《文献翻译作业》由会员分享，可在线阅读，更多相关《文献翻译作业（9页珍藏版）》请在金锄头文库上搜索。
1、家畜繁殖学文献翻译作业12动科3班付越2012513038指导老师：张居农 正文： INTERACTIONS OF MANAGEMENT AND DIET ON FINAL MEAT CHARACTERISTICS OF BEEF ANIMALSDr. Francis L. FluhartyDepartment of Animal Sciences, The Ohio State University1680 Madison Ave., Wooster, OH 44691ph: (330) 263-3904, fluharty.1osu.eduWhy are some calves actua
2、lly worth more than others to feedlots and packers even though the cattle are similar in breed, type, frame size, and muscle thickness? Today, the answer is likely to be differences in average daily gain, feed efficiency, yield grade, marbling score, or percent retail yield. As a seedstock or cow-ca
3、lf producer, how do you select breeding animals and manage their offspring so that the calves actually achieve their optimum genetic potential? These are questions that you may need to be able to answer as the beef industry continues to move from a commodity market to a value-based, grid marketing i
4、ndustry where individual animals are identified and priced according to their consumer desirability. To answer these questions, you probably need to understand some basics of ruminant nutrient use as well as some windows of opportunity that exist where management can improve carcass characteristics
5、so that your cattle achieve their genetic potential.First, you need to understand that all nutrients (energy, protein, vitamins, minerals, and water) are used in a hierarchy that goes from maintenance development growth lactation reproduction fattening. This means that an animal must have sufficient
6、 nutrients to maintain its body before bone or muscle growth can occur, and these must occur before fattening can occur. In breeding cattle, lactational anestrous occurs when an animal that is nutrient deficient, but milking heavily, cant rebreed. The second thing that you need to understand about r
7、uminant nutrition is that feed is digested in the rumen by ruminal bacteria that attach to the surface of a feed particle to digest it. In ruminants, maintaining the digestive organs (rumen, reticulum, omasum, abomasum, small intestine, and large intestine) plus the liver and kidneys can take as muc
8、h as 40-50% of the energy and 30-40% of the protein consumed in a day. Forage diets that are very bulky and only 40-60% digestible increase the weight of the digestive tract, because more undigested feed remains in each segment of the digestive tract. In contrast, grain-based diets result in decreas
9、ed organ weights compared with forages, because grains are 80-100% digestible, and have a much smaller particle size, which allows them to have a faster rate of digestion and passage through the digestive tract. The result is that grain is more digestible than forage, plus it decreases an animals ma
10、intenance requirement by resulting in less digestive organ mass, leaving more nutrients for muscle growth and fattening. Feedlots take advantage of the energy content and digestive characteristics of grains to finish cattle. However, if you have a grass-based system for your cows (like most of the w
11、orld), you arent going to switch to grain. One way to increase an animals performance with forages is grinding the forage to increase its digestibility by making more surface area available to ruminal bacteria and increasing the rate of passage of the forage through the digestive tract, decrease the
12、 bulk fill inherent with the forage, and decrease the animals maintenance requirement by decreasing the digestive tract weight. However, increasing the surface area of a forage diet is not the only answer, because not all gain is the same, and what you feed an animal affects the carcass characterist
13、ics.Producing consistently tender meat, and reducing excess external fat production while maintaining intramuscular fat deposition are still three of the major challenges in the beef industry, even though they were recognized in the 1992 National Beef Quality Audit sponsored by the National Cattleme
14、ns Association. Nutrition and genetics are the two major factors contributing to these concerns. Excessive external back fat and internal seam and KPH fat production causes inefficiencies in both feedlots, due to the higher energy cost of depositing fat compared with protein, and the packing industr
15、y, due to the high cost of trimming and the low price received for the fat. Developing management strategies to produce well-marbled, tender meat products are critical to the advancement of a high-quality beef industry.Typically, cattle are finished on high concentrate diets for a period of time ran
16、ging from 80-280 days prior to slaughter. This finishing period allows for more rapid, efficient growth, and increased intramuscular fat (marbling) deposition so that the cattle carcasses grade choice compared with cattle grown on forage-based feeding systems. In general, tissues are deposited in the order of: 1. brain, 2. bone, 3. muscle, and 4. fat, however, some animals seem to t
