Investigation of infertility problems in dairy herds

Abstract.Ten dairy herds reporting acute fertility problems were investigated by analysing records and cows, metabolic profiles, tests for infectious agents and milk hormone assays. The main problems were : heat detection (2), endometritis (3) and inadequate nutrition (5). In one herd no cause has yet been identified. On all farms the problem had been present from the start of the breeding period. Management changes, delayed analysis of herd records and over-estimation of forage nutritive value were underlying problems. A diagnostic analysis/decision process to highlight problems early is essential to minimise loss.</jats:p

An investigation into the relationship between milk progesterone concentrations in fore-milk and composite milk samples

AbstractMilk progesterone concentrations are generally estimated on a composite, “jar”, sample from the bulk milk collecting jar, with concentrations &gt;3 ng/ml considered as indicative of the presence of luteal tissue. However, on a number of dairy farms composite sampling is not possible as they operate a direct pipeline milking system, without milk meters, and the only practical means of obtaining a milk sample is via fore-milk sampling. The objective of this study was to investigate the relationship between progesterone concentrations, as estimated by an ELISA procedure, in fore-milk strippings and composite milk samples. A significant relationship (r2 = 0.83) was obtained between the progesterone concentration in composite milk and fore-milk samples; y = 1.52 - 1.41(0.163)x, where y = log10(composite progesterone) and x = log10(fore-milk progesterone). A milk progesterone concentration of 3 ng/ml in composite milk corresponded to a milk progesterone concentration of 1.47 ng/ml in fore-milk. Using this relationship progesterone profiles may be compared between herds where milk samples have been obtained by either composite milk or fore-milk sampling. In addition, composite milk samples only should be used with qualitative on-farm assays.</jats:p

An investigation of the key factors influencing reproductive performance in dairy herds in Northern Ireland

AbstractPoor reproductive performance is a major problem on dairy farms across Northern Ireland and the United Kingdom (UK) as a whole, and recent studies suggest that the problem is increasing. In order to identify the key factors influencing reproductive performance at farm level, a major research initiative was established in 1998 with the objective of collating a comprehensive database on reproductive performance from 20 herds, representing over 2000 dairy cows, across Northern Ireland. Preliminary results for five herds from the first year of the study indicate a high heat detection rate (84%) across all farms. The mean intervals to first observed heat and to first service for cows calved within 19 days of the start of the breeding season were similar between herds (42.8 ± 14.0 days and 50.0 ± 11.0 days respectively). In contrast, the interval to first service for all recorded services was 89.8 ± 66.3 days and varied considerably between farms (69.9 to 112.7 days). Investigation of progesterone profiles indicates that 62.3% of cows had resumed normal cyclic activity by 40 days post calving. Of the cows with atypical ovarian patterns, 19.4% were classified as prolonged post-partum anoestrus with a further 12% exhibiting at least one post-partum prolonged luteal phase.</jats:p

Modelling converted seismic waveforms in isotropic and anisotropic 1-D gradients: discontinuous versus continuous gradient representations

Over the past decade, there have been numerous receiver function studies directed at imaging the lithosphere-asthenosphere boundary (LAB). Although it is generally accepted that receiver function phases observed in these studies are derived from physical mode conversions at depth within the lithosphere-asthenosphere transition, it is still debatable as to whether these phases are directly indicative of the LAB. This is because interpretation of receiver function LAB signals relies on understanding the elastic characteristics of the Earth’s outer thermal boundary layer. The main issues for receiver function imaging are the sharpness of the elastic material property transition and, more importantly, what specifically are the material gradients. To test the various transition models, a forward modelling approach is required that allows accurate waveform synthetics for a range of discontinuous and continuous gradients in anisotropic, elastic media. We present a derivation of the reflection and transmission response for continuous one-dimensional (1-D) gradients in generally anisotropic elastic media. We evaluate the influence of 1-D isotropic and anisotropic elastic gradients on the seismic waveform by comparing numerical results of models for discontinuous and continuous transitions. The results indicate that discontinuous representations using layers each with uniform parameters and with thicknesses on the order of approximately 1/3 to 1/8 of the dominant seismic wavelength can be used to accurately model P-to-S and S-to-P mode conversions due to continuous transitions of both isotropic and anisotropic elastic properties. From a practical point of view, when comparing synthetic modelling with observation, this constraint can be relaxed further. The presence of signal noise and/or the result of receiver function stacking techniques will likely obscure these subtle waveform effects. Hence this study suggests that accurate synthetic waveforms for LAB transitions can be modelled with discontinuous gradient representations using a reasonable number of discrete transition layers with layer thicknesses no greater than 1/2 to 1/3 the dominant seismic wavelength