Variation in kale and fodder beet yield and quality over winter affects nutrient supply to non-lactating dairy cows at the Southern Dairy Hub

Abstract

Estimating crop quality and quantity is important for feed budgeting and nutritional balancing of diets for winter grazing. Commonly, farmers measure crop dry matter (DM) yield in autumn, but few complete quality tests. We assessed the DM yield and quality of
late spring sown kale and fodder beet (FB) from early autumn to late winter over five years at the Southern Dairy Hub, Southland, New Zealand. Yield and quality parameters were analysed over time since sowing, using polynomial data fitting. We hypothesised that
crop yields would remain stable during winter grazing, but that the supply of nutrients would vary, driven by a decline in the leaf proportion. Overall, crops showed rapid growth prior to winter but stable yields during winter grazing, but there was year to year variation in apparent growth trends and yields. The proportion of FB bulb increased over winter relative to the total crop yield for all cultivars and years. Fodder beet leaf was numerically higher in multiple nutrient concentrations (crude protein, Ca, Mg, P, S) compared to the bulb. For both crops, nutrients had only small fluctuations in concentration over time. Completing yield assessments in late autumn would give farmers a useful baseline yield indication for winter. Crop quality tests are recommended to identify any nutritional deficiencies that need addressing to ensure good animal health and performance.