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    Use of New Zealand native browse shrubs on sheep and beef hill country farms : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at the School of Agriculture and Environment, Massey University, Palmerston North, Manawatū, New Zealand
    (Massey University, 2023) Wangui, James Chege
    Sheep and beef cattle farming on hill country through the historic clearing of native vegetation for pasture has caused biodiversity loss and increased the risk of soil erosion. Exotic tree species such as poplar and radiata pine can be used to control erosion, but there is current interest in using native plants on the hill country for indigenous biodiversity restoration in addition to erosion control. However, there is limited information on the forage value, biomass, carbon stock, and potential economic impacts of native plants compared to exotics species. This thesis was aimed to address the lack of information available on native shrubs and their comparison to exotics trees and shrubs. The forage feeding value results revealed that native shrubs had consistent nutritional composition across seasons, higher metabolizable energy, and lower crude protein than the exotic shrub Salix schwerinii (Kinuyanagi). Findings on in vitro fermentation characteristics showed that native shrubs were highly digestible, yielded higher volatile fatty acids, microbial proteins, and greenhouse gases than S. schwerinii. Estimation of biomass revealed that the native shrubs were similar in aboveground biomass accumulation, but differed in allocation to foliage, branch, and stem. Melicytus ramiflorus (Mahoe) had lower foliage biomass while Coprosma robusta (Karamū) had lower branch biomass, among the evaluated shrubs. Estimated carbon stock accumulation was higher for Pittosporum crassifolium (Karo) due to a greater woodier portion (branch and stem) than M. ramiflorus and C. robusta but lower than exotic trees. The data from the native shrub studies was used in the bioeconomic model and showed that planting native shrubs or radiata pine on steep slopes equal to 10% of the farm area would reduce farm feed supply. This reduction would result in a decrease in sheep flock size and sheep flock net cashflow, particularly with higher planting rates and with of radiata pine. While radiata pine had a surplus overall farm net cashflow, native shrubs had negative cashflow due to high seedling costs and low carbon income, making their use on the farm currently unprofitable at the modelled prices. The study's findings suggest that replacing exotic trees with native shrubs can provide high-quality summer browse for livestock. The decision to plant native shrubs on steep hill country slopes would depend on the farmer’s financial situation and interest in biodiversity conservation and profits. However, reducing planting costs and increasing the carbon price would be necessary to make investing in native shrubs profitable and more attractive to farmers.
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    Willow fodder blocks for growth and sustainable management of internal parasites in grazing lambs : a thesis presented in partial fulfilment of requirements for the degree of Master in Veterinary Science at Massey University, New Zealand
    (Massey University, 2005) Diaz Lira, Carolina Macarena
    A rotational grazing experiment was conducted for 14 weeks in the summer/autumn of 2004/2005 on the lower eastern North Island, New Zealand, to compare the efficacy of grazing willow fodder blocks containing condensed tannins (CT), for sustainable control of internal parasites in 180 Suffolk x Romney weaned lambs. One third of the lambs grazed control perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture only, another third grazed pasture for 3 weeks followed by willow fodder blocks for 1 week (repeating the rotation; restricted access) and the last third of the lambs grazed on willow fodder blocks for the duration of the experiment (full access). All lambs were effectively treated with anthelmintics at the start of the experiment. Each group was divided into undrenched lambs and lambs regularly drenched every 4 weeks. Each of the six groups grazed separate areas at the same dry matter (DM) allowance, using rotational grazing with weekly breaks. Undrenched lambs would be trigger drenched if the faecal egg count (FEC) geometric mean of the group exceeded 1000 eggs/g wet faeces and/or liveweight gain (LWG) was reduced to zero and/or any one individual lamb exceeded 2500 eggs/g wet faeces, which never occurred. Rectal faecal samples for FEC, larval counts (LC) and visual dag formation (Dag Score; DS) were assessed initially and at two week intervals throughout the experiment. All lambs were slaughtered at the end of the experiment, fatness (GR) and carcass weight (CW) measurements were recorded and representative samples of the abomasum, small intestine and large intestine were collected in the three undrenched treatments to determine total worm burdens. Primary growth legume content in willow fodder blocks was similar to that of control pasture (20%), but willow fodder blocks secondary growth legume content (30%) was greater than in secondary growth control pasture (22%). Primary growth pre-grazing herbage mass (approximately 4800 kg DM/ha) and post-grazing herbage mass (approximately 3400 kg DM/ha) in willow fodder blocks (full and restricted access) was higher than that of control pasture (4400 and 3000 kg DM/ha respectively). Secondary growth pre and post-grazing herbage mass was similar in willow fodder blocks and control pasture (4200 and 3000 kg DM/ha respectively). Secondary growth mass of fodder trees (775 kg DM/ha) in the willow fodder block full access treatment was higher than primary growth (562 kg DM/ha). Pre-grazing herbage dead matter content was consistently higher in secondary growth (20-40%) than in primary growth (8-10%), for both control pasture and fodder blocks. Condensed tannin concentration in willow fodder block herbage was 14.5 g/kg DM compared to the CT levels (6.2 g/kg DM) detected in control pasture diet selected. However, CT concentration in willow fodder block trees was particularly high (approximately 45.5 g/kg DM). In vitro OMD, DOMD and ME concentrations were higher for selected tree browse in willow fodder blocks (0.71; 0.65 g/kg DM; 10.6 MJ/kg DM respectively) when compared to herbage selected in either willow fodder blocks or control pasture (0.65; 0.60 g/kg DM; 9.7 MJ/kg DM respectively). Regularly drenched lambs had significantly higher LWG and carcass weight gain (CWG) than undrenched lambs (p < 0,05) in all three groups. Lambs in willow fodder block full access had the highest LWG in drenched as well as undrenched lambs of 182 g/day and 154 g/day respectively. Due to hot and dry summer conditions, growth rates of all treatments declined in the second half of the experiment as herbage nutritive value declined. Undrenched willow fodder block full access had the highest CWG amongst all undrenched treatments. Carcass weight gain reduction of undrenched lambs versus drenched lambs for the full access to willow fodder block group (12 g/day) was half of the reduction between control pasture groups (24 g/day). Dag score increased with time until Day 70 of the experiment, with no differences between the six treatment groups. From Day 70 until the end of the experiment, dag scores of lambs grazing willow fodder block full access were consistently lower than lambs grazing willow fodder block restricted access or control pasture and were lower for drenched than for undrenched lambs. Drenched groups maintained low FECs throughout the experiment, whereas FECs of undrenched groups progressively increased with time. Both DS and LWG were similar for drenched lambs grazing control pasture and undrenched lambs grazing willow fodder block full access. The parasites established in greatest numbers in undrenched lambs grazing control pasture were Teladorsagia trifurcata, Nematodirus spathiger, Trichostrongylus vitrinus, Trichostrongylus colubriformis followed by Trichostrongylus axei and Teladorsagia circumcincta. At slaughter, undrenched lambs grazing on willow fodder block full access had significantly lower Nematodirus spathiger, Trichostrongylus vitrinus and Trichostrongylus colubriformis worm burdens when compared to undrenched lambs grazing control pasture (p < 0.05), but greater burdens of Haemonchus contortus (p = 0.0299). Undrenched lambs grazing willow fodder block with restricted access had significantly lower Teladorsagia circumcincta, Teladorsagia trifurcata, Trichostrongylus vitrinus and Trichostrongylus colubriformis worm burdens than undrenched lambs grazing control pasture (p < 0.05). It was concluded that parasitism restricted lamb growth in all three undrenchcd grazing systems, showing a progressive increase in FEC over time. However, the reduction in carcass weight gain was greatest for undrenched control lambs and least for undrenched lambs with full access to willow fodder blocks. Grazing undrenched lambs on restricted and full access willow fodder blocks showed lower burdens of some parasites at slaughter compared to undrenched lambs grazing control pasture, which could be due firstly to an increased CT present in both willow and in fodder block herbage and their possible effects in increasing protein absorption. Secondly, CT could have interrupted parasite life cycles and/or. thirdly, decreased L3 larval consumption could have occurred due to taller plant morphology of the trees, hence reducing the reinfection rate. There seemed to be no direct effect on killing established parasites, as if that had happened, there should have been a decrease in FEC in the first half of the experiment, before any effects of reinfection took place. CT-containing forages could be used in conjunction with live weight gain monitoring and/or body condition score for the control of gastrointestinal nematodes, but it still needs further evaluation and a close collaboration of researchers and farmers.
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    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
    (Massey University, 2007) Musonda, Kelvin
    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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    Environmental effects of densely planted willow and poplar in a silvopastoral system : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph. D.) in Agroforestry, Institute of Natural Resources, Massey University, Palmerston North, New Zealand
    (Massey University, 2007) Hussain, Zaker
    New Zealand, having large areas of hilly landscapes, is subject to the risk of soil erosion, and summer and autumn droughts that limit pasture growth, which in turn affects the livestock-based economy. The nitrogen and phosphorus input in fertilisers coupled with livestock excreta and soil disturbance impose a serious threat to downstream water quality. The planting of trees is one option used to decrease soil erosion, increase the quantity of forage and manage runoff. To date, research has mainly focused on wide spaced poplar trees for feed quality and their effects on understorey pasture growth. However, there is increasing interest in the use of densely planted willow and poplar for fodder purpose. The effects of young (< 5 yrs old) willow and poplar planted at close spacing on runoff, soil erosion, growth of understory pasture and nutrient losses have never been studied in New Zealand. Three field trials (two at Crop and Research Unit, Moginie, Manawatu and one at Riverside Farm, Masterton) were conducted between October 2004 and November 2006 that incorporated comparative establishment and growth of densely planted willow and poplar and their effects on soil moisture, runoff, sediment load and nutrient losses from grazed and fertilised farmland. It was concluded that densely planted willow and poplar (3-4 yrs) reduced total nitrogen (TN) and dissolved reactive phosphorus (DRP) by 47 % each and sediment load by 52 %. Young trees reduced surface runoff and soil moisture more as they aged. However, due to their deciduous nature willow and poplar were not effective in reducing surface runoff in winter and early spring. Sheep preferred camping under trees, especially in late spring and summer, and this led to greater deposition of dung and urine under trees than open pasture. Sheep grazing, especially in winter, significantly increased sediment and nutrient loads in runoff water. The N and P fertiliser application increased nutrient load in runoff water well above the threshold level required to initiate algal growth to create eutrophication. Densely planted willow and poplar significantly reduced understorey pasture growth by 23 % and 9 %, respectively, in their second year at Moginie, mainly due to shade, but coupled with soil moisture deficit in summer. The pasture growth in a willow browse block was 52 % of that in open pasture as a result of shade and differences in pasture species composition. Sheep browsing reduced willow leaf area significantly. Willow and poplar survival rates were similar (P > 0.05) after two years of establishment (100 % vs 90.5 %, respectively). However, willow grew faster than poplar in height (1.90 vs 1.35 m), stem diameter (43.5 vs 32.6 mm), canopy diameter (69 vs 34 cm) and number of shoots (8.7 vs 2.3) at the age of two years, respectively. The research clearly demonstrated that densely planted young willow and poplar trees can reduce runoff, sediment load and nutrient losses from farmland to freshwater, but shade and soil moisture can limit pasture growth under trees. It is recommended that willow and poplar should be planted at wide spacing on the whole farm to minimise loss of pasture. Where blocks of trees are necessary, such as willow browse blocks, sheep browsing can be used as a tool to reduce shade to improve pasture growth. Livestock access to riparian strips should be minimal to avoid livestock camping that can have deleterious effects on water quality.