The effect of grazing willow (Salix spp.) fodder blocks upon reproductive rate and management of internal parasites in mated hoggets : a thesis presented in partial fulfilment of the requirements for the degree of Master in Animal Science at Massey University, Palmerston North, New Zealand
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Date
2007
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Massey University
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Abstract
A grazing experiment was conducted for 116 days from 19 January to 15 May in the late summer/autumn of 2006 at Massey University's Riverside dryland Farm, near Masterton (New Zealand) to compare the effect of grazing willow fodder blocks or control perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture, during the pre-mating and mating periods, on gastrointestinal parasitism control and reproductive rates in 7 months old ewe hoggets. A rotational grazing system with 348 Romney weaned hoggels was used. Hoggets were randomly allocated to three treatment groups (116/group), being: control pasture with regular anthelmintic drenching, control pasture with trigger drenching (drenched only when mean faecal egg count of each group exceeded 1000 eggs/g wet faeces) and willow fodder blocks with trigger drenching. Four replicated pasture areas and five replicated willow fodder blocks were rotationally grazed by single groups of animals, using animals as the replicates for statistical analysis. The fodder blocks contained small trees and a mixture of herbage growing under the trees. After mating, the three groups were joined together and managed as one group until the end of the experiment at weaning, on 7 January 2007. Hogget live weight (LW), dag scores, faecal egg counts (FEC) and reproductive rate at foetal ultrasound scanning, lambing, docking and weaning were measured. Ewe hogget wool production was measured at weaning. Relative to control pastures, fodder block herbage was of lower dead matter content and its legume content was slightly higher. Total N concentration (35 g/kg dry matter; DM), organic matter digestibility (OMD; 0.68) and metabolisable energy (ME; 10 MJ/kg DM) were similar for fodder block pasture and control pasture; the selected tree fodder had lower concentrations of N (24 g/kg DM) and was higher in OMD (0.74) and ME (10.4 MJ/kg DM). Tree fodder contained higher concentrations of CT (22.9 g/kg DM) compared to 1.6 g/kg DM in control pasture and herbage in willow fodder blocks. Grazing willow fodder blocks increased LWG (approximately 97 g/day vs. 86 g/day; P< 0.0001) and increased reproductive rate corrected to equal LW by approximately 17% units (P<0.05), due to increases in both oestrus activity (P<0.01) and conception rates (hoggets pregnant/100 hoggets mated; P<0.05). Calculated daily DM (1.41 kg) and ME (14 MJ) intake were similar in all groups. Calculated daily CT intake (6.0g vs. 2.1g) and CT intake/100 g CP intake (2.2 g vs. 0.7 g ) was higher for willow fodder block hoggets than for the control pasture groups; this may have increased the flow of undegraded dietary protein (UDP) to the small intestine, leading to increases in reproductive rate of this group. Grazing willow fodder blocks failed to reduce the number of anthelmintic drenches (3) needed to maintain FEC below 1000 epg wet faeces, but was successful in reducing dag score relative to grazing conventional ryegrass/white clover pastures. It was concluded that grazing willow fodder blocks can play a beneficial role in sustainable farming systems as it can sustain animal growth rates, increase reproductive rate and reduce dag formation in parasitized hoggets. These benefits were associated with reduced dead matter content and increased legume content in fodder block herbage and with increased intake of secondary compounds from the trees. However, both pasture and trees need to be managed as a tree/pasture system in order to produce herbage of higher nutritive value and more efficiently utilise willow fodder blocks as a supplementary feed. After 6 years of grazing in this manner, the survival rate of the trees was approximately 85 %
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Fodder trees, Willow, Sheep, Feeding and feeds, Parasites