Lake Nash Breeder Herd Efficiency Project

Summary

This document reports on an observational study conducted on the commercial cattle operation, Lake Nash Station in the Barkly tableland of Northern Territory. At initiation of the project, it was intended that the study would be conducted for three seasons (2000 to 2002) following a set-up year in 1999. The project was concluded at the beginning of 2002, one season early, due to unforeseeable weather and personnel circumstances. While these circumstances prevented the anticipated outcomes for the study, results from the data collected are presented and considered to be of some value.

The main objectives of the trial were:

• To measure and report on the effect of dry and wet season supplementation on breeder herd efficiency (kg of calf weaned per 100 kg of cow mated) for three successive years at Lake Nash Station.

• To measure and report on supplement intake, pasture crude protein, phosphorus and in vitro digestibility, faecal phosphorus and crude protein levels and cow body condition monthly for three years and analyse the relationships between each for three breeding herds.

The presence of diseases known to affect the reproductive performance in bulls and /or cows for three successive years was also reported.

A demonstration was established on Lake Nash Station in three separate paddocks using Santa Gertrudis breeders and three different supplementation regimes i.e. nil supplement, wet season supplement and wet and dry season supplement. No replication of treatment groups was established.

A subset of maiden heifers were selected at the start of the trial and these females were monitored for reproductive disease.

Animal production data for the Barkly Tableland region was collected over a three year period from 1999 to 2001 and the results were analysed. Unfortunately due to the gaps in the data collected accurate and detailed analyses were unable to be produced. However estimates of conception rates, weaning rates and even an attempt at producing a Breeder Cow Efficiency Index for each of the mobs involved in the trial were produced. These indices will form a valuable bench mark for any further work that is undertaken in this region. Weaner weights varied between the groups from 196 kg to 222 kg. It would appear that the use of Charolais bulls may have had an impact on increasing weaning weights by increasing hybrid vigour.

Valuable pasture monitoring occurred for the duration of the project and seasonal variations of protein, biomass, dry matter digestibility and phosphorus have been recorded. NIRS technology was implemented and the results should be very useful for producers wishing to implement supplementation strategies over the dry season.

Diseases affecting reproductive performance in the herd were studied. While positive serological findings were detected for viral diseases such as Bluetongue, Bovine Ephemeral Fever and Infectious Bovine Rhinotracheitis and for the bacterial disease Leptospirosis, it would appear that none of these diseases are causing significant reproductive losses in the region. Akabane infection was also detected and this may have caused some reproductive loss. Trichomoniasis was prevalent in the bulls but its impact was unable to be quantified - 12 bulls were culture positive for Tritrichomonas foetus. No Campylobacter fetus was cultured from the trial bulls but five of fifteen cows sampled with vaginal swabs were positive to the Vibrio IgA ELISA.

Losses of around 17.1% between pregnancy tested and weaning were identified. This will prove to be useful data for further research in the area of calf wastage,

This study never attempted to be an “on farm” replicated trial as the budget was small and beyond the scope of funds allocated. While the findings relating to supplementation were not significant, the methodology and sampling techniques developed for the project have enabled producers in the region to commence data collection and establishment of their own benchmarks for their breeder herds in the Barkly Tableland.

This project recommends that further work in calf wastage be undertaken in northern Australia and that NIRS technology be supported to increase producer awareness as to when to supplement. More work needs to be undertaken to develop a practical Breeder Cow Efficiency Index which can be applied to all herds in northern Australia.