1a. Objectives (from AD-416):
Objective 1: Determine the nutrient value and environmental consequences of novel feed products. Objective 2: Improve determination of dynamic changes in nutrient requirements as the animal’s physiological status changes to allow for timed nutrient delivery. Objective 3: Determine the role of malnutrition during critical periods in developmental programming and epigenetic effects that alter lifetime production potential and product quality. Objective 4: Determine metabolic and physiological mechanisms responsible for variation in feed efficiency that is under genetic control.
1b. Approach (from AD-416):
Feed costs represent the single largest input in both beef and swine production; however, less than 20% of the feed energy is converted to edible product. Improving the efficiency that feed is converted to animal products has the potential to improve the economic efficiency of animal production while improving the sustainability of animal agriculture. To maximize feed efficiency the correct profile of nutrients are matched to meet an animal’s needs for its current biological status (growth, pregnancy, lactation, previous nutrient history, and disease). In order to provide the correct profile of nutrients, the nutrient composition of feeds and the dynamic nutrient requirements of the animal must both be identified and then synchronized. There is genetic variation amongst animals in their ability to utilize feed. Multiple genes are associated with the regulation of feed intake, and the utilization of ingested nutrients. Differential expression of these genes results in variation of feed efficiency amongst animals within populations, and these genetic differences potentially change the nutrient requirements of the animal. Nutrient status during critical periods of development (fetal and peripuberal) can permanently modify the expression of genes changing the lifetime feed efficiency of an animal. Identifying the role of nutrition in regulating gene expression is needed to develop nutrition management strategies across generations of animals in a production system.
3. Progress Report:
One hundred and twenty-eight steers were placed on one of four fiber inclusion levels to determine the optimum fiber level on a diet that includes distiller’s grains. Feed intake and growth data were collected over a 140-day feeding period. Steers were slaughtered and carcass quality was determined. Twenty-four nursery pigs were assigned to one of three dietary regiments to determine the role of antimicrobials in improving feed efficiency by improving gut health. One of the antimicrobials is lysozyme while the other is a traditional antibiotic. Pigs were slaughtered and jejunum samples were mounted on Ussing chambers to access mucosal barrier function. Samples have been stored to determine the rates of glucose and amino acid absorption. Seventy-seven light weight mature cows were assigned to one of three dietary supplements to determine the effect of protein availability on body weight gain. Cows were fed a fixed amount of feed over a 13-week period to achieve a body condition score of 4.5. Cows were then given free access to grass hay and a protein supplement for 56 days. Daily feed offered, weekly feed refusals, and diweekly body weights were measured. Sixty-six heifers were developed on two diets to add to the population of cows being evaluated for lifetime productivity. Six hundred and nineteen cow’s production records were recorded in the previous year. Six heifers were developed on each of the two diets and slaughtered. Ovarian and mammary tissues were collected. Ovarian follicle number, global methylation of the ovary and mammary gland were tested. Production records were collected on 307 cows that had experienced different fetal nutrition. A region on chromosome 4 has been investigated for a role in beef steer gain and feed intake. A specific gene involved in cell signaling has been associated with these traits in cattle. In addition, several steers with extreme feed efficiency traits have been sequenced for differences in chromosomal regions that ultimately produce proteins. Experimental treatments were applied to 135 cows. Adipose and muscle biopsies were collected during feed restriction and then again during realimentation. Expression data from both tissues was collected on 86 cows for genes involved in cattle feed intake and gain.
1. Lysozyme is an alternative to antibiotics for young pigs consuming manufactured liquid diets. Antibiotics have been fed at subtherapeutic levels as growth promoters for more than 50 years and the majority of swine produced in U.S. receive antibiotics in their feed at some point during the production process. The addition of antibiotics to swine diets benefits producers by improving feed efficiency and decreasing susceptibility to bacterial infections. Recently, however, swine producers have been pressured to reduce or remove dietary antibiotics. The identification of suitable alternatives to antibiotics will enable the swine industry to effectively transition away from dietary antibiotic use. ARS research conducted at the U.S. Meat Animal Research Center, Clay Center, Nebraska, determined that feeding a natural antimicrobial, lysozyme, to young pigs consuming a liquid diet was as effective as antibiotics in increasing growth performance, improving gastrointestinal health, and decreasing pathogen shedding. This research has demonstrated an effective alternative to traditional antibiotics in swine diets.
2. Roughage concentration can be decreased in finishing cattle fed distillers grains without adversely affecting cattle performance or carcass quality. Distillers grains are by-products of grain fermentation used to produce ethanol and contain relatively high amounts of fiber compared with the grains and concentrates they replace in feedlot diets. Typical finishing diets in the U.S. contain between 8 and 9% roughage. ARS research conducted at the U.S. Meat Animal Research Center, Clay Center, Nebraska, evaluated the effects of roughage concentration in diets based on dry-rolled corn with wet distillers grains and solubles and found that lower levels of fiber could be used in finishing diets when distillers grains are included in the diet. This research has demonstrated an effective alternative to traditional antibiotics in swine diets. This research has provided cattle feeders with information to make management decisions about diet formulation.
3. Discovery of genetic markers associated with feed efficiency in beef cattle. Residual feed intake (RFI), the difference between the amount of feed that an animal is expected to consume and the actual amount consumed, is a measure of feed efficiency. The ability to choose animals by their genetic make-up that are more efficient will result in cost savings for producers, as these animals will consume less feed and feed is the most costly portion of beef cattle production. ARS research at the U.S. Meat Animal Research Center, Clay Center, Nebraska, studied six genetic markers that are predictive for differences in feed efficiency in beef steers were identified in a region on the bovine chromosome 14. These markers were also evaluated for their effects on meat quality and carcass traits to determine whether they would impact weight and eating quality. The markers were not associated with marbling and tenderness, thus they are unlikely to impact beef quality. The markers identified may be potentially useful for the genetic selection of feed efficient cattle.
Hales, K.E., Cole, N.A., MacdDnald, J.C. 2012. Effects of corn processing method and dietary inclusion of wet distiller's grains with solubles on energy metabolism, carbon-nitrogen balance, and methane emissions of cattle. Journal of Animal Science. 90:3174-3185.