Detailed Explanation of Key Technologies for Producing High-Quality Fattened Lambs
High-quality fattened lambs refer to lambs produced by crossbreeding excellent meat sheep breeds with local breeds, weaned at 2~3 months of age, fattened for 4~6 months, and reaching a body weight of 35~40 kg. Compared with traditional feeding methods, the breeding cycle is shorter, feed input is less, and the slaughter rate, meat yield, commercial rate and meat quality are improved, which is more conducive to organized specialized and intensive production. Since 2009, Yanggu County has undertaken the Shandong Province High-Quality Fattened Lamb Production Technology Promotion Project for several consecutive years. Through project implementation, technologies such as economic crossbreeding, estrus synchronization, artificial insemination and intensive fattening have been promoted to produce high-quality fattened lambs, achieving significant economic benefits. The key technical measures are summarized as follows:
1 Economic Crossbreeding Technology
The introduced high-quality meat sheep breeds are selected as the sire, and the local Small-Tailed Han sheep is used as the dam for economic crossbreeding, with all crossbred offspring used for fattened lamb production. The first filial generation has many advantages such as strong vitality, fast growth and development, high feed utilization rate, uniform product specifications and good meat quality.
1.1 Key Points for Sire Selection (1) Select breeds with good production performance and relatively stable heritability of various traits; (2) Select breeds with relatively fast early development, good meat quality and good meat-type body conformation; (3) Select breeds with relatively abundant genetic resources that meet the requirements of meat sheep fattened lamb production. After several years of practice, Yanggu County ultimately selected the Dorper sheep as the crossbreeding sire.
1.2 Key Points for Dam Selection The Small-Tailed Han sheep is selected as the dam, with 3 key points for selection. (1) Select individuals with high reproductive capacity, choosing from individuals that have given birth once, with priority given to those that produced 2 or more lambs in the first parity; (2) Select individuals with strong lactation ability and good maternal instincts; (3) Select ewes in relatively good body condition (upper-medium body condition score).
2 Estrus Synchronization Technology
Estrus synchronization is a technology that uses certain hormones and drugs to synchronize the estrous cycle of ewes, artificially controlling a group of ewes to come into estrus together within a certain period of time. The application of estrus synchronization and artificial insemination technology can achieve centralized mating, centralized lambing, centralized fattening and centralized slaughter in production, realize three lambings in two years for ewes, reduce labor intensity and improve breeding efficiency.
2.1 Selection of Drugs and Tools (1) CIDR vaginal sponges and CIDR applicators are produced by the original Pfizer company of New Zealand; (2) Pregnant Mare Serum Gonadotropin is produced by Ningbo Sansheng Pharmaceutical Co., Ltd.
2.2 Operation Methods for Treating Ewes (1) On any day of the estrous cycle, clean the ewe's vulva with clean water and alcohol cotton balls; (2) Place the vaginal sponge into the CIDR applicator; (3) Insert the CIDR applicator loaded with the vaginal sponge deep into the ewe's vagina and place the vaginal sponge properly; (4) Remove the CIDR applicator; (5) On the 12th day, remove the CIDR vaginal sponge, use a vaginal speculum to open the vagina, and flush with physiological saline (add 4 million IU penicillin and 4 million IU streptomycin per 500 ml); (6) While removing the sponge, inject 500 IU PMSG intramuscularly into the neck of each ewe. Generally, treated ewes come into estrus together within 2~3 days and can be mated.
2.3 Precautions (1) When using progesterone vaginal sponges, the combined injection of Pregnant Mare Serum Gonadotropin (PMSG) gives very good results, but the cost is relatively high. (2) In production practice, ewes in relatively good body condition should be selected for estrus synchronization, because the body condition of ewes directly affects the effect of estrus synchronization. (3) Special care must be taken when injecting Pregnant Mare Serum Gonadotropin (PMSG) to avoid leaving the drug outside the ewe's body. (4) The number of ewes treated per day should be arranged according to the mating capacity of the rams, and the number of ewes in estrus on that day should be controlled so that mating occurs as soon as estrus occurs.
3 Artificial Insemination Technology
3.1 Estrus Identification of Ewes (1) When ewes are in estrus, they often appear excited and restless, with abnormal behavior, frequently wagging their tails, being sensitive to external stimuli, having reduced appetite, showing mating desire, actively approaching rams, and standing still when chased or mounted by rams; (2) The vulva is relaxed, congested, swollen, and the clitoris is erect; (3) The vagina is congested, relaxed, and secretes mucus; (4) The duration of estrus
is generally 36~60 h, and the average estrous cycle is 21 d; (5) When estrus ends, the ewe refuses the ram's approach and mounting.
3.2 Teaser Testing The ratio of teaser rams to ewes should preferably be 1:40~50. After the teaser ram enters the ewe flock, any ewe found standing still and actively approaching the ram or accepting mounting by the ram is a ewe in estrus.
3.3 Semen Collection and Dilution (1) Semen collection: The collector squats on the right side of the teaser ewe, holds the artificial vagina in the right hand at an angle of 35~40 degrees to the ground, close to the rump of the teaser ewe. When the breeding ram mounts the teaser ewe's back and extends its penis, the collector quickly uses the left fingers to gently support the penile prepuce and guide the penis into the artificial vagina. After the ram ejaculates, immediately hold the artificial vagina upright, expel the air, remove
the semen collection cup, cover it with the cup lid, attach the ram's identification tag and send it to the semen processing room. The ejaculate volume of a ram is generally 1~1.5 ml; (2) Semen quality examination: Normal sheep semen is milky white, odorless or slightly fishy (semen with a putrid odor or red or brown color must not be used); take 1 drop of raw semen or semen diluted with physiological saline and observe sperm motility and density under a microscope at 300~600 times magnification. (3) Semen dilution: Milk-based diluent is made from fresh milk from healthy cows or ewes, disinfected in a water bath (92~95°C) for 15 min, cooled to below 40°C, and added with 100,000~200,000 IU penicillin per 100 ml; glu-cit-
rate diluent (glucose 3 g, sodium citrate 1.4 g, distilled water added to 100 ml). Take 80 ml of the above solution, add 20 ml egg yolk and 100,000 IU penicillin; physiological saline (0.85% sodium chloride solution). The dilution factor should be determined by semen density, motility rate and the selected diluent. Each insemination dose is 0.1~0.2 ml, maintaining the number of effective sperm at over 20 million.
3.4 Semen Preservation and Transport (1) After the collected semen passes quality examination, it should be quickly diluted, packaged and cooled. Ice blocks should be placed in the thermos bottle used for transporting semen to keep the semen temperature at 2~5°C, and vigorous shaking must be strictly prevented; (2) When inseminating, take it out of the thermos bottle and raise the semen temperature to 18~25°C at room temperature (warming in warm water); (3) Semen that has been transported and preserved can only be used for insemination after passing semen quality examination.
3.5 Insemination (1) Insemination time: Ewes may only be inseminated after estrus identification and health examination. Insemination is generally carried out 12~24 h after the ewe comes into estrus; (2) Insemination site: Clean the vulva, gently insert the disinfected vaginal speculum into the vagina, open the vagina, locate the external opening of the cervix, then insert the insemination instrument into the external opening of the cervix to a depth of about 1~2 cm;