Effect of feeding sweet potato vine-based diets as partial milk substitutes for dairy calves in Uganda

Abstract

Abstract
A study was conducted to determine the potential of sweet potato vine-based diets as partial milk substitute (PMS) for dairy calves. Twenty five Friesian bull-calves weighing 38.7 ± 4.56 kg were fed composite meals containing 0, 30, 40, 50 and 60% air-dried sweet potato vines (SPV) as partial milk substitutes in a completely randomized design (CRD) over a seventy day period. Dietary treatments were introduced 15 days after calving. Milk offered was reduced by one litre every fortnight until 70 days after birth. Proximate and mineral analyses were carried out for ingredients and dietary treatments. Feed intake (FI), average daily weight gains (ADG), feed: gain ratio and variable cost per unit of gain were computed over the experimental period.
The use of the PMS reduced the amount of milk consumed per calf by 120 litres over the 70-day period. Mean daily intake of dry matter was higher (p<0.05) for calves fed PMS (1.09 x103 gd-1) than those fed on milk and pastures (912 gd-1). Daily crude protein intake for calves fed PMS (216 g d-1) was comparable to the 220 gd-1 among calves fed milk + grazing (M + G) while daily energy intake increased from 9.91 to 11.4 MJ d-1 respectively. The ADG of calves were higher (p<0.05) among calves fed PMS (299 gd-1) than those fed milk and grazing (175 gd-1). Feed: gain ratio decreased from 21.7 (control) to 10.2 (PMS). Weaning weights were higher among calves fed PMS (64.9 kg) compared to 53.9 kg for the control. Net variable cost per unit of gain was more than halved when the calves were fed PMS comprising 30 – 60% SPV. Farmers can reduce costs of calf rearing and increase their income from sale of milk by using SPV meals as partial milk substitutes.