Following the rapid increase in FB use in the mid 2010s, farmers and veterinarians became increasingly concerned about potential negative carryover effects on animal performance. Increased body condition score at calving in cows wintered on FB has resulted in more metabolic disease, e.g. milk fever and liver disfunction at parturition which may affect colostrum quality. Differences in nutrient intake between kale and fodder beet diets in late gestation, as detected by blood mineral status, has the potential to affect calf size at birth, growth of replacement heifers and their subsequent performance.
A series of studies undertaken at SDH to investigate wider implications of FB feeding to those being investigated in the farm systems study include:
A comparison of BCS gain, nutrient intake and early lactation milk production of cows offered two feeding levels of winter diets differing in crop type (FB and kale).
Measurement of the health and wellbeing status of cows feed fodder beet or kale at two allocations by testing blood parameters and activity measures during winter.
Determining if winter crop type and dry matter allocation affected colostrum quality in mixed age cows at their first milking post calving.
A comparison of the growth of rising one-year-old dairy heifers grazing either kale or FB from May until August and determine if crop type affected grazing behaviour and rumination.
Investigating any cumulative effects of dam (through en utero effects), on offspring winter diet at 1 and 2 years old (kale or fodder beet) on performance of heifer replacements from birth until the end of their first lactation.
Crop type had a greater impact on cow performance than allocation rate.
Cows wintered on FB had better reproductive performance and greater average milk solids yield than cows wintered on kale.
Later calving cows are less likely to be pregnant at the end of mating.
Body condition score loss in the first six weeks was not affected by crop type or allocation level.
Feeding FB increased blood magnesium but decreased blood phosphorus (if not supplemented with P), total protein and urea levels compared with cows fed kale.
Crop type had a bigger effect on blood metabolite concentrations than did the daily allocation of crop (kg DM/cow).
Achieving recommended dietary protein intake is difficult with FB diets especially in the last 4 weeks of pregnancy and for rising 1-year-olds.
Colostrum quality was not affected by crop type or allocation level but there is significant variation between individual animals and between quarters within an animal most likely linked to colostrum intake by the calf.
Cows wintering on FB walked more and had fewer, longer lying bouts. However, lying time will be affected by the soil conditions in individual paddocks.
Consideration should be given to the diets of heifer replacements in winter to ensure they achieve minimum dietary requirements, particularly of protein and phosphorus.
Dam and heifer diet did not affect milk production for the first lactation, however differences in liveweight, reproduction and blood metabolites indicate possible negative impacts of feeding heifers FB during winter, particularly if the dam is also wintered on FB.