Pasture-based dairy farmers are struggling against rising feed costs and stagnant milk prices. To combat the effect of increasing feed prices on the profitability of a pasture-based dairy farm, levels of concentrate supplementation can be decreased to lower input costs. It is evident that the profitability of a pasture-based dairy farm can be improved through the reduction in concentrate supplementation level while (where possible) the herbage allowance and quality is increased. Profitability studies however failed to include the effect of increase of land use, due to an increased pasture allowance that leads to decreased stocking rate. Plant-biostimulants like fulvic acid and bioflavonoids can increase pasture quantity, thereby improving stocking density. The gap in profitability studies to examine the economic effect of a combined application of reduction of concentration supplementation and the increase in pasture quantity and quality through the application of fulvic acid and bioflavonoids has to the best of the author’s knowledge not been investigated. This study aimed to quantify the effect of reduced concentrate supplementation rates in the production of pasture fed lactating Jersey cows. Simultaneously, the effect of plant-biostimulant treatment, fulvic acid and bioflavonoid, on a mixture of perennial ryegrass and clover pasture was also studied. Lastly, the effect of reduced concentrate feeding and increased pasture allowance on the profitability of Jersey cows was investigated.

    For the first study, a 3.3 Ha pasture paddock consisting of homogenic one-year old perennial ryegrass and clover pasture were used. A randomized block design with three blocks and two treatment factors (each at two levels) were adopted viz. 12 experimental plots. The first factor was the grazing cycle in two contrasting seasons (summer 2021 and winter 2021). For the second factor an untreated control was compared to a commercial plant-biostimulant cocktail treatment. Two plots per block were treated with the biostimulants.

    Biostimulant treatment affected pasture botanical composition, resulting in lower ryegrass content in both a winter and summer grazing cycle (P < 0.01). The biostimulant treatment had no effect on the chemical composition nor Stellenbosch University https://scholar.sun.ac.za iii the total yield of perennial ryegrass/clover pasture within a seasonal grazing cycle. There was however a tendency (P = 0.08) for biostimulant treatment to improve herbage yield in the summer grazing cycle. For the second study twenty-four lactating multiparous Jersey cows for both a winter and summer season were used. A randomized block design was used where cows were randomly assigned to one of two treatments: four kilogram concentrate supplement per day with 12 kg (DM) pasture allowance (LC) and eight kg concentrates supplement per day with 8 kg (DM) pasture allowance (HC).

    The long-term effects of reduced concentrate supplement feeding were also investigated after the completion of the winter and summer trials. During the long-term evaluation, the cows in both treatment groups grazed pasture ad lib with 4 kg/day concentrate supplementation. Milk yield, 4% fat corrected milk yield and energy corrected milk yield remained unchanged regardless of concentrate supplementation rate in both the summer and winter trials. Milk protein yield and milk protein content were not affected by treatment in the winter trial. In the summer trial treatment influenced milk protein yield (P < 0.01) but not milk protein content. Milk protein yield was higher for the HC treatment. Milk fat yield, milk fat content, somatic cell count, body weight and condition score were not affected by treatment in both the winter and summer trials. Milk urea nitrogen levels was affected by concentrate supplementation rate (P < 0.01) in the winter trial but not in the summer trial. Milk urea nitrogen levels were higher for cows in the LC treatment (9.11 mg N/dL) than cows in the HC treatment (6.56 mg N/dL) during the winter trial.

    The cows in the LC and HC treatment groups managed to maintain their body condition score and body weight in both the winter and summer trials up to 150 days after the end of each respective trial. Milk yield after each trial followed the shape of a standard lactation curve and milk yield gradually decreased towards the drying off period. Lastly, the effect of reduced concentrate feeding and increased pasture allowance on the profit margin over feed cost per cow/day, per cow/hectare and per cow/month of multiparous lactating Jersey cows in the summer and winter seasons was determined. In the winter trial lowering of concentrate supplementation proved to be profitable when enough good quality pasture is available based on both per cow per day (P = 0.03) and monthly performances (P = 0.04). There was also no negative effect of reduced concentrate supplementation levels on per cow per hectare performance. The only benefit of reduced supplementation levels in the summer trial was based on the profit margin per cow per day. Higher supplementation levels proved more profitable (P < 0.05) on per cow per hectare performance with no difference in profit margin between treatments based on a monthly basis. Although biostimulant application did not improve pasture yield, farmers can still increase farm profitability through reduced supplement rates and increased pasture allowance when good quality pasture is available.

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