Effects of diet type on nutrient utilization and energy balance in drylot heifers1. (13th January 2020)

• Record Type: Journal Article
• Authors: Baber, Jessica R; Wickersham, Tryon A; Sawyer, Jason E; Freetly, Harvey C; Brown-Brandl, Tami M; Hales, Kristin E
• Is Part Of: Journal of animal science. Volume 98:Number 1(2020)
• Publication Date: 2020-01-13
• Subjects: diet type -- energy balance -- heifers -- limit feeding; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/skaa006
• Languages: English
• ISSNs: 0021-8812

Abstract

Abstract: Feeding cattle in intensified settings allows cow-calf producers to decrease their reliance on grazed forage and utilize alternative feedstuffs. During times of intense management, diet type may alter energy utilization. Fourteen pregnant MARC III heifers (405 ± 44 kg BW) were used in a 180 d experiment to determine effects of diet type on nutrient and energy utilization. Heifers were randomly assigned to one of two treatments, a forage diet (FOR ; 2.10 Mcal metabolizable energy [ME]/kg; 95.75% forage) or a concentrate diet (CONC ; 2.94 Mcal ME/kg; 71% concentrate), and individually fed to meet maintenance energy requirements (0.135 Mcal ME/kg BW 0.75 ). The CONC diet contained dry-rolled corn, corn stalks (10.16 cm grind size), soybean meal, corn silage (approximately 45% corn grain; stored in a plastic bag), dicalcium phosphate, urea, and a premix pellet; FOR contained alfalfa hay (harvested at mid-bloom), corn silage, dicalcium phosphate, and a premix pellet. Measurements of energy intake and digestibility were measured over a 4-d period on days 116, 172, and 235 of gestation. Using portable headbox calorimeters, measurements of O2, CO2, and CH4 gases were collected over a period of 24 h. Data were analyzed in a completely randomized design with diet as fixed effect. Dry matter and organic matter digestibility were greater for CONC than FOR ( P < 0.01). Intake of gross energy (GE) and digestible energy (DE) were greater for FOR ( P < 0.01), but by design, ME intake was not different between treatments ( P = 0.26). Energy lost as methane (% of GE intake) was not different between treatments ( P = 0.49). The ratio of ME to DE was greater for CONC (86.8 vs. 82.8; P = 0.01) than FOR. Heat production relative to ME was not different between treatments ( P = 0.85). Maternal tissue energy did not differ and was 1.2 Mcal/d for CONC and 0.9 Mcal/d for FOR ( P = 0.73). Greater nitrogen (N ) consumption was observed for FOR (192.2 g/d) than CONC (134.0 g/d; P < 0.01), and retained N was greater for FOR than CONC ( P < 0.01) on days 116 and 235 of gestation. Neither concentrate-based or forage-based diets affected body condition score ( P = 0.26). Heifers fed concentrate-based diets retained more energy in part because they had larger calves, but this energy was not recovered in maternal tissue.