Genetics – Applications to Agriculture Leaving Certificate Agricultural Science Genetics – Applications to Agriculture

Artificial Insemination Artificial insemination is extremely important in farm and herd management. It involves the artificial insertion of sperm cells into a female. The sperm (contained in semen) is obtained from genetically suitable males, selected for their characteristics. It is used to improve the genetic quality of the herd. Semen is collected, diluted and stored (usually in liquid nitrogen as it doesn’t damage the sperms cells but also extends their life) before being inserted into the female while in heat.

Advantages of AI Can allow for one bull to serve up to 60,000 females. Bull is not exposed to genital diseases. Semen can be stored for many years. Farmers can choose from a huge range of sires, depending on the use of the offspring. Fertilisation is more likely from AI. More accurate calving times. No need to purchase and care for a bull, meaning it is much safer for the farmer.

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Disadvantages of AI Timing and heat detection are critical – more work for the farmer at this stage. More expensive if animals heat periods are missed. Missing heat periods also increases calving interval.

Sexed Semen Typically semen contains 50% X chromosome sperm cells and 50% Y chromosome sperm cells. Sexed semen is semen that is chemically treated to contain more X chromosomes than Y. This ensures that more females are born than males. This is mainly used in the dairy industry to produce replacement heifers. Sexed semen is typically 70-80% X chromosomes

Keeping a Bull Advantages: No heat detection required – bull does it for the farmer Repeat services don’t cost anything Disadvantages: Can be dangerous and difficult to manage Expensive fencing required. All offspring will be the same breed. Bull serves heifers not required for breeding or serve them too early.

Embryo Transplantation Embryo transplantation involves producing offspring with superior genetic information. It has a number of stages: Cows with the desired genetic traits are given hormones to promote multiple ovulations The eggs are surgically removed. The eggs are fertilised with sperm in-vitro. The fertilised eggs are then inserted into other cows where they continue to develop. The offspring are born and reared as normal.

Mutations Mutations are spontaneous changes in the DNA sequence of an organism, which may or may not lead to a genetic disorder. Mutations can be caused by numerous factors including: X-Rays UV Light Radon Gas Asbestos Carcinogenic chemicals Radiation

Performance & Progeny Testing Performance testing involves keeping a record of an individual animal’s performance in terms of growth rate, food conversion (FCR), yields etc and comparing them with similar animals in similar conditions. Progeny testing compares records of an animal’s offspring with the offspring of other animals kept in similar conditions in terms of growth rate, food conversion (FCR), yields etc. Both factors are important for stock selection and selection for AI. Both are practiced mainly on bulls.

Inbreeding vs. Cross Breeding Inbreeding involves mating animals of the same breed (related animals). There are advantages and disadvantages to the practice and the rate of in-breeding is increasing nationally. Breeding closely related animals is not necessarily good farm practice and can cause genetic mutations, BUT is practiced to improve genetic traits of purebred animals (Line Breeding). Cross breeding involves breeding two pure breed animals (of different breeds), producing offspring of superior quality to the parents. Cross breeding results in HYBRID VIGOUR, when the offspring out performed the parents. Cross breeding is good farm practice.

Cross Breeding

Cross Breeding - 2

Genetic Problems (2009, Q7)

Genetic Problems (2008, Q7)

Genetic Problems (2007, Q7)

Genetic Problems (2006, Q7)

Breeding Strategy Exercise You are working as an agricultural consultant and a client has come to you for advice. The client wishes to establish a closed herd beef enterprise. Provide your client with advantages and disadvantages to your recommendations on the following queries: Advise the client on the breed or breeds he or she should use to optimise maternal and terminal traits. Should your client use a crossbreeding or pure breeding strategy or both? Should the client keep a bull or use AI or both?