Abstract

The objective was to test the effect of fescue cultivars and supplemental feeding of cows grazing fescue pastures on cow performance and pasture management. Primiparous and multiparous Angus-based crossed cows (n = 48) averaging 140 ± 0.5 days of gestation at turnout, were randomly allocated and stratified to pasture treatment by parity. Each pasture contained three cows of different ages, consisting of a young (first-calf heifer), middle-aged (3-5 yrs.), and old (≥ 6 yrs.) cow. Treatment was a 2 by 2 factorial design with two types of pasture (toxin producing: TOXIC or non-toxin producing fescue: NONTOXIC) and two levels of supplemental feeding (non-supplemented: NON or supplemented at 1% of body weight on a dry matter basis of corn silage: SUPP). Toxic fescue pastures consisted of K-31 endophyte infected tall fescue (n = 8) tested at 1709 ppm ± 0.36 for ergot alkaloids with an 89.1% infection rate. Non-toxic pastures consisted of novel (MaxQ) and endophyte free varieties (n = 8). Cows were fed silage (32-42% dry matter and 7.83% crude protein) daily in fence-line bunks, with feeding amount being adjusted at each weigh date. Cows were weighed on 2 consecutive days prior to turnout (~middle of the second trimester), beginning of the third trimester, ~2 weeks prior to the estimated calving date for herd, and at peak lactation (~60 days after calving). Body weight (BW), body condition score (BCS), hair score (based on a 1-5 scale; HS), hair length measured over the 3rd rib (HL), and rump fat (RF) measurements were taken at each weigh date during gestation. Calves were weighed at birth and used in weigh-suckle-weigh to estimate milk output. Forage accumulation (FA) and forage mass (FM) were estimated every 28 days using the paired-cage method. There were no grass type x supplementation interactions (P > 0.19) for any measurement, other than HS and HL. Prior to calving, there was a tendency for cows grazing NONTOXIC to have heavier weights (P = 0.10); this continued through peak lactation (P = 0.10). Supplementation did not affect BW (P > 0.32), BCS (P > 0.22), or RF (P > 0.21) during gestation; but during lactation SUPP increased BCS (P = 0.007) over NON. Hair length and HS were greater for cows grazing TOXIC pastures at the beginning of third trimester (P = 0.06) and immediately prior to calving (P = 0.04). NONTOXIC-NON cows had a greater reduction in HL than those grazing TOXIC-NON with supplementation on both grass types being intermediate (P = 0.05). Calf birth weight and estimates of milk output were not different for grass type or supplementation (P > 0.23). Forage mass tended to be 11% greater in TOXIC pastures than NONTOXIC (P = 0.06) and SUPP pastures tended to have 6% greater FM than NON (P = 0.09). Non-toxic pastures, overall, result in greater cattle performance. Supplementation did not offset toxicity but did result in greater available forage.

Keywords: Fescue toxicosis, endophyte, cow-calf, gestation

How to Cite:

Farney, J. K. & Jones, T. M., (2025) “Effects of Supplementing Corn Silage to Fall-Calving Heifers and Cows Grazing Tall Fescue on Cow Performance”, Kansas Agricultural Experiment Station Research Reports 11(2). doi: https://doi.org/10.4148/2378-5977.8684