Comparison of animal performance of domestic herbivores grazing on partially improved heath lands

Abstract

Animal performance (live-weight changes, LWC) of 5 mares, 5 cows, 35 goats and 35 ewes suckling their offspring, managed on natural shrub land with an area (24%) of improved pasture, was compared across the grazing season. Mothers’ live weight (LW) was recorded in the beginning and thereafter monthly until the seasons’ end. Their offspring were weighed at turn-out and at weaning. Grazing season was divided into four seasons: spring (May to July), summer (July to end of September), autumn (end of September to end of November) and winter (end of November to January). On the overall grazing season, animal species had a significant (P<0.01) effect on LWC (g/day/livestock unit-LU). While cows lost weight (-170 g/day/LU), mares, goats and ewes were able to increase their LW in 63, 76 and 64 g/day/LU, respectively. LWC differed significantly (P<0.001) between animal species in all periods. All four species had positive LWC in the spring (859, 842, 377 and 308 g/day/LU in cows, mares, ewes and goats, respectively) as a result of a higher improved pasture availability (6.8 cm). In the summer and autumn, when the sward height decreased (4.6 and 2.9 cm, respectively) cows, mares and goats lost weight (average of -189, -194 and -72 g/day/LU), especially in the summer, while ewes were able to increase their LW (129 g/day/LU). In the winter, cows and mares increased their weight loss rate (-1,878 and -604 g/day/LU) and ewes showed negative LWC (-290 g/day/LU). Contrastingly, goats were able to increase their LW (64 g/day/LU). Within the offspring, lambs showed the highest LW gains (1,083 g/day/LU), while kids the lowest ones (696 g/day/LU), but not significantly different from those observed in calves and foals. These presented similar LWC from turn-out to weaning (804 and 785 g/day/LU, respectively).