Growth and development Part two: Genetic factors: breeds Animal sex and hormones Climate Revision

Genetic factors… Genetic factors contribute significantly to G. and D. and the efficiency of livestock production. Farmers look for breeds that have desirable traits/characteristics for growth and production. There is a lot of variation between breeds. Farmers can manipulate the genetic ability of stock by selecting between breeds and within a breed.

Hybrid vigour… Farmers can achieve increased performance by mating a breed of livestock with a different breed. They will produce offspring that can be more productive … this is called HYBRID VIGOUR. Ie. A Fresian cow can be mated with a Jersey bull to produce a Jersey/Fresian cross calf which has the ability to be more productive than its parents.

A "terminal" ram is normally a breed different from your ewes that is used to breed your whole flock to produce crossbreeds with traits that are BETTER than the animals you started with. Its known as "hybrid vigor" or "heterosis", meaning a crossbreed is likely to get the best traits of both the parent breeds. The "terminal" sire is the one that connects all the lambs to a common set of genes, while the ewes are usually not related Some breeds are know for being good mothers and having twins or triplets. Other breeds are more known for their muscling and growth rates. Take a ewe from the first group and mate it with a ram from the second, and theoretically you’ll get one that is a good mother, has twins or triplets AND grows fast and produces lots of meat

This table shows that by crossing a terminal sire with a purebred increased the productivity of the offspring… A terminal sire is often used in dairy breeding systems to mate cycling females at the end of the breeding season. The terminal sire is usually a meat breed. PurebredTerminal sire X purebred cow Weaning weight (kg) Productivity

Cross-breeding Sheep breeders have introduced many different sheep breeds from overseas which have different characteristics that can improve the productivity of a sheep flock. A common method is to purchase a purebred ram that has certain characteristics and mate the ram over the ewe flock… thus producing offspring with improved genetic ability.

Ie. Milking ability The East Friesian (sheep) is known for its milk production ability. Ewes crossed with East Friesian will produce up to 30% more milk and 20% more milk energy than Romneys. East Friesian cross ewes rearing twins can produce up to 36% more milk in early lactation…. Young stock receiving more milk from their mothers have more chance of growing faster. East Fresian ewes Romney Ram

Characteristics of different sheep breeds… There is a large range of animal breeds in NZ, for a range of purposes, and are utilized depending on the farmers livestock system…

Sheep breeds Breed Early Lambing Fecundity Growt h rate Carcass quality Milking ability Wool weight Wool bulk Low mature weight Border Leicester ✔✔✔✔ Coopworth ✔✔✔✔✔✔✔ Corriedal e ✔✔✔ East Fresian ✔✔ ✔ ✔ Finn ✔✔ ✔✔✔ Merino ✔✔✔✔✔✔ Perendale ✔✔✔✔✔✔ Poll Dorset ✔✔✔ ✔✔✔ Romney ✔✔✔✔ Texel ✔✔✔ ✔

Dual purpose.. A dual purpose breed will have more emphasis on wool and meat…ie. Romneys, Coopworths, Corriedales, Perrendales. The NZ Romney and Coopworth are suitable for wet areas, whereas Corriedales thrive in dry environments. Perrendales do well in hard, hill country. Perendale

Crossing sire or terminal sire The Border Leicester is crossed with breeding ewes to produce heavyweight lambs for the meat trade. The Poll Dorset is used as a terminal sire and crossed with ewes at the end of the season Border Leicester Poll Dorset

Wool: Merino is a fine wool breed with a fibre diameter of microns Meat: The Texel is a speciality meat breed, with excellent growth rates and carcass weights Fecundity: Means the number of offspring produced. The Finn produces a great number of lambs and reach puberty early. Milk: The East Fresian is a milking breed. It also lambs early and has good fecundity and growth rates. Texel

Task: Write a summary/definition of the breeds in the chart provided You might wanna use this site : heep-breeds

Cattle breeds: BreedGrowth rate and mature size Lean to fat ratio Age at pubertyMilk production Jersey ✔✔✔✔✔✔✔✔ Angus ✔✔✔✔✔✔✔✔✔✔ Hereford ✔✔✔✔✔✔✔✔✔✔ Shorthorn ✔✔✔✔✔✔✔✔ Holstein ✔✔✔✔ ✔✔✔✔✔✔✔ Simmental ✔✔✔✔✔✔✔✔✔✔✔✔✔✔✔✔ Salers ✔✔✔✔✔✔✔✔✔✔✔✔ Limousin ✔✔✔✔✔✔✔✔✔✔✔✔✔ Charolais ✔✔✔✔✔✔✔✔✔✔✔✔✔✔ Piedmontese ✔✔✔✔✔✔✔✔✔✔

Salers Simmental Charolais

Growth rate: The beef breeds Simmental and Salers have excellent growth rates and reach a large mature weight. A large mature weight doesn’t mean animals grow slower, it just takes longer to reach full size. Meat: The beef breeds Charolais, Limousin, and Piedmontese produce more lean meat than fat. NZ’s popular breeds Angus and Hereford are not as efficient at producing lean meat. Age at Puberty: The Angus and Hereford are common beef breeds for NZ hill country. The reach puberty early and grow to a good mature size. Milk production: Jersey and Holstein Friesian are commercial milking breeds.

Breeding within breeds… Within a breed there is sufficient variation in G. and D. traits to make significant changes through selection and breeding. A sheep farmer may select livestock based on weaning weight, hogget oestrus activity or fleece weight. By selecting for certain traits a farmer can achieve improved genetic gain. Heritability is represented as a proportion that has values between zero and one. Zero= the trait isnt inherited and one means it is always passed on. Traits such as live weight have high heritability values of 0.3 to 0.4. Heritability values for reproductive traits tend to be low (0.0 to 0.2).

Heritability… TraitHeritabilityLevel of genetic gain SHEEP Weaning Weight Hogget Oestrus Medium High DAIRY CATTLE Milk yeild0.2Medium BEEF CATTLE Weaning weight Mature cow live weight Carcass weight Medium High PIGS Carcass lean0.5High This table represents the level of genetic gain that can be achieved through selection and breeding

Growth traits: The heritability of weaning weights (sheep and beef) is a medium value ( ). By selecting young animals that reach weaning weights early the genetic performance of the herd or flock is improved. For pigs or beef the heritability is high ( ), genetically improving carcass weights leads to overall improvement in growth rates.

Development traits: Sheep that start there oestrus cycle early increase there chances of successful mating at tupping time. Hogget oestrus activity has a high value of Production traits: Heritability for milk yeild is a medium value. The dairy herd can be improved by breeding from cows with that produce more milk. A ram smelling the scent of a ewe is a sign of him checking to see if the ewe is in oestrus