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

Simple Summary

Supplementing non-structural carbohydrates can enhance feed intake, performance, and nitrogen use in dairy cows grazing protein-rich swards. The present study thus analyzed the effects of feeding lactating cows two types of cereal grains, when their majority was either offered before or after grazing an alfalfa-ryegrass sward. Results showed that supplementing corn meal as a slowly degradable starch source after grazing and oat meal as a rapidly degradable starch source before grazing may improve milk yield and nitrogen use in grazing dairy cows. Hence, matching the choice of concentrate feed and the timing of its supplementation may aid to reduce nitrogen emissions from pasture-based dairy cattle systems while making use of the local, human-inedible forage resources from grasslands.

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.

Dwarf versus tall elephant grass in sheep feed: which one is the most recommended for cut-and-carry?

Tall- and dwarf-sized elephant grass cultivars have been developed for cut-and-carry system. Dwarf clones have better digestibility; on the other hand, tall-sized cultivars are more productive. The aim was to verify which grass would be most recommended for cut-and-carry: tall-sized (Elephant B and IRI-381) or dwarf (Taiwan A-146 2.37 and Mott) elephant grass cultivars to feed 24 male sheep, aged between 4 and 5 months, uncastrated, weighing approximately 24.08 ± 1.76 kg body weight which were sampled on intake, digestibility, performance, ingestive behavior, nitrogen balance, microbial protein synthesis, metabolic parameters, and ruminal degradability. This research was divided into two experiments: experiment 1 lasted 38 days, seven for adaptation and 31 for data collection. Elephant grass cultivars were supplied with a mineral mixture. Data collected were intake, digestibility, ingestive behavior, metabolic parameters, microbial protein synthesis, and performance submitted to a completely randomized design. For experiment 2, three rumen fistulae animals were sampled, lasting 20 days. In this case, a randomized block in split-plot design was applied. Both designs were with P < 0.05 and analyzed through SAS statistical software. Mott and Taiwan A-146 2.37 cultivars provided greater intake, digestibility, weight gain, feeding time, nitrogen retention, production and efficiency of microbial protein synthesis, dry matter (DM) and neutral detergent fiber (NDF) degradability, and DM, crude protein, and NDF, but shorter rumination time rather than Elephant B and IRI-381. There was also a significant difference for glucose, triglycerides, plasma urea, total serum protein, urinary urea (mg/L), and urea excretion in urine (mg/day). Dwarf elephant grass cultivars as Mott and Taiwan A-146 2.37 have greater nutritional value than tall-sized Elephant B and IRI-381. Dwarf elephant grass is recommended for cut-and-carry system.