An evaluation of the profitability of supplementing dairy cows at different stages in the lactation : A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours, Lincoln University

The objective of this study was to assess the effects of supplementing dairy cows at different stages of the lactation on their production and profitability. The study involved using a linear programming model which maximised the profitability in terms of the gross margin per hectare. The results were analysed in two sections. The first took into consideration the basal pasture ration, which could be changed for each run. The second section analysed the optimal run (the run with the greatest gross margin), in terms of the value of supplementing at different stages in the lactation. The results showed that the greatest returns can be achieved by supplementing in early-mid lactation. Subsidiary effects such body weight change, pasture transferred from one period to the next and stocking rate were also optimised by the model. Results from the optimal run illustrated that to maximise gross income, the supplementation practices that should be adopted require; • Concentrate to be fed out in early lactation (weeks 1-4) • Pasture silage to be made on the property in early lactation and fed out in late lactation • Maize silage to be fed out in mid to late lactation • Additional pasture to be used as a supplementation in early, early-mid and late lactation, but not in mid-late lactation (weeks 21-32) • Body weight loss to occur from weeks 1-12 (early lactation) and gain to occur from weeks 21-40 (late lactation). • Nitrogen, at a rate of 50 kg/ha, to be applied 3 times to gain a response in early and late spring and autumn. The model appeared to represent a real-world situation well, supporting the results from previous studies carried out in this area