Lamb Growth Traits Research Articles

Effect of Gender on Growth and Carcass Traits of Romney Marsh Lambs

The aim of present study was to assess the effect of the gender on growth and carcass traits in lambs of the Romney Marsh breed. The experimental animals were male lambs (n = 12) and female lambs (n = 12) of the Romney Marsh breed. All lambs were twins and all their mothers were on the second parity. With regard to body weights and daily gains (DGs), the gender had a significant effect only on birth weight and DG from birth to the slaughter, while in all monitored intervals the DGs were higher in male lambs (MLs). The lamb gender did not have a significant effect on the easy of lambing, body condition score, depth of musculus longissimus lumborum et thoracis (DMLLT) and thickness of backfat (TBF). However, values for DMLLT and TBF were higher in female lambs (FLs), which in case of DMLLT was not expected. Regarding the carcass traits, the gender had a significant effect only on the weights of kidney, kidney fat, leg and shoulder and on the proportions of kidney fat and shoulder. Interestingly, the gender had no significant effect on the conformation and fatness, while slightly better carcass conformation and slightly higher fatness were found in FLs. It can be concluded that FLs of the Romney Marsh breed showed comparable values for both the growth and carcass traits with MLs. Moreover, a slightly higher fatness of FLs is a prerequisite for better juiciness and tenderness of their meat, when this fact can be considered as a benefit in the marketing.

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.

The effect of genotype and sex on growth and carcass traits of lambs

Submitted 2020-07-24 | Accepted 2020-08-31 | Available 2020-12-01 https://doi.org/10.15414/afz.2020.23.mi-fpap.276-281 The objective of the present study was to investigate the effect of genotype and sex on growth and carcass traits of grazing lambs. A total of 32 lambs (16 Improved Jezersko-Solcava - JSR and 16 crossbreds with Texel - JSRT, 8 males and 8 females within each genotype) were included in the study. The lambs were grazed together with their dams from the beginning of the grazing period and had free access to commercial concentrate from the age of 10 days. Lambs were weaned at the average body weight of 22.9 kg. Feeding with a concentrate was finished when lambs achieved 35 kg of body weight and were slaughtered. Daily gains from birth to slaughter and from weaning to slaughter were calculated. Several carcass traits were determined. JSRT lambs had significantly higher daily gain from birth to slaughter, hot and cold carcass weights, and dressing percentages compared to JSR lambs. Carcass conformation was higher in JSRT than JSR carcasses. Also, carcasses of JSRT were shorter and wider than JSR carcasses. Rib eye muscle areas of JSRT lambs were significantly larger, and the colour was significantly lighter. Males had significantly higher average daily gain from birth to slaughter and from weaning to slaughter than females. Females had higher dressing percentages and subcutaneous and internal fatness scores than males. Females had significantly higher amount of kidney fat. The colour of males’ meat was significantly lighter than that of females. Crossbreeding with Texel rams improved growth and carcass traits of lambs, and males had better growth performance and several carcass traits than females. Keywords: lambs, commercial crossbreeding, sex, growth, carcass trait References Blasco, M. et al. (2019). Effect of Texel crossbreeding on productive traits, carcass and meat quality of Segurena lambs. Journal of the Science of Food and Agriculture, 99, 3335-3342. https://doi.org/10.1002/jsfa.9549 Cardoso, M. T. M. et al. (2013). Performance and carcass quality in three genetic groups of sheep in Brazil. Revista Brasileira de Zootecnia, 42(10), 734-742. https://doi.org/10.1590/S1516-35982013001000007 Claffey, N. A. et al. (2018). Effect of breed and castration on production and carcass traits of male lambs following an intensive finishing period. Translational Animal Science, 2, 407-418. https://doi.org/10.1093/tas/txy070 Do Prado Paim, T. et al. (2013). Performance, survivability and carcass traits of crossbred lambs from five paternal breeds with local hair breed Santa Ines ewes. Small Ruminant Research, 112, 28-34. https://doi.org/10.1016/j.smallrumres.2012.12.024 Facciolongo, A. M. et al. (2018). Effect of diet lipid source (linseed vs. soybean) and gender on performance, meat quality and intramuscular fatty acid composition in fattening lambs. Small Ruminant Research, 159, 11-17. https://doi.org/10.1016/j.smallrumres.2017.11.015 Freitas-de-Melo, A. et al. (2019). Behavioral pattern in Texel x Corriedale terminal crossbreeding: Maternal behavior score at birth, lambs’ feeding behaviors, and behavioral responses of lambs to abrupt weaning. Journal of Veterinary Behavior, 30, 9-15. https://doi.org/10.1016/j.jveb.2018.10.007 Nunes, I. A. et al. (2019). Performance, carcass characteristics, and centesimal composition of meat from Santa Ines lambs and Texel crossbred lambs (Santa Ines × Texel). Canadian Journal of Animal Science, 99(2), 228-236. https://doi.org/10.1139/cjas-2016-0231 Perez, P. et al. (2007). Gender and slaughter weight effects on carcass quality traits of suckling lambs from four different genotypes. Small Ruminant Research, 70, 124-130. https://doi.org/10.1016/j.smallrumres.2006.01.013 SAS. (2014). SAS/STAT® 13.2 User’s Guide. SAS Institute Inc., Cary, NC, USA. Scales, G. H. et al. (2000). Effect of sire breed on growth, carcass, and wool characteristics of lambs born to Merino ewes in New Zealand. New Zealand Journal of Agricultural Research, 43(1), 93-100. https://doi.org/10.1080/00288233.2000.9513412

96 Cover Crop Grazing and Backgrounding on Carcass Quality

Abstract Integration of sheep into cropping systems via cover crop grazing leases has potential to benefit sheep producers with a source of inexpensive, high quality forage. We examined this potential by comparing lamb growth and carcass traits of four rearing systems: grain-finished control (GR), cover crop brassica-finished (CCB), cover crop mixture-finished (CCM), and background on brassica and finished on grain (BK-GR). Dorset x Polypay lambs (n = 60; 3 pens or pastures, 5 lambs each) were blocked by body weight and randomly assigned to treatment. All diets were provided to maximize voluntary dry matter intake. Lambs were harvested after 6 wks of feeding for GR and 8 wks for CCB, CCM and BK-GR (BK-GR = 4 wks brassica then 4 wks grain). Grain-fed lambs (GR and BK-GR, 442 g/d) grew faster than pasture-fed lambs (CCB and CCM, 152 g/d) prior to harvest (Table 1, P &amp;lt; 0.01) and attained greater body mass (HCW), muscling (LEA, EMD), fatness (BF, BWF) and yield grade (all P &amp;lt; 0.05). Growth of pasture-fed lambs declined 38% over time (247 wk 1–4 vs. 152 g/d wk5-8; P &amp;lt; 0.05). Pasture-fed lambs were leaner than grain-fed lambs (BF, yield grade; P &amp;lt; 0.01), yet attained a yield grade 2 average. Background lambs (BK-GR) exhibited a 107% increase in growth when fed grain (232 g/d pasture vs. 481 g/d grain, P &amp;lt; 0.01) and were fatter (BF, P &amp;lt; 0.05) yet had reduced eye muscle depth (P &amp;lt; 0.01) at harvest than GR lambs. Lambs did not differ in growth or any carcass measurement according to pasture type (CCB vs. CCM). We conclude that 8 wks of cover crop finishing produced acceptable carcass weight and finish. Backgrounding on cover crops followed by 4 wks of grain finishing results in marked compensatory gain with lambs achieving the same carcass size and similar qualities to lambs fed only grain.

Feeding Tall Fescue Seed during Mid and Late Gestation Influences Subsequent Postnatal Growth, Puberty, and Carcass Quality of Offspring.

Simple SummaryLittle is known about the exposure to ergot alkaloids, a class of mycotoxins, during fetal development on subsequent post-weaning growth, puberty, and carcass quality of the offspring. This study evaluated post-weaning growth, puberty attainment, and carcass quality in lambs that were exposed to endophyte-infected or endophyte-free tall fescue seed during different stages of gestation. Puberty was delayed in ewe lambs that were exposed to ergot alkaloids during late gestation. Ergot alkaloid exposure had minor effects on growth and carcass traits in wether lambs fed high concentrates but alterations in fat deposition and tenderness were observed. These results indicate that exposure to ergot alkaloids during gestation does alter subsequent post-weaning puberty attainment and body composition of the offspring.Weaned lambs (n = 82), born to ewes fed endophyte-free (E−) or endophyte-infected (E+; 1.77 mg hd−1 d−1 ergovaline + ergovalinine) tall fescue seed from d 35 to 85 of gestation (MID) and/or d 86 of gestation to parturition (LATE), were used to examine how ergot alkaloid exposure during fetal development altered subsequent puberty attainment or carcass quality. Lambs were weaned at 75 d of age and separated by sex to assess puberty in ewe lambs (n = 39) and to evaluate growth, carcass and meat quality in wethers (n = 43). Data were analyzed with maternal fescue treatment, stage of gestation, and two-way interaction in the model. Age at puberty tended (P = 0.06) to be longer for ewe lambs born to dams fed E+ fescue during LATE gestation versus those fed E−. Post-weaning average daily gain tended to be higher (P = 0.07) for wether lambs born to dams fed E+ fescue seed during MID gestation compared to E−. Exposure to ergot alkaloids during fetal growth altered (P < 0.10) longissimus muscle weight and color, lipid deposition, fatty acid composition, and shear force values of semimembranosus muscle in wether lambs. These results indicate that exposure to ergot alkaloids in utero does alter subsequent post-weaning puberty attainment and body composition in offspring.

Estimation of genetic parameters and selection response for reproductive and growth traits in Rideau-Arcott sheep

The goal of this study was to estimate genetic parameters and predict direct and correlated response to selection for lamb growth traits and ewe reproductive traits, based on single-trait selection or combining multiple traits in an optimum index that targets total litter post-weaning weight in the first lambing as the main selection goal. Heritability estimates ranged from 0.04 to 0.19. Genetic correlations between growth and reproductive traits ranged from −0.24 to 0.15. The indirect response to selection for reproductive traits in later lambings, by selecting on first lambing performance, was 11%–25% greater than direct selection. The response to indirect selection for composite reproductive traits, i.e., total weaning weight or total post-weaning weight, by selecting on individual lamb weaning weight or post-weaning weight was 1%–69% greater than direct selection, but it was accompanied by a negative response on litter size. However, combining alternate growth and reproductive traits in optimum selection index resulted in correlated response of up to 96% greater than direct selection response for reproductive traits without a negative response on litter size. Therefore, multiple trait selection using an index of component traits was more effective than direct selection for a composite trait.

The influence of lamb rearing system on ewe milk and lamb growth traits in dairy sheep

1. Antonič J., Tančin V., Uhrinčať M., Mačuhová L., Mačuhová J., Jackuliaková L., 2013. The effect of exogenous oxytocin on milkability and milk composition in ewes differed in milk flow pattern. Small Rumin. Res. 113, 254–257, https://doi.org/10.1016/j.smal.... CrossRef Google Scholar

The size of fat tail does not have an effect on growth performance and carcass characteristics in Lori-Bakhtiari lambs

• Fat tail size has a wide variety in Lori- Bakhtiari sheep breed. • Fat tail size had no effect on feed intake and feed conversion ratio. • Fat tail size had no effect on growth traits of Lori-Bakhtiari lambs breed. • The small size of fat tail can reduce the feeding period and increase the profit. • Fat tail size affects the distribution of fat deposition in other parts of the body. This study compared the growth performance and carcass characteristics of Lori-Bakhtiari lambs with three types of fat tail. Thirty lambs were divided into three groups according to the size of their fat tail: big (BF), medium (MF), and small (SF) fat tail. The weaned lambs were finished over 100 days, and their average daily gain (ADG) and feed intake (FI) were measured, and the feed conversion ratio (FCR) was calculated accordingly. At the end of experiment, all lambs were slaughtered and the fat surrounding their intestines and abdomen as visceral fat (VF) and their kidneys and pelvic fat (KPF) as internal fat were weighed. The hot carcasses were weighed and the fat tails were cut and weighed for each carcass. Finally, the subcutaneous fats (SCF) related to the left side of the carcasses were dissected and weighed. ADG, FI, and FCR were not affected by the size of the fat tail. Final body weights of BF, MF, and SF were 59.0 ± 0.71, 58.7 ± 0.68, and 59.8 ± 0.70 kg, respectively (P >0.05). The weight of the fat tail was 8.7 ± 0.29, 7.6 ± 0.28, and 6.3 ± 0.28 kg for BF, MF, and SF lambs, respectively ( P < 0.0001). An inverse relationship was found between the weight of the fat tail and other fat components of the carcass. The weight of the SCF differed among the lambs ( P < 0.05), and was 3566±387.7, 4395±372.1, and 4743±383.4 g in BF, MF, and SF lambs, respectively. Additionally, the KPF weight was 179±54.8, 268±52.6, 415±54.2 g for BF, MF, and SF lambs, respectively ( P < 0.05). Lambs with SF had the heaviest VF followed by MF and BF (1086±96.0, 629±93.2, and 418±97.1 g, respectively; P < 0 .0003). Total carcass fat and total body fat were similar among the lambs, while the carcass weight without fat tail (CWFT) and carcass weight without fat tail and SCF (NCW) were greater in SF lambs than in MF and BF lambs ( P <0.05). It can be concluded that the lambs with SFs are not superior to those with BFs in terms of FI, weight gain, or FCR, but lambs with SF reached the desired body condition score for slaughtering sooner than those with BF, which in turn prevents the storage of more fat in the other fat depots, especially VF, and reduces the length of the finishing period, thus reducing the production costs.

Analysis of Candidate Genes for Growth and Milk Performance Traits in the Egyptian Barki Sheep.

Simple SummaryThe Barki sheep breed is one of the main sheep breeds in Egypt, and it is well adapted to the harsh desert conditions in the Mediterranean zone. Growth performance has an important role regarding the supply of red meat for human consumption. In addition, milk production is very important to adequately feed newborn lambs and prevent them from starvation. In this study, segregating single nucleotide polymorphisms (SNP) were identified in the coding regions of eight candidate genes for growth and milk traits by direct sequencing. Subsequently, a population of Barki ewes and lambs was screened for these SNPs, and associations between genotypes and traits of interest were assessed. Out of the candidate genes, SNPs of LEP, STAT5A, PRL, and GHRHR were significantly associated with phenotypes. This study provides first insights into the genetics of milk and growth traits in the Barki sheep. The findings concluded that LEP, STAT5A, PRL, and GHRHR might be regarded as candidate genes to improve the Egyptian Barki sheep breed. The most common sheep breeds of Egypt are Ossimi, Rahmani, and Barki breeds. The latter one is well adapted to the challenging desert environment, characterized by food shortage and a high temperature fluctuation. Growth performance of Barki sheep has an important economic value in terms of minimizing the shortage of mutton meat in Egypt. Further, milk production is of great importance for feeding newborn lambs. Eight candidate genes, recently associated with production traits in different breeds, were used to study the effect of genotype on lamb growth and ewe milk traits. The examined genes were LEP, IGF1, DGAT1, STAT5A, PRL, CSN1S2, GHR, and GHRHR, of which one representative single nucleotide polymorphism (SNP) located in the coding region was selected for genotyping. Data from 251 Barki sheep were used in this study. Association analysis between SNPs and lamb growth traits identified rs420693815 of the LEP gene to be significantly associated with weaning weight and average daily gain. In ewes, significant effects on milk yield and composition have been estimated for LEP (rs420693815), STAT5A (rs161082816), PRL (rs422713690), and GHRHR (rs414991449). The results indicated that these genes might be considered as interesting candidates for further investigations to improve growth and milk performance in Barki sheep.

Serum metabolomic fingerprints of lambs fed chitosan and its association with performance and meat quality traits

Chitosan (CHI) is a natural biopolymer with antimicrobial, anti-inflammatory, antioxidant and digestive modulatory effects, which can be used in the ruminant diet to replace antibiotics. The aim of this study was to evaluate the effects of CHI on lamb growth traits, nutrients digestibility, muscle and fatty deposition, meat fatty acid (FA) profile, meat quality traits and serum metabolome. Thirty 30-month-old male lambs, half Suffolk and half Dorper, with an average BW of 21.65 ± 0.86 kg, were fed in a feedlot system for a total of 70 days. The lambs were separated into two groups according to the diet: the control (CON) group which received the basal diet and the CHI group which received the basal diet with the addition of CHI as 2 g/kg of DM in the diet. Lambs supplemented with CHI had a greater (P< 0.05) final BW, DM intake, final body metabolic weight (P< 0.05) and lower residual feed intake than the CON group. Animals fed CHI had a greater (P< 0.05) starch digestibility at 14 and 28 days, average daily gain at 14, 42 and 56 days, greater feed efficiency at 28 days and feed conversation at 14 and 42 days in feedlot. Most of the carcass traits were not affected (P> 0.05) by the treatment; however, the CHI supplementation improved (P< 0.05) dressing and longissimus muscle area. The treatments had no effect (P> 0.05) on the meat colour and other quality measurements. Meat from the CHI-fed lambs had a greater concentration (P< 0.05) of oleic-cis-9 acid, linoleic acid, linolenic-trans-6 acid, arachidonic acid and eicosapentaenoic acid. According to the variable importance in projection score, the most important metabolites to differentiate between the CON and the CHI group were hippurate, acetate, hypoxanthine, arginine, malonate, creatine, choline, myo-inositol, 2-oxoglutarate, alanine, glycerol, carnosine, histidine, glutamate and 3-hydroxyisobutyrate. Similarly, fold change (FC) analysis highlighted succinate (FC = 1.53), arginine (FC = 1.51), hippurate (FC = 0.68), myo-inositol (FC = 1.48), hypoxanthine (FC = 1.45), acetate (FC = 0.73) and malonate (FC = 1.35) as metabolites significantly different between groups. In conclusion, the present data showed that CHI changes the muscle metabolism improving muscle mass deposition, the lamb’s performance and carcass dressing. In addition, CHI led to an alteration in the FA metabolism, changes in the meat FA profile and improvements in meat quality.

PSX-19 Factors affecting growth and carcass trait performance of Canadian heavy lambs

Abstract The profitability of meat lamb production is strongly dependent on growth and carcass trait performance of market lambs. The objective of this research was to test the significance of non-genetic factors on growth, ultrasound, and carcass traits of Canadian heavy lambs. Hot carcass weight (HCW, kg), fat depth at the GR site (FATGR, mm), average carcass conformation score (CONF, points), and total carcass value (PRICE, $CAD) were measured for 8,865 purebred lambs marketed through Quebec’s Heavy Lamb Sales Agency. Corresponding management information and growth trait records for over 19,000 animals with carcass records and their relatives were extracted from the Canadian Sheep Genetic Evaluation System. Single-trait mixed linear models in SAS were used to test the significance (P &amp;lt; 0.05) of various non-genetic effects, after a Scheffe adjustment for multiple comparisons. All models included categorical fixed effects of sex (male or female), breed (Hampshire, HA; Suffolk, SU; Canadian Arcott, CD; Polled Dorset, DP; Rideau Arcott, RI; Polypay, PO), dam age at parity (1 to 7+ years), and birth and rearing type (born as single, twin, or triplet and more, and reared as single or multiple), and a random effect of contemporary group. Linear covariates of slaughter age or carcass weight were included in the carcass trait models, while a scanning weight covariate was used for ultrasound trait models. Male lambs were found to be significantly heavier during growth, had greater HCW and PRICE, and lower FATGR and CONF than female lambs. As expected, terminal breeds (HA, SU, CD) tended to have greater growth, greater HCW and PRICE, and lower FATGR than maternal (DP, RI, RV, PO) breeds. This information could be utilized by Canadian sheep producers to manage their flocks to maximize the revenue of lambs marketed through price grid classification systems.

Evaluation of selection program by assessing the genetic diversity and inbreeding effects on Nellore sheep growth through pedigree analysis.

ObjectiveThe main objectives of the present study were to assess the genetic diversity, population structure and to appraise the efficiency of ongoing selective breeding program in the closed nucleus herd of Nellore sheep through pedigree analysis.MethodsInformation utilized in the study was collected from the pedigree records of Livestock Research Station, Palamaner during the period from 1989 to 2016. Genealogical parameters like generation interval, pedigree completeness, inbreeding level, average relatedness among the animals and genetic conservation index were estimated based on gene origin probabilities. Lambs born during 2012 and 2016 were considered as reference population. Two animal models either with the use of Fi or ΔFi as linear co-variables were evaluated to know the effects of inbreeding on the growth traits of Nellore sheep.ResultsAverage generation interval and realized effective population size for the reference cohort were estimated as 3.38±0.10 and 91.56±1.58, respectively and the average inbreeding coefficient for reference population was 3.32%. Similarly, the effective number of founders, ancestors and founder genome equivalent of the reference population were observed as 47, 37, and 22.48, respectively. Fifty per cent of the genetic variability was explained by 14 influential ancestors in the reference cohort. The ratio fe/fa obtained in the study was 1.21, which is an indicator of bottlenecks in the population. The number of equivalent generations obtained in the study was 4.23 and this estimate suggested the fair depth of the pedigree.ConclusionStudy suggested that the population had decent levels of genetic diversity and a non-significant influence of inbreeding coefficient on growth traits of Nellore lambs. However, small portion of genetic diversity was lost due to a disproportionate contribution of founders and bottlenecks. Hence, breeding strategies which improve the genetic gain, widens the selection process and with optimum levels of inbreeding are recommended for the herd.

Correlations between growth and wool quality traits of genetically divergent Australian lambs in response to canola or flaxseed oil supplementation.

The correlations between growth and wool traits in response to canola and flaxseed oil supplementation were evaluated in Australian prime lambs. Sixty dual-purpose prime lambs including purebred Merino and crossbred lambs were allocated to one of five treatments of lucerne hay basal diet supplemented with isocaloric and isonitrogenous wheat-based pellets. Treatments were: no oil inclusion (Control); 2.5% canola oil; 5% canola oil; 2.5% flaxseed oil and 5% flaxseed oil, with lamb groups balanced by breed and gender. Each lamb was daily supplemented with 1kg of pellets and had free access to lucerne hay and water throughout the 7-week feeding trial, after a 3-week adaptation. Individual animal basal and supplementary pellet feed intakes were recorded daily, while body conformation traits, body condition scores and liveweights were measured on days 0, 21, 35 and 49. The lambs were dye-banded on the mid-side and shorn before commencing the feeding trial and mid-side wool samples were collected from the same dye-banded area of each lamb at the end of the experiment. Correlations between wool quality traits and lamb performance were non-significant (P>0.05). Oil supplementation had no detrimental effect on lamb growth and wool quality traits (P > 0.05). Gender significantly affected wither height gain and fibre diameter. There were significant interactions between oil supplementation and lamb breed on chest girth. The correlations between clean fleece yield (CFY) and other wool quality traits were moderate ranging from 0.29 to 0.55. Moderate to high correlations between fibre diameter (FD) and other wool quality traits were detected (0.46–0.99) with the strongest relationship between FD and wool spinning fineness (SF). The relationship between CFY and wool comfort factor (CF) were positive, while negative relationships between CFY and the others were observed. A combination of 5% oil supplementation and genetics is an effective and strategic management tool for enhancing feed efficiency and growth performance without negative effects on wool quality in dual-purpose lamb production. This is a good outcome for dual-purpose sheep farmers. It essentially means the absorbed nutrients in supplemented lambs yielded good growth performance without any detrimental impact on wool quality; a win-win case of nutrient partitioning into the synthesis of muscle and wool without compromising either traits.

Rambouillet and Romanov reciprocal breed effects on survival and growth traits of F1 lambs and on reproductive traits of F1 ewes.

Objectives were to estimate reciprocal effects of Romanov and Rambouillet breeds on survival, growth, and reproductive traits of F1 progeny and direct breed effects (Suffolk and Composite - ½ Columbia, ¼ Hampshire, and ¼ Suffolk) on survival and growth traits of the subsequent terminally sired lambs. Mature Rambouillet ewes (n = 243) were exposed to 20 Romanov rams over two seasons producing 621 lambs for evaluation of growth and survival traits with 274 F1 ewes being evaluated for reproduction traits through 4 yr of age. Similarly, mature Romanov ewes (n = 116) were exposed to 20 Rambouillet rams producing 601 lambs for evaluation of growth and survival traits with 176 F1 ewes being evaluated for reproduction traits through 4 yr of age. A total of 433 of those F1 ewes produced 3,431 lambs (1,552 litters) from 1,634 exposures to terminal sires over 4 yr. Terminal sires consisted of 38 Suffolk and 44 Composite rams. Reciprocal crossbred ewe lambs were produced from dramatically different uterine and neonatal environments, with litter size at birth from Romanov dams exceeding those from Rambouillet dams by 1.52 lambs (P < 0.001) and birth weight of lambs from Romanov dams averaged 3.41 kg compared with 4.26 kg from Rambouillet dams. Differences in BW were still evident at 140 d (P < 0.001) for dam-reared lambs. However, reciprocal ewe first breeding BW of both types were similar (P = 0.38). Minimal differences were observed in performance of reciprocal cross ewes through 4 yr for productivity, longevity, or progeny growth and survival. One exception was BW at 140 d where an interaction of dam breed with terminal sire breed reached significance for both dam-reared (P = 0.05) and nursery-reared (P = 0.02) lambs. This interaction was due to the lower weight of Composite-sired lambs out of reciprocal cross ewes born from Rambouillet dams. Composite rams increased number born (P < 0.01) and number weaned (P < 0.05) of the reciprocal cross ewes. Suffolk rams increased (P < 0.001) BW and growth rates from birth to 140 d of terminal progeny. Thus, there were little cumulative differences accrued over the 4 yr and no differences were detected for cumulative kilogram of lamb generated at 140 d per ewe exposed. The practical outcome of this evaluation was that performance levels of both types of Romanov crossbred ewes was similar allowing the industry to produce the desired crossbred ewes without needing large purebred ewe flocks of the less numerous Romanov breed.

Genetic and non-genetic factors influencing the live weight of artificially-reared lambs

The Spooner Agricultural Research Station (ARS) of the University of Wisconsin-Madison housed the only dairy sheep research flock in North America at the time of its closing in 2016. Multiple experiments conducted at the Spooner ARS determined that raising dairy lambs on milk replacer can be profitable and has since become a common practice in many U.S. dairy flocks. While the genetic basis of early growth traits in naturally-reared lambs has been extensively researched, little is known about the extent to which direct and maternal additive effects influence these traits in artificially-reared animals. The traits analyzed were birth weight (BW0) and 30 d adjusted weaning weight (BW30). Univariate models first determined the significant non-additive genetic effects on BW traits. Lacaune breed composition negatively affected (P < 0.01) both BW traits. Individual heterosis positively influenced (P ≤ 0.04) both BW traits, but only BW0 was positively influenced by maternal heterosis (P < 0.001). A bivariate model was used to estimate genetic and non-genetic relationships among BW0 and BW30. The estimated direct heritabilities of BW0 and BW30 were 0.27 ± 0.04 and 0.39 ± 0.05, respectively. The higher than generally reported heritability for BW30 was likely due to a decrease in environmental variation associated with artificial rearing. Lamb BW traits were estimated to be highly phenotypically (0.54 ± 0.02) and genetically (0.63 ± 0.07) correlated. Additive maternal genetic effects explained a substantial proportion of the phenotypic variation of BW0 (0.25 ± 0.02). Although only artificially-reared lambs were included in the analyses of BW30, additive maternal genetic effects were non-zero (0.13 ± 0.02). The sale of market lambs represents a significant source of revenue for U.S. dairy sheep producers, and knowledge of the factors affecting lamb performance has important economic implications.

Effect of crossbreeding on growth, feed efficiency, carcass characteristics and sensory traits of lambs from Lori-Bakhtiari and Romanov breeds

This study compares the growth performance, carcass characteristics, and sensory traits of pure lambs of Lori-Bakhtiari fat-tailed sheep (LL genotype) and their crosses with Romanov tailed sheep breed (RL genotype). After weaning, the average daily gain (ADG) and feed conversion ratio (FCR) of male lambs were recorded at a fattening period of 80 days. Twenty-three male lambs were slaughtered, and the left sides of the carcasses were separated into six pieces to determine the lean meat, bone, subcutaneous fat (SCF), and inter muscular fat (IMF). Genotypes had different ADG (LL: 296.50 ± 11.57 v. RL: 249.11 ± 12.92 g/day) and FCR (LL: 6.12 ± 0.26 v. RL: 6.98 ± 0.30) (P < 0.05). The fat-tail weight in the crossbred lambs was about 80% less, but the weights of SCF and IMF were 55% and 33% greater than the purebred lambs, respectively (P < 0.01); however, the difference in the back-fat thickness (12–13th rib) was not significant between the two genotypes (LL:4.29 ± 0.32 v. RL:4.62 ± 0.37 mm) (P = 0.41). While abdominal fat (AF) was 65% greater than that of the purebreds (P < 0.001), the total body fat in the crossbred lambs was about 34% less than the purebreds (P < 0.001); it had been displaced with about 23% more lean meat (P < 0.001). A trained panel evaluated the tenderness and flavor of the LL and RL meat through a sensory evaluation. Tenderness score (LL: 6.75 ± 0.94 v. RL: 5.16 ± 0.94) was significantly affected by the genotype (P < 0.01); however, the panelists could not detect a significant difference in flavor score between the two genotypes (LL: 7.01 ± 0.82 v. RL: 6.85 ± 0.82). It can be concluded that crossbreeding the indigenous Lori-Bakhtiari sheep with Romanov breed can significantly improve carcass traits and increase meat production. The present data showed that, even though crossbred lambs could not compete with purebred in terms of ADG, FCR, and tenderness, the lower total body fat in crossbred lambs (34%) compensated the inferior high fat in the Lori-Bakhtiari breed.

Genetic parameter estimates for growth traits in Katahdin sheep using different models

Se estimaron parámetros genéticos para características de crecimiento en corderos Katahdin, usando seis variantes del modelo animal. Se usó información de pesos al nacimiento (BW; n= 13,099), al destete ajustado a 75 d (WW; n= 11,509) y posdestete ajustado a 120 d (AW; n= 6,886) tomada durante 7 años (2004-2010) en 20 estados de la República Mexicana. Los análisis se hicieron ignorando o incluyendo efectos maternos. El modelo más sencillo incluyó el efecto genético aditivo directo como el único efecto aleatorio. El modelo más completo incluyó los efectos genéticos directo y materno, la covarianza entre ellos, y el efecto del ambiente permanente materno. Para seleccionar el mejor modelo se usó la prueba de razón de verosimilitud. Cuando los efectos maternos no fueron incluidos en el modelo, los estimadores de la heredabilidad directa y de la varianza genética directa resultaron sobreestimados. Las heredabilidades directas con el mejor modelo fueron 0.18 ± 0.03, 0.30 ± 0.04 y 0.20 ± 0.05 para BW, WW y AW, respectivamente. Las heredabilidades maternas también variaron dependiendo del modelo, de 0.05 a 0.23, 0.00 a 0.12, y 0.09 a 0.25 para BW, WW y AW. El ignorar los efectos maternos en el modelo resultaría en una evaluación genética equivocada para las características de crecimiento en borregos Katahdin.

Influence of distiller's dried grains with solubles on ram lamb growth and reproductive traits.

The hypothesis of this experiment was that increasing the inclusion level of distiller's dried grains with solubles (DDGS) in the diets would decrease semen quality but have no negative effects on growth performance. Following the removal of DDGS from the diet, it was hypothesized that the ram lambs would recover and become reproductively sound, independent of treatment. To test this hypothesis, Suffolk and Hampshire ram lambs (n = 112) were allocated to 4 treatments (n = 4 pens per treatment; 7 rams per pen) in a completely randomized design. Dietary treatments were 60% corn, 25% oats, and 15% commercial lamb pellet (CON), 15% of the ration as DDGS substituted for corn (% DM basis; 15DDGS), 30% of the ration as DDGS substituted for corn (% DM basis; 30DDGS), and 45% of the ration as DDGS substituted for corn (% DM basis; 45DDGS). Lambs were fed for 112 d on their respective treatment, after which they were placed on the CON ration until day 168. Lambs were weighed on consecutive d at the beginning (days 0 and 1) and end (days 167 and 168) of the study. Scrotal circumference was measured on all lambs on days 84, 112, 140, and 168. Semen samples were collected on a subset of 64 rams (4 rams per pen) to evaluate semen quality on days 84, 112, 140, and 168. Blood samples were collected on the same subset of rams every 14 d throughout the study. A quadratic effect on BW on day 112 and overall BW (P = 0.03 and P = 0.005, respectively), ADG on day 112 and overall ADG (P = 0.02 and P = 0.02, respectively), DMI (P = 0.007) on day 112, and a cubic effect (P = 0.05) for overall G:F were observed. Overall and day 168 scrotal circumference had a quadratic (P = 0.05) response. A linear increase in spermatozoa concentration on day 168 was observed (P = 0.03) as DDGS concentration increased in the treatment diets, although rams in this stage of the study were no longer receiving DDGS. Overall, testosterone concentrations exhibited a linear decrease (P = 0.005) as DDGS increased in the diet. The linear increase (P = 0.04) on day 168 in morphologically normal sperm as DDGS increased in the diets indicated that all rams, regardless of treatment, would have passed a reproductive soundness exam. In the current study, no negative effects were observed in lamb feedlot or reproductive traits due to increasing DDGS in the diet, indicating that DDGS may be included at levels up to 45% of growing lamb diets.

Growth, meat and feed efficiency traits of lambs born to ewes submitted to energy restriction during mid-gestation

The objective of this study was to evaluate the effects of the energy restriction of gestation of adult ewes from day 45 to day 115 on lamb live performance parameters, carcass and meat traits. In experiment I, dietary energy was restricted at 70% of the metabolizable energy (ME) requirements, after which ewes were re-fed ad libitum until lambing. In experiment II, dietary energy was restricted at 60% of the ME requirements, and ewes were re-fed to ME requirements until lambing. All ewes grazed together from the end of the restriction periods to weaning. Lambs were weaned and lot fed until slaughter. Feed intake, weight gain and feed efficiency were recorded, and body fat thickness and ribeye area (REA) were measured in the longissimus thoracis muscle. After slaughter, carcass weight and yield, fat depth, carcass and leg length, and frenched rack and leg weights and yields were determined. Muscle fiber type composition, Warner-Bratzler shear force, pH and color were determined in the longissimus lumborum muscle. In experiment I, energy restriction followed by ad libitum feeding affected lamb birth weight (P<0.05); however, no effects (P>0.05) were observed on later BW, REA, BF or carcass traits. Lambs born to non-restricted-fed ewes had higher (P<0.05) weight and yield of the frenched rack cut and their meat tended (P=0.11) to be tender compared with that of lambs from restricted ewes. The percentage of oxidative muscle fibers was lower for lambs born to non-restricted ewes (P<0.05); however, no effects of ewe treatment were observed on other muscle fiber types. For experiment II, energy restriction followed by ME requirements feeding, affected (P<0.01) pre-weaning live weight gain, weaning and final weights. Lambs from restricted ewes had higher (P<0.05) feed intake as % of leg weight and a trend to be less efficient (P=0.16) than lambs from unrestricted dams. Ribeye area and BF were not influenced by treatment. Treatment significantly affected slaughter weight, but had no effects on carcass yield and traits or on meat traits. The results obtained in both experiments indicate submitting ewes to energy restriction during gestation affects the performance of their progeny but the final outcome would depend on the ewe’s re-feeding level during late gestation and the capacity of the offspring to compensate the in utero restriction after birth.

Ground Juniperus pinchotii and urea in supplements fed to Rambouillet ewe lambs: I. Feedlot growth traits, blood serum parameters, and fecal characteristics.

Ground woody products and urea are low-cost roughage and N sources. Rambouillet ewe lambs ( = 48, 6 lambs/treatment; initial BW = 42 kg ± 3.8) were used to evaluate effects of using ground (juniper) and urea in supplements on feedlot lamb growth traits, blood serum parameters, and fecal characteristics. In a randomized complete block design (40 d), lambs were individually fed an ad libitum basal sorghum-Sudangrass hay diet, which was fed separate from 1 of 8 supplemental diets (6 lambs/diet; 533 g of supplement/d, as-fed basis). Treatment structure was a 4 × 2 factorial: 4 concentrations of ground juniper (JN: 15%, 30%, 45%, or 60% of DM) and 2 concentrations of urea (UR: 1 or 3% of DM). Lamb growth traits were evaluated on d 0, 5, 12, 19, 26, 33, and 40; blood serum was evaluated on d 6 to 8, 20 to 22, and 34 (at h 3 and 6), and feces was evaluated on d 35. Compared to lambs fed all of the other treatments, lambs fed JN60UR1 or JN60UR3 had reduced supplement DMI (negative quadratic, = 0.007). Hay and total DMI were variable across day (JN × UR × day, < 0.04), but no linear or quadratic trends were detected ( > 0.10). A JN × day interaction was detected ( < 0.001) for lamb BW and the JN × day negative quadratic trend ( = 0.02) for BW was influenced by reduced ADG (linear decrease, < 0.001) of lambs fed JN60. Lambs supplemented with UR3 vs. UR1 tended ( = 0.06) to have reduced BW but had similar ( > 0.17) ADG and G:F. Lamb G:F fluctuated across day (JN × day, = 0.007), but the JN × day quadratic trend ( < 0.001) was mainly due to reduced G:F in lambs fed JN45 or JN60 diets. As the percentage of JN increased in the supplement, serum IGF-1 linearly decreased ( = 0.04), and serum urea N quadratically increased ( < 0.001). The UR × hour interaction ( < 0.001) for serum urea N resulted from a greater decline from 3 to 6 h after feeding in lambs supplemented with UR1 vs. UR3. Increasing JN concentration tended to quadratically increase ( = 0.09) fecal DM and linearly decrease ( = 0.002) fecal N, but an effect due to dietary UR was not detected ( > 0.34). Results indicated that daily supplement DMI was restricted only by using JN60. However, a 60% JN-based supplement will not make an effective rangeland supplement for growing ewe lambs, and using 3% UR should not be considered, especially since daily UR intake was not restricted enough to be considered safe.