LEVEL OF SUPPLEMENTAL FAT IN PREGNANT BEEF COW DIETS DURING MID-TO-LATE GESTATION: EFFECTS ON PERFORMANCE OF THE DAM AND PROGENY FROM BIRTH TO WEANING
Date
2024-04-24
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0002-2783-6225
Type
Thesis
Degree Level
Masters
Abstract
A 2-year study evaluated the effects of feeding a canola-based (7.4% ether extract) pellet to gestating cows on cow performance, reproductive efficiency, milk yield and composition, blood metabolite concentrations, and calf performance until weaning. Each yr, 72 pregnant cows were stratified by stage of gestation (111 ± 20 d) and body weight (BW; 619 ± 50 kg), allocated to 12 pens in a randomized complete block design. Pens were randomly assigned to 1 of 3 replicated (n = 4/yr) dietary treatments: 0 (CON), 150 (LOW), and 300 (HIGH) g of fat/d from canola pellet (DM basis). Diets were formulated to be isonitrogenous (CP: 8.40 ± 0.40%) and isocaloric (TDN: 59.78 ± 1.05%), while meeting NASEM (2016) nutrient requirements for pregnant beef cattle. Treatments were fed during the last two trimesters of gestation (148 ± 3 d) based on a dry matter intake of 1.89% of treatment average BW and transitioned to a common diet at the end of the feeding trial. Orthogonal contrasts were used to assess linear and quadratic relationships between fat inclusion and dependent variables. Differences were detected in body condition score (BCS; 1-5 scale; P = 0.03) and rib fat thickness (P < 0.05) at the start of trial, thus were included as covariates in the analysis of all related variables at subsequent time points. BW and conceptus corrected BW tended to linearly increase (P = 0.10 and 0.07, respectively) and the percentage of thin cows (BCS ≤ 2.5) linearly decreased (P = 0.01) across treatments at calving. As fat inclusion increased, BCS change from calving to breeding and weaning (P < 0.01 and 0.01, respectively) and BCS at breeding (P < 0.01) quadratically decreased. There was a quadratic response (P = 0.03) in pregnancy rate to fat inclusion, maximizing at 150 g/d of added fat. Although fat inclusion tended to linearly decrease (P = 0.10) male birth weight, there were no differences (P ≥ 0.34) in progeny weaning weight or average daily gain from birth to weaning for either sex. Fat supplementation at 150 g/d optimized reproduction without negative impacts on pre-weaning progeny growth and profitability.
Description
Keywords
Canola, Supplementation, Lipids
Citation
Degree
Master of Science (M.Sc.)
Department
Animal and Poultry Science
Program
Animal Science