar in CP (15.5%) and ME (2.68 Mcal/kg). Treatments were initiated at 50 +/- 5 d of gestation. The control, Se-wheat, Se3, and Se15 treatments provided 2.5, 75, 75, and 375 microg/kg of BW of Se, respectively. Ewe jugular blood samples were collected at 50, 64, 78, 92, 106, 120, and 134 d of gestation. Fetal serum samples were collected at necropsy on d 134. In Exp. 2, pregnant ewe lambs (n = 36; BW 53.8 +/- 1.3 kg) were allotted randomly to treatments in a 2 x 2 factorial arrangement. Factors were nutrition (control, 100% of requirements vs. restricted nutrition, 60% of control) and dietary Se (adequate Se, 6 microg/kg of BW vs. high Se, 80 microg/kg of BW). Selenium treatments were initiated 21 d before breeding, and nutritional treatments were initiated on d 64 of gestation. Diets were 16% CP and 2.12 Mcal/kg of ME (DM basis). Blood samples were collected from the ewes at 62, 76, 90, 104, 118, 132, and 135 d of gestation. Fetal blood was collected at necropsy on d 135. In Exp.1, dietary Se source and concentration had no effect (P > 0.17) on maternal and fetal serum IGF-I, triiodothyronine (T(3)), or thyroxine (T(4)) concentrations. Selenium supplementation increased (P = 0.06) the T(4):T(3) ratio vs. controls. In Exp. 2, dietary Se had no impact (P > 0.33) on main effect means for maternal and fetal serum IGF-I, T(3), or T(4) concentrations from d 62 to 132; however, at d 135, high-Se ewes had lower (P = 0.01) serum T(4) concentrations than adequate-Se ewes. A nutrition by Se interaction (P = 0.06) was detected for the T(4):T(3) ratios; ewes fed restricted and adequate-Se diets had greater (P = 0.10) T(4):T(3) ratios compared with the other treatments. Nutrient-restricted ewes had lower (P < 0.05) serum IGF-I, T(3), and T(4) concentrations. Fetal serum IGF-I concentrations were lower (P = 0.01) in restricted-vs. control-fed ewes; however, fetal T(3) and T(4) concentrations were unaffected (P > 0.13) by dietary Se or maternal plane of nutrition. These data indicate that dietary Se may alter maternal T(4):T(3) ratios. In addition, nutrient restriction during gestation reduces maternal IGF-I, T(3), and T(4) and fetal IGF-I concentrations.     

Effects of supplementing with calcium salts of palm oil fatty acids or hydrogenated tallow on ewe milk production and twin lamb growth

Two experiments were conducted with Polypay ewes nursing twin lambs to evaluate the effects of supplementing fat (calcium salts of palm oil fatty acids or hydrogenated tallow) on ewe lactation. In Exp. 1, ewes were fed a 52% concentrate:48% hay-based diet (as-fed basis) consisting of alfalfa hay (n = 4), endophyte-free fescue hay (n = 4), or fescue hay with 3.7% fatty acids (n = 4) from d 4 to 56 of lactation. In Exp. 2, ewes were fed similar diets that had endophyte-free fescue hay (n = 6), fescue hay with 3.7% fatty acids (n = 5), or fescue hay with 3.1% tallow (n = 6) from d 14 before lambing until d 57 of lactation. Diet formulations with supplemental fat were more nutrient dense, and treatments were fed to meet ewe nutrient requirements; this caused diets with added fat to be offered at 10 and 17% lower rates than unsupplemented diets in Exp. 1 and 2, respectively. Lambs were maintained to consume only ewe milk. Ewe milk production and composition were determined using a portable milking machine following a 3-h separation from lambs. In Exp. 1, milk fat content was increased (P < 0.01) when ewes consumed fescue hay with fatty acids vs. the fescue hay diet (11.4 vs. 8.3%). Ewes fed fescue hay with fatty acids lost the most (P < 0.05) weight over lactation (-8.6 kg) compared with ewes fed the alfalfa hay (-2.4 kg) and fescue hay (-3.8 kg) diets. Other milk measures, lamb gain, and production efficiencies were not changed. In Exp. 2, ewes supplemented with fatty acids produced more (P < 0.05) milk fat than those fed tallow (290 vs. 210 g/d). The proportion of synthesized milk fat 14:0 was decreased (P < 0.01), but the percentage of incorporated 16:0 increased (P < 0.05) when fatty acids were fed. Dietary fat digestibility by ewes was increased (P < 0.01) by fatty acid supplementation but decreased (P < 0.01) when tallow was added. Although ewe weight measures were not changed in Exp. 2, twin lamb gain per ewe organic matter intake was most efficient (P < 0.05) when ewes were supplemented with fatty acids. Results suggest that feeding hydrogenated tallow decreased nutrient availability for ewe milk fat production. A complete diet based on endophyte-free fescue hay can replace a traditional alfalfa hay diet, whereas supplementing with the calcium salts of palm oil fatty acids may be more feasible when energy is limiting during ewe lactation.     

Effect of excess degradable intake protein on early embryonic development, ovarian steroids, and blood urea nitrogen on days 2, 3, 4, and 5 of the estrous cycle in mature ewes

Two trials were conducted to determine whether feeding excess degradable intake protein (DIP) during a synchronized estrous cycle and the first 5 d after breeding alters early embryonic development, ovarian steroids, or BUN concentrations in ewes. Ewes were group-fed in Trial 1 (T1) and individually fed in Trial 2 (T2) either 100 (control; T1, n = 15; T2, n = 12) or 200% (high-protein; T1, n = 16; T2, n = 12) of the NRC protein recommendation for maintenance during a synchronized estrous cycle until surgery in the next cycle. Ampullae (AMP), isthmi (IST), and uterine horns (UT) of high-protein and control ewes were removed on d 2 (T1), 3 (T2), 4 (T1), or 5 (T2) after breeding. In T1, jugular blood samples were taken once daily starting on d 2 of the synchronized cycle, and in T2 on d 2, 9, 15, 16, and 17, and in both trials from estrus (d 0) to the day of surgery. Ampullae, IST, and UT flushings were examined microscopically for the presence of embryos, embryo condition, and embryo cell number. There was no trial x treatment interaction (P > or = 0.10), so data for both trials were pooled. Concentrations of BUN were higher (P < 0.05) in high-protein-fed ewes than in control ewes during the synchronized cycle and the first 5 d of the next cycle. Progesterone concentrations of the synchronized cycle did not differ (P > 0.10) between treatments. During the first 5 d of the next cycle, estradiol-17beta concentrations were lower (P = 0.06) in high-protein-fed than in control ewes. Progesterone increased (P < 0.05) to higher concentrations by d 5 in high-protein-fed ewes than in control ewes. More (P < 0.05) embryos were found in AMP of high-protein-fed ewes than in AMP of control ewes on d 4. Fewer (P = 0.05) embryos were found in UT of high-protein-fed ewes than in UT of control ewes on d 4. More embryos were found in UT of high-protein-fed ewes than in UT of control ewes on d 5. Fewer (P = 0.05) embryos were found in IST of high-protein ewes than in the IST of control ewes on d 5. Embryos of high-protein-fed ewes had more (P < 0.05) cells than embryos from control fed ewes on d 5. Feeding ewes excess DIP protein during an estrous cycle and the first 5 d after breeding initially impeded embryo transport; thereafter, embryo transport and development through the oviduct was accelerated.     

Maternal undernutrition during early to mid-gestation in the ewe results in altered growth, adiposity, and glucose tolerance in male offspring

This study utilized maternal undernutrition from early to midgestation in the ewe to determine the impact(s) of intrauterine growth restriction on postpartum growth of male offspring and the potential mechanisms involved. Multiparous ewes were fed 50% (nutrient-restricted) or 100% (control-fed) of their nutrient requirements (NRC, 1985) between d 28 and 78 of gestation, and then all ewes were fed 100% of the NRC requirements from d 79 through lambing. Male lambs born to nutrient-restricted (n = 9) and control-fed (n = 9) ewes exhibited similar BW (5.8 vs. 6.0 +/- 0.3 kg) and crown-rump lengths (53.8 vs. 55.4 +/- 1.0 cm) at birth. At 63 and 250 d of postnatal age, wether lambs were subjected to a glucose tolerance test, in which a bolus of glucose was administered i.v. to evaluate changes in glucose and insulin concentrations. After i.v. glucose administration at 63 d of age, lambs from nutrient-restricted ewes exhibited a greater area under the curve for glucose (AUCg; 6,281 vs. 5,242 +/- 429; P < 0.05) and insulin (AUCi; 21.0 vs. 8.6 +/- 1.9; P < 0.001) than lambs from control-fed ewes. After glucose administration at 250 d of age, lambs from nutrient-restricted ewes had greater AUCg (7,147 vs. 5,823 +/- 361; P < 0.01) but a lower AUCi (6.4 vs. 10.2 +/- 1.9; P = 0.05) than lambs from control-fed ewes. Lambs from nutrient-restricted ewes were heavier (26.6 vs. 21.8 +/- 2.3 kg; P < 0.05) and had more backfat (0.30 vs. 0.21 +/- 0.03 cm, P < 0.05) by 4 mo of age than the lambs from control-fed ewes. At slaughter at 280 d of age, lambs from nutrient-restricted ewes remained heavier than lambs from control-fed ewes, had greater (P < 0.05) amounts of kidney and pelvic-area adipose tissue, and tended (P < 0.10) to have reduced LM and semitendinosus muscle weights as a percentage of HCW. These data demonstrate that a bout of maternal undernutrition during early to midgestation in sheep increased BW and fat deposition during adolescence and dysregulated glucose uptake in the absence of any change in birth weight.     

Index selection in terminal sires improves early lamb growth

The use of terminal sires (TS) for crossbreeding is integral to the UK sheep industry where approximately 71% of market lambs are sired by TS rams. Early growth of these crossbred lambs affects profitability. The objectives of this study were i) to evaluate the effectiveness of index selection among TS on BW and ADG of their crossbred offspring; and ii) to compare the efficacy of that selection within TS breeds. The most widely used TS breeds in the United Kingdom are Charollais, Suffolk, and Texel. These participated in sire referencing schemes in which they were evaluated on a lean growth index designed to increase carcass lean weight at a given age. From 1999 to 2002, approximately 15 high and 15 low lean growth index rams per breed (93 in total, differing in index on average by 4.6 SD) were selected from within their sire referencing schemes and mated to Welsh and Scottish Mule ewes. Their crossbred offspring were reared commercially on 3 experimental farms in England, Scotland, and Wales. A total of 6,515 lambs were born between 2000 and 2003. Lambs were weighed at birth (BWT), 5 wk (5WT), and 10 wk (10WT), and their ADG from birth to 10 wk was calculated. Lambs sired by high index rams were on average, across breeds, heavier at all ages (P < 0.01) with 0.07 ± 0.03, 0.3 ± 0.1, and 0.4 ± 0.1 kg greater BWT, 5WT, and 10WT, respectively. Their ADG was 5.1 ± 1.9 g/d greater than low-index-sired lambs (P < 0.01). Suffolk-sired lambs were on average heavier at all ages, with greater ADG, whereas Charollais-sired lambs were lightest with smallest ADG. Overall, there was no significant interaction between sire index and sire breed (P > 0.10). Within Suffolk-sired lambs, there was little difference between high and low index sires for the traits studied (P > 0.3). High and low index Charollais-sired lambs differed in BWT (0.09 ± 0.04 kg) and 5WT (0.3 ± 0.1 kg), and Texel-sired lambs differed in 5WT (0.5 ± 0.1 kg), 10WT (0.9 ± 0.2 kg), and ADG (10.2 ± 3.3 g/d; P < 0.01). Lambs from Scottish Mule dams were heavier, with greater ADG, than lambs born to Welsh Mules (P < 0.01). Lambs reared in Scotland were heavier at all ages (P < 0.01). The results suggest that using index selection in TS can improve the growth of their commercial offspring reared on grass.     

Usefulness of subjective ovine milk scores: I. Associations with range ewe characteristics and lamb production

Range ewes are commonly evaluated for milking ability by producers to determine the ewe's ability to rear lamb(s). The U.S. Sheep Experiment Station has subjectively scored (low, average, high) a ewe's milking ability within 24 h of lambing for many years. The relationship of subjective milk scores with lamb production was investigated using lambing records of Columbia (n = 1,731), Polypay (n = 1,129), Rambouillet (n = 1,704), and Targhee (n = 1,638) ewes. The incidence of high milk scores increased from less than 10% at first parity to 29 to 40% at second and greater parities. At maturity, Columbia ewes (38%) had the highest percentage of high milk scores. A positive association existed between ewe BW and her milk score at third and later parities. Ewes with high milk scores gave birth to heavier lambs (P < 0.05), whereas ewes with low milk scores were associated with lighter (P < 0.05) lambs at birth. Ewes with low milk scores weaned less (P < 0.05) total weight than ewes with better milk scores across all age groups for all breeds. Lighter weaned litter weights from ewes with low milk scores were linked to lighter birth weights and fewer weaned lambs. Differences for litter weight weaned between ewes with average and high milk scores were generally observed at 2 and 3 yr of age, when litter weights were heavier among ewes with high milk scores (P < 0.05) for all breeds. Between the ages of 1 and 3 yr, Columbia, Polypay, Rambouillet, and Targhee ewes with an average milk score weaned heavier (P < 0.05) litters (average differences of 10, 9, 13, and 12%, respectively) than ewes with low milk scores. For all breeds at all ages, individual lamb weaning weights were heavier (P < 0.05) when they were reared by ewes with high milk scores compared to lambs reared by ewes with low milk scores. Results suggest that milk score is an economically important trait in these four breeds and should be considered in management and breeding objectives; at a minimum, the incidence of low milk scores should be kept as small as possible.     

Effects of diet and Aspergillus oryzae extract or Saccharomyces cervisiae on growth and carcass characteristics of lambs and steers fed to meet requirements of natural markets

Two studies were conducted to determine the effects of diet and feed additive on growth and carcass characteristics of lambs and cattle destined for all natural markets. In Exp. 1, 48 Dorset × Hampshire lambs (initial BW 29.4 ± 0.1 kg) were used in a randomized complete block experiment to determine the effects of Aspergillus oryzae extract, Amaferm (AMF) supplementation (1 g/d) in an 85% concentrate diet on growth and carcass characteristics. Lambs were allotted to 12 pens (4 lambs per pen), and blocked by sex and BW. Lambs were fed until the average BW of each pen reached a target BW (55.4 kg for wethers and 50.0 kg for ewes), at which time the entire pen of lambs was slaughtered. Amaferm resulted in a greater (P=0.07) G:F. In Exp. 2, 168 crossbred steers (initial BW 300 ± 0.7 kg) were used in a trial with a 3 × 2 factorial arrangement of treatments to examine the effects of 0.5 g/d of Saccaromyces cervisiae boulardii CNCM 1079-Levucell SB (LEV), or 3 g/d of AMF with 2 corn sources, dry whole-shelled corn or high moisture corn, on growth and carcass characteristics. Neither LEV nor AMF improved (P>0.10) carcass characteristics compared with control or non-feed-supplemented steers. Addition of LEV to high-concentrate, corn-based diets did not improve (P>0.10) growth performance of feedlot steers. However, addition of AMF to a diet composed of dry whole-shelled corn resulted in an improvement (P<0.05) in G:F (0.208 vs. 0.194). Results indicate that at the amounts fed, AMF may improve G:F for lambs and steers fed dry corn-based finishing diets.     

Sodium chlorate reduces the presence of Escherichia coli in feces of lambs and ewes managed in shed-lambing systems

Our objective was to establish doses of orally administered NaClO(3) that reduced the presence of generic Escherichia coli in intestines of ewes and neonatal lambs managed in a shed-lambing system. Neonatal lambs (n = 32; age = 7.1 ± 1.2 d; BW = 6.8 ± 1.0 kg) and yearling ewes (n = 44; BW = 74.8 ± 5.6 kg) were used in 2 experiments. In both experiments, lambs and ewes were randomly assigned to 1 of 4 groups, and groups were randomly assigned to 1 of 4 treatments. In Exp. 1, neonatal lambs were given single, aqueous, oral doses of saline (control; NaCl, 30 mg·kg of BW(-1)) or 30, 60, or 90 mg of NaClO(3)·kg(-1) of BW. At 25.9 ± 1.3 h after treatment, lambs were euthanized, and intestinal contents were collected aseptically. In Exp. 2, ewes were given single, aqueous, oral doses of saline (NaCl, 150 mg·kg of BW(-1)) or 150, 300, or 450 mg of NaClO(3)·kg(-1) of BW. At 24.0 ± 0.8 h after treatment, fecal samples were collected aseptically from the rectum of each ewe. For both experiments, generic E. coli were enumerated from intestinal contents and feces within 4 to 12 h after collection. In Exp. 1, the effect (P = 0.08) of NaClO(3) on the presence of generic E. coli in colon contents was dose-dependent. This effect was linear (P < 0.01) and negative, which indicated that as NaClO(3) dose increased, generic E. coli that could be isolated from colon contents decreased. Specifically, lambs dosed with 60 and 90 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of content than control lambs (P < 0.06). Lambs dosed with 90 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of content than lambs dosed with 30 mg of NaClO(3)·kg(-1) of BW (P = 0.09). Sodium chlorate dose did not influence (P = 0.58) the presence of generic E. coli in contents collected from the cecum. In Exp. 2, the effect (P < 0.0001) of NaClO(3) on the presence of E. coli in fecal contents from ewes was dose-dependent. This effect was quadratic (P < 0.0001) and negative; ewes dosed with 150, 300, and 450 mg of NaClO(3)·kg(-1) of BW had fewer E. coli cfu·g(-1) of feces than control ewes. No differences in E. coli cfu·g(-1) of feces were detected between NaClO(3) treatments (P = 0.88 to 0.97). Based on these results, a single oral dose of at least 60 and 150 mg of NaClO(3)·kg(-1) of BW in neonatal lambs and yearling ewes, respectively, significantly decreased the presence of generic E. coli in contents from the lower intestine.     

Synchrony of nutrient supply to the rumen and dietary energy source and their effects on the growth and metabolism of lambs

The objective of the current series of experiments was to assess the effects of dietary synchrony of OM and N supply to the rumen, achieved by altering the sequence of feeding individual ingredients and in diets with different energy sources, on the metabolism and performance of growing lambs. In Exp. 1, the in situ degradability coefficients of OM and N were determined for five feed ingredients and subsequently was used to formulate two diets, based either on barley or sugar beet pulp, to have a similar predicted nutrient content. Within each diet, specific ingredients were shifted between the 0900 and 1600 feeding to provide either a synchronous, intermediate, or asynchronous supply of OM and N to the rumen. In Exp. 2, these diets were fed at a restricted level to 48 growing lambs with an initial live weight of 25.1 +/- 4.22 kg and a slaughter weight of 41.4 +/- 1.94 kg. There was no significant effect of dietary treatment on live weight gain or feed conversion efficiency. Lambs fed the synchronous diets deposited more kidney knob and channel fat than lambs on the asynchronous or intermediate diets (P < 0.05), whereas lambs fed the barley-based diets deposited more carcass (P < 0.05) and noncarcass (P < 0.001) fat than lambs on the sugar beet-based diets. Lambs fed the asynchronous diets retained less energy over the course of the experiment than lambs on the intermediate or synchronous diets (P < 0.05), and had a lower energy efficiency (0.079, 0.097, and 0.093 MJ retained/ MJ of intake, respectively, P < 0.05). Lambs fed the barley-based diets retained more energy than lambs on the sugar beet-based (P < 0.001) and had a higher energy balance (0.095 vs. 0.084 MJ retained/MJ intake, respectively; P < 0.01). Plasma ammonia concentrations mirrored ruminal ammonia concentrations on the barley-based diets, but not sugar beet-based diets. In Exp. 3, lambs fed the sugar beet-based diets had a higher digestibility of OM and NDF (P < 0.001). By contrast, lambs on the barley-based diets had a higher level of purine derivative excretion and microbial N production (P < 0.001). The results indicate that neither dietary synchrony nor energy source significantly influenced growth rate. However, both the asynchronous and sugar beet pulp-based diets resulted in a lower efficiency of dietary energy use, and the avoidance of asynchronous patterns of nutrient release within the rumen can improve energy efficiency in growing lambs.     

Effects of number of lambs suckled and supplemental protein source on lactating ewe performance

Effects of number of lambs suckled and supplemental protein source on ewe performance were determined. Lactation performance of ewes nursing twin or triplet lambs was compared in Exp. 1 and 2. In Exp. 1, ewes giving birth to and nursing triplets produced 21% (P less than .05) more milk/unit metabolic body weight, were 10% more efficient in the conversion of feed to milk and produced 26% (P less than .05) more kg of lamb/ewe on d 42 of lactation than did ewes giving birth to and nursing twins. In Exp. 2, lactation performance of ewes giving birth to triplets and rearing only two lambs was compared with performance of ewes giving birth to triplets and rearing three lambs. Ewes rearing three lambs produced 28% (P less than .08) more milk and were 26% (P less than .05) more efficient in converting feed to milk than were those rearing two lambs. This suggests that direct nursing stimulation of the mammary gland is responsible for the improvement in milk production observed when ewes nurse additional lambs. The efficacy of slowly degradable protein sources for improved lactation was studied in Exp. 3 and 4. When blood meal was fed to twin-rearing ewes at 3.30% of the diet (25% of total dietary protein), milk production was greater (3,176 vs. 2,506 g/d, P less than .05) and efficiency of milk production was greater (1.05 vs .79 g milk/g feed, P less than .05) than when ewes were fed supplemental soybean meal. Ewes in this experiment fed supplemental meat and bone meal also tended to produce more milk than those fed soybean meal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Examination of non-genetic factors affecting the growth performance of djallonke sheep in soudanian zone at the Okpara breeding farm of Benin

A study was carried out at the Okpara breeding farm in Benin. Records on 558 lambs of the Djallonke sheep breed, born from 1997 to 2000, were used to determine the weekly growth curve from birth up to 119 days of age. Non-genetic factors affecting lamb weights at birth and at 30, 60, 90 and 120 days and average daily gains from 0 to 30 days, from 0 to 60 days, from 0 to 90 days and from 0 to 120 days were investigated. A linear model comprising the fixed effects of birth season, birth year, parity number of ewe and sex of lambs was used for analysis of variance by least squares. All fixed effects were significant for weight at 30 and 60 days and average daily gains at 30 days, with the exception of the parity of the ewe for birth weight, weight and average daily gain at 90 days. All fixed effects tended to cancel out for weight and average daily gains by 120 days. Lambs born in the dry season were the heaviest. Single lambs and male lambs were heavier than twins and females. Lambs from ewes of 3rd and 4th parity were heavier, with higher, average daily gains.     

Inheritance of fecal egg count and packed cell volume and their relationship with production traits in sheep infected with Haemonchus contortus

This study describes responses to artificial infection with Haemonchus contortus in ewes and lambs of 50% Dorset, 25% Rambouillet, and 25% Finn-sheep ancestry and provides estimates of genetic parameters for measures of parasite resistance. One hundred ninety-eight ewes out of 64 sires, and 386 lambs out of 25 sires were evaluated in autumn and spring of 2 yr. Ewes were dewormed shortly after weaning their lambs and lambs were dewormed at about 120 d of age. One week after deworming, ewes and lambs were dosed with approximately 10,000 infective larvae of H. contortus. After infection, BW, fecal egg counts (FEC), and packed cell volume (PCV) were measured weekly for 7 wk in lambs kept in drylot and fortnightly for 11 wk in ewes on pasture. Summary traits were defined as initial PCV, mean BW across all times, and means for PCV (MPCV) and log-transformed FEC (MLFEC) at wk 3 to 7 after infection for lambs and wk 3 to 11 after infection for ewes. Ewes and lambs did not lose weight overall in any year or season, but there was no consistent effect of year or lambing season on mean LFEC or mean PCV during infection in either ewes or lambs. Yearling ewes were less resistant to infection than older ewes, with lower PCV (P < 0.05) and higher LFEC (P < 0.05). During infection, PCV was positively correlated with BW and negatively correlated with LFEC in both ewes and lambs. In lambs, heritabilities were 0.39 (P < 0.01) for PCV, 0.10 (P < 0.05) for LFEC across all measurement times, and 0.19 (P < 0.01) for three measures of LFEC taken at the peak of infection. Heritability estimates for ewes were 0.15 (P < 0.05) for PCV and 0.31 (P < 0.01) for LFEC. Repeatabilities for LFEC and PCV across measurement times were moderate in ewes and lambs. Correlations between dam and lamb records for MLFEC were generally low, suggesting different mechanisms of resistance in lambs and nonlactating ewes. Ewes with higher genetic merit for growth as lambs were less resistant to infection as adults, but genetic merit for fertility and prolificacy were not related to parasite resistance. Lambs with higher genetic merit for body weight were more resistant to infection. Selection for resistance to H. contortus is therefore possible and should not adversely affect growth of lambs and fertility of ewes in this production environment.     

Maternal nutrition during pregnancy influences offspring wool production and wool follicle development

The effects of maternal nutrition on offspring wool production (quality and quantity) were evaluated. Primiparous Rambouillet ewes (n = 84) were randomly allocated to 1 of 6 treatments in a 2 × 3 factorial design. Selenium treatment [adequate Se (ASe, 9.5 μg/kg of BW) vs. high Se (HSe, 81.8 μg/kg of BW)] was initiated at breeding, and maternal nutritional intake [control (CON, 100% of requirements) vs. restricted (60% of CON) vs. overfed (140% of CON)] was initiated at d 50 of gestation. Lamb birth weight was recorded at delivery, and all lambs were placed on the same diet immediately after birth to determine the effects of prenatal nutrition on postnatal wool production and follicle development. At 180 ± 2.2 d of age, lambs were necropsied and pelt weights were recorded. Wool samples were collected from the side and britch areas, whereas skin samples were collected from the side of each lamb only. Although Se status did not influence side staple length in males, female lambs born from ewes on the ASe treatment had a shorter staple length (P < 0.05) when compared with females from ewes on the HSe treatment. Maternal nutritional intake and Se status did not influence (P ≥ 0.23) wool characteristics on the britch. However, at the britch, wool from female lambs had a reduced comfort factor (P = 0.01) and a greater (P = 0.02) fiber diameter compared with wool from male lambs. Maternal Se supplementation, maternal nutritional plane, sex of the offspring, or their interactions had no effect (P > 0.13) on primary (29.10 ± 1.40/100 μm(2)) and secondary (529.84 ± 21.57/100 μm(2)) wool follicle numbers. Lambs from ASe ewes had a greater (P = 0.03) secondary:primary wool follicle ratio compared with lambs from HSe ewes (20.93 vs. 18.01 ± 1.00). Despite similar postnatal diets, wool quality was affected by maternal Se status and the maternal nutritional plane.     

Body weight and tissue gain in lambs fed an all-concentrate diet and implanted with trenbolone acetate or grazed on alfalfa

Targhee x Hampshire lambs (average BW 23 +/- 1 kg) were used in two experiments to determine the effects of finishing on concentrate with an anabolic implant or forage grazing after concentrate feeding on growth, organ and viscera weights, and carcass tissue accretion. In Exp. 1 and 2 lambs were penned by sex and assigned for slaughter at initial (23 kg), intermediate (37 kg), or end BW (ewes, 47.7; wethers 50.4 kg). From 23 to 37 kg BW, lambs were fed all-concentrate diets in drylot (DL) or grazed on alfalfa (ALF). Experiment 1 was a 2 x 2 factorial with 28 lambs; factors were wether vs ewe lambs and unimplanted vs DL implanted with trenbolone acetate-estradiol benzoate. There were no differences in organ and viscera weights due to implant status. However, ADG (P < .03) and lean gain (P < .02) were greater for implanted than for unimplanted wethers (507 vs 357 g and 1,314 vs 656 g, respectively). Ewes did not respond to the implant. Fat accretion was not affected by implantation. Experiment 2 was a 2 x 3 factorial with 42 lambs; factors were wether vs ewe lambs and drylot during growing and finishing phases (DL-DL) vs drylot during growing and alfalfa grazing during finishing (DL-ALF) vs alfalfa grazing during growing and finishing phases (ALF-ALF). In Exp. 2, ADG of DL-DL lambs was greater (P < .01) than ADG of DL-ALF or ALF-ALF lambs. Lambs on ALF-ALF had smaller (P < .05) livers and rumen/reticulum weights but heavier (P < .04) kidney, omasum, small and large intestine, and cecum weights than those on DL. In Exp. 2, DL-ALF and ALF-ALF lambs had overall hindsaddle lean gain equal to those on DL-DL with less mesenteric fat and 100 g less separable fat. Finishing lambs on alfalfa reduced fat accretion without decreasing lean accretion, whereas trenbolone acetate implants for lambs fed concentrate increased BW gain and lean accretion without affecting fat accretion.     

Effect of whole-crop pea (Pisum sativum L.) silages differing in condensed tannin content as a substitute for grass silage and soybean meal on the performance, metabolism, and carcass characteristics of lambs

Two experiments were conducted to investigate the effect of inclusion of whole-crop pea (WCP) silages, differing in condensed tannin content, as a substitute for grass silage (GS) and soybean meal on lamb metabolism, performance, plasma metabolites, digestibility, and carcass characteristics. In both experiments lambs were offered either solely GS or a 50:50 mix on a DM basis of GS with either low-tannin (LTPS) or high-tannin (HTPS) pea silage ad libitum. Each forage mix was fed with either 400 g/d of low-protein (LP) concentrate or 400 g/d of LP with an additional 200 g/d of pelletized soybean meal (HP), resulting in 6 dietary treatments. Experiment 1 examined the effects of the diets on metabolism, digestibility, and N balance using 6 lambs in 4 periods of 21 d in an incomplete crossover design. Experiment 2 used 48 lambs and examined the effects of the diets on ADG, plasma metabolites, and carcass characteristics over 56 d. Both experiments were analyzed using a 3 × 2 factorial arrangement of treatments. In Exp. 1, lambs offered the LTPS diets had a greater (P < 0.05) digestibility of DM and OM than those offered the GS diets. Lambs offered the WCP silages had an increased (P < 0.05) N intake, N output, and digestibility of GE compared with those offered GS. Mean N digestibility was greatest (P < 0.05) in lambs offered LTPS. Lambs offered HP diets had increased (P < 0.001) digestibility of DM, OM, GE and N, and N- intake, output, retention, and digestibility compared with those offered the LP diets. In Exp. 2, there was no effect (P > 0.05) of forage type on intake, slaughter BW, or feed conversion efficiency (FCE). However, lambs offered the LTPS had a greater (P < 0.05) ADG than those offered the GS diets. Feeding diets containing HP increased (P < 0.001) total DMI, slaughter BW, ADG, and FCE. Lambs offered the WCP had a greater (P < 0.05) plasma β-hydroxybutyrate and urea concentration compared with those offered the GS diets. Feeding lambs HP diets increased (P < 0.05) plasma urea and total protein. Forage mix had no effect (P > 0.05) on carcass composition except for fat depth, which was greater (P < 0.05) in lambs offered WCP silage. Diets containing the HP increased (P < 0.05) carcass weight, hind leg circumference, chop dimensions, and kidney weight. It was concluded that lambs offered LTPS performed better than those offered GS and that LTPS has a concentrate sparing effect. Additionally, the increased tannin concentration in HTPS did not increase performance over lambs offered either GS or LTPS.