Supplementation of Spring Pasture with Harvested Fodder Beet Bulb Alters Rumen Fermentation and Increases Risk of Subacute Ruminal Acidosis during Early Lactation

Abstract

In a cross-over design, eight rumen cannulated dairy cows were used to explore the industry-recommended method for dietary transition to fodder beet (FB: Beta vulgaris L.) on changes to rumen fermentation and pH, milk production, dry matter intake (DMI) and the risk of subacute ruminal acidosis (SARA) during early lactation. Cows were split into two groups and individually allocated a ryegrass (Lolium Perenne L.) and white clover (Trifolium repens L.) diet (HO) or the same herbage supplemented with 6 kg DM/cow of harvested fodder beet bulbs (FBH). Dietary adaptation occurred over 20 days consisting of: stage 1: gradual transition to target FB intake (days 1–12, +0.5 kg DM of FB/d); stage 2: acclimatization (days 13–17) and stage 3: post-adaption sampling (days 18–20). Response variables were analyzed as a factorial arrangement of diet and stage of adaption using a combination of ANOVA and generalized linear mixed modelling. Dietary proportion of FB represented 22, (stage 1), 32 (stage 2) and 38% (stage 3) of daily DMI. One cow during each period developed SARA from FB and the duration of low pH increased with FBH compared to the HO treatment (p < 0.01). Rumen concentrations of lactic and butyric acid increased with FBH but concentrations of acetate, propionate and total volatile fatty acids (VFA) declined by 9.3% at day 20, compared to the HO treatment (p < 0.01). Treatments did not affect milk production but total DMI with supplemented cows increased during the final stage of adaptation and feed conversion efficiency (FCE kg milk/kg DM) declined with the FBH treatment. The occurrence of SARA in 25% of animals fed FB suggest it is a high-risk supplement to animal health and further evaluation of industry-recommended methods for feeding FB at the individual- and herd-scale are needed.

Rumen function and grazing behavior of early-lactation dairy cows supplemented with fodder beet

“…All procedures were approved by the Lincoln University Animal Ethics Committee (AEC 2018-22). The current study is a continuation of previous research that investigated the effect of FB supplementation on diet adaptation and milk production where cow management, experimental design, treatments, and management of forage and FB have been described previously (Fleming et al, 2020b…”

“…The FB ('Enermax. D') were sourced from another farm and transported to the experimental site before the commencement of each period to maintain the bulb's chemical composition (Fleming et al, 2020b). Fodder beet was harvested, and residual leaf was removed before transportation.…”

“…Before the beginning of the experiment, approximately 20 rectangular quadrats (0.2 m 2 ) were collected from each paddock, and an additional 2 quadrats from each allocation were collected every third day of the experiment. Samples were washed, oven-dried, and weighed to determine DM content and to develop a regression equation for estimating herbage mass using sward height, as reported previously (Fleming et al, 2020b).…”

“…Chemical components (CP, ADF, NDF, and OM) were determined by near-infrared spectroscopy (NIRS; FOSS NIRS Systems 5000). Three FB were randomly selected from the face of the stack to analyze DM and chemical composition (Fleming et al, 2020b). Briefly, FB were cut into 4 equal sections by halving the bulb lengthways and then halving lengthways again.…”

Subacute Ruminal Acidosis in Zebu Cattle: Clinical and Behavioral Aspects

“…As the clinical symptoms of SARA in the herd are more subtle, animals can suffer repeatedly from this “silent” condition, which will decrease their performance and reduce their weight gain [ 8 , 9 , 10 ]. In addition to this, SARA causes the reduction of several commensal cellulolytic rumen bacteria species [ 11 ].…”