Performance of dairy cows and calves in agro-pastoral production systems
Sammanfattning: Seasonal changes in pasture quality and quantity and cattle management routines were examined on 10 farms in southwest Uganda in order to evaluate how these factors affected milk yield, live weight and body condition in cows and daily weight gain in calves in agro-pastoral production systems in a semi-arid environment. Mean available herbage mass ranged between 0.6-1.6 ton dry matter (DM) per hectare, with the highest value found in October and the lowest in February-May. Mean metabolisable energy content in pasture ranged between 5.8-7.7 MJ/kg DM and mean crude protein content between 5.4-9.1% during the study period. Mean daily milk yield during lactation months 0-6 was significantly higher for cows in parity ≥3 (8.7 kg) than cows in parity 2 (7.7 kg) and parity 1 (6.9 kg). Crossbreeds with >75% Holstein-Friesian (HF) and <25% Ankole had significantly higher daily milk yield (8.6 kg) than cows with 75% HF (7.7 kg) and 50% HF (6.9 kg). Cows milked twice per day had 1.9 kg higher daily milk yield than cows milked only once per day. Daily milk yield per cow decreased by 0.1-0.5 kg when dry season length increased by 10 days, with the strongest effect in early lactation. Kraaling cows at night affected milk yield negatively. Calving month and pasture availability affected cow live weight, but had no effect on body condition score and milk yield. Daily weight gain for calves was 288, 315 and 442 g/day at age 0-2, 2-6 and 6-9 months, respectively. Average live weight for calves at age 6 and 9 months was around 90 kg and 120 kg, respectively. Daily weight gain of calves at age 6-9 months increased by 81 g for each additional percentage of crude protein in pasture (p<0.05). Crosses with >75% HF had 60 g lower daily weight gain than crosses with 75% HF and 25% Ankole at age 0-6 months (p<0.05). Birth month had no significant effect on calf weight gain. In conclusion, the large differences in animal performance observed between farms indicate good potential for increased productivity by changing management routines. Calf growth was negatively affected by increased HF, while it had a positive impact on milk yield. This should be considered in future breeding and feeding strategies. The generally low pasture quality is most likely a limiting factor for milk productivity, as even crossbreed cows with a high inclusion of HF had only moderate milk production.
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