Breeding objectives for beef cattle in New Zealand

Authors
Dorian J. Garrick and Paul L. Charteris
Institute of Veterinary, Animal & Biomedical Sciences,
Massey University, Palmerston North, New Zealand

Summary

Sustainable genetic improvement programmes must achieve genetic advance in bull breeding herds; transfer of genes (bulls) from breeding herds to commercial herds; and financial rewards to producers and breeders that at least cover the costs of generating and using improved bulls. Genetic progress in bull breeding herds (which represent some 4% of beef breeding cows in New Zealand) are determined solely by the selection decisions of bull breeders. However, financial rewards for the bull buyers rely on improved profitability of the progeny of these bulls in commercial farm systems. One component of profitability is determined by the extent to which the cattle provided by the producer meet the needs of the processors and, ultimately, the consumers. The biological traits that influence profitability thus vary depending upon your perspective - as a bull breeder, commercial beef producer, or processor. For many New Zealand farmers, one goal is to increase profit per ha. Management techniques (including the use of fertilisers, different pasture species and grazing systems) can be used to increase pasture production and feed utilisation. Genetic improvement offers one option for increasing the efficiency with which consumed pasture is converted into profit. One objective is therefore to increase profit per kg DM. Selection objectives based on this producer approach to profitability are being progressively introduced to beef producers via an internet-based sire selector.

Keywords: Breeding objectives, beef cattle, profitability

Introduction

A selection objective defines the extent to which changes in various traits impact on the satisfaction of the livestock manager. In most farming circumstances, satisfaction is largely (but not wholly) determined by profitability. Within certain constraints, the selection goal is to improve the profitability of a farming system. This goal can be formally described in a two-step process. First, one identifies the traits that influence profit. Second, the relative emphasis of each trait in the list is determined by considering the impact of a small change in that trait, on overall farm profit. This paper considers the development and application of selection objectives to the improvement of beef cattle in New Zealand.

Bull breeder perspectives

Bull breeders profits are determined by the proportion of bull calves that are sold for breeding, the average premium received for breeding bulls relative to slaughter cattle and the costs associated with reproductive management, pedigree and performance recording, veterinary intervention, marketing and feeding. The proportion of bull calves that are sold for breeding, and the average price for these bulls are major determinants of bull breeders profitability. In an ideal world, the average price of these bulls would relate to the expected performance of the offspring of these bulls and their lifetime ability to service cows. The number of services produced per bull depends upon their longevity and their serving capacity. In practice, sale prices are often more related to the weight of the bull on the day of the sale. Accordingly, bull breeders have rapidly responded by breeding cattle with greater propensity to grow, and accordingly, larger mature sizes. Other characteristics such as the reproductive performance of the daughters are important to producers but, for various reasons, have little impact on sale prices of bulls.

A survey of bull breeders representing three New Zealand breed Societies using Group Breedplan (Angus, Hereford and Simmental) was undertaken as a first step to encourage breeders to formally characterise their selection objectives. The breeders identified the fact that the importance of various traits depended upon whether bulls were used in a terminal sire role (primarily by dairy farmers in the case of Angus and Hereford bulls), or whether daughters were to be retained for breeding. Accordingly, their responses, in order of importance, were sought separately for these two production circumstances and are shown in Tables 1 (Simmental) and 2 (Angus).

Table 1 Simmental Breeder Survey Responses

Table 2 Angus Breeder Survey Responses

Table 3 Hereford Breeder Survey Responses

The breeders were asked to rank these traits from the perspective of the bull buyers, and not from the perspective they use in their own selection decisions. Interestingly, reproductive performance (serving capacity, libido, cow fertility and calving ease) were identified as being of paramount importance. Meat yield (which is not significantly rewarded at present) was identified to be of moderate importance.

Commercial producer perspectives

The profits of commercial producers are determined by reproductive rate (usually expressed as calves weaned per cow exposed); feeding costs (relating to the quantity of feed consumed by the cow and the growing offspring in relation to alternative uses of the feed, such as for sheep); and average market returns for store or prime stock. Producers can quantify the effects of outputs on income, such as from changing the number of sale animals, or their average carcass weight, but have more difficulty quantifying the relative feed consumption of cattle of different weights and growth characteristics. Accordingly, calculations have been undertaken using models of a New Zealand farm, incorporating feed costs, and also by using BreedObject, parameterised for a range of New Zealand management and production circumstances. Some limitations of BreedObject in these circumstances are that it does not account for the use of bulls in a crossbreeding role (see Figure 1) and it is hard to describe the opportunity feed costs that exist in practice when sheep and beef cattle are run together in a competitive fashion on the same farm. However, to fully account for all these peculiarities can lead to development of models that are overly complex. No doubt, such models will be developed in future.

Figure 1. Breeding bull destinations in New Zealand

All domestic and export beef processors were surveyed to identify those traits that were important or not important in influencing their plant profitability and meeting the requirements of their customers. The meat quality attributes vary in importance in different markets and processors were asked to reply separately with respect to the North American markets for processing beef and the Asian markets for table beef. Their responses are shown in Figures 2 and 3. The triangles require some explanation. The left-hand edge represents the least important response and the right-hand edge represents the most-important response. Small triangles therefore represent consistent responses. The apex of the triangle represents the average of the ten processor responses.

Figure 2 Processor requirements for North American processing beef.

Processor perspectives

Two findings were of interest from this survey. First, the wide range of responses between companies for the same trait (e.g. marbling), which may reflect real differences in niche markets or simply imagined differences in market needs. Second, the high level of importance attached to the attributes of table beef important to consumers, namely taste, flavour, juiciness and tenderness.

Figure 3 Processor requirements for Asian Table beef.

Use of selection objectives

Given estimated breeding values (EBVs) for each trait in the objective, an index estimate of overall merit can be used for selection. In practice, EBVs will not be available for all traits in the objective, and this in itself is a useful outcome of deriving a selection objective. This identifies research areas that need to be addressed in order to meet future needs of industry. EBVs for some traits in the objective can be calculated from characters measured on the farm. For example, fertility traits may be assessed from information on days to calving and scrotal circumference, and lean meat yield may be assessed from liveweight and ultrasound measures. The approach used in Breedplan is to calculate EBVs for each character measured on the farm rather than only for traits in the objective. This has the disadvantage of increasing the array of available EBVs which can serve to erode selection differentials. That is, breeders who dislike an individual animal will usually be able to find at least one unfavourable EBV so that they can justify the culling of the animal on an apparently objective basis. A preferred approach is to rank animals on overall merit alone and then apply independent culling levels to other characteristics such as single trait EBVs and conformation.

Selection objectives are used to identify the relative importance of traits in the objective such that single (index) measures of an individual's merit can be used for selection and culling. Such index values are widely used in the New Zealand dairy industry and in Animalplan for ranking sheep. The dairy industry index values (known as Breeding Worth, BW) are expressed in dollars profit per 4.5 tonnes DM consumed and are comparable across-breeds for straight- and cross-bred animals. For cows, farmers do not ordinarily see the component trait EBVs. In the case of sheep evaluations, animals are normally ranked on index values and these ranks, along with the component EBVs, are used for selection purposes. Many breeders and producers in New Zealand would use index measures of overall profit for the selection of beef cattle, should these be routinely available.

Currently it is difficult to include measures of meat quality in the selection objective due to non-existent or inconsistent pricing signals for such traits (Figures 2 and 3). However, when establishing selection objectives some account should be made of anticipated future market requirements. The consequences of failing to include meat quality traits in the selection objective would result in little change in these traits which may affect future market share or market returns.

A collaborative project between Massey University and Dr. Scott Newman at Tropical Beef Centre, Rockhampton is to trial the delivery of customised sire summaries, ranking bulls in order of their index merit for the users production and marketing circumstances. This system will be available via Internet and farmers will select various criteria to customise their search, including bounds on individual EBVs. This approach could later be extended to enable customised cow rankings as well as providing options to match sires to crossbreeding role.