Energy costs of feeding excess protein from corn-based by-products to finishing cattle

Abstract

The increased use of by-products in finishing diets for cattle leads to diets that contain greater concentrations of crude protein (CP) and metabolizable protein (MP) than required. The hypothesis was that excess dietary CP and MP would increase maintenance energy requirements because of the energy costs of removing excess N as urea in urine. To evaluate the potential efficiency lost, two experiments were performed to determine the effects of feeding excess CP and MP to calves fed a finishing diet at 1 × maintenance energy intake (Exp. 1) and at 2 × maintenance intake (Exp. 2). In each experiment, eight crossbred Angus-based steers were assigned to two dietary treatments in a switchback design with three periods. Treatments were steam-flaked corn-based finishing diets with two dietary protein concentrations, 13.8% CP/9.63% MP (CON) or 19.5% CP/14.14% MP (dry matter basis; ECP), containing corn gluten meal to reflect a diet with excess CP and MP from corn by-products. Each period was 27 d in length with a 19-d dietary adaptation period in outdoor individual pens followed by a 4-d sample collection in one of four open circuit respiration chambers, 2-d fast in outdoor pen, and 2-d fast in one of four respiration chambers. Energy metabolism, diet digestibility, carbon (C) and nitrogen (N) balance, oxygen consumption, and carbon dioxide and methane production were measured. At both levels of intake, digestible energy as a proportion of gross energy (GE) tended to be greater (P < 0.06) in ECP than in CON steers. Metabolizable energy (ME) as a proportion of GE tended to be greater (P = 0.08) in the ECP steers than in the CON steers at 2 × maintenance intake. At 1 × and 2 × maintenance intake, urinary N excretion (g/d) was greater (P < 0.01) in the ECP steers than the CON steers. Heat production as a proportion of ME intake at 1 × maintenance tended (P = 0.06) to be greater for CON than for ECP (90.9% vs. 87.0% for CON and ECP, respectively); however, at 2 × maintenance energy intake, it was not different (63.9% vs. 63.8%, respectively). At 1 × maintenance intake, fasting heat production (FHP) was similar (P = 0.45) for both treatments, whereas at 2 × maintenance intake, FHP tended to be greater (P = 0.09) by 6% in ECP than in CON steers. Maintenance energy requirements estimated from linear and quadratic regression of energy retention on ME intake were 4% to 6% greater for ECP than for CON. Results of these studies suggest that feeding excess CP and MP from a protein source that is high in ruminally undegradable protein and low in protein quality will increase maintenance energy requirements of finishing steers.

Geometric Stoichiometry: Unifying Concepts of Animal Nutrition to Understand How Protein-Rich Diets Can Be “Too Much of a Good Thing”

“…In many cases, however, consumers may be constrained to diets that are richer in protein relative to carbohydrate and lipid than is optimal (Rothman et al, 2011;Jensen et al, 2014;Nyffeler et al, 2016;Remonti et al, 2016;Wiggins and Wilder, 2018). Animals must then use protein as a source of energy, potentially leading to the onset of toxicity via deamination and release of ammonia and incurring various energetic and other costs associated with metabolic transformations, synthesis of reduced forms of N and excretion (Bender, 2012;Piper et al, 2017;Reed et al, 2017;Jennings et al, 2018). High dietary nutrient content can thus be "too much of a good thing" (Boersma and Elser, 2006).…”

Effects of wet corn distiller’s grains with solubles and nonprotein nitrogen on feeding efficiency, growth performance, carcass characteristics, and nutrient losses of yearling steers12

“…Zinn et al (1997) concluded that N excretion through urine in beef steers required 7.9 Kcal/g of N and Tyrrell et al (1970) determined that 10.8 Kcal of digestible energy were required per g of excess urinary N excretion in dairy cows. Jennings et al (2018) noted that maintenance energy requirements of steers increased approximately 4 to 6% when dietary CP concentrations were increased from 13.5 to 18% using a corn-based protein (corn gluten meal) source.…”

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

“…In the body, excess N is converted to urea in the liver and then excreted in the urine. Jennings et al (2018) conducted two experiments to determine the effects of feeding excess CP and MP (using corn gluten feed and corn gluten meal) on the maintenance-energy requirements of steers fed a finishing diet at 1 or 2 • maintenance-energy intake. Maintenance-energy requirements, estimated from linear and quadratic regression of energy retention on metabolisableenergy intake, were 4-6% greater for steers overfed CP (19.5% CP with 14.14% MP) than for control steers receiving 13.8% CP with 9.63% MP.…”

“…Maintenance-energy requirements, estimated from linear and quadratic regression of energy retention on metabolisableenergy intake, were 4-6% greater for steers overfed CP (19.5% CP with 14.14% MP) than for control steers receiving 13.8% CP with 9.63% MP. Jennings et al (2018) suggested that feeding excess CP and MP from a protein source that is high in RDP and low in protein quality will increase maintenance-energy requirements of finishing steers.…”

“…There has been little effort to reduce or manipulate the feeding of N in feedlots, in part due to logistics (such as labour, feedmill and feed-delivery management) and to the low purchase cost of urea and high-protein by-products. The impacts of excessive dietary N on the animal are equivocal (Gleghorn et al 2004;Jennings et al 2018), but the excreted excess N poses important environmental costs, and the energetic costs to the animal of excess protein may be underestimated. This review discusses recent advances in the protein nutrition of lot-fed cattle, and their application in Australia, Canada and the USA, and examines the need, scope and considerations for improved N efficiency in grain-finished beef production.…”