Waikato NZPIM - Heifer Grazing Project

DairyNZ. (2016, April). Heifer grazing project: Waikato NZIPIM [Handout]. Hamilton, New Zealand: DairyNZ

This was a meeting reviewing the Dairy NZ Heifer Grazing Project. It explained why the project was started in 2014 and looked at the results of the industry performance.

In 2012 heifers registered in MINDA Weights were 11% behind their growth rate target at 22 months and 73% were more than 5% behind target. In 2015 some progress has been made and on average the stock are still 11% behind target but the tail end has been reduced and 59% are more than 5% behind target.

It appeared that the hardest target to hit is the daily live weight gain for the 9-15 month period and this corrects by the time the heifers are18 months old. This could be down to a multitude of factors - is this period the same in Autumn born heifers? or is it the seasonality of climate, pasture quality and intakes?

The issues identified as stopping heifers from meeting their live weight gains were

  •Relationship Management
  •Knowledge for management
  •Pricing
  •Industry leadership

The group discussed the heifer requirements through their growing period and calculating a pricing model based upon other farming enterprises.

There was some thought from some of the attendees that there should be no restriction of the heifers growth and the heifer should achieve optimum or accelerated growth from birth through to entering the herd at calving. That it was simply due to a lack of quality feed and the heifer should be supplemented with feed to ensure her needs are met.

 

 

There was some discussion over where the responsibilities lay for management issues. There is a Dairy NZ checklist available that was in the hand out from the day that could be included in a contract. If this is decided before the agreement starts it resolves any future disputes that could have occurred.

The biggest concern is that heifers will not achieve the target average daily gain and fail to reach their target live weight at the end of the contract. I am looking at whether the pastoral system is able to feed the heifers appropriately and to achieve the targets required.

 

Heifer Grazing Focus Fielday- Dairy NZ

Dairy NZ. (2016, April). Heifer grazing focus farm: King Country [Handout]. Hamilton, New Zealand: Dairy NZ

Attending the Dairy NZ Heifer Grazing Focus Farm Fielday I found to be of great interest. Held in the King Country it looked at a pastoral based heifer grazing system questioning

• What does good look like?
• what is a realistic growth rate target?
• What farm systems achieve industry targets?
• What is a fair price?

The summary was given as follows

 

Growth Rates

The Focus Farm looked at growth rates they achieved throughout the year on the pastoral system. It clearly shows that the farm had a variable growth rate through the year. This is a seasonal variation and can be forecast with great predictability as it shows a clear pattern. 

 

The following graph shows the industry targets plotted against the predicted growth rates for the farm and the average live weights as they happened.

 

This information shows me that there is a variation in heifer growth rates in the pastoral system. The focus farm clearly hit their daily live weight gain target on average with some variation throughout the year.

Use of breeding values for live weight to calculate individual live weight targets for dairy heifers

This paper models the LW targets at any stage of a heifers development. Modelling the speed of live weight growth allows heifer rearers at any weighing date evaluate the heifer LWT and benchmark it to where she should be according to the mature herd live weight.

It examines how the genetic potential of the heifer varies so much the growth has to be mapped against a model mapped to its genetic mature live weight. The data showed that puberty does occur at a target percentage of the live weight and therefore proves that hitting live weights is critical to ensure successful mating in the spring. Knowing the mature weight and therefore being able to extrapolate the critical weight to hit at certain periods during the growth period is invaluable to ensure the heifer is able to enter the herd successfully.

There is some feedback at meetings I have attended that the linear LWT gain is not as applicable to the pastoral system. That the speed of heifer growth will be directly proportionate to the quality and availability of the pasture. Any period of limitation which slows growth is then followed by a period of high quality feed which ensures the heifer has accelerated growth and this averages out to an average daily gain that achieves the overall goal. 

 J. R. BRYANT, C.W. HOLMES, N. LOPEZ-VILLALOBOS, L.R. MCNAUGHTON, I. M. BROOKES, G.A. VERKERK, and J. E. PRYCE (2004) Use of breeding values for live weight to calculate individual live weight targets for dairy heifers, Proceedings of the New Zealand Society of Animal Production, 64, 118-121

 ABSTRACT

Replacement heifers need to reach specific target live weights (LW) to ensure they calve as two year olds, and subsequently achieve high milk yields and good fertility. Currently, different LW targets are recommended for heifers based on their expected mature LW according to appearance or breed. However, the mature LW is difficult to estimate without knowledge of the animals’ genetic potential for LW. The objective of this paper is to develop and validate a growth model which uses estimated breeding values for LW (EBV LW) of individual heifers of any breed to calculate target LW from birth to maturity. Predicted live weights are presented for a range of four EBV LW, from –40 to 100 kg. These values were very similar to other published target values. Data from the Dexcel Holstein Friesian Strain Trial was used to validate the model with respect to LW and age at puberty. For LW at puberty the predicted values were significantly correlated (P<0.05), but were marginally higher (3-5%) than the actual values. A report can be formulated to enable farmers to identify individual heifers which are below (or above) their target LW at any date.

     

Effect of heifer live weight on calving pattern and milk production

This paper looks at the lost opportunity of an undergrown heifer and the cost of her not making her live weight target at first calving. If she enters the lactation with significant growth to make up then the feed conversion into milk will be lower than what it could have been as energy will be partitioned into her own growth. Her voluntary feed intake will also be limited by her size. If a 9% milk solids test is assumed, the expected response is about two kilograms of milk solids per lactation for every one percent increase in target live weight attained. For a heifer with a pre-calving target of 500 kg, five kilograms is equal to one percent of live weight.

The report found that regular monitoring is required as accurate live weight gain information is required to plan the feed intakes for the heifers. I have found this to be true in my own experience as calves with a very low ADG have been thought by the grazier to be doing very well and in fact they have been going backwards. Regular monitoring can pick this up before the condition scoring perception was able to.

LR McNaughton* and T Lopdell (2013) Effect of heifer live weight on calving pattern and milk production, Proceedings of the New Zealand Society of Animal Production, 73, 103-107

Abstract

Many heifers on New Zealand dairy farms fail to reach their target live weight. This failure leads to lost milk production and poorer reproductive performance. This study investigated effects of breed and region on heifer live weight and also effects of pre-calving heifer live weight (18–21 months) on milk production. Less Friesian heifers reached their target live weight than Jerseys, or Crossbreds (85.3 versus 89.3 versus 88.1%; P <0.001). Heifers born in Otago (91.9%) and Taranaki (91.8%) were the closest to achieving their target live weight, whilst those born on the West Coast (85.6%) and Northland (86.0%) had the greatest number of heifers not reaching their target. Heifers that had only one calving recorded on the database were a significantly lower percentage of target live weight than those heifers that had two calvings recorded (83.5% versus 87.1%; P <0.001). In heifers with a live weight record between 18 and 21 months of age, every 1% increase in the percentage of target live weight attained was associated with an increase in milk volume of 23 ± 0.6 litres in the first lactation and 24 ± 0.9 litres in the second lactation. Further work is required on the economics of feeding heifers to achieve their target live weight.

Tracking Liveweights using MINDA

Most heifers will be weighed regularly and the results compared to industry targets to ensure that the growth rates are optimum.

Many farmers will be uploading the data into MINDA which can easily convert the data into easily read tables and graphs. This identifies the mob averages and how they are tracking. It also will group the heifers and identify those that are at target weight and growing well, below target but growing well and below target and not growing so that plans can be put in place to take action.

LIC (2015) MINDA Weights: Better liveweight analysis. Retrieved from http://www.lic.co.nz/lic_MINDA_Weights.cfm

MINDA Weights provides graphical illustrations of whether individual animals are achieving their current ideal live weights, and allows you to assess how they are doing in terms of recent growth rate.

Monitor the live weight of your youngstock with MINDA weights to ensure they are reaching their growth potential and are in prime condition for mating and calving.

Track young stock weights (for animals 0-24 months) against targets generated from live weight breeding values (generated from parentage history) so that you can see at a glance how your mob's live weight is tracking against its genetic potential.

Monitor whether your stock fall into the 'underweight', 'on target' or 'above target' segments within your herd and track this progress over time.

  
 
   

Growth targets and rearing strategies for replacement heifers in pasture based systems: a review

This paper is interesting because it looks at how the pre-weaning growth is the most important part of the heifer rearing programme and if the heifer isn't reared properly from birth with adequate access to colostrum and feed. Large average daily gains in the pre puberty period can adversely affect the growth of mammary secretory tissue.

Low live weight heifers at 15 months are low live weight compared to the rest of the herd until at least their third lactation.

The next question this draws up is where should the mature live weight be drawn from? Should it be the genetic potential mature weight or the average herd live weight? The herd's mature weight could, therefore, be a function of historical heifer growth trajectory and projecting heifer growth on data from cows that were poorly grown as heifers would perpetuate the cycle of poor productivity.

40% calves suffer from failed passive transfer of immunoglobulins caused by a failure to feed enough colostrum quickly enough to the new born calf. Calves with FTP will have increased rates of mortality and morbidity. It also reduces DM intake and milk production later on.

It is often reported anecdotally that graziers receiving calves at weaning that the 'tail end calves' never do very well and will always be behind the rest of the mob. This paper recognises accelerated ADG in the first eight weeks is associated with enhanced mammary development and identifies further work is required to understand the relationship between early life average daily gain and gastro-intestinal development.

 It is interesting the way that different speeds of average daily gain has a different effect on mammary development at different stages of the heifers path to maturity. The links showing in the papers reviewed that an accelerated ADG pre wean has a positive impact on mammary development and subsequent lactation after the first calving. Then some studies will show a negative correlation between accelerated growth and mammary development from post weaning through to puberty.

 It is hard to achieve a linear ADG in the grazed pasture growth system. This is due to the high NDF levels in summer restricting the VFI and reducing the ME of the pasture available to the heifer and low growth rates in the winter reducing the level of feed available. The question is can the pastoral system be manipulated to match the needs of the heifer and use the natural pastoral growth cycle to feed the heifer to her own benefit and use compensatory growth to accelerate the ADG when required?

 Though stair step methods of gain using compensatory growth have been shown to have poor utilisation of energy for live weight gain and was used for lay down of fatty tissue rather than lean tissue.

J. R. Roche, N. A. Dennis, K. A. Macdonald, C. V. C. Phyn, P. R. Amer, R. R. White and J. K. Drackley (2015) Growth targets and rearing strategies for replacement heifers in pasture-based systems: a review, Animal Production Science, 55(7), 902-915

Conclusions and further research

Mature Lwt is hard to define, because it is dependent on both the genotype of the heifer and the environment in which she is managed. Furthermore, there does not appear to be a significant advantage to defining a mature Lwt for individual heifers compared with an average mature Lwt for the herd. Although accepted as dogma that heifers should calve between 80% and 90% of mature Lwt, the advantage of achieving this target is not clear. The effects of pre-pubertal and post-pubertal ADG on milk production and reproduction are inconsistent, as long as the heifer has had sufficient ADG to reach puberty before the desired breeding date. That said, there is morphological and physiological evidence that accelerated pre-pubertal ADG reduces mammary parenchymal development; what is not clear, however, is whether, or not, there is compensatory development of the mammary gland during the gestational allometric development phase. What is also not clear is whether accelerated growth trajectories result in changes to the composition of nonmammary tissue and whether this could potentially have negative effects in the calved heifer. Further research is required in these areas. Consideration should also be given to the trajectory of gain, whether periods of restriction and re-alimentation increase the amount and activity of mammary secretory tissue and whether the advantage can be exploited in pasture-based systems. Further work is required to understand why such a high proportion of calves fail to receive sufficient high-quality colostrum to ensure adequacy of immunoglobulin transfer. The importance of colostrum in the lifetime productivity of the replacement animal has been known for decades. Therefore, the failure of this vital practice on farm is worthy of social study and increased extension effort. A growing area of interest is the pre-weaning nutrition of the calf and, in particular, the first 8 weeks of life. Research has indicated a significant return on limited additional investment during this time. However, the majority of that work has been undertaken in high-production, housed dairy systems. Further research is required in grazing systems and, in particular, research efforts should focus on determining whether the window of opportunity is even shorter than has been indicated.

      

Effect of feeding and bodyweight on growth, milk production and fertility

This paper forms some of the basis of the Dairy NZ table of heifer growth stage live weight targets. It shows the acceptance of pasture based heifer rearing programmes having a lower first calving live weight.

With the genetic advances made in the last twenty years it has been agreed that heifers need to be grown to a better weight as they enter the herd to ensure their genetic potential is met.

Historical studies have shown that accelerated growth pre puberty can result in reduced mammary tissue development. But further analysis of the studies and adjustments made for breeding worth give inconsistencies in the results. The paper reports heifers reared at 0.6-0.8kg LW/day pre puberty there was no effect on milk production. It could be that the higher bodyweight at calving offsets any negative effect of accelerated growth pre puberty. The report did identify that postpubertal accelerated growth systems, even in grazed systems, does induce greater intensity of mammary development and in the first lactation increase milk production.

So the question is does the grazed system actually suit the proven method of stair-step compensatory growth patterns?

K. A. Macdonald, J. W. Penno, A. M. Bryant, and J. R. Roche (2005) Effect of Feeding Level Pre- and Post-Puberty and Body Weight at First Calving on Growth, Milk Production, and Fertility in Grazing Dairy Cows, J. Dairy Sci. 88, 3363–3375, 

Abstract

Heifer growth rate and BW at first calving are regarded as important benchmarks in dairy farm management (Sejrsen and Purup, 1997; NRC, 2001). Increased growth rate can reduce the time the heifer spends in a nonproductive state (Capuco et al., 1995; Sejrsen and Purup, 1997), but excessive prepubertal growth rates have been linked to reduced milk production (Harrison et al., 1983; Sejrsen et al., 1983; Ingvartsen et al., 1988; Sejrsen and Purup, 1997). In addition, recommendations on optimum first-calving BW vary widely.  In high concentrate intensive feeding systems, it is recommended that Holstein-Friesian (HF) cows achieve 540 to 650 kg of BW before first calving (Keownand Everett, 1986; Heinrichs, 1993; Hoffman, 1997); a more modest first-calving BW is accepted in pasturebased systems (490 to 550 kg; McLean and Freeman, 1996; Holmes et al., 2002).