Recipient Organization
LINCOLN UNIVERSITY
820 CHESTNUT ST
JEFFERSON CITY,MO 651023537
Performing Department
Agriculture
Non Technical Summary
The trend of decline in consumption of meat products has been the major motivation leading to selection for a changed carcass composition of food animals. Increased concern for the health aspects of meat has led consumers to demand products with a higher ratio of lean to fat tissues, which is a signal that the sheep meat industry will be only be sustained if it supplies desirable quality products to markets. Sheep farming is still an important enterprise for many producers and a viable protein resource for human consumption, for which it demands a premium price for its high-quality meat in the US market. Ultrasound scanning is becoming a preferred, noninvasive, precise, and speedy real-time test tool in meat animal selection and marketing. Application of Ultrasound Scanning in sheep marketing and selection may help improve the selection efficiency, speed, and accuracy for breeding methods as well as shorten the breeding interval and generation length. With this technology, sheep producers are able to select animals based on leaner muscle and lower fat content carcass predictability without any invasive assessment of animals. Therefore, this proposal seeks to conduct lean meat selection in Katahdin sheep, evaluate lean meat selection efficiency, enhance lean carcass quality traits, and increase sheep farming profitability. Developing a lean sheep selection index should improve breeding efficiency, selection response, and genetic progress in meat yield and quality characteristics.
Animal Health Component
80%
Research Effort Categories
Basic
10%
Applied
80%
Developmental
10%
Goals / Objectives
This project seeks to establish a lean muscle meat sheep flock selected on the objective ultrasound measurements in live animals for predicted carcass traits and evaluate the selection efficiency, response, and genetic gain in Katahdin sheep flocks. Sheep are an ideal livestock species for operations with small acreage. In fact, most US operations raise fewer than 100 head, and 85 percent of all farms owned fewer than 100 sheep. There are more than 2,200 farms involved in raising about 185,000 sheep and goats in Missouri, with a great potential for market expansion. Sheep are seasonal (fall) breeders, with a five-month gestation period, and with lambing in the following spring and the marketing of lambs occurring from late summer to fall. Consequently, it takes about nine to 10 months to produce meat products for consumption. There is an urgent need for producers and consumers to demonstrate a highly efficient meat sheep selection and marketing system.This proposal is to investigate the efficiency of lean meat selection in Katahdin sheep, develop a lean meat breeding index, and demonstrate a sustainable lamb production system. Ultrasound scanning is becoming a preferred, noninvasive, precise, and speedy real-time test tool in meat animal selection and marketing. With this technology, sheep producers are able to select animals based on leaner muscle and lower fat content carcass predictability without any invasive assessment of animals. However, there is little experimental data and technical information available about the selection of lean muscle efficiency, response, and genetic gain when applying the ultrasound measurement technique in the US sheep industry. Currently, there is no selection or genetic evaluation of lamb carcass traits in hair sheep breeds and an urgent need for producers and consumers to demonstrate a highly efficient meat sheep selection and marketing system. Therefore, this lean muscle selection project will facilitate the selection of animals with greater muscling and the potential for higher-yielding lamb carcasses to produce progeny with a higher carcass weight and a valuable shelf product as well as increase the genetic gain in lean muscle traits. The project is to accomplish the following three objectives:(a) To establish a lean meat sheep flock selected on ultrasound-measured carcass traits from the loin eye muscle area, loin eye muscle depth, loin eye muscle width, and backfat thickness.(b) To develop a lean sheep index for breeding animal selection, postweaning growth rate, and estimated progeny performance differences in high lean muscle and low lean muscle lines.(c) To compare the weaning weight, postweaning growth, and reproduction performance of high and low lean selection flocks.
Project Methods
(1). Experimental design, expected progeny differences, and breeding value: This is a within-breed selection program applying a predicted lean meat index based on objective ultrasound-measured parameters (i.e., LEA, LEW, LED, and BFT). These carcass traits are highly heritable, so a significant selection response and genetic gains are expected in the selected flock. The progeny data will include birth weights, ADG, postweaning weight (PWW), and ultrasound-measured parameters (LEA, LED, LEW, and BFT). The carcass trait expected progeny difference (EPD) values will be derived from ultrasound measurements for selection lists. Ultrasound-measured EPDs will be used in animal selection decisions, along with postweaning growth, visual appraisal, and pedigree information. The NSIP Carcass Plus index will be adapted as selection index.(2). Animal identification, recording, and sampling:Ear tags and identification - Rams and lambs will be tagged with ear tag identification, and all bred ewes will be tagged with a plain plastic ear tag on the left ear and an electronic identification ear tag (EID) on the right ear.Progeny lambs - All newborn lambs will be identified with ear tags and recorded for the dam and sire IDs as well as for birth weight, birth/rearing ranks, fate, and health status.Animal health and welfare - Body condition score, FAMACHA© score, WBC,RBC (hematocrit%), and cell types will be monitored at planned intervals.Animal performance measurements - Weaning weight (90 d), ADG, postweaning weight (at 4, 5, and 6 months), and mature (12-month)/breeding weight (mixed ages) will be recorded at planned intervals. Live weights will be recorded with a Tru-Test electronic scale and an EID reader unit or tag reader. Performance traits for ewes will be measured, including pregnancy rate, lambing percentage, birth weight, birth/rearing rank, number of lambs weaned, and weaning weight/per ewe.Ultrasound-measured carcass trait measurements - Breeding rams and mixed ewes will be measured once with a 3.5 MHz linear carcass probe set over the loin area between the 12th and 13th ribs prior to breeding season or replacement. Lambs will be measured at weaning (90 d) and postweaning (120, 150, and 180 d), corresponding to the live weight recording and other performance assessments for EPDs and lean index calculation. Body weight and ultrasound scanning will be obtained at the same time or not more than a week apart, if measured separately.Blood sampling - Animals (7 ml/hd) will be sampled via jugular venipuncture (purple-top tube) with 18-gauge needles to measure packed cell volume (PCV) and other hematologic parameters for breeding ewes (at either breeding/allocation or early pregnancy diagnosis and also at lamb weaning), and their blood vital parameters monitored: white blood cell, red blood cell (hematocrit %), and cell types.(3). Experimental site and animal resource: Lincoln University's James N. Freeman Farm will be used for animal grazing, breeding, lambing, field operations, and management sites. Katahdin is the breed of choice because the sheep flock was already adapted to the local farming environment and management system. According to our previous experience with animal breeding trials, a number of breeding sires (5 rams x 2 lines) will each mate with 15 ewes to form a selection line (n = 75) and control flock (n = 75). Animals will be ultrasound-scanned for predicted carcass traits, including LEA, LED, LEW, and BFT, using an approved ultrasonic instrument and by an NSIP-certified operator/s.(4). Synchronization of estrus with CIDRs option: Rams will be isolated from ewes prior to breeding. Ewes will be estrus-synchronized using a dose-controlled CIDR insertion device (EASI-BREED CIDR, Pfizer Animal Health)/per ewe for 12 days prior to mating. After removing the device, synchronized ewes will be flocked for mating for one or two estrus cycles.(5). Pre-breeding nutrient flushing option: Feeding ewes to gain weight beginning about two weeks before breeding is called flushing, which may increase the lambing percentage by increasing the number of eggs that the ewes ovulate in estrus.(6). Breeding ewes, sires, and single-sire group mating: Ten rams tested for breeding soundness will be selected and saved for the breeding program. One hundred fifty ewes will be selected from the screened ewes and divided into two selection lines (HL and LL), with each line having 75 breeding ewes and five rams.Single-sire or sire group breeding: Five HL rams each will be assigned 15 mixed-age HL ewes in a separate pen or paddock for two-cycle mating (35 d). Five LL rams each will be assigned 15 mixed-age LL ewes in a separatepaddock for two-cycle estrus mating (35 d).(7). Pregnancy diagnosis and lambing records: All bred ewes will be subjected to an early pregnancy diagnosis (40-50 d postbreeding) using a standard ultrasound transducer, and pregnant ewes will be transferred to lambing paddocks prior to the parturition period.(8). Late gestation and early weaning supplementary feeding option: During the early spring, demands for nutrients increase with late gestation and lactation. Therefore, adequate stockpiled pasture grazing, hay or dietary supplementation will be considered. Preweaning lambs/kids will be preferentially grazed or fed by setting up creep feeding along the ewe/doe grazing pastures if required by seasonal pasture conditions.(9). Ultrasound scanning procedures for carcass traits Ultrasound-measurable traits planned for recording in this project include loin eye muscle area (LEA, in.2/cm2), loin eye muscle width (LEW, in./cm), loin eye muscle depth (LED, in./cm), and backfat thickness (BFT, mm). The LEA is defined and measured between the 12th and 13th ribs lateral and perpendicular to the vertebral column and parallel to the rib covering all the longissimus dorsi muscle; the LEW is measured as the widest distance between two points from the upper and lower edge of the longissimus dorsi muscle; and the LED is measured as the deepest distance between two points from the outer edge of the LEA, whereas the BFT is measured between the longissimus dorsi muscle and subcutaneous fat membrane layer, at the 12th rib. Breeding rams and mixed ewes will be measured once prior to breeding/allocation with a 3.5 MHz linear carcass transducer over the loin area between the 12th and 13th ribs. Lambs will be measured at weaning (90 d), postweaning (120 d, 150 d, and 180 d), and maturity(12 mo.) corresponding to the live weightand other performance assessments for EPDs and lean index calculation.(10). Internal parasite and other illness surveillance: Disease prevention is vital to the success of any livestock operation or project. The animals in both the selection and control groups will be subjected to routine monitoring for disease and sickness, especially internal parasites and foot health conditions. Deworming, foot-bathing, or hoof trimmings will be completed when necessary.(11). Data collection and statistical analysis: Birth weight, weaning weight, marketing weight, ADG, breeding weight, fecal egg count, BW, BCS, PCV, FAMACHA© score, other performance data or comparisons (e.g., hematologic parameters), and other comparisons will be analyzed using the GLM procedure of SAS® with repeated measures (SAS® Institute Inc., Cary, NC 2004). Apparent heritability parameters will be estimated using the logistic linear model described by Gilmour et al. (2002). The number of lambs born (NLB) and weaned (NLW) per ewe lambed will be analyzed as categorical variables. Pearson correlations and simple regression analysis will be performed following the procedures "proc corr" and "proc reg" of SAS® (2004) to determine the relationship between ultrasound measures and live weights. The partial correlation coefficients using a GLM procedure (multivariate analysis of variance) will be conducted for growth (ADGs at intervals) and body condition scores.