Impacts of naturally acquired protozoa and strongylid nematode infections on growth and faecal attributes in lambs

On two separate sampling occasions, faecal samples were collected from lambs (2-5 months of age) grazing pasture on two separate sheep farms in southern Western Australia. Live weight, body condition score (BCS), faecal consistency score (FCS) and faecal dry matter percentage (DM%) were measured. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60 kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and β-giardin) and patent strongylid nematode infections (ITS-2 nuclear ribosomal DNA for Haemonchus contortus, Teladorsagia circumcincta, Trichostrongylus spp. Chabertia ovina and Oesophagostomum spp.). Faecal worm egg counts (WECs) were performed using a modified McMaster WEC technique. The WECs were adjusted for FCS and transformed using log(10)(adjusted WEC+25) prior to statistical analyses. Cryptosporidium, Giardia and Trichostrongylus spp. detected by PCR were associated with an increased risk of non-pelleted faeces (FCS ≥ 3.0) for both flocks. Cryptosporidium-positive lambs were 2.8-11.6 times more likely to have non-pelleted faeces and Giardia-positive lambs were 2.4-14.0 times more likely to have non-pelleted faeces compared to lambs negative for each respective parasite. Lambs positive for both Cryptosporidium and Giardia were 2.9-11.8 times more likely to have non-pelleted faeces than lambs positive for only one or neither of these parasites. Mixed internal parasite infections were found to have greater impacts on FCS and BCS than single infections. A higher number of internal parasites detected per lamb was associated with lower BCS and more loose faeces. The relationship between parasite detection and live weight or growth rate were inconsistent for both flocks. Adjusted WEC was correlated with FCS and faecal DM% for one flock only, although little or no correlation was found with live weight and growth rate for both flocks. Cryptosporidium ubiquitum and Cryptosporidium parvum were the most prevalent Cryptosporidium species isolated in the two flocks. Giardia assemblage E was the most commonly isolated genotype assemblage from both flocks, while assemblage A was isolated almost as frequently as assemblage E in the one flock. One flock was a potential source of zoonotic Cryptosporidium and the other flock was a potential source of zoonotic Giardia.     

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).     

湖羊羔羊早期断奶前后瘤胃发酵与微生物区系的变化

本试验旨在研究湖羊羔羊早期断奶前后的瘤胃发酵与微生物区系变化，为幼龄反刍动物瘤胃发育变化理论以及羔羊的早期培育等提供依据。选择初生重接近的湖羊公羔（3.81 kg±0.55 kg）16只，1~7日龄饲喂母乳，8日龄与母羊分离，开始饲喂代乳粉（按8日龄体重的2%，分3次等量饲喂）和开食料（自由采食），35日龄断奶。分别于断奶前（21日龄）、后（42日龄）各选择5只羔羊进行屠宰，采集瘤胃内容物，测定瘤胃发酵、酶活和微生物区系。结果表明，断奶后羔羊的瘤胃总挥发性脂肪酸、乙酸、丙酸、丁酸及纤维素酶和α-淀粉酶活性均极显著高于断奶前（P<0.01）。断奶后瘤胃菌群多样性和丰富度均低于断奶前（P<0.05）。断奶前后的优势菌门均为拟杆菌门（Bacteroidetes）和厚壁菌门（Firmicutes），其中，拟杆菌门为第一优势菌门，在断奶前后分别占61.96%和65.36%，厚壁菌门为第二优势菌门，在断奶前后分别占32.08%和24.03%；两菌门之和在断奶前后分别占瘤胃总菌门的94.04%和89.39%。断奶前后的优势菌属均为unidentified_Prevotellaceae，分别占21.85%和38.49%。断奶前后羔羊瘤胃微生物的功能没有显著变化，都主要集中在复制和修复、碳水化合物代谢和翻译等途径。以上结果说明，羔羊早期断奶后的瘤胃发酵和酶活增强，菌群多样性和丰富度有所降低，在早期断奶前后的优势菌群和功能相似。     

Cryptosporidium and Giardia associated with reduced lamb carcase productivity

On two extensive sheep farms in southern Western Australia, 111 (Farm A) and 124 (Farm B) female crossbred lambs (2-6 weeks old) were randomly selected and individually identified using ear tags (a numbered tag and radio-frequency tag) at marking. On five separate occasions, faecal samples were collected and live weight, body condition score (BCS), faecal consistency score (FCS), breech fleece faecal soiling score and faecal dry matter percentage (DM%) were recorded. Lamb hot carcase weight (HCW) and dressing percentage were measured at slaughter. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60 kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and triosephosphate isomerise [tpi]) and Campylobacter jejuni (16S rRNA). Observation of Eimeria oocysts and faecal worm egg counts (WECs) were performed using a modified McMaster technique. The WECs were adjusted for FCS for analyses. Faecal samples were screened for patent strongylid infections using PCR (specifically ITS-2 nuclear ribosomal DNA for Teladorsagia circumcincta, Trichostrongylus spp. and Haemonchus contortus). Lambs positive for Cryptosporidium at least once had lighter HCWs by 1.25 kg (6.6%) (P=0.029) and 1.46 kg (9.7%) (P<0.001) compared to lambs never positive for Cryptosporidium for Farms A and B respectively. Similarly, dressing percentages were 1.7% (P=0.022) and 1.9% (P<0.001) lower in Cryptosporidium-positive lambs on Farms A and B respectively. Lambs positive for Giardia at least once had 0.69 kg (P<0.001) lighter HCWs and 1.7% (P<0.001) lower dressing percentages compared to lambs never positive for Giardia on Farm B only. Cryptosporidium-positive lambs at the second sampling were 4.72 (P=0.010) and 3.84 (P=0.002) times more likely to have non-pelleted faeces compared to Cryptosporidium-negative lambs for Farms A and B respectively. Breech fleece faecal soiling scores of Cryptosporidium-positive lambs were 3.36 (P=0.026) and 2.96 (P=0.047) times more likely to be moderate to severe (scores 3-5), compared to negative lambs at the second sampling for Farms A and B respectively. Live weight, growth rate and BCS were inconsistently associated with protozoa detection across different samplings and farms. Adjusted WEC was correlated positively with FCS and negatively with faecal DM%, differing between sampling occasions and farms. Campylobacter jejuni prevalence was very low (<1%). Adjusted WEC were not correlated with carcase attributes, growth rates or live weights. This study is the first to quantify productivity consequences of naturally acquired protozoa infections in lambs managed under extensive farming conditions.     

Pre-weaning growth performance of crossbred lambs (Dorper × indigenous sheep breeds) under semi-intensive management in eastern Ethiopia

A study was conducted to assess the effect of genetic and non-genetic factors (litter size, sex of lamb, and parity of dam) on pre-weaning growth performance of crossbred lambs (75 % Dorper (DR) 25 % indigenous lambs; and 50 % Dorper 50 % indigenous lambs) under semi-intensive husbandry practices in eastern Ethiopia. Data from a total of 275 Dorper sire breed × indigenous (Blackhead Ogaden [BHO] and Hararghe Highland [HH]) crossbred lambs with different genetic group of the parental breeds were collected for three consecutive years (2009 to 2011). Pre-weaning growth performance attributes of crossbred lambs studied were birth weight, weaning weight, and pre-weaning average daily gain. Data were analyzed using the GLM procedure of SAS (2003). Breed group and non-genetic factors significantly affected pre-weaning growth performance. Lambs with 75 % Dorper and 25 % indigenous had higher (P?<?0.01) birth weight than 50 % DR and 50 % HH but similar to 50 % DR and 50 % BHO. Weaning weight and pre-weaning live weight gain were higher (P?<?0.01) for ¾DR¼BHO and ¾DR¼HH than 50 % Dorper inheritance. Single-born lambs had higher weight at birth, weaning weight, and pre-weaning average daily gain as compared to twins. Sex comparison is significant (P?<?0.05) and male lambs recorded highest pre-weaning growth performance compared to female counterparts. Parity, season, and lambing year significantly (P?<?0.01) influenced the pre-weaning growth of crossbred lambs. Therefore, it could be concluded that 50–75 % Dorper inheritance improved pre-weaning growth performance of indigenous breeds of Hararghe Highland and Blackhead Ogaden sheep. The result also suggested culling of ewes older than fourth parity to improve the pre-weaning growth performance of lambs.     

Effects of genetic and environmental factors on pre-weaning and post-weaning growth in West African crossbred sheep

Effects of genetic and environmental factors on pre-weaning and post-weaning growth were studied in West African crossbred sheep. Effects of lamb genotype (7/8 Sahelian–1/8 Djallonké, 3/4 Sahelian–1/4 Djallonké and 1/2 Sahelian–1/2 Djallonké; hereafter denoted 7/8Sa, 3/4Sa and 1/2Sa, respectively), parity, type of birth, sex of lamb and year-season of lambing on birth weight, weaning weight, 8-month weight and pre- and post-weaning growth rates were determined. At birth 7/8Sa and 3/4Sa lambs were heavier (p<0.01) than 1/2Sa lambs. Lambs born to first-parity ewes were lighter (p<0.01) at birth than lambs of older ewes. At weaning and 8 months of age, lambs born to fourth-parity ewes were heavier (p<0.05) than those born to ewes of the other parities. Parity did not have any significant effects on pre-weaning growth rate. Lambs born in the rainy season of 2001 were significantly heavier at birth and at 8 months of age than those born in the dry season of 2001/02, but there was no difference between the two groups at weaning. Pre-weaning growth rate was significantly faster in lambs born in the dry season of 2001/02 but the reverse was true for post-weaning growth rate.     

湖羊羔羊早期断奶前后瘤胃发酵与微生物区系的变化

本试验旨在研究湖羊羔羊早期断奶前后的瘤胃发酵与微生物区系变化,为幼龄反刍动物瘤胃发育变化理论以及羔羊的早期培育等提供依据。选择初生重接近的湖羊公羔(3.81 kg±0.55 kg)16只,1~7日龄饲喂母乳,8日龄与母羊分离,开始饲喂代乳粉(按8日龄体重的2%,分3次等量饲喂)和开食料(自由采食),35日龄断奶。分别于断奶前(21日龄)、后(42日龄)各选择5只羔羊进行屠宰,采集瘤胃内容物,测定瘤胃发酵、酶活和微生物区系。结果表明,断奶后羔羊的瘤胃总挥发性脂肪酸、乙酸、丙酸、丁酸及纤维素酶和α-淀粉酶活性均极显著高于断奶前(P<0.01)。断奶后瘤胃菌群多样性和丰富度均低于断奶前(P<0.05)。断奶前后的优势菌门均为拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes),其中,拟杆菌门为第一优势菌门,在断奶前后分别占61.96%和65.36%,厚壁菌门为第二优势菌门,在断奶前后分别占32.08%和24.03%;两菌门之和在断奶前后分别占瘤胃总菌门的94.04%和89.39%。断奶前后的优势菌属均为unidentified_Prevotellaceae,分别占21.85%和38.49%。断奶前后羔羊瘤胃微生物的功能没有显著变化,都主要集中在复制和修复、碳水化合物代谢和翻译等途径。以上结果说明,羔羊早期断奶后的瘤胃发酵和酶活增强,菌群多样性和丰富度有所降低,在早期断奶前后的优势菌群和功能相似。     

Effects of concentrate feeding systems,genotype and sex on productive performance and meat quality of Norwegian lambs

Abstract

Two factorial experiments, I and II, were carried out in this study using 84 lambs (140±1.24 days old, 40.00±0.75 kg live weight) divided into six groups. Two levels of concentrate supplementation; restricted (0.4 kg concentrate/lamb/day) or ad libitum, two breed types; Norwegian White lamb or Nor-X and two sex types; ram or ewe lambs, were investigated. In experiment I, a 2×2×2 factorial arrangement of treatments (level of supplementation, sex, and breed) was imposed whereas a 2×2 arrangement of treatments (level of supplementation and breeds) was studied in Experiment II. Each of the two experiments lasted for four weeks. Lambs on ad libitum access to concentrate grew at 231 g d^–1 and 125 g d^–1 faster than those on restricted access in Experiment I and II, respectively. Moreover, ram lambs grew at 64 g d^–1 faster than ewe lambs. Lambs on ad libitum access to concentrate had about 5 kg heavier carcasses than that on restricted access. Ewe and ram lambs on ad libitum allowance to concentrate had 4.2 kg and 5.6 kg, respectively, higher carcass weight than those on restricted allowance. The two levels of concentrate supplementation had limited effects on the meat sensory qualities. Meat taste intensity increased with level of concentrate supplementation. Difference in meat tenderness between ram and ewe lambs was only evidenced on ad libitum concentrate feeding. Irrespective of stage of growth (Experiment I vs. II) and concentrate supplementation level, Nor-X lambs were superior to Norwegian White lambs with respect to carcass conformation scores. Based on results from sensory assessments of meat, ram lambs should be slaughtered before October to avoid off-flavour on meat.     

Molecular identification of naturally acquired strongylid infections in lambs--an investigation into how lamb age influences diagnostic sensitivity

Faecal samples (n=1155) were collected from n=111 (Farm A) and n=124 (Farm B) 2-6 week old female lambs on two farms in southern Western Australia across five sampling occasions (spanning 8 months). Genomic DNA was extracted directly from faecal samples and screened by PCR for ITS-2 nuclear ribosomal DNA to detect patent strongylid infections, specifically Teladorsagia circumcincta, Trichostrongylus spp., Haemonchus contortus, Oesophagostomum spp. and Chabertia ovina. The minimum amount of extracted genomic DNA necessary for successful PCR amplification was 2.0-5.0 pg. During the five sampling occasions for the two farms, the sensitivities for WEC and PCR identification of strongylid infections varied, with levels of agreement between the two sets of diagnostic results ranging from 85 to 100%. Strongylid species prevalences were high (90.3-97.3%), with T. circumcincta and Trichostrongylus spp. the most prevalent species and together they were the most common mixed strongylid infection; H. contortus was not identified in either flock. T. circumcincta was the only species associated with an increased risk of non-pelleted faeces on Farm B, where T. circumcincta-positive lambs were 2.3 and 2.6 times more likely to have non-pelleted faeces than negative lambs at the second and final samplings, respectively. The highest strongylid prevalence, mixed strongylid prevalence and mean number of strongylid species detected per lamb coincided with the highest average flock faecal worm egg counts (WECs) on both farms. There was a positive correlation between the number of strongyle species detected per lamb and both WEC and adjusted WEC (P<0.01; r(2) 0.026-0.591). These results indicate that strongylid eggs were likely to be the main source of strongylid DNA in the faecal DNA extracts. Despite the progress made by the molecular approach utilised in this study, it is incapable of distinguishing between patent and non-patent sources of strongylid DNA. However there is potential for further investigation into the development of a similar molecular procedure which could be used for early larvae detection on pastures.     

Risk Factors for Lamb Mortality in Sahelian Sheep on a Breeding Station in Ghana

A retrospective cohort study was designed to examine the effect of sex, season of birth, type and year of birth, and birth weight on lamb mortality. The method used involved analysis of breeding records for Sahelian sheep kept on a breeding station at Pong-Tamale in northern Ghana from 1994 to 2000. The pre-weaning and post-weaning mortalities were 10% (n = 505) and 19% (n = 453), respectively, while the overall mortality from birth up to 12 months of age was 28% (n = 505). Compared to the pre-weaning period, the post-weaning period recorded significantly higher proportions of deaths in male, single-born, lambs born in the rainy or dry seasons, and in lambs with low (<3 kg) or high (> or =3 kg) birth weight. The odds and risks of death for male lambs were about one and a half times those for females at post-weaning. Lambs born in the dry season had significantly higher mortality than those born in the rainy season. Lambs that died by the time of weaning were not significantly different in weight at birth from those that survived. The mean birth and weaning weights of single-born lambs were significantly higher than those for twins. The mean pre-weaning ADG was significantly higher in lambs born as singles compared to that for twins. The season of birth had influence on mean birth weight, with those born in the rainy season having significantly higher weights than those born in the dry season. The year of birth significantly affected birth weight, weaning weight, weight at 12 months and ADG at all stages of the lambs' life. The study concluded that the most significant risk factors for lamb mortality included sex of the lamb, season of birth and birth weight. The last two could be manipulated, to some extent, to reduce lamb mortality.     

凉山半细毛羊育成期生长发育的研究

凉山半细毛羊 4月龄公、母羔体重在 2 6kg以上 ,哺乳期内生长迅速 ,一月龄日增重接近 30 0g ,哺乳期内近 2 0 0g。随着年龄增长 ,生长速度逐渐变慢 ,5～ 1 2月龄公、母羔日增重分别降至 80 8g和 5 7 9g。1 5岁时公、母羊体重分别达到 60 4kg和 46 1kg。 2 5岁成年母羊体重 5 4 5kg。     

Factors affecting productivity of Rambouillet ewes mated to ram lambs

Objectives of this study were to estimate the magnitude of the effects of various factors associated with ewes and their ram lamb mates on fertility, prolificacy, lamb survival, lamb weaning weight and ewe productivity and to estimate the heritability and repeatability of each trait. Records from 731 ewe-years, 75 ram lamb sires and 616 lambs born from the University of Illinois Rambouillet flock were used. Ewes mated to single-born ram lambs had higher fertility rates (P less than .01), gave birth to lambs with higher survival rates (P less than .01), weaned lighter (P less than .05) individual lambs but weaned more weight of lamb per ewe exposed (P less than .01) than ewes mated to multiple-born ram lambs. Ram lamb breeding weight, ram lamb scrotal circumference, ewe breeding weight and ewe age had relatively large and positive effects on the composite trait of weight of lamb weaned per ewe exposed and significant effects on a number of the component traits. Heritability and repeatability estimates were, respectively, as follows: fertility, 3%, 3%; prolificacy, 34%, 19%; lamb survival, 15%, 8%; lamb weaning weight, 7%, 36%; and ewe productivity, 27%, 10%.     

Lamb wool shedding is a good predictor of ewe wool shedding

Interest in reducing labour costs due to shearing has led to development of breed types that shed their wool naturally. Selection at young ages can facilitate response. Reliability of predictions of adult from lamb wool shedding (WS) is thus key in the design of breeding programmes to increase shedding. Our objectives were to estimate heritabilities and genetic relationships between WS measured once in lambs and repeatedly in ewes and to assess the accuracy of lamb WS EBV to predict ewe WS EBV based on a multi-trait threshold or a repeatability model. Data were 4,971 lamb and 3,335 ewe WS records on a Romanov, White Dorper and Katahdin composite flock. For the multivariate model, WS heritability ranged from 0.47 ± 0.03 in lambs to 0.59 ± 0.04 at 1 year of age. For the repeatability model, WS in adult ewes was moderately heritable (0.50 ± 0.03) and repeatable (0.60 ± 0.02). Genetic correlations were 0.72 ± 0.04, 0.65 ± 0.05, 0.50 ± 0.09 and 0.51 ± 0.09 between lamb WS and 1st through 4th record, respectively. Given the moderately high heritability and high correlations between WS performance in lambs and ewes, selecting animals early in life would effectively increase WS in crossbred flocks.     

Influence of dietary palm oil supplementation on serum lipid metabolites, carcass characteristics, and lipid composition of carcass tissues of growing ram and ewe lambs.

The objective of this research was to determine the influence of dietary palm oil supplementation on carcass characteristics and lipid composition of tissues from growing lambs. Twenty-eight Suffolk x Hampshire lambs were weaned at 60 d of age (average 36 kg BW) and assigned to a 2 x 2 factorial arrangement consisting of diet (control [NPO] or 10.6% added dietary palm oil [PO]) and sex (ram vs ewe). The NPO diet (77% forage and 23% concentrate) contained 11.2% CP and 2.66 Mcal of ME/kg. Palm oil replaced molasses in the PO diet. Lambs were individually given ad libitum access to feed for 60 d to a final BW average of 50.1 kg. Lipid composition of the longissimus muscle and corresponding subcutaneous (s.c.) adipose tissue was determined by gas-liquid chromatography (GLC). Lambs fed PO were fatter (P less than .01) than lambs fed NPO (.77 vs .56 cm, s.c. fat). Diet had no effect on cholesterol content of lean tissue; however, feeding PO increased the saturated fatty acids of lean tissue. The s.c. fat from lambs fed PO had less (P less than .01) cholesterol (64.79 vs 89.67 mg/100 g) and more saturated fatty acids than that from lambs fed NPO. Ewes were fatter (P less than .01) than rams, yet they had less cholesterol content in the s.c. adipose tissue (68.71 vs 85.74 mg/100 g). High amounts of dietary palm oil fed to growing lambs caused changes in fatty acid deposition and cholesterol metabolism and may be a useful investigative tool to study lipid metabolism in growing ruminants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of performance of F1 Romanov crossbred ewes with wool and hair breeds during spring lambing under intensive and extensive production systems

The objective was to evaluate wool (Dorset and Rambouillet) and hair (Dorper, Katahdin, and White Dorper) breeds for their ability to complement Romanov germplasm in two distinct production systems by estimating direct sire and grandsire effects on lamb growth, survival, and ewe productivity traits. Rams of the five breeds (n = 75) were mated to Romanov ewes (n = 459) over a 3-yr period to produce five types of crossbred lambs (n = 2,739). Sire breed (P > 0.06) did not impact body weight or survival traits of the first-generation crossbred (F1) lambs. The productivity of retained crossbred ewes (n = 830) mated to Suffolk and Texel terminal sires was evaluated at 1, 2, and 3 yr of age in each production system. In the intensive production system, labor and harvested feed were provided for sheep that lambed in March in barns, and ewes were limited to rearing two lambs with additional lambs reared artificially. Ewes in the extensive production system lambed in May on pasture and were responsible for rearing all lambs born with no labor or supplemental feed provided before weaning. A total of 1,962 litters and 4,171 lambs from 2,229 exposures to two terminal sire breeds (Suffolk and Texel) were produced in the experiment. Crossbred ewes in the intensive production system were mated in October, resulting in larger litter sizes than crossbred ewes mated in December for the extensive production system. However, single- and twin-born lamb mortality was similar between the two systems that differed greatly in labor, feed, and facilities. Lambs produced in the intensive system received concentrate feed from an early age and were heavier at 24 wk of age than lambs produced in the extensive system. These outcomes resulted in greater 24-wk litter weight in the intensive than in the extensive system (P < 0.0001). Unexpectedly, the relative performance of crossbred types did not differ importantly between production systems. White Dorper × Romanov crossbred ewes had numerical advantages in productivity in each system; however, differences between ewe types were not significant. In the extensive system, without labor and shelter at lambing or supplemental feed until weaning, 3-yr-old crossbred ewes of all types averaged 1.78 lambs marketed per ewe lambing, and 40% of the ewes that gave birth to triplets weaned their entire litters. These results document that prolific sheep and extensive systems can be successfully combined if appropriate crossbred types are used.     

Feed efficiency, growth rates, body composition, milk production and milk composition of Targhee sheep selected for increased weaning weight

Lactation and growth of three contemporary lines of grade Targhee sheep developed from the same genetic base were characterized by three experiments performed over a period of 2 yr. Two lines (HW and DH) had been selected for 120-d weaning weights for 24 yr prior to beginning these experiments. A third line (C) was a randomly selected control. Year I experiment contrasted 10 DH with 7 C ram lambs fed to 58 kg. Year II experiments utilized 9 C, 14 DH and 10 HW ram lambs and 11 ewes suckling twins from each line. All Year II ram lambs were born and weaned as twins, then fed to 50 kg. Mature DH and HW ewes were heavier (P less than .05) than C ewes (65.2 and 68.8 vs 54.9 kg), and the DH and HW lambs grew faster than C lambs both before (P less than .05) and after weaning (P less than .05). While both DH and HW lambs drank more milk (2,419 and 2,368 vs 2,059 g X d-1 X pair-1; P less than .10) only HW ewes showed a trend towards greater potential milk production than controls (HW = 2,774 vs C = 2,155 g X d-1 X ewe-1 P less than .12). The HW lambs tended to be leaner than C lambs (P less than .05), but DH lambs did not differ from either line. Lambs from DH and HW lines required less post-weaning feed (121.9 and 129.3 vs 152.0 kg P less than .05) and exhibited 17 and 16% greater weight per day of age at 50 kg than controls (P less than .05). The DH line displayed lower feed: gain ratios than controls in both post-weaning trials (6.68 vs 7.30 to 58 kg; 5.83 vs 6.24 at 50 kg; P = .06).     

Performance of hair sheep composite breeds: resistance of lambs to Haemonchus contortus

This study was designed to evaluate breed differences in resistance to Haemonchus contortus in lambs. A total of 181 ewe lambs representing crossbred Dorsets (DO) and Dorpers (DP; out of 1/2-Dorset, 1/4-Rambouillet, 1/4-Finnsheep ewes) and straight-bred Katahdins (KT) were evaluated over 3 yr. An additional 144 DO, DP, KT, and Barbados Blackbelly x St. Croix (HH) wethers were evaluated over 2 yr. Lambs were weaned at 60 to 90 d of age. After deworming at about 4 mo of age, ewe lambs received approximately 10,000 infective larvae and were evaluated for parasite resistance in drylot, whereas wethers were evaluated on pasture under conditions of natural infection. Each sex was analyzed separately. Egg counts per gram of feces (FEC), log-transformed FEC (LFEC), packed cell volumes (%), and body weights (kg) measured at 3, 4, 5, and 6 wk after deworming and reinfection were analyzed. Breed influenced all traits (P < 0.05) except BW in ewe lambs and PCV in wethers. Year and week influenced (P < 0.05) all traits. At most times, DP had the highest FEC, DO had the lowest PCV, and KT and HH had lower FEC and higher PCV than either DO or DP. Clearly, Dorper sheep were not more resistant to parasites than DO, but they were able to cope with infection better by maintaining similar or higher (P < 0.05) PCV and similar BW. Katahdin and HH were more resistant, with lower FEC (P < 0.05) than DO or DP. Breed differences were more apparent when infection levels were higher; DO and DP were less affected when infection levels were low and when animals were on a better plane of nutrition. Caribbean hair sheep originated in hot, humid regions of West Africa. They and the derivative Katahdin breed seem relatively resistant to parasitism. The Dorper, in contrast, was developed in more arid regions and exhibited little parasite resistance.     

Flock dynamics of desert Barki sheep in relation to age structure

Reproduction data of 8689 ewe records spread over 40 years (from 1960 to 2000) representing 2952 breeding Barki ewes were used in this study. The flock belonged to the Desert Research Center in Egypt. Flock dynamics of nine age groups (2–10 yrs) were assessed. Two parameters were used to evaluate flock dynamics, net reproduction rate (R_o) (number of ewe- lambs reaching joining age and produced by each ewe during its lifetime in the flock) and intrinsic rate of increase (r_m) (flock growth when no resource is limiting). Age of ewe had a highly significant (P < 0.01) effect on number of ewes lambing per ewe joined (E_PJ), number of lambs born per ewe joined (L_BJ), number of lambs weaned per ewe joined (L_WJ) and number of ewe lambs reaching joining age per ewe joined (L_EJ.J). All estimates tended to increase with dams age up to four years and decreased thereafter. The results of R_o and r_m showed that the studied flock must consist of 5 age groups to maintain its size and replace itself. It may be recommended to cull the breeding ewe at the age of 6 years to accelerate genetic improvement.     

Growth hormone, insulin, prolactin and glucose levels in ewe and ram lambs during normal and compensatory growth

Two trials were conducted to determine the effect of compensatory growth on plasma glucose and serum growth hormone (GH), prolactin (PRL) and insulin concentrations in lambs. The trials consisted of a normal growth (NG) period (4 to 7 mo of age), a restricted feed/weight loss period and a compensatory growth (CG) period. The lambs in Trial 1 were 13 mo of age and in Trial 2, 11 mo of age at the start of the respective CG periods. Compensatory growth rate was 61 to 67% greater than NG rate in Trial 1 and 2, respectively. Twenty-four hour blood collections were performed during NG and CG in each trial. Normal growth blood collection for Trial 1 was performed in April (ram, n = 7; ewe, n = 6) and the CG blood collection in November (ram, n = 6; ewe, n = 6) while for Trial 2 blood collection dates were November (ram, n = 6; ewe n = 6) and March (ram, n = 4; ewe, n = 5). Trial 1 ram lambs had lower plasma glucose concentrations during CG than during NG while plasma glucose concentration was not altered in ewe lambs. Type of growth had no effect on plasma glucose in Trial 2. There was a type of growth by sex interaction for insulin in both Trial 1 and Trial 2. Insulin concentration decreased during CG in ram lambs but remained unchanged (Trial 1) or increased in ewe lambs (Trial 2) during CG. The effect of CG on PRL concentration in Trial 1 was confounded by photoperiod and the only effect in Trial 2 was a small decrease in the amplitude of PRL peaks during CG. The overall mean GH concentration (GHmn) was increased (P less than 0.01) two fold during CG in Trial 1. This effect was also seen in Trial 2 but the increase was sex dependent (P less than 0.005) with the effect of CG on GHmn in ram lambs being six times that seen in ewe lambs. The GH profile characteristics responsible for the increase in GHmn during CG differed between sexes and trials.     

Winter-feeding systems for gestating sheep I. Effects on pre- and postpartum ewe performance and lamb progeny preweaning performance

Mature pregnant crossbred ewes (n = 90) were used in a randomized complete block design and assigned to 1 of 3 winter-feeding systems differing in primary feed source: haylage (HL), limit-fed corn (CN), or limit-fed dried distillers grains (DDGS). Effects of these winter-feeding strategies on ewe and lamb performance were determined. Diets were formulated to meet or exceed NRC (1985) nutrient requirements during gestation and were fed from about d 60 of gestation until parturition. All ewes were fed a common diet postpartum. Every 2 wk during gestation, BW and BCS were collected and diets were adjusted to maintain similar BW gain for ewes fed CN and DDGS vs. HL. At 80 and 122 d of gestation, jugular blood samples were collected at 0, 3, 6, and 9 h postfeeding to measure plasma glucose, insulin, NEFA, and blood urea nitrogen concentrations. At birth, 6 lambs per treatment were killed to measure body composition. At 28 ± 2 d postpartum, milk yield was measured. Lambs were weaned at 61 ± 4 d of age. During mid gestation (d 60 to 115), BW gain of ewes was similar among treatments; however, at d 115 of gestation ewes fed HL had a smaller (P = 0.04) BCS than ewes fed DDGS or CN. Plasma glucose concentrations were greater (P ≤ 0.004) in ewes fed CN than in those fed HL or DDGS just before feeding on d 80 and 122 of gestation, whereas ewes fed DDGS vs. CN or HL had greater (P ≤ 0.04) plasma insulin concentrations at 3 h postfeeding. At parturition, ewe BW was greatest for DDGS, least for HL, and intermediate for CN (P ≤ 0.003). Ewes fed CN and DDGS had greater BCS at parturition than those fed HL, but by weaning, ewes fed DDGS had greater BCS (P ≤ 0.05) than those fed CN or HL. Birth BW tended (P = 0.09) to be heavier for lambs from ewes fed CN and DDGS than from those fed HL prepartum, but there was no difference (P = 0.19) due to ewe gestation diet on lamb BW at weaning. At birth, lamb muscle, bone, organ, and fat measures were not affected (P > 0.13) by treatment. Ewe milk production and lamb preweaning ADG were also similar (P > 0.44) among treatments. Prepartum dam winter feed source did not have detrimental effects on pre- or postpartum ewe performance, but altered prepartum maternal nutrient supply during gestation, which affected birth weight but not preweaning growth or mortality.