(178) Protein and Energy Supplementation to Beef Heifers During Mid-Gestation and the Impacts on Calving and Male Offspring Morphometric Characteristics at Birth

Abstract Authors: Jennifer L. Hurlbert¹; Brooklyn M. Kuzel¹; Shelby Sullivan¹; Kevin K. Sedivec²; and Carl R. Dahlen¹

1. North Dakota State University Department of Animal Sciences, Fargo, ND, USA

2. North Dakota State University, Central Grasslands Research Extension Center, Streeter, ND, USA

Abstract Text:

The objective of this study was to evaluate the impacts of providing a protein and energy supplement to beef heifers during mid-gestation on calving outcomes and morphometric characteristics of the male offspring at birth. Angus-based heifers (n = 44; initial body weight [BW] = 426.7 ± 30 kg), each pregnant with a male calf from a single artificial insemination breeding, were ranked by BW and randomly assigned to receive one of two diets from d 90 to 186 of pregnancy. Treatment diets were: 1) a forage-based diet targeting a BW gain of 0.28 kg/heifer/d (CON; n = 22); or 2) a forage-based diet plus a corn-based protein/energy supplement targeting a BW gain of 0.79 kg/heifer/d (SUPP; n = 22). Actual BW gains during the treatment period were 0.25 kg/heifer/d and 0.75 kg/heifer/d for CON and SUPP dams (P < 0.0001), respectively. Following the treatment period, all dams were managed on a common diet through parturition. At calving and pre-suckling, BW of the dam and neonatal calf (n = 21 CON; n = 21 SUPP) were recorded and calving date was recorded to calculate gestation length. Dams were assigned a calving ease score from 1 to 5 (1: unassisted birth to 5: cesarean). Additionally, a single quarter of the udder was completely milked to estimate colostrum volume and mass. The placenta was collected upon expulsion and rinsed, weighed, and total number of cotyledons counted. In the period shortly after birth, calves were assigned a vigor score of 1 to 5 (1: nursed independently to 5: stillborn). At 24 h after colostrum consumption, calf BW was recorded and morphometric characteristics were evaluated, including chest and abdominal circumference, crown-rump length, shoulder-to-hip length, hip width, and hip height. Individual animal served as the experimental unit, and data were analyzed using the MIXED procedure of SAS. Significance was considered at P ≤ 0.05 and tendencies were considered at 0.05 < P ≤ 0.10. Dam BW was not different (P = 0.15) at calving; however, calves born to SUPP dams were approximately 2.5 kg heavier (P ≤ 0.04) at birth and 24 h compared with CON. Chest circumference was also greater (P = 0.05) and abdominal circumference and hip height tended (P ≤ 0.10) to be greater in SUPP calves than in CON. No differences were observed (P ≥ 0.18) for measurements including crown-rump length, shoulder-to-hip length, hip width, or vigor score between SUPP and CON calves. Furthermore, gestation length, calving ease, colostrum production, placental weight, and number of cotyledons were not different (P ≥ 0.13) for CON and SUPP. These data show that providing supplemental protein and energy and greater rates of gain during the second trimester of pregnancy supported increased birth weight and body measurements in the neonatal calf, but did not impact maternal BW at calving, colostrum production, or placental characteristics. Further evaluation of growth performance and metabolic phenotype in the F1 male offspring at later postnatal timepoints will help determine whether maternal nutritional management during gestation induces long-term programming outcomes that could enhance offspring productivity and contribute to global food security.