Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Master of Science (MS)

Department / School

Animal Science

Abstract

Dried distillers grains plus solubles (DDGS) contain a significant amount of fat and undegradable intake protein, both of which have been shown to increase reproductive performance when supplemented to primiparous heifers. However, the mechanisms leading to enhanced reproduction have not been fully defined. Therefore, the objectives of this research were to evaluate the effects of DDGS in late gestation limit fed heifer diets on pre and postpartum heifer performance, the percentage of heifers that initiated estrous cycles before the start of the breeding season, pregnancy distribution, pregnancy rates, and circulating concentrations of growth hormone (GH), insulin-like growth factor-I (IGF-I) and non esterified fatty acids (NEF A). Over two years, 201 crossbred beef heifers were blocked by previous development and stratified by expected calving date, BW, and BCS. Heifers were randomly allotted to one of two diets that were similar in energy and adequate in DIP and fed from approximately d 190 of gestation through parturition. Diets were ground grass hay, DDGS or soybean hulls, and a supplement specific to each diet. Cow BW and BCS were measured at the start of treatment, prior to parturition, at the start of the breeding season, and at weaning. Blood samples were collected from cows prior to calving and weekly following calving for 4 weeks (year 1) and 6 weeks (year 2). There were no treatment x year interactions, thus only main effects of treatment are reported. Both DDGS and SBH treated heifers had positive BW changes over the feeding period, but DDGS heifers had a greater (P < 0.01) BW change compared to SBH heifers. Initial and final BCS and BCS change were similar (P ~ 0.26) between DDGS and SBH. Treatment did not influence (P 2:0.12) BW or BCS change during the postpartum period. Calving ease, calf vigor, calf birth weight, weaning weight, and average daily gain from birth to weaning were similar (P ~ 0.41) between treatments. Treatment did not influence the proportion of cows cycling (68% and 74%, DDGS and SBH respectively; P = 0.46) or pregnancy distribution (P ~ 0.26). However, a greater (P = 0.04) percentage of DDGS animals became pregnant compared to SBH animals (94 % and 84%, respectively). In both years there were no effects of treatment (P ~ 0.17) or treatment x time (P 2: 0.52), but time influenced (P SO.OS) circulating concentrations of GH, IGF-I and NEFA. Circulating concentrations of GH were elevated at calving and decreased through d 4 after calving in both years. Systemic IGF-I concentrations in both years were elevated around calving and decreased (P < 0.05) through d 8 or d 6 (year 1 and 2, respectively) and remained similar (P > 0.10) for the duration of the sampling period. Circulating concentrations of NEF A increased from calving through d 8, and gradually declined through d 20. In conclusion, prepartum diets containing DDGS as a source of fat and UIP may benefit pregnancy in well maintained primiparous beef heifers. However, the mechanism by which prepartum fat and UIP influence the reproductive axis remain unclear.

Library of Congress Subject Headings

Heifers -- Feeding and feeds

Distillers feeds

Proteins in animal nutrition

Oils and fats in animal nutrition

Heifers -- Reproduction

Format

application/pdf

Number of Pages

96

Publisher

South Dakota State University

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