Enteric methane, lactation performances, digestibility, and metabolism of nitrogen and energy of Holsteins and Jerseys fed 2 levels of forage fiber from alfalfa silage or corn silage

Abstract

Our objective was to determine the effects of replacing alfalfa silage (AS) neutral detergent fiber (NDF) with corn silage (CS) NDF at 2 levels of forage NDF (FNDF) on enteric methane (CH 4 ), lactation performance, ruminal fluid characteristics, digestibility, and metabolism of N and energy in Holstein and Jersey cows. Twelve Holstein and 12 Jersey cows (all primiparous and mid-lactation) were used in a triplicated splitplot 4 × 4 Latin square experiment, where breed and diet formed the main and subplots, respectively. The 4 iso-nitrogenous and iso-starch dietary treatments were arranged as a 2 × 2 factorial with 2 levels of FNDF [19 (low FNDF, LF) and 24% (high FNDF, HF) of dry matter] and 2 sources of FNDF (70:30 and 30:70 ratio of AS NDF to CS NDF). Soyhull (non-forage NDF) and corn grain were respectively used to keep dietary NDF and starch content similar across diets. Total collection of feces and urine over 3 d was performed on 8 cows (1 Latin square from each breed). The difference in dry matter intake (DMI) between Holsteins and Jerseys was greater when fed AS than CS. Compared with Jerseys, Holstein cows had greater body weight (48%), DMI (34%), fat-and protein-corrected milk (FPCM; 31%) and CH 4 production (22%; 471 vs. 385 g/d). However, breed did not affect CH 4 intensity (g/kg of FPCM) or yield (g/kg of DMI), nutrient digestibility, and N partitioning. Compared with HF, LF-fed cows had greater DMI (10%), N intake (8%), and FPCM (5%), but they were 5% less efficient (both FPCM/ DMI and milk N/intake N). Compared with HF, LFfed cows excreted 11 and 17% less urinary N (g/d and % of N intake, respectively). In spite of lower (2.5%) acetate and higher (10%) propionate (mol/100 mol ruminal volatile fatty acids) LF-fed cows had greater (6%) CH 4 production (g/d) than did HF-fed cows, most likely due to increased DMI, as affected mainly by the soyhulls. Compared with AS, CS-fed cows had greater DMI (7%) and FPCM (4%), but they were less efficient (5%), and CH 4 yield (g/kg of DMI) was reduced by 8%. In addition, per unit of gross energy intake, CS-fed cows lost less urinary energy (15%) and CH energy (11%) than did AS-fed cows. We concluded that, in contrast to level and source of FNDF, breed did not affect digestive and metabolic efficiencies, and, furthermore, neither breed nor dietary treatments affected CH 4 intensity. The tradeoff between CH 4 and N losses may have implications in future studies assessing the environmental effects of milk production when approached from a whole-farm perspective.

Effect of source and level of forage in the diet on in vitro ammonia emission from manure of Holstein and Jersey dairy cows

“…M. E. Uddin* and M. A. Wattiaux † NDF on cow performances, feces and urine output, and fecal and urinary N excretions in Holsteins and Jerseys, while maintaining similar starch, total NDF, and CP across diets (Uddin et al, 2020a). We found that low-forage NDF (LF)-fed cows excreted 17% less urinary N (expressed as percent of N intake) than high-forage NDF (HF)-fed cows.…”

“…Although laboratory-scale measurements capture the effects of manure composition on NH 3 emission, they do not account for differences in daily output of manure among treatments, as observed in Uddin et al (2020a). Results presented in Uddin et al (2020a) indicated that cow breed and dietary forage NDF affected fecesto-urine ratio, daily excretion of fecal and urinary N, and fat-and protein-corrected milk (FPCM) production.…”

“…Although laboratory-scale measurements capture the effects of manure composition on NH 3 emission, they do not account for differences in daily output of manure among treatments, as observed in Uddin et al (2020a). Results presented in Uddin et al (2020a) indicated that cow breed and dietary forage NDF affected fecesto-urine ratio, daily excretion of fecal and urinary N, and fat-and protein-corrected milk (FPCM) production. Therefore, we calculated manure NH 3 -N emissions adjusted for daily manure volume, FPCM, and manure N excretion, and we called these variables the "scaled-up" variables expressed in the following ways: grams of NH 3 -N/cow per day, grams of NH 3 -N/kilogram of FPCM, grams of NH 3 -N/ kilogram of raw manure, and NH 3 -N as percentage of total manure N excreted.…”

“…The manure used in this study was collected from a companion study in which we describe dietary treatments in detail and report cow performance, manure production, and manure N excretion data (Uddin et al, 2020a). An institutional animal care and use committee-approved protocol was followed for animal use and care during manure collection, which was conducted at the Dairy Cattle Center, University of Wisconsin-Madison.…”

“…In each chamber, approximately 16 g of reconstituted manure was incubated on a petri dish. The reconstitution was done to maintain the same feces-to-urine ratio as produced by each cow (wet weight basis), as reported in Uddin et al (2020a). Upon thawing and proper mixing, the required amount of feces was placed first in a petri dish, which was temporarily covered with parafilm until addition of urine.…”