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Item Growth of dairy heifers on alternative forages and the effects of heifer live weight on reproductive parameters at first breeding : a thesis presented in partial fulfilment of the requirements for the degree of Masters of AgriScience in Agriculture at Massey University, Palmerston North, New Zealand(Massey University, 2015) De Clifford, Ross PatrickDairy heifers in industry at present are frequently falling short of the recommended liveweight targets. Rearing of dairy heifers is expensive and involves a two-year non-productive period after which, if she becomes pregnant, income can be received from milk production. Milk yield in first and second lactation is affected by a heifer’s live weight prior to calving and therefore meeting liveweight targets is critical for subsequent milk production. Those heifers that fail to become pregnant are of considerably lower value than those that become pregnant. To maximise the chance for heifers to become pregnant, heifers need to have completed a number of oestrus cycles prior to the planned start of mating. Mating of heifers during the third oestrus cycle compared with the first oestrus cycle after reaching puberty, provides an increased probability of the heifer becoming pregnant. This thesis contains two experiments. The aim of the first experiment was to measure the effects on average daily gain, wither height, girth and crown-to-rump length, of feeding 6-month-old dairy heifers on alternative feeds, over the summer period when pasture quality and availability is limiting. Sixty 6-month-old Friesian-Jersey crossbred heifers were assigned to 1 of 3 treatments (pasture (P), conserved forages (C) or Lucerne (L), with all treatments receiving supplementary meal). Heifers were weighed at 0, 3 and 6 weeks of treatment period, and wither height, girth and crown-to-rump length were measured at the start and end of the experiment. L heifers had a greater (P<0.05) average daily gain (1.22 ± 0.03 kg/day) than P heifers (0.57 ± 0.03 kg/day), and C heifers were intermediate (0.78 ± 0.03 kg/day). The aim of the second experiment was to determine the effect that live weight, percentage of individual liveweight target achieved and achieving individual liveweight target at 6, 9, 12 and 15 months of age had on 5 reproductive parameters: reaching puberty by 12 & 15 months of age; becoming pregnant during a 7 week mating period; becoming pregnant in the first 3 weeks of mating; and becoming pregnant in the first 6 weeks of mating. Heifer live weights were recorded approximately every month. Scanning of the heifers’ ovaries at 12 and 15 months of age was completed to determine whether each heifer had reached puberty by the respective age. Natural mating was completed over a seven-week period, and age of the fetus was estimated at pregnancy scanning was to determine in which cycle the heifer became pregnant. There was no effect on the pregnancy parameters measured as a result of live weight, reaching live weight target and the percentage of liveweight target achieved. Heifers that were heavier at 6, 9 and 12 months of age had an increased likelihood of reaching puberty by 12 months of age. Increased average daily gain was achieved from heifers grazing Lucerne, with supplementary meal also fed, although these increased average daily gains had limited benefit on reproductive performance of the heifers at first breeding.Item Synchronization of follicular development, oestrus and ovulation using oestradiol benzoate and progesterone in dairy cattle : a thesis presented in partial fulfillment of the requirements for the degree of Master of Philosophy (Veterinary Clinical Science) at Massey University(Massey University, 2000) Abdullah, PuniminThe aim of oestrus synchronisation in cattle is to achieve a close synchrony of oestrus and ovulation with high submission rates. The status of follicular wave development at the time of treatment has been responsible for a large portion of the variability in ovarian response to treatments employed. The control of oestrus and ovulation require firstly that the life span of the corpus luteum is reduced, and secondly that follicular wave emergence is synchronized so that a healthy, oestrogen active dominant follicle is present at the end of the treatment. A clinical trial was conducted to determine the effective dosage of oestradiol bezoate in combination with progesterone on follicular dynamics, oestrous behaviour and time of ovulation when treatment was administered intravaginally. Intravaginal treatment with 2 mg or 7 mg oestradiol benzoate and progesterone on day 3 of the oestrous cycle was effective in inducing atresia of the dominant follicle and a new cohort of follicles began to emerge, on average, 2.5 ± 0.93 days after treatment. However, the IBD Onsettl2TM drug adminstration device, failed to maintain the required progesterone output and plasma concentrations during the treatment period. This resulted in failure to synchronize oestrus and ovulation. IBD Onsett12TM, as a single application intravaginal drug delivery device for the purpose of controlling the oestrus cycle in cattle, was further evaluated in cycling and non-cycling cows and compared to the CIDR oestrus synchronization program. A total of 350 Friesian or Friesian cross cows in five herds were involved in the trial. The retention rate for the IBD Onsett12TM was significantly lower than the CEDR (65.12% vs. 99.44%, χ2 = 73.528, P = 0.001), and the synchronized conception rate from the CIDR protocol was significantly higher than the IBD Onsett12TM among cycling and non-cycling cows (χ2 = 15.087, P = 0.02). The IBD Onsett12 oestrus synchronization program was effective in inducing fertile synchronized oestrus in some cycling and non-cycling cows, but resulted in a low synchronized conception rate. Manipulation of follicular development and controlling the oestrous cycle length will synchronize oestrus more precisely and control the time of ovulation more exactly to allow a single fixed-time insemination. Controlling the time of new follicular wave emergence and synchronizing the follicular wave status in dairy cows at random stages of the oestrous cycle would provide a more practical and less variable method of synchronization than those of the past. A clinical trial was conducted to control both follicular development and luteal function. Twenty randomly cycling, non-lactating dairy cows were randomly assigned to two treatments; 1) 2 mg oestradiol benzoate injected intramuscularly and 200 mg of progesterone subcutaneously, 9 days before prostaglandin (500 μg cloprostenol) and a second injection of 1 mg oestradiol benzoate 24 hours after prostaglandin treatment (ODB, n = 10). 2) 10 μg busereiin injected 7 days before prostaglandin (500 μg cloprostenol) and a second injection of 10 μg busereiin 48 hours after prostaglandin treatment (GnRH, n = 10). An acute short-acting treatment with progesterone and oestradiol benzoate or busereiin was effective in inducing atresia of the dominant follicle. A new follicular wave emerged earlier in the GnRH treated group than in the ODB treated group (2.22±0.15 vs. 3.60±0.22 days, P = 0.001). An LH surge occurred earlier after a second buserelin treatment on day 9 than after a second oestradiol benzoate treatment on day 10 (4.0 ± 1.0 vs. 22.80 ± 1.20 hour, P = 0.001). The mean time of ovulation after the second oestradiol benzoate or buserelin treatment was not significantly different between the ODB and the GnRH group (1.70 ± 0.30 vs. 1.56 ±0.18, P = 0.692). The proportion of cows that were observed in oestrus was higher in the ODB group than the GnRH group (100% vs. 55.6%, χ2 = 5.630, P = 0.018). In conclusion, progesterone and oestradiol treatment intravaginally or intramuscularlly was effective in synchronizing follicular wave emergence. Administration of oestradiol benzoate 24 hours after prostaglandin given 9 days after an initial progesterone and oestradiol treatment produced the oestrus synchrony, induced an LH surge and provide a degree of synchrony in the time of ovulation. This program showed potential in manipulating follicular development and luteal function and has the possibility allowing fixed-time insemination. However, the efficacy of the EBD Onsett12TM as a single application intravaginal drug delivery device to control the oestrous cycle or as progesterone-releasing device in cattle did not demonstrate satisfactory results when used in these trials. This might arise from the complexity of the drug delivery system. Nevertheless, the concept of delivering multiple drugs at different rates and times may have many benefits to the end user when current design and use problems arc resolved.Item A study of adjustment factors for the weaning weights of Hereford and Angus calves : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University(Massey University, 1975) Nicoll, Geoffrey BlairFrom the files of the Beef Cattle Weight Gain Performance Recording Scheme of the New Zealand Meat Producers Board and the New Zealand Wool Board, the weaning weights of 7771 Hereford calves born in 18 herds, and 16666 Angus calves born in 37 herds, from 1964 to 1972, were analysed. Objectives of the study involved estimation of the effects of age and sex of calf, and age of dam, in order that methods of adjustment currently used in the National Beef Recording Service for these environmental influences could be evaluated. Each calf was classified according to herd, year of birth, age-of-dam group, and sex, with age at weaning as a covariate. The data were analysed within breeds by least squares to investigate the main effects of these five factors and the first-order interactions among herd, year, age-of-dam group, and sex effects. The importance of each interaction was examined by comparing the proportionate reduction in intra-class residual variation after all main effects had been fitted. The results of the analyses of main effects indicated that for each breed, all effects contributed to more than a 2 percent reduction in intra-class residual variance. The results of the interaction analyses showed that only the herd x year interaction for Hereford calves, and the herd x year and herd x sex interactions for Angus calves, contributed to at least a 2 percent reduction in residual variance after all main effects had been fitted. Within-subclass linear regression coefficients of weight on age at weaning for Hereford and Angus calves, were 0.70 ± 0.01 and 0.62 ± 0.01 kg/day, respectively. Least-squares estimates for sex indicated that the weaning weights of Hereford and Angus males were heavier than those of females by 29.8 and 25.6 kg, respectively. Estimates for age of dam indicated that the weights of Hereford calves out of dams of 2, 3, 4, 5 and, 10 years of age and older, deviated from the weights of Hereford calves out of mature dams (6 to 9 years-old) by 33.3, 17.6, 8.7, 3.8 and 2.2 kg, respectively. The corresponding deviations for Angus calves were 22.7, 15.2, 7.9, 5.4 and 1.4 kg. Estimates for age-of-dam effects were also obtained by best linear unbiased estimation procedures from the records of 7698 Hereford calves out of 2901 dams, and 14198 Angus calves out of 5086 dams. Differences in the estimates of deviations of non-mature from mature dam age groups derived by least squares and by best linear unbiased estimation, were in general relatively small. In relation to the procedure currently used in the National Beef Recording Service, alternative adjustment procedures derived for age at weaning involved additive and multiplicative applications of linear regression of weight on age for each breed. The current procedure, for both breeds, was the least effective in reducing the dependence of adjusted weight on age, whilst the procedure additively applying linear regression of weight on age was the least effective in reducing intra-class residual variance. Adjustments determined for age-of-dam effects by least squares and by best linear unbiased estimation, were considered to differ only slightly from current industry adjustment factors, with the exception of factors applicable to Angus calves out of 3-year-old dams. Examination of the variances within age-of-dam groups, and of the reductions in residual variances within herd-year-sex subclasses, indicated the applicability of additive, rather than multiplicative, adjustment factors for each breed. Comparisons of additive and multiplicative adjustment factors for sex effects were varied. Multiplicative adjustments were more appropriate in equalizing variances within sex groups, whilst additive adjustments were more appropriate in reducing residual variance within herd-year subclasses.Item The use of oestradiol benzoate and progesterone to synchronise oestrus in dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science at Massey University(Massey University, 1995) Hanlon, David WilliamCurrent oestrus synchronisation regimes for cattle are based on synchronising the end of the progestational phase of the oestrous cycle so that ovulation occurs simultaneously in treated animals. The end of the progestational phase can be synchronised through inducing premature luteolysis using prostaglandin F2α and its analogues or by artificially extending dioestrus using exogenous progesterone treatment. The time taken for subsequent follicular maturation and ovulation tends to be inconsistent between animals, which contributes to the poor fertility obtained following fixed-time insemination after oestrus synchronisation treatments. The variable rate of follicular development occurring after a synchronous decline in plasma progesterone levels is a major limiting factor in achieving a degree of synchrony of oestrus and ovulation which would allow for fixed-time insemination. Controlling the time of ovulation using exogenous oestrogen to induce a preovulatory LH surge is a potential method by which the variability in timing of ovulation may be reduced. Alternatively, re-setting follicular wave patterns in different animals at the commencement of synchrony treatments using exogenous oestrogen, so that follicular wave emergence is synchronised, is another method by which the variability in timing of ovulation could be reduced. A clinical trial was conducted involving 750 dairy heifers in 13 herds to determine the effects of 0.5 mg oestradiol benzoate administered intramuscularly 24 hours after removal of progesterone-containing intravaginal devices (CIDR-B) on the occurrence and timing of oestrus, synchronised pregnancy rate and synchronised conception rate in dairy heifers. Within each herd heifers were randomly allocated to one of two oestrus synchronisation treatments. All heifers received a CIDR-B progesterone-containing intravaginal device with an attached 10 mg oestradiol benzoate capsule for 12 days. Twenty-four hours after CIDR-B removal one group received an intramuscular injection of 0.5 mg oestradiol benzoate and the other group received an intramuscular injection of a placebo. Heifers were inseminated to detected oestrus 48 and 72 hours after device removal. Administration of oestradiol benzoate 24 hours after removal of CIDR-B devices significantly increased the number of heifers exhibiting oestrus within the observation period (96.1%; vs 90.5%, p <0.01). It also altered the onset of oestrus so that significantly more heifers were in oestrus (86.6% vs 72.3%, p<0.01) and conceived (47.1% vs 37,5%, p<0.05) by 48 hours after device removal. The overall synchronised conception rate and synchronised pregnancy rate were unaffected by treatment. The effects of the same oestrus synchronisation treatment, on the time to oestrus, ovulation, and peak LH concentration were examined in dairy heifers. Treatment with oestradiol benzoate tended to reduce the time from device removal to LH peak in randomly cycling heifers (median time to LH peak 40.1 hr vs 63.9 hr, p=0.07), but treatment with oestradiol had no significant effect on the time to LH peak, standing oestrus or ovulation in heifers synchronised during late dioestrus. The effects of oestradiol benzoate on the dominant follicle and corpus luteum of cows treated with progesterone (CIDR-B) at different stages of the oestrous cycle were investigated. Treatment with oestradiol benzoate on day 3 of the oestrous cycle caused atresia of the dominant follicle present at CIDR-B insertion and resulted in the early emergence of the subsequent follicular wave. Treatment with oestradiol benzoate on days 6, 9, 12 and 15 of the oestrous cycle had no effect on follicular characteristics or the emergence of the subsequent follicular wave. Treatment with oestradiol benzoate had no effect on the day of onset of regression of the corpus luteum regardless of the stage of the oestrous cycle at CIDR-B insertion. The effectiveness of re-using CIDR-B devices to synchronise returns to oestrus in non-pregnant dairy heifers was examined. After an initial CIDR-B synchronisation programme in dairy heifers, the used CIDR-B devices were re-inserted 14 or 16 days after first insemination, for a period of 5 days. Re-insertion of used CIDR-B devices significantly increased the number of non-pregnant heifers detected in oestrus and inseminated by 48 hours after device removal (45.2% vs 27.3%, p<0.05, in herds where CIDR's were re-inserted on day 14; 48.8% vs 13.6%, p<0.05, in herds where CIDR's were re-inserted on day 16). Re-insertion at 14 or 16 days after first insemination was equally effective in increasing visible returns to service. Conception rate was unaffected by CIDR-B treatment. In conclusion, intramuscular administration of oestradiol benzoate 24 hours after the removal of CIDR-B progesterone-containing intravaginal devices increases the number of heifers exhibiting oestrus at an earlier time after device removal. The administration of oestradiol benzoate appears to reduce the variability in timing of LH peaks typically occurring in a herd of synchronised heifers due to different stages of follicular development being present at the time of CIDR-B removal. Treatment with oestradiol benzoate at the start of CIDR-B treatment appears to have no significant effect on synchronising follicular wave emergence in different animals other than those in early metoestrus. Administration of oestradiol benzoate after treatment with exogenous progesterone therefore appears to offer the most potential in controlling the time of oestrus and ovulation and allowing for fixed-time insemination.Item Inbreeding and population structure studies in the New Zealand Angus breed : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University(Massey University, 1977) Cheong, Weng KeongThe breed structure and genetic history of the New Zealand pedigree Angus breed were analysed by Robertson and Asker's (1951) modification of the Wright-McPhee (1925) pedigree sampling method. The pattern of the breed structure obtained is generally similar to that found in other studies, but it is both diffuse and dynamic owing to the present rapid expansion of the breed. There are changes taking place in the herd composition of the major breeders' herds and many new herds have yet to find their level in the structure. Considerable emphasis has been placed on the use of imported animals in the development of the breed. Of all herds registering in Volume 61 of the herd book, 20.5% used imported sires, and the percentage of genes in the breed in 1966/67 derived from animals imported since 1863 was 85.4. The most important herd in 1969 has a genetic contribution to the breed of 21.9 per cent:, while the contributions of the four next most important herds were 8.72, 8.7, 4.7 and 3.7 per cent. In the four-generation pedigrees from which these figures were derived, the contribution of imported animals was 42.4%. The relationship between herd size and importance of the herd was considered. Herd duration was also discussed, in so far as it relates to improvement of the breed. The animal with the highest relationship to the breed was Blackleg (11.65% in the 1900 pedigree sample). But overall, the most important animal over the period 1900-1966/67 was Lancer of Advie. Of the 33 sires and 9 dams whose direct relationships are 3.0% or more in any of the 8 sample years, 19 sires and 3 dams were imported. The total inbreeding in 1966/67 (base year 1863) was 1.80%. This comprised 0.09% current inbreeding, 0.95% long-term inbreeding, and 0.76% strain inbreeding. The index of subdivision calculated from the non-current and long-term inbreeding is 1.79, indicating that there is only a slight tendency towards family formation in the breed. The effective generation length is approximately 5.6 years. About 50-56% of the animals in the 1966/67 sample were sired by bulls 4 years old or younger, while about 38% are from dams 4 years or younger. It is unlikely that there is much genetic variation between herds. This is because bulls from major breeders' herds are used widely throughout the breed while about 80 percent of sires and 37 per cent of dams are bred in herds other than the one in which they were used.Item Effects of crossbreeding and selection on the productivity and profitability of the New Zealand Dairy Industry : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand(Massey University, 1998) López-Villalobos, Nicolás; López-Villalobos, NicolásThis aim of this thesis was to evaluate some effects of crossbreeding on the New Zealand dairy industry. The study started with a review of crossbreeding parameters, followed by the development of two models. A farm model was developed to evaluate the productivity and profitability (net income per hectare) of mating strategies involving the main breeds farmed in New Zealand; Holstein-Friesian (F), Jersey (J) and Ayrshire (A). Under current production costs and values for milk and beef, dairy herds using rotational crossbreeding systems had higher net income per hectare than straightbred herds. The ranking of mating strategies on profitability altered with changes in the relative values of fat and protein (1:4, 1:2.2 and 4:1) but rotational FJ and FJA herds had higher net incomes than straightbred herds across three values for the fat to protein ratio and two values for meat (current and 50% higher than current). An industry model was constructed to evaluate the effects of mating strategies on the rate of genetic gain and the productivity (yields of milk, fat and protein) of the dairy industry over 25 yr. The mating strategies simulated were upgrading to F (UPGF), upgrading to J (UPGJ), upgrading to A (UPGA), rotational crossbreeding using two or three breeds, and use of best bulls (UBB) irrespective of breed. Upgrading to either J or F increased the number of potential bull mothers from 0.27 million to 2.03 and 2.15 million and resulted in genetic gains of 0.27 genetic SD/yr, for both options. Rotational FJ decreased the number of potential bull mothers to 0.17 million and resulted in a genetic gain of 0.24 genetic SD/yr. Upgrading to F and UPGJ resulted in divergent averages of live weight and yields of milk, fat and protein per cow. On the basis of production per hectare, UPGF resulted in lower stocking rate, higher milk yield, and less fat and protein than UPGJ. Effects of the rotational FJ strategy on live weight per cow, and yields of milk per cow and per hectare, were slightly different from the average values for UPGJ and UPGF, due to the effects of heterosis. The farm and industry models were combined to calculate industry profit for the different mating strategies for 25 yr. Industry yields of standardised whole milk powder, butter and casein were calculated from industry yields of milk and its components. Profitability was calculated as income from dairy products and salvage animals less on-farm costs of production and off-farm costs of milk collection, manufacture and marketing. The ranking of the different mating strategies was affected by the value for butter. When marginal butter sales (above the total industry yield in the base year) were worth only NZ$0.45/kg, UPGF resulted in the highest industry net income (NZ$1119 million) followed by straightbreeding (NZ$1086 million) and rotational FJ (NZ$1076 million). However, if the marginal value of butter production was assumed to be equal to the average base value, then UPGJ resulted in the highest industry net income (NZ$1185 million) followed by rotational FJ (NZ$1177 million) and UBB (NZ$1173 million). Despite the widely different mating strategies used for 25 yr, the largest difference in net income was only 10%. Rotational crossbreeding systems can increase the profitability of commercial herds, but wide implementation of crossbreeding in the dairy industry reduces the number of active cows (bull mothers) and therefore penalises the rate of genetic gain of the entire population. Future values of dairy products have a major impact on the relative value of breeds and are therefore important to any decisions about mating strategies.