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Heifer-calf and fattening strategies

 

Previous ACIAR-funded projects found low reproductive performance of Bali heifers, high mortality of calves and poor growth rates of cattle in villages, and identified specific researchable issues that need to be resolved to be able to develop practical recommendations for farmers.  Specific objectives of this small research activity were: 

  1. Determine the reproductive performance of first calf Bali heifers and identify the factors which affect performance.
  2. Develop liveweight gain response curves to feeding cassava by-products to Ongole bulls which will have application to fattening systems across Indonesia.
  3. Review and recommend a supplement strategy(s) for survival of calves from cows facing severe nutritional shortages.

Initially an extensive review was undertaken of calf supplementation. In association with this a large number of separate experiments was undertaken to examine methods to detect oestrus, milk production in Bali cows and heifers in villages and finally reproductive parameters with Bali heifers and cows. A feeding experiment was done with onggok (cassava bagasse), palm kernel cake and copra meal to develop liveweight gain response curves to inclusion of onggok in fattening diets. Another feeding experiment examined the differences in liveweight gain between Bali bulls and Hissar x Bali bulls in fattening systems.

The review of calf supplementation concluded that supplementation the pre-weaned calf should result in reduced mortality and increased liveweight of calves at weaning and improved body condition score, reproduction performance and subsequent milk production of cows. Supplementation of the cow prior to or during lactation will enhance these beneficial responses. If farmers co-ordinated calving then fixed time, batch weaning would provide calves of similar age and condition for further fattening operations at a larger scale. It was also concluded that despite the biological benefits of these strategies, farmers need a long-term business plan/vision to receive any financial return on their investments during this period. Ultimately for such a system to be sustainable, farmers need to receive a return on their investment either by maintaining these increased growth rates through to slaughter (males) or puberty (females) or by receiving a premium price for heavier weaners by specialised backgrounders or traders willing to negotiate on a measured liveweight basis. 

A series of experiments monitoring oestrous activity in heifers and cows developed a faecal assay procedure to detect changes in progesterone. It was concluded that faecal progesterone could be used as a method to detect oestrous activity in heifers and cows and that this would have wide application in field based studies. Limitations in application are outlined in the report. The Vaginal Electrical Conductivity (VEC) procedure was also evaluated but found to be not useful in routine evaluation of oestrous activity.  An extensive analysis of historical data from various ACIAR projects into reproduction of Bali cows and heifers across the eastern islands of Indonesia was undertaken. This confirmed previous analyses about the low reproduction of Bali cows in villages but also identified the high reproductive potential of this breed of cattle if certain conditions are met, namely, identification of oestrus, access to a bull in a timely manner, weaning of the calf at 4-6 months and reasonable Body Condition Score (BCS) of the cow or heifer (>3 out of score 5). First calf cow reproduction was specifically analysed and this was very low primarily due to low BCS, low weight and poor mating activities as well as the higher feed requirement as these young cows were still growing. If these were addressed then reproduction rate could approach that of more mature cows. In villages reproduction of first calf cows and older cows was often very low but variable (37.2 to 85.7% pregnant within 100 days). 

This study highlighted data quality (observations and records) as a major issue in such analysis and emphasized the need for closer observation of oestrous behaviour (and training to detect oestrus) and the deployment of more objective measures or techniques of oestrous activity. Methods to improve experimental observation of oestrus and mating procedures were examined by studying faecal progesterone profiles, protein hormones (leptin and IGF-1) and vaginal electrical conductivity. Milk production and interaction with lactation anoestrus was examined but no relationship was found and low milk production of cows in villages was confirmed (1.5L/d).
Lactation anoestrus appeared not to be a major issue. The marked exception to this was the first calf cows where most of the moderate body condition score (BCS) cows showed anoestrus for 100 days after calving suggesting that post-partum anoestrus (PPA) was an issue and related to BCS. Management of the cow and heifer for BCS and timely access to a bull or AI would be a simple and effective strategy to increase reproductive rate for the vast majority of cows and heifers.

BCS at calving proved to be the simplest way to manage cows and heifers for high reproduction and aiming for a BCS of at least >3 would appear to be a good strategy. This agrees with other studies with other genotypes but there is a suggestion that some Bali cows can maintain high reproduction at low BCS even in the range 2.5-3 from some of the current observations. A previous study (Straw Cow project, Mayberry et al. (2016) outlined that it was difficult to maintain high BCS (>3) and very difficult to increase BCS in lactating and dry cows and heifers. This was supported in the current project (although with very low animal numbers) where even a high leucaena diet required some grain supplement to increase BCS to >3.5.

BCS is a simple management tool which is a reliable indicator of level of nutrition. Level of nutrition and BCS are key factors which influence onset of oestrus in cattle of all breeds and the effects are thought to be mediated by the protein hormones, leptin and IGF-1. Here IGF-1 increased in the predictable manner with a higher level of nutrition but with leptin there were no such changes in Bali cattle. 

The use of onggok as a high energy by-product to increase growth rates and BCS was evaluated in a feeding experiment which developed a response curve relationship to the inclusion of onggok. The current experiment used Madura bulls (236+ 29 kg) and used a combination of onggok, palm kernel cake and copra meal in a response curve relationship from 30-70% onggok. A ration of 40% onggok, 40% a mixture of palm kernel cake and copra meal and 20% elephant grass gave the best liveweight gain (0.83 kg/d).  The liveweight gain response to onggok inclusion with terms for crude protein intake (CPI) (g/kg W.day) and Metabolisable energy intake (MEI) (MJ/day)) was a quadratic relationship of: 

Average Daily Gain (kg) = -0.886 + 0.01382 MEI + 0.3532 CPI. 

Reasons for the low liveweight gain at high onggok inclusion are not known but it was not related to HCN content of the onggok (which was very low) or excretion of thiocyanate which was also very low. Hissar x Bali bulls grew faster on a leucaena and corn grain based diet than Bali bulls (0.61 vs 0.85kg/d).

In conclusion, this study has shown that Bali cows and heifers have high fertility and that management in terms of low BCS and poor access to a bull or AI in a timely fashion most likely accounts for reports of poor reproduction. There was also evidence that a small proportion of cows and first-calf cows had a long inter-calving interval and in those intensive studies this appeared to be due to post-partum anoestrus related primarily to low BCS. It may be concluded that Bali cows and heifers are inherently highly fertile and that a simple management system of a target BCS at calving (>3), access to a bull or AI from 40 days post-calving and weaning of calves at 4-6 months of age (or earlier if BCS is declining fast due to poor nutrition) will enable annual calving or weaning percentage of approximately 80% to be achieved. Heifers need to continue to grow and hence they require better nutrition than cows during the latter stages of gestation and first lactation if they are to achieve high reproduction levels after the first calf.  It was also found that liveweight gain (kg.d) of HissarX bulls was significantly higher than that of Bali bulls. A combination of onggok (40%) and protein meal (40%) will promote high liveweight gain in fattening systems and also be a useful strategy to increase BCS of cows and heifers when required to improve reproduction rate.