Effects of Type of Concentrate and Timing of Supplementation on Feed Intake, Nitrogen Use, and Performance in Lactating Dairy Cows Grazing an Alfalfa-Ryegrass Sward

Abstract

The aim was to analyze the effects of two cereal grains differing in nutritional composition and starch degradation characteristics and the timing of their supplementation on feed intake, rumen microbial protein synthesis (MPS), performance, and nitrogen use of lactating dairy cows grazing an alfalfa-ryegrass sward. Four dietary treatments were tested in 24 lactating Brown Swiss cows in an incomplete 4 × 3 Latin square design. Cows were supplemented with 3.5 kg/d (as-fed basis) of a corn-based or an oat-based concentrate mixture (CM), of which either the majority (2.5 vs. 1.0 kg/d) was offered before or after grazing. Feed intake was similar across diets, but the interaction between type of CM and timing of supplementation affected eating time (p = 0.010), milk protein (p = 0.013) and energy-corrected milk yields (p = 0.025), efficiency of rumen MPS (p = 0.094), and nitrogen use efficiency (p = 0.081). Most of these variables were greater when the majority of the corn-based CM was offered after grazing and the oat-based CM before grazing. Supplementing slowly degradable starch sources after and rapidly degradable starch sources before grazing may improve the efficiency of rumen MPS, milk performance, and nitrogen use efficiency in dairy cows grazing alfalfa-ryegrass swards.

Timing of High-Energy Supplementation to Early-Season-Pasture-Forage Fed Continuous Culture

“…Microbial efficiency tended to increase (P ≤ 0.09) as a result of the PM feedings. Similar results were reported Dickhoefer et al [27] when corn was supplemented to dairy cows after grazing mixed alfalfa-ryegrass pasture as the majority of their daily dietary nutrient allotment. The efficiency at which degraded feed N was converted to microbial N was greatest in the PM (P = 0.05) with SUPP B having a more efficient conversion (P = 0.002) of degraded feed N to microbial N than SUPP A.…”

“…Based on nutrient content, early-season pastures in the Appalachian region of the United States can be of substantial quality. Predictive modeling systems such as those found in several versions of the beef and dairy nutrient requirement reports [1] and numerous other implicative reports [2,3] suggest that ruminants grazing moderate to high-quality cool season pastures typically consume excess digestible protein.…”

“…AM = Supplement fed at 0700 hr, PM = Supplement fed at 1900 hr, Sup. = supplement2 Nonstructural carbohydrate (sugars + starch)3 Total carbohydrate digested (NDF + NSC), g/day…”

Estimation of microbial protein synthesis in the rumen of growing lambs based on the purine derivative excretions and the dietary forage-to-concentrate ratio

“…Chen and Gomes [ 9 ] stated that the efficiency of MPS increases due to an increase in the passage rate of digestible rumen materials. The efficiency of MPS when consumed as high-quality forage by animals is often recorded to be high (30–45 gm of microbial nitrogen per kg of digestible organic matter), while the efficiency of MPS is much lower than 20% when low-quality forage is consumed by the animals [ 20 ], as reported previously [ 21 , 22 ].…”

Predicting nitrogen excretion of cattle kept under tropical and subtropical conditions using semimechanistic models

“…The database used for model evaluation was compiled from eight N balance studies performed in El Salvador, Kenya, and Peru by the Group of Animal Nutrition and Rangeland Management in the Tropics and Subtropics and local partners during the past 8 years (Corea et al, 2017;Sainz-Sánchez et al, 2018;Ali et al, 2019aAli et al, , 2019bAloba, 2022;Castro-Montoya et al, 2019;Corea et al, 2020;Sainz-Sanchez et al, 2019) (Table 1).…”