|Su, Huawei - UNIVERSITY OF WISCONSIN|
|Akins, Matthew - UNIVERSITY OF WISCONSIN|
|Esser, Nancy - UNIVERSITY OF WISCONSIN|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2017
Publication Date: 8/11/2017
Publication URL: http://handle.nal.usda.gov/10113/5733334
Citation: Su, H., Akins, M.S., Esser, N.M., Ogden, R.K., Coblentz, W.K., Kalscheur, K., Hatfield, R.D. 2017. Effects of feeding alfalfa stemlage or wheat straw for dietary energy dilution on nutrient intake and digestibility, growth performance and feeding behavior of holstein dairy heifers. Journal of Dairy Science. 100:7106-7115.
Interpretive Summary: The primary goal for raising dairy heifers is to rear these animals at a desirable growth rate with minimum economic cost, but without reducing their future lactation performance. High-quality forage diets that are appropriate for lactating cows may lead to excessive weight gains and over-conditioning for dairy heifers, so many producers dilute the diets with a low-quality forage such as wheat straw. Alfalfa stems, a by-product of a novel alfalfa harvest fractionation technology being developed, have the potential to be used as a dilutant in heifer diets. Our study compared 3 diets: i) a control diet comprised of alfalfa haylage and corn silage that exceeded energy requirements for pregnant heifers; ii) a diet comprised of similar components, but diluted with alfalfa stemlage; and iii) a diet comprised of similar components, but diluted with chopped wheat straw. Diluting dietary energy density by adding alfalfa stemlage or chopped wheat straw was an effective method of controlling energy intake and maintaining desirable body condition and growth rates. This occurred despite the fact that heifers sorted out some of the low-quality forage and favored the high-quality forage, a practice that increased linearly over time following feeding, and with the alfalfa stemlage diet sorted more severely than the diet diluted with chopped wheat straw. We conclude that alfalfa stems are a potentially useful low-energy feedstuff resource and, with proper feeding management, can be used in heifer feeding programs with success.
Technical Abstract: Feeding high-quality forage diets may lead to excessive weight gains and over-conditioning for dairy heifers. Restriction of energy density and dry matter intake by using low-energy forages, such as straw, is a good approach for controlling this problem. Alfalfa stems contain high fiber and moderate protein content and have the potential to be used to replace straw to reduce dietary energy. The objective of this study was to compare nutrient intakes, digestibilities, growth performance, and feeding behaviors of dairy heifers offered an alfalfa silage/corn silage high-energy diet (HE; 13.1% crude protein, 65.4% total digestible nutrients, 39.7% neutral detergent fiber) with 2 energy-diluted diets that replaced various proportions of the corn or alfalfa silages with either alfalfa stemlage (STM; 12.6% crude protein, 59.1% total digestible nutrients, 46.4% neutral detergent fiber) or chopped wheat straw (WS; 12.6% crude protein, 61.9% total digestible nutrients, 43.7% neutral detergent fiber). Seventy-two pregnant Holstein heifers (16.8 ± 1.3 mo) were stratified into 3 blocks (24 heifers/block) by initial body weight (light, 440 ± 18.0 kg; medium, 486 ± 18.6 kg; heavy, 534 ± 25.1 kg), with each block composed of 3 pens (8 heifers/pen), with diets assigned randomly to 1 pen within the block. Diets were offered in a 56-d feeding trial. Both dry matter intake and energy intake were decreased with the addition of low-energy forages to the diets, but no differences in dry matter intake were observed across diluted diets. Digestibility of dry matter, organic matter, neutral detergent fiber, and apparent N were greater for HE compared with diluted diets, and for WS compared with STM. Total body weight gain (74 vs. 56 kg) and average daily gain (1.32 vs. 1.00 kg/d) were greater for heifers offered HE compared with diluted diets. Feed efficiency tended to be less for heifers offered the diluted diets compared with HE (10.7 vs. 8.6 kg of feed/kg of gain). Heifers did not sort for or against particles when offered HE. However, increased sorting behavior was observed for diluted diets. Compared with ad libitum feeding dairy heifers a diet with high nutrient content forages (corn silage and alfalfa silage), use of diet diluted with alfalfa stemlage or wheat straw is an effective feeding management strategy to control total daily dry matter and energy intake by increasing gut fill, and maintain desirable body condition and growth rates, even though the diluted diets had greater sortability.