Lecture 3: Animal breeding and genetic

Transcription

1 Lecture 3: Animal breeding and genetic In this lesson you will study some of the key terminologies commonly used in Animal Breeding and Genetic. You will be divided into small groups of 6-8 students and each group will discuss some aspects relating to heat detection and some aspects of pig reproductive biology. At the end of this lesson, you will be asked to do some exercises about those terms to make sure that you understand and use them correctly. v Key terminologies -Abbreviated (adj): ngắn (về thời gian) -Artificial insemination (n): thụ tinh nhân tạo -Beef (n): Thịt bò, bò nuôi thịt -Boar (n): heo nọc -Breed (n): giống -Bulbourethral gland (n): tuyến hành niệu quản -Calving interval (n): khoảng cách lứa đẻ (đối với bò) -Capacitation (n): khả năng -Colostrum (n): sữa đầu -Conception (n): sự thụ thai -Corpora lutea (corpus luteum, n): hoàng thể -Dairy (n): sự sản xuất sữa và các sản phẩm từ sữa, trại bò sữa, cửa hàng bán sữa -Delivery (n): quá trình sinh con, đẻ con -Dry period (n): thời gian (giai đoạn) cạn sữa -Ejaculate (n): sự xuất tinh, sự phóng tinh -Estrus synchronization (n): lên giống đồng loạt -Farrowing (n): sự đẻ -Fertility (n): khả năng sinh sản, tỷ lệ đẻ -Fertilization (n): sự thụ thai, sự thụ tinh -Follicle (n): nang noãn -Genetic variability (n): khả năng biến dị di truyền -Genetic variation (n): sự biến dị di truyền -Genetically (adv): về mặt di truyền, có liên quan đến di truyền -Gestation (n): thời kỳ (giai đoạn) mang thai, thai kỳ -Gestation sow (n): nái mang thai -Gilt (n): cái hậu bị -Gonadotrophic (adj): hướng sinh dục -Hand mating (n): ghép phối -Heat (estrus, estrous, n): sự động dục, sự động hớn, sự lên giống -Herd (n): đàn (bò, dê) -Heritability (n): hệ số di truyền -Hypoxia (n): thiếu oxy -Improvement (n): tiến bộ, cải tiến

2 -Inseminate (v): gieo tinh, thụ tinh -Interstitial (adj): kẽ -Lactation (n): sự tiết sữa -Lactation sow (n): nái nuôi con -Libido (n): khát dục, dục tính -Litter size (n): kích cỡ ổ đẻ -Luteinizing hormone (n): kích thích tố tạo hoàng thể -Milk ejection (n): sự tiết sữa -Mortality (n): sự chết, tỷ lệ chết -Nursing interval (n): khoảng thời gian giữa 2 lần bú -Offspring (n): con, đời con -Ovarian (adj): thuộc buồng trứng, liên quan đến buồng trứng -Ovulate (v): rụng trứng -Ovulation (n): sự rụng trứng -Ovum (ova, n): trứng -Parity (n): lứa đẻ -Parturition (n): sinh con, quá trình sinh đẻ -Pig production (n): chăn nuôi heo -Placenta (n): nhau thai -Prenatal (adj): tiền sinh (trước khi sinh) -Prolificacy (n): sự mắn đẻ (đẻ nhiều, đẻ sai) -Prostate (n): tuyến tiền liệt -Puberty (n): sự thành thục sinh dục -Receptor (n): thụ thể -Regression (n): sự thoái hóa -Reproduction (n): sự sinh sản -Selection (n): sự chọn lọc -Seminal vesicle (n): túi tinh -Service (n): sự giao phối -Sow (n): heo nái -Sperm (semen, n): tinh dịch -Spermatogenesis (n): sự sinh tinh -Spermatozoa (n): tinh trùng -Stillborn (n): chết khi sinh -Suckle (v): bú, cho bú -Symptom (n): triệu chứng -Testicular (adj): thuộc dịch hoàn -Trait (n): tính trạng -Udder (n): bầu vú -Weaning (n): cai sữa

3 v Reading Heat detection A number of both beef and dairy producers use artificial insemination and hand mating each year. One of the major problems with these programs is heat (estrus) detection. An experienced observer with a well-trained eye can do a good job by observing the herd for ½ to 1 hour early in the morning and ½ to 1 hour in the evening. Heat detection is more an art than a science, and not everyone can do a good job of it. The observer must be taught to regconize the signs of estrus and must be aware that some cows show only abbreviated signs of estrus. If heat periods are missed or incorrectly identified, increased calving intervals will result, with longer dry periods and reduced profits. It is extremely important that cows be inseminated at the proper time in relationship to ovulation. Estrus synchronization can be used to help reduce the time spent on heat detection. Some aspects of pig reproductive biology Reproduction is an essential process for the maintenance of a species. It has to be genetically controlled to ensure that the reproductive process is repeated with a strong degree of precision. Yet a considerable genetic variability exists between breeds for both male and female reproductive traits. For instance, average litter size of mature sows varies from four to 16 piglets per litter among breeds. These differences, combined with the appreciable genetic variation that also exists within breeds, have given the opportunity for substantial genetic improvement of sow prolificacy over the last 15 years (up to 30% of the mean in some breeds). The main consequence of increased litter size has undoubtedly been large gains in the efficiency of pig production systems, but it has also resulted in some adverse effects, such as weaker estrus symptoms or lower piglet survival. Such unfavourable correlative trends not only reduce the positive short-term effects of selection on efficiency, but may also have long-term consequences, such as decreased fertility owing to an increased proportion of undetectable estrus or, for piglet mortality, may raise ethical problems. This emphasizes the importance of a broad perspective of the consequences of genetic improvement, which generates new questions, such as the societal or ethical consequences of selection, but it also strengthens the need for a good knowledge of the genetic (co) variation of a large number of potentially important traits. Puberty in gilts, usually defined as the moment of first ovulation, occurs at 3 4 months of age in the earliest maturing breeds (Chinese) and at an average of 6 7 months of age in the most widely used Western breeds. It generally coincides with the first estrus, though ovulation without external manifestation of estrus (silent heat) occurs occasionally in pigs, and generates a steroidsecreting activity of the corpora lutea. Age at puberty is quite tedious to measure and is often replaced in field studies by age at first mating or at first farrowing. Although strongly correlated, the two traits differ owing to the large variability in management strategies between breeders.

4 Ovulations then occur every 3 weeks during the second half of a 2 3 day estrous period in the absence of gestation, and have a mean duration of 2 5 h. The estrous cycle is controlled by gonadotrophic hormones. Follicle stimulating hormone (FSH) stimulates recruitment and development of ovarian follicles. Ovulation and corpora lutea formation are stimulated by luteinizing hormone (LH). Ovulation rate increases with estrus and parity number until the fourth or fifth parity. Conception rate in the pig is high (80 90%) and has increased with the generalization of multiple matings (two or sometimes three services 12 or 24 h apart during estrus). Fertilization of the ova begins a few hours after mating after a necessary period of spermatozoa capacitation. Fertilization rate is generally close to 100%. The rate of prenatal mortality in pigs is 30 40% on average. The largest part of losses (20 30%) occurs during the first month of gestation, with an additional 5 10% of fetal loss during late gestation. Farrowing lasts 3 5 h on average, with large variations between sows. It is initiated by the piglets, which produce corticosteroids, resulting in a production of prostaglandin by the placenta, which causes the regression of the corpora lutea and the initiation of the farrowing process. Parturition and the first few days after birth are critical periods for piglet survival. Up to 10% of piglets are stillborn in some populations, predominantly as a result of hypoxia during delivery. After birth, the time to get the udder, suckle and ingest an appropriate amount of colostrum and milk is a major determinant of piglet survival and growth. The sow has a strong control of milk ejection, with duration of milk flow of s, and an average nursing interval of less than an hour. Colostrum and milk production are difficult to measure directly, but can be indirectly estimated from piglet weight gain. Colostrum is essentially produced during the first 24 h after parturition, and amounts to 4 kg on average. Milk production peaks at around 21 days of lactation, and may reach 1 kg daily for each piglet in sows nursing piglets. With very few exceptions, the lactating sow has a very limited follicular development, and does not ovulate or show any estrus symptoms. The total removal of the sow from her litter at weaning normally results in an acceleration of follicular growth and in ovulation within 4 10 days. Spermatogenesis in the boar starts at 4 6 months of age in most pig breeds, but may begin before 100 days of age in some early maturing breeds, such as the Chinese Meishan. Sperm quality and quantity then steadily increase with testicular development, testosterone production and libido until sexual maturity at 6 8 months of age, and then at a much lower rate until boars reach their adult body size. A parallel rise in male accessory glands (the seminal vesicle, prostate and bulbourethral glands), which produce 95% of the seminal plasma, results in a correlated increase in the volume of the ejaculate. Sexual activity is controlled by gonadotrophic hormones. FSH stimulates spermatogenesis, whereas LH stimulates steroid hormone (testosterone, but also other steroids such as androstenone) synthesis and secretion by the interstitial Leydig cells. The action of LH is dependent on the FSH induction of LH receptors on the Leydig cells. Boar ejaculate is characterized by its large volume (around 300 ml on average) and spermatozoa number (80 to 120 billion when semen is collected once a week), which corresponds to total sperm reserves and widely exceeds daily sperm production (10 to 20 billion spermatozoa a

5 day). As a consequence, spermatozoa number per ejaculate steadily decreases when the boar is used or ejaculate is collected more than once a week, in spite of a slight increase in sperm production with ejaculation frequency. Large amounts of spermatozoa and semen are necessary to ensure normal conception rate and prolificacy (50 ml of semen and 3 billion sperm are usually considered as minimum requirements for artificial insemination). Frozen boar semen can successfully be employed, with comparable or slightly lower conception rate and litter size than fresh semen, but it remains rather expensive and requires good technical expertise, so its commercial use remains quite limited. v Assignment 1. Search for hidden words between letters of the alphabet. Find at least 8 words and write down their meanings. G R E T I C U L U M E L L N U R S E S O R I Y K E T U I Y R M T M C A R L N N T I T P E O O G U T A N E H C B L V Y H L A R A A L E Y A E I T E T I C L E S S T E E I L E U M G I Y M U C O S A B K S S 2.Translate the following paragraph into Vietnamese The first objective of a breeding program is to produce the most improvement per unit of time, as stated by Dickerson and Hazel (1944). They showed that selection response depends on three parameters, which may differ between the sexes, i.e. selection accuracy (defined as the correlation between the aggregate genotype and the selection criterion), selection intensity or standardized selection differential, and generation interval. Genetic gain increases if selection intensity increases, if accuracy of estimating the genetic value increases or if generation interval decreases. Genetic variation is considered to be a given constant, although it might be differentially expressed (e.g. in heat- or disease-challenged environments). Accuracy of the genetic evaluation depends on the availability of observations and on the heritability of the trait under scrutiny. The main basis of observations is records on an animal s own performance. In addition, other sources of information are performance records on parents, offspring and other relatives. v Văn phạm: Key stress rule pattern -Bất kể các ký tự a, e, i, o, u, y, w là nguyên âm, phụ âm hay phần cuối của từ, chúng được phát âm như sau:

6 a e i o u y w /ey/ /iy/ /ay/ /ow/ /yuw/ /wye/ /dʌbəәl yuw/ -Các ký tự nguyên âm trong tiếng Anh được chia thành 3 nhóm cơ bản: nguyên âm đầy đủ (nhấn chính, nhấn phụ) và nguyên âm giảm (không nhấn). -Nguyên âm trượt (nhấn chính) -Nguyên âm không trượt (nhấn phụ) -Nguyên âm giảm (không nhấn) iy, ey, ay, ɔy, ow, uw, aw, ȝr I, Ɛ, ӕ, ʌ, Ɑ, Ʊ, ɔ əә, i -Những từ nhấn âm chính có phần cuối theo qui tắc nhấn âm chính. Phần cuối này có các đặc điểm sau: +Chứa các chuỗi kí tự sau: ia, io, iu, ienc (C: kí tự phụ âm) +Có ít nhất 1 âm bên trái của nó Ví dụ 1: Những từ có phần cuối theo qui tắc nhấn âm chính med(iate prem(ium rat(io convenience consortium eviction Ví dụ 2: Những từ có phần cuối không theo qui tắc nhấn âm chính dial carrier lion -Phần cuối (ia, io, iu, ienc) theo qui tắc nhấn âm chính có thể kết hợp với các kí tự sau: +Cách 1: +Cách 2: i + nguyên âm + *Các nguyên âm khác: obvious *Các phụ âm khác: radiant i + nguyên âm + (Có hoặc không có thêm nguyên âm và phụ âm theo sau) *Phần cuối trung tính: ratios, obviously *Phần cuối cơ bản: mediate, mediating

7 -Trong qui tắc nhấn âm chính: ea cũng được tách thành 2 âm nguyên âm giống như cấu trúc i+ nguyên âm và u+nguyên âm Ví dụ 3: creat(ion react(ion Bài tập 1: Gạch dưới âm chính và đánh dấu nhấn lên âm chính. Đọc lớn mỗi từ. ambitious sectioning admission pronunciation influential acquisition maturation initiation petitioned vacationed senior partially audiences auctioned olympiads