Feedlot cattle nutrition and management
Richard Zinn, Professor, Animal Science, 1004 E. Holton Rd., El Centro, CA 92243, 760 356 3068, firstname.lastname@example.org
A series of trial will be conducted evaluating metabolizable amino acid nutrition of the calf-fed Holstein, role of feed additives including prebiotics, tannins, chelated chromium, and virginiamycin on growth-performance and carcass traits, sugar and fodder beets as partial replacement for corn in finishing diets, and degradable intake protein requirements of calf-fed Holsteins when metabolizable protein intake exceeds requirements (as is the case with higher levels of distillers dried grains supplementation
Project is part of a continuing effort by University of California toward enhancing efficiency of feedlot cattle production through improvements in nutrition, health and management.
(The following bolded items are all separate projects by Dr. Zinn)
Amino acid nutrition of calf-fed Holstein: Metabolizable protein requirements are based on requirements for maintenance (3.8 LW0.75) plus gain [protein gain/(0.83- (0.00114LW) when LW is less than 300 kg, else protein gain/0.49], where protein gain = (ADG * (268 - (29.4 * (retained energy/ADG))), and retained energy = 0.0557 * (LW*(478/mature weight))0.75 * ADG1.097. The metabolizable amino acid requirements are then estimated based on the average amino acid composition of bovine tissue (metabolizable protein requirement x respective amino acid content of standard bovine tissue). During the early growing period, ADG and feed efficiency of feedlot calves are predictable functions of metabolizable amino acid supply with respect to requirements (Zinn, 1988; Zinn and Shen, 1998; Zinn et al 2007). Metabolizable amino acid requirements were derived by feeding diets that were first limiting in methionine (metabolizable methionine requirement = 1.565 + 0.0234ADG(268 - (29.4 * 0.0557BW0.75ADG1.097)/ADG) + 0.0896BW0.75). Requirements for the other essential amino acids were then estimated based on relationships between methionine and other amino acids in a standard reference protein (bovine muscle protein). Estimates of amino acid requirements derived in this manner (Zinn and Shen, 1998) were in close agreement with the more factorialzed approach of NRC (2000), lending strong support to the metabolizable amino acid concept. Receiving diets for feedlot cattle of diverse initial weights and backgrounds should be formulated to provide a minimum of 2.1 and 7.0 g/kg dietary DM intake of metabolizable methionine and lysine, respectively. However, achieving these constraints can be challenging. Corn and corn co-product feedstuffs are poor sources of ruminal escape lysine, and conventional supplemental proteins (soybean meal, canola meal, cottonseed meal) are relatively poor sources of metabolizable methionine. Fishmeal is an excellent source of metabolizable methionine and lysine. However, due to negative effects on diet acceptability, its inclusion rate should not exceed 3% of dietary DM (and, it is has become very expensive). Alternatively, there remains considerable interest in balancing dietary metabolizable amino acid constraints for feedlot calves using protected amino acids, particularly methionine and lysine (Hussein and Berger, 1995; Klemesrud et al., 2000). This study will further understanding in use of protected amino acids for balancing formulations to meet requirements.
Tannins: Preliminary work of Barajas et al (2010) indicate that low-level tannin supplemenation may enhance energy intake and daily weight gain of feedlot cattle independently of its effects toward enhancement of metabolizable amino acid supply to the small intestine (Mezzomo et al (2011).
Prebiotics: Prebiotics are partially hydrolyzed microbials that may benefit the host
by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the
colon” (Gibson and Roberfroid, 1995). Of particular interest are the mannin oligosaccharides that comprise cell walls of yeasts. These have been shown to be highly inhibitory of intestinal colonization of infectious coliform bacteria (Soderholm and Perdue, 2001). To date, no work was been reported evaluating prebiotic supplementation of feedlot cattle.
Chelated chromium: The feeding of supplemental chromium to feedlot cattle in USA was approved in 2012. This will be the beginning of a series of studies evaluating the influence of its effects on growth-performance and carcass traits of calf-fed Holstein and conventional crossbred cattle.
Virginiamycin: Virginiamycin is an antimicrobial derived from Streptomyces virginiae that inhibits growth of gram-positive bacteria (Cocito, 1979). In a summary of 7 dose-response studies with feedlot cattle (Rogers et al., 1995), dietary supplementation with 19 to 27 mg of virginiamycin/kg (DM basis) enhanced ADG (4.6%) and G:F (3.6%) and reduced (38%) the incidence of liver abscess. The effect on liver abscess incidence is due to direct inhibitory action on growth of Fusobacterium necrophorumand Actinomyces pyogenes (Nagaraja and Chengappa, 1998). The basis for improved growth-performance isless certain. Virginiamycin inhibits growth of ruminal lactic acid-producing bacteria, limiting ruminal lactate accumulation (Hedde et al., 1980; Nagaraja et al., 1987; Hynes et al., 1997; Clayton et al., 1999; Coe et al.,1999). Thus, virginiamycin might reduce risk of lactic acidosis and associated digestive dysfunctions after ruminal overload of rapidly fermentable carbohydrate (Owens et al., 1998). Virginiamycin might also enhance postruminal nutrient uptake. In swine, virginiamycin enhanced digestion of DM, N, and energy (Ravindranet al., 1984), ME (Vervaeke et al., 1979), and minerals (Ravindran et al., 1984; Agudelo et al., 2007). These benefits were attributable to prolonged intestinal retention time (28 to 33%, Ravindran et al., 1984) and to reduced intestinal bacterial evolution and corresponding organic acid production (Vervaeke et al., 1979). In a previous study conducted at this center, Salinas et al (2009) observed that supplementation of calf-fed Holstein steers with 22.5 mg/kg of virginiamycin may enhance G:F and apparent dietary NE. The effects of virginiamycin supplementation on characteristics of ruminal fermentation and total tract digestion are small and do not account for improvements in growth performance.
Beets: For 2010, beet yields in the U.S. averaged 62.2 t/ha. However, in the Imperial Valley (predominant cattle feeding region for the state of California), clean beet yields averaged 98.8 t/ha (USDA, 2010); 9 Imperial Valley beet growers topped the 2004 world record (148 t clean beets/ha), setting the new record at 156 t clean beets/ha (Lilleboe, 2010). With an average DM content of 23% (Milford, 2006), clean beet DM yields in the Imperial Valley averaged 22.7 t/ha, 277% the 2010 average DM yield for corn grain (8.2 t corn gain DM/ha; USDA, 2011b). In previous work conducted at this center (Arrizon et al 1012), dried shredded sugarbeets replaced SFC in finishing diets at inclusions of up to 40% without having detrimental effects on diet acceptability, daily BW gain, and carcass characteristics. Dried shredded sugarbeets had 82% the NE value of SFC (DM basis). The proposed trials will further evaluate the feeding value of both sugarbeet as well as fodder beets.
Degradable intake protein: This project evaluates the basic-applied concept regarding degradable protein requirements of feedlot cattle for microbial growth when dietary metabolizable protein intake exceeds requirements for animal growth. In the western US considerable DDG is fed as an alternative energy source in steam-flaked corn-based finishing diets. Typical levels of inclusion of DDG are 15 to 20%. These diets, although high in crude protein, do not meet NRC (1996) requirements for DIP without additional urea supplementation. However, no research has been published that evaluates the efficiency of N recycling when total dietary CP is fed in excess of requirements, and/or the consequences of limiting ruminal microbial growth and dietary energetic efficiency while otherwise meeting metabolizable protein requirements. Our hypothesis is that as level of metabolizable protein intake exceeds requirements for animal growth (protein is being used as an energy source), the requirement or degradable intake protein decreases (due to efficient recycling). By demonstrating the reduced need for supplemental urea in steam-flaked corn-based diets, the proposed research could lead to considerable formulation savings (in the present study the savings could be as much as $7.44/ton of complete mixed diet; $241.90 vs $234.46). Of course, the work would also have positive environmental implications with respect to N excretion.