The matron of honour

Paul Charteris
Institute of Veterinary, Animal and Biomedical Sciences
Massey University

In New Zealand the beef breeding cow has developed a complementary role to sheep in mixed livestock farming systems. However, her traditional position as a complement to sheep farming has been challenged by many farmers over the last decade as efforts are made to improve breeding cow profitability (Webby and Thompson, 1994). The beef breeding cow of the future has been termed the high-octane cow (Lowe, 1994), acting both in a complementary role and as a direct competitor to sheep on the basis of financial performance. This article will give an overview of beef breeding cow efficiency and its importance to New Zealand production systems.

Efficiency is generally measured as a ratio of outputs to inputs, and for beef cattle production can be defined in terms of economic or biological parameters. Only 6% of the total dietary energy expended in beef production is used for protein deposition in market progeny (ie meat production). Pork and broiler chicken production are much more efficient at 14% and 21% of energy expended respectively, although the pasture finished cattle graze a feed source which cannot be utilised by monogastric species or by humans. However such simple input/output efficiency relationships may not be appropriate in New Zealand beef cattle production systems where cows are used in other roles such as improving pasture quality.

One explanation for the lower efficiency of beef cattle production in comparison to monogastric species is the high cost of energy required for maintenance. Seventy one percent of total energy expenditure in beef cattle production is used for maintenance and 70% of that maintenance energy is required by the cow herd (Ritchie, 1995). Therefore, 50% of energy required for beef cattle production is required for maintenance of the cow.

Results from a series of US studies show there is positive genetic relationship between breeding cow maintenance requirements and genetic potential for production traits such as growth rate and milk production. Available data also indicates that as a consequence of high maintenance requirements, cows having a high potential for productivity may be at a disadvantage in a feed limiting environment, such as on hard hill country. The increased feed requirements of high producing cows may be accounted for by the increased mass of visceral organs of high producing cows, especially the digestive tract and liver which have very high energy requirements. Furthermore, the increased energy requirement of heavily muscled cows may result in higher energy expenditure since more energy is required to maintain a given weight of body protein than a comparable weight of body fat. High maintenance cows tend to have large mature size, high visceral organ weight, high lean tissue weight, low fat weight, high calf weaning weights and feed inputs. Farmers need to aim for a balance between these characteristics depending on the feed resources of the farm and the market to which progeny are sold.

Prior to weaning it is the prenatal and then the milking and mothering ability of the dam that provides an important component of the calves environment. Although the milking and mothering ability of the dam is an environmental effect on the calf, it is affected by the genotype of the dam for milking and mothering ability. There fore the weaning weight of calves is determined by:

1. the genotype of the calf for preweaning growth (direct genetic effect)
2. the genotype of the dam for milking and mothering ability (maternal effect)
3. the effects of environment

Improving calf weaning weight through the maternal effect is a more energetically efficient means of improving calf weaning weight than through the direct genetic effect since improvement via the latter option will also result in an increase in cow size and subsequent maintenance requirements (through a positive genetic correlation between weaning weight-direct and mature live weight). Improving calf weaning weight through improved maternal performance also increases cow feed requirements, however these increased feed requirements are apparent during lactation and are not carried over through the following winter.

There is a small negative correlation between maternal and growth genes, suggesting genes which partition food toward increasing body reserves (such as calf growth rate) are partly incompatible with genes used for milk production (Garrick, 1990). Opportunity exists to improve production efficiency by selecting dam lines specifically for maternal superiority and sire lines for direct effects on growth. Such a mating plan is already widely used in the beef industry with sire lines represented by high growth rate, high yielding terminal sire breeds and dam lines by British breeds.

On Limestone Downs, a 3200 ha sheep and beef farm managed near Port Waikato, the role of the beef breeding cow has changed from an animal viewed as complement to sheep to being a direct competitor. This change was largely as a result of increased beef returns relative to sheep, development of the farm with fencing, water, fertiliser and development of a cow capable of higher performance through crossbreeding. Two management decisions were made to increase herd performance, firstly, the decision was made to calve heifers down first at 2-years of age, given priority feeding, no particular management difficulties were found with this practice. Secondly, a Hereford bull was mated over the Angus cow herd. The results of these two management changes are shown in Table One.

Table One Mean calf live weights from Limestone Downs (cow weaning weights shown in parenthesis) Lowe, 1994.

The Friesian breed was introduced into the rotational crossbreeding programme developed to maintain a breeding cow herd comprised of cows with varying portions of Friesian, Angus and Hereford genes - a high octane cow. A fourth breed, the Simmental was introduced to be used as a terminal sire over cows which are not required to breed replacements. To maintain her place in the Limestone Downs herd, the beef breeding cow must now produce steer calves capable of reaching target carcass weights before their second winter and heifers which can wean a calf at two years of age and themselves be slaughtered at 260 kg some six months later. In terms of breeding cow efficiency, the crossbred cow with Friesian breeding placed ahead of the Angus x Hereford cow, however the liveweight loss of the Friesian cow during lactation needs to be diverted from some other enterprise, a feed cost which cannot be ignored. The higher efficiency of the Beef x dairy cow (with or without fostering an extra calf) was found by Morris et al, 1993).

Table Two Comparison of biological and economic efficiency of different beef breeding cow policies (Morris et al, 1994)

1. Traditional: A 450 kg straightbred beef cow of British breed type with a 90% weaning rate and an average calf weaning weight at 200 days of 200 kg
2. Beef x dairy: crossbred cows mated to a terminal sire e.g. a 400 kg cow Angus x Jersey cow with a 90% weaning rate and an average calf weaning weight of 250 kg at 200 days of age
3. Beef x dairy (twin): the same cow as in 2 but with a second (Friesian bull) calf fostered, 90% weaning rate and 80% success rate with fostering, giving a weaning rate of 162%

The beef breeding cow contributes to financial performance of the farm directly, through sale of offspring and through her own slaughter value and indirectly through maintaining pasture quality- especially during autumn. It was noted by Webby and Thompson (1994) that from a survey of Waitomo beef farmers, the indirect benefits of the beef breeding cow were listed in order of importance as being, 1. complementary grazing, 2. self-replacing 3. maintaining pasture quality 3. low risk, flexible enterprise with a diversity of income and 4. easy to manage in relation to other stock classes

In conclusion, the optimal beef breeding cow can be defined in a number of ways, however Duello (1995) reminded cattle producers to keep the big picture in mind, " sound, practical, reproductively efficient cattle with good temperaments and longevity will NEVER go out of style.

Duello, D. 1995. A seedstock producer's perspective. Customer focused beef production. Palmerston North, 30 March, 1995.

Garrick, 1990. Maternal effects on growth in beef cattle. Proceedings of Australian Association of Animal Breeding and Genetics, 11: 397-400.

Lowe, K.I. 1994. Managing the high performance beef cow - where to next?. Proceedings of the New Zealand Society of Animal Production, 54: 315-317.

Morris, S.T.; Brookes, I.M.; Parker, W.J.; McCutcheon, S.N. 1994. Biological efficiency: How relevant is this concept to beef cows in a mixed livestock, seasonal pasture supply context? Proceedings of the New Zealand Society of Animal Production, 54: 333-336.

Ritchie, H. 1995. The optimum cow - what criteria must she meet?. Proceedings of the beef improvement federation, 27^th research symposium and annual meeting. 126-145.

Webby, R.W.; Thompson, R.D. 1994. The current status of the beef breeding cow in New Zealand mixed livestock production systems. Proceedings of the New Zealand Society of Animal Production, 54: 311-314.