Browsing by Author "Morris, Stephen Todd"

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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