Browsing by Author "Morris, Stephen Todd"

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    A study of out-of-season lamb production in the lower North Island of New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University
    (Massey University, 1992) Morris, Stephen Todd
    The objective of this study was to evaluate out-of-season lamb production in the lower North Island of New Zealand. Ewes representing three crosses (Border Leicester x Romney (BR), Poll Dorset x BR (PBR) and Suffolk x BR (SBR)) and three birth years were reared, under commercial farming conditions, to enter an out-of-season lambing experiment. Suffolk x BR hoggets had significantly (P < 0.01 ) heavier 1 6 month liveweights than PBR or BR hoggets. There were inconsistent differences in liveweight between PBR and BR ewe hoggets. Border Leicester x Romney hoggets produced more (P < 0.01 ) greasy wool at the yearling shearing than PBR or SBR hoggets. The same sheep were then assigned to one of two lambing policies (June or August) at their 2-year-old mating and remained within that policy while they were evaluated for their 2-year-old (1987, 1988, 1989) and 3-year-old (1988, 1989, 1990) lambing performance. Lambing policy did not influence the proportion of mated ewes that lambed but there were more (P < 0.05) multiple births in the August-lambing ewes. Birth weights and weaning weights of the June-born lambs were significantly (P < 0.00 1 ) lower than those of their August-born counterparts. June-lambing ewes produced more (P < 0.00 1 ) wool (on average by 0.5 kg) than August-lambing ewes. Border Leicester x Romney ewes produced more (P < 0.00 1 ) greasy wool per year (by 0.7 to 1 .2 kg) than PBR ewes while PBR ewes outperformed SBR ewes (by 0.3 to 0.5 kg) for annual greasy wool production. Reproductive differences between the ewe crosses were small and non-significant, although PBR ewes reared the heaviest lambs. In an attempt to determine when the extra wool growth occurred in June-lambing compared to August-lambing ewes, six-weekly midside patch wool growth measurements were taken throughout a 1 2-month period on a sample of the same three ewe crosses described earlier. lt was found that the seasonal decline in wool growth rate that normally occurs over the winter months in August lambing ewes was minimised in June-lambing ewes. Associated with this effect was a significant (P < 0.05) increase in mean fibre diameter and an increase in staple strength at the following October shearing in June-lambing ewes. The next experiment was designed to determine the relationships between sward surface height, intake and production for lactating June-lambing ewes. The organic matter intake (OMI) of June-lambing ewes was not influenced by a range (2.6 - 7.8 cm) of sward surface heights (SSH) during week 3 of lactation. Between weeks 4 and 7 of lactation, ewe OMI increased up to a SSH of 7.8 cm while in week 8 of lactation there was no increase in OMI between ewes grazing 4.4 or 7.8 cm swards. Sward surface height had no effect on ewe midside wool growth, mean fibre diameter or lamb growth but ewes on the 2.6 cm sward lost 8-1 0 kg more liveweight during lactation than those on the 4.4 and 7.8 cm swards. These results suggest that June-lambing ewes in good condition can maintain lamb growth at low (2-3 cm) SSH but at the expense of ewe l iveweight loss. The final trial investigated the effect of SSH on ewe intake and performance during the last month of pregnancy in June- and August-lambing ewes. Ewe OMI, condition score and liveweight gain increased as SSH increased from 2.0 to 8.0 cm. There was no effect of SSH on ewe m idside wool growth, mean fibre diameter or lamb birth weights. June-born lambs were significantly (P < 0.05) lighter at birth than August-born lambs across all SSH treatments. At the same SSH, Junelambing pregnant ewes achieved similar OMI to those of August-lambing ewes. The results of these studies are discussed in the context of the development of out-of-season lambing systems for the lower North Island of New Zealand.
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    A study of some factors affecting the post-partum oestrous interval in suckled angus cows : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science at Massey University
    (Massey University, 1976) Morris, Stephen Todd
    The objectives of this study were to determine the length of interval from parturition to first oestrus and investigate factors that might influence this interval. Sixty-one records were collected in 1975 from the breeding herd at Massey University's No. 3 sheep farm Tuapaka, another 207 records covering the years 1971 to 1973 and 1975 were obtained from the herd of the Whatawhata Hill Country Research Station, Ministry of Agriculture and Fisheries, Hamilton. The Massey herd consisted of Angus cows aged 4-years and older while the Whatawhats Angus herd consisted of cows aged 2-years and older. Oestrus was detected at each location by the use of chin-ball mating harnesses attached to entire or vasectomised bulls. Management of the cows followed normal New Zealand hill country practices with the exception that in the Massey herd post-calving treatments were imposed. These treatments were: (i) On the hill throughout the trial (H) (ii) Removed from the pad at birth (PB) (iii) Removed from the pad at 20 days (P20) (iv) Removed from the pad at 4O days (P4O) After calving, cows and calves were grouped into three blocks according to calf age with treatments nested within blocks. The analysis consisted of a study of the relationships between the length of the interval from calving to first oestrus and the nutritional treatments, milk production, cow liveweight changes, and calf variables. The least squares means for post-partum interval to first oestrus were 79.2 days and 74.5 days for the Massey and Whatawhata herds, respectively. The regression of calving date significantly (P<0.01) influenced the post-partum interval in the Massey herd, but the effects of block, treatment, age of dam and sex of calf were non-significant. For the Whatawhata herd, year of record (P<0.001), age of dam (P<0.01) and the regression of calving date (P<0.001) all influenced the post-partum Interval. The sire of calf at foot and sex of calf were non-significant while the regression of cow liveweight change post-calving to mating approached significance (0.05