Genetics

Weekly genetics review: Bringing your new bulls home

Genetics editor Alastair Rayner, 10/08/2021

IN THE leadup to a bull sale, most bull buyers are focussed on the process of identifying and selecting the right targets. These areas along with the actual process of bidding and purchasing tend to take attention off the other equally important part of the sale transaction – bringing the bulls home.

As a process, sale-time can be the cause of considerable amounts of stress for bulls. In the lead-up to sale, bulls are often handled more frequently as vendors wash them down, clip excess hair, apply paint brands and draft into sale pens.

Sale time is often an additional stress event with bulls being inspected and moved by many people over the course of a morning.

Post-sale, the transport of bulls to their new home can often result in further stress. It is not unusual for bulls to be trucked some distance to a new location – often interstate. The impact of travel and confinement – often with unfamiliar animals – as well as weather events or climatic change encountered during travel all contribute to the amount of stress and fatigue bulls will experience over the sale process.

As a result, many bulls suffer a drop in their fertility levels, post-sale.

This is described as Relocation-induced Depressed Fertility (RDF). The MLA Bull Power report, prepared by Dr Richard Holroyd and several other leading researchers, considered RDF to be a fairly significant issue for many owners and properties.

The Bull Power report suggests that there can be several different causes of RDF that may occur during transport, or soon after arrival at the new property.

The stress of transport has been suggested to be very similar in effect to elevated testicular temperatures. This can cause testicular changes and may influence the morphology of the bull’s semen as a result.

RDF was initially considered to be a concern largely for bulls travelling longer distances as well as being relocated into more challenging environments. However, part of the Bull Power research, considered the feedback of a number of vets and others within the industry.

The research suggests that RDF can equally be an issue with bulls being moved over shorter distances and into environments that were not necessarily that harsh or challenging.

Within the Bull Power project, a large number of bulls representing Bos Indicus, British and Tropical Composites were measured using Bull Breeding Soundness Examinations in the period between sale and joining.

The research found up to half failed the BBSE in the three-month period after the sale. While this number is a major concern, it was interesting to note that the failure to pass appeared unrelated to the genotype of the bull, the age of the bull, its property of origin or nutrition prior to the sale.

The principal causes of many of the failures of these bulls to pass their BBSE after arrival appeared to be directly related to nutritional stress.

Bulls that lost significant levels of body condition also had a reduction in scrotal circumference. The data found a high proportion of bulls that had significant loss for both body condition and scrotal size also produced semen that had less that 50pc normal sperm.

However, it was also found that when nutrition and body condition improved, that loss of fertility was reversed. In fact, the study found that RDF was an issue for bulls within six months of arrival in a new location. One other key finding of note was that Bos Tarus (British breeds) appeared to suffer the greatest drops in fertility as a result of poor nutrition.

Setting a program in place

Given these results, it is worth setting a program in place for new bulls focused on reducing the impact of RDF and ensuring bulls are fit to start work at joining.

Traditionally new bull management focusses primarily on the immediate introduction of bulls to a new property. These recommendations include:

  • Avoid mixing bulls for different properties of origin in the yards together
  • Allow bulls some company in the form of steers or older cows
  • Provide some hay and water in the yards

It’s generally recommended that bulls should be given a few days to settle before moving them out into paddocks.

Most advice doesn’t address the issues of RDF – primarily that of nutrition. Bulls will take some time to adjust to a new location and to adjust to new grazing conditions. The impact of temperature, humidity and unfamiliar pastures/feeds all contribute to reduce feed intake and lead to weight loss and to fertility depression.

As part of the planning around bull purchases, it is worth considering how nutrition can be maintained while bulls acclimatise to new locations. In some cases, it may be providing access to good quality forage along with better pastures for a few weeks while bulls adjust.  It may also require re-thinking paddocks to help bulls adjust to the temperatures of a new location.

It is worth recognising that the stresses of sale and transport, along with adjusting to a new location will take some time for bulls to recover from.

By planning to minimise the impacts these have, the period of time where bulls may be less fertile can be potentially reduced.

 

Alastair Rayner is the Principal of RaynerAg, an agricultural advisory service based in NSW.  RaynerAg is affiliated with BJA Stock & Station Agents.  He regularly lists and sell cattle for clients as well attending bull sales to support client purchases.  Alastair provides pre-sale selections and classifications for seedstock producers in NSW, Qld, and Victoria.  He can be contacted here or through his website www.raynerag.com.au

 

 

 

 

 

 

 

 

 

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