Management Solutions for Beef Cows

S.T. Morris, Institute of Veterinary, Animal & Biomedical Sciences,
Massey University

and P.L.Hughes, Taihape & Waimarino Veterinary Services

A talk delivered at Otago/Southland Beef Council, Fox Glacier Hotel, Thursday 14 September 2000

Summary

* Breeding cow management is based on matching cow nutritional requirements to the pasture growth curve of a property (or district).

* Cows at calving should be in condition score range of 2.5 - 3.0.

* Feeding levels of cows post calving is critical to avoid losses from metabolic disorders and ensure good production (calf weaning weights and subsequent pregnancy rates).

* Cows have high feed demands in early-mid lactation and can consume 20kg DM/day. This is an asset in regions with major grass surpluses in the late spring/summer.

* Cows are one of the few classes of stock available to 'tidy up' rank pasture. They can spend a four to five month period post weaning achieving this and lose 10% of body weight without detriment to subsequent production. This needs to be factored into any gross margin comparison with other livestock enterprises.

* Breeding bulls should be tested for breeding soundness.

* Cows calved correctly in relation to the pasture growth curve, in condition score range 2.5 - 3.0, mated to tested bulls should achieve a 95% pregnancy rate in a 52-55 day mating interval.

* Heifers above a critical mating weight and mated to tested bulls for 42-45 days should achieve an 84% pregnancy rate.

Introduction

The management strategy of a beef cow breeding herd is determined by a balance of feed supply patterns, competing resources and market requirements. There are major benefits from running beef cows on hill country farms arising from their flexible feed demand which can be aligned with the seasonal pasture growth curve. An additional benefit is their ability to assist in the management of pasture quality. Hill country farmers marketing weaners in the autumn will generally put in place a strategy to cope with calving, ahead of the spring pasture growth, in order to supply the market with older, and therefore larger, weaners. Farmers marketing progeny in the following spring or autumn, or finishing, have the flexibility of being able to calve at a more appropriate time in relation to their pasture growth curve. An appreciation of the pasture growth curve of a farm is fundamental to the management of any pasture based production system. This is, however, particularly critical to the cow breeding herd as not only will under nutrition at crucial times i.e. calving, cause poor production, but large losses (>20%) can be experienced from Hypomagnasaemia (grass staggers).

Such losses of a capital intensive item, which at best is only giving a modest financial return, will obviously render the breeding cow operation uneconomic. With appropriate management, breeding cows can, however, fill an important niche on hill country, particularly when the pasture growth curve has a large summer surplus and a contrasting winter deficit. In such situations, cows can maintain the advantages of cattle in a sheep and beef enterprise while protecting the farmer from the financial risks associated with cattle trading (particularly spring to autumn trading).

In the North Island there have been several trends apparent in the last decade. Cow numbers have tended to stabilise at around two thirds the level of the 1973-75 highs. There has been a trend away from autumn weaner selling; the Taihape weaner yarding in 1998 being approximately one third of the 1979 figure. Increased sheep to cattle ratios, subdivision, development of tussock land, and fertiliser applications, have all made cow management more specialised. Overall, there has been a trend towards later (October) calving with a low cost all grass wintering system and later sale of progeny, (after first winter or finishing). This trend has been supported by Taihape trials where calves born significantly later (55 days) have achieved the same liveweights at two and a half years as their earlier born counterparts. Significant improvements in cow performance and survival have resulted. The costs and labour inputs of feeding hay for long periods ($20-$30/head), and long term problems of pasture quality with saving it standing from the early autumn, have also contributed to the trend away from late winter (August/September) calving.

Beef Cow Nutrition

Good nutrition in beef cow production, as with any animal production, is paramount. Animal health and production problems, more often than not, simply have nutrition as a basis. Beef cows have the advantage that high levels of nutrition are only required for a specific period of the year. They have the disadvantage, however, that if the nutritional requirement is not met over that critical period, not only poor production will result but large losses can occur. For simplicity we can divide the annual nutritional requirements of mature spring calving cows into the following periods: Post-weaning; Pre-calving; Post-calving; Post-mating. Throughout this section body condition scoring has been used as an aid to feeding and management of the herd at critical periods of the yearly production cycle. Condition scoring provides a measure of the level of body reserves of a cow which is independent of liveweight, and a more reliable description of its condition than is liveweight alone. The method involves assessing the level of fat cover on two areas of the cow's body (see figure 1). A 0-5 scale (in increments of 0.5) is used.

Figure 1: Body Condition Scoring (BCS) for Beef Cows.

(1) Post-Weaning (weaning up to 4-6 weeks pre-calving)

Weaning of beef calves normally occurs at five to seven months of age. It can be carried out successfully at four months (this can be an appropriate drought management strategy) provided appropriate provision for post-weaning feed is made. In the beef cow calendar this leaves around five months of the year that beef cows are low priority stock and can function as 'work horses' eating rank pasture, and controlling shrub re-growth. During this time, priority can be given to other classes of stock and cows become one of the few groups available that can be restricted in the interests of better pasture development. This is a major justification for maintaining a breeding cow herd on hill country. Not only has it significant advantages for the farm as a whole, but it has in fact been shown to be beneficial for the cows to lose around 10% of live weight in the post- weaning period. Cows losing that order of weight will have better longevity and will suffer no reduction in performance, provided their nutritional requirements are met in the pre- and post-calving periods. Cows too fat (in excess of condition score 3.5) at calving are more prone to calving difficulties and much more prone to metabolic disorders.

A reduction in intake should not be carried out too rapidly with fat cows, as even in autumn (or indeed any time of the year) fat cows can suffer from hypomagnasaemia disorders if subjected to sudden severe restrictions of intake. Another factor to consider is that cows are such good foragers they place themselves at risk from misadventure, like falling from rim-rocks, when being used to 'tidy up' paddocks with natural hazards. Some farmers have been rotating their cows behind the ewes in a winter rotation. In such situations cow intakes are kept very low e.g. Angus cows 3-3.5kg DM/ day. This shows their efficiency and supports the contention that an efficiently managed beef cow could have a true winter stock unit cost of 3.5 stock units.

Minimising cow-herd feed requirements during maintenance periods can have a significant impact on overall feed efficiency and therefore profitability. This should be a consideration when establishing appropriate stock unit equivalents. The ability of beef cows to lose weight through the winter is dependent on body condition. Obviously thin cows (condition score less than 2.0) cannot be fed below maintenance for extended periods.

(2) Pre-calving (from 4-6 weeks pre-calving to calving)

Cows that have lost in the order of 10% body weight post weaning will need to regain this liveweight pre-calving. If they do not, there is a risk they will be simply too weak at calving - prone to metabolic problems - and their calf losses will be high (10%-20%). A relatively short period (4 weeks) of good nutrition (8kgDM/ day) is usually sufficient enough to have the cows gain the liveweight taken off since weaning. Note that the calf is gaining at 250 grams/day in utero during the last month of pregnancy. If feed is available, weight gain on cows will be easier to achieve pre-calving than during early lactation and is unlikely to have any significant effect on calf birth weights, except at extremes. If cows calve in good condition (condition score 2.5 - 3.0) it will make the mating condition target of 3.0 a lot easier to meet.

While poor pre-calving nutrition and body condition score will exacerbate post-calving under-nutrition problems, priority in terms of feed allocation should be given to the post-calving period. This can be achieved by shedding cows out from a moderate plane of nutrition to a high plane as they calve, or by strip grazing, or simply by shifting into saved feed at the start of calving. Whatever system is used to apportion feed, it is the condition score at calving that is critical. This is one of the most critical points in cow management.

(3) Post-calving (calving to mating)

This is the most critical period of nutrition from all aspects of cow production and survival. Experience suggests that a feed budget should allow for a cow to eat in excess of 12kg DM /day from the day of calving. How this is achieved will depend on the time of calving, but even herds calving close to their pasture growth curve will need to save feed forward from late winter. The area chosen for calving should be easy contour and free of hazards like creeks, tomos and swamps as these cause significant calf losses. Post-calving nutrition is critical for several reasons:

(a) Cow survival - the majority of cow deaths from hypomagnasaemia disorders occur post- calving and peak in the second week of lactation as the demands of the calf increases. Losses of 20% have been commonplace on properties prone to it. An aged fat cow (condition score in excess of 3.5), eating short, recently grown, spring feed in the second week of lactation, facing inclement weather, represents the classic scenario. With appropriate nutrition, annual losses from this condition in all grass programmes can be held at 1-2%. If nutrition is compromised, a strategy to supply magnesium, either through calcined magnesite on hay (60gms cow/day) or "agrifeed" licks, or possibly through slow release rumen bullets (75 day product available), must be used. Magnesium salt blocks are commonly used but they will certainly not stop deaths in the face of an outbreak. This is a complex condition and is difficult to treat (survival with treatment less than 30%), provision of good quality pasture above 2500kg DM/ha (12cm high) is the key to its prevention. Other metabolic conditions like milk fever and ketosis play a very minor role in beef cow losses and are also prevented by correct cow condition at calving and post-calving nutrition.

(b) Calf growth rates - cows will buffer their calves when under-fed in early lactation by losing liveweight to maintain milk production. However, trials have shown that poor conditioned cows subjected to low post-calving nutrition wean calves up to 24% lighter than well fed cows. Experience in Taihape hill country with later calving also supports this. In one of our trials a group of calves were born approximately 50 days later than the main line but were only 25kg lighter at weaning (March). The cows in this later calving group were in better condition and had been better fed during lactation.

However in high producing Hereford x Friesian cows in a condition score of 2.5 or better at calving it may be necessary to hold feed back for first 3-4 weeks post-calving. This is because the calves are unable to consume all the milk produced by these high producing cows. A recent trial indicates that a sward (pasture) height of 6cm is sufficient for Hereford x Friesian heifers during the first month of lactation, increasing to 10-12cm during the second month of lactation (Peachey and Morris 1998)

(c) Subsequent cow pregnancy rate and calving pattern - pregnancy is the most important production parameter in beef cow management, in fact for beef production in general. There are two aspects to consider whether the cow is pregnant or not and when the pregnancy was achieved. Cows fed in excess of 12kgDM/day from calving and consuming up to 20kgDM/day prior to mating should be near a condition score of 3.0 by mating. In this condition they will have good conception rates (>95%) over a mating interval of 52-55 days, which is the aim when using tested bulls. If these criteria cannot be met, a longer mating interval may be required.

Under-nutrition in the period from calving to mating will certainly depress pregnancy rates. There have been numerous trials to illustrate this, e.g. Table 1.

This depression in pregnancy rate is produced as a result of lengthening of the post partum anoestrous period and a reduction in conception rates. A cow has only 85 days to get pregnant to calve on a 365 day schedule. Anoestrus periods longer than 85 days, and/ or low conception rates leaving the cow empty at 85 days, will result in a later calving next year. If these factors leave the cow empty after around 120 days then she will generally be unable to get in calf because of bull withdrawal. Fig 2 illustrates this point.

Figure 2: Influence of post-calving (calving to joining) pasture allowances on interval from calving to first oestrus (Nicol and Nicoll 1987).

While nutrition is generally the most important factor affecting the post partum anoestrous period, there is also an influence from season and age of cow, as shown below in Figure 3 and Table 2.

Figure 3: The relationship between post-partum anoestrous interval and calving date for Angus cows at Invermay (Montgomery 1984)

In the field these factors often compound. However an achievable objective is to have high pregnancy rates (95%) and cows calving on a 365 day schedule to a restricted mating interval (52-55 days). A concentrated calving pattern is in itself essential for ease of management (particularly nutritional) and gives significant financial returns in terms of total weight of weaner produced. An average calf weaning weaning weight of 220 kg should also be easily achievable. A sound nutritional programme should be self perpetuating on an annual basis.

(4) Post-Mating (mating - weaning)

Using a 52-55 day mating interval for mature cows, calves will be aged round 80-140 days at bull withdrawal. Weaning can be carried out at this stage but very high quality feed is required to achieve weights in the same order as later-weaned calves (six months). Cows in a condition score of 3.0 or better at mating can be used in the late summer-autumn period to clean up low quality summer pasture with calves at foot. They will lose body weight (20kg) to better milk production for calves and minor effects in calf weaning weights can result. Some care is obviously required as calves are also competing for available pasture. The main advantage of early weaning appears to be in retaining cow body condition which, if the previous management has been correct, should not be an important issue. However in case of droughts, and a resultant wish to graze cows off the farm as part of the drought management strategy, early weaning can be practised.

Overview - Matching beef cow nutritional requirements to Taihape hill country pasture growth.

A stylised cow nutrition requirement graph (based on the principles already discussed) can be matched to a pasture growth curve for the Taihape district, (Figure 4). A mid October (10th) to end November calving span best suits the grass growth pattern. This is now common practice, with individual farmers making appropriate adjustments to suit their own property's actual grass growth pattern. Figure 4 illustrates these requirements and shows the effects of matching pasture growth curves and cow feed requirements to various calving dates.

Figure 4: Taihape hill country pasture growth and generalised cow feed requirements for a September, October, November and December calving.

Other Aspects of Beef Cow Production

(1) Bull soundness

Bull soundness examinations, are an integral part of beef cow production. The test includes a physical examination, scrotal circumference measurement and a reproductive test using a yard mating test. This test used in Taihape on approximately 300 commercial bulls each year since 1981, has detected 30% unsound on initial examinations and 20% unsound on an annual basis. The modified yard test has been used where bulls either pass or fail as suitable to mate 45 cows, with a split category of A & B pass. The majority of bulls culled have simply been unable to achieve service and the benefits of the test are very obvious. Testing is best carried out close to mating, provided there is a strategy for replacing culled bulls. Larger properties achieve good pregnancy tests with three tested bulls serving mobs of around 120 cows. The test does not guarantee that the bull will stay sound during mating, through injury etc., so supervision over mating is essential. Yearling bulls can also be used successfully at a ratio of 1 bull to 30 cows.

(2) Breed

The Angus and Hereford and their cross cow has predominated in the North Island and performs well. Some infusion of Friesian blood has occurred and Hereford x Friesian cows sourced from the dairy industry are now commonplace on hill country farms. The use of a terminal sire has been popularised which, while achieving obvious gains in weaner growth rates, has confused some farmers on the selection of their replacement heifers in self replacing herds. The most reliable NZ data on breed differences available was generated in the 1970s through the beef breed evaluation trials. The American strains of Angus and Herefords etc. would not have been involved in these trials. A summary of the trials (Table 4) illustrates that no single breed encompasses all beef production requirements. Maternal performance is not compatible with optimum carcass performance. The maintenance cost of a cow is 75% of the annual feed requirements and is simply higher for larger animals. The trends are to use a beef x dairy cross cow (mated to a terminal sire) for weaner production (all female replacements purchased) and improved Angus / Hereford cross cows for the larger self-replacing herds.

Table 4: Ranking of Breeds as Terminal Sires or as Parents of a First Cross Cow.

(3) Heifer Management

Regardless of age at mating, heifers must achieve a critical mating weight where they are all cycling at bull introduction. This will vary, depending on breed, but should result in an 84% in-calf rate in a 42-45 day mating interval. This has been readily achieved with 15 and 27 month old heifers in the Taihape region. Information showing heifers in calf in the first 45 days have a better lifetime performance (approx`10%) has resulted in the widespread adoption of this mating interval. Mating heifers two to three weeks prior to the MA cows has some merits in that it focuses attention on them at calving and allows some compensation for their longer post calving anoestrus period (approx. 20days) and smaller calves (-20kg weaning). However as mentioned earlier, it is negated by the longer post-partum oestrus interval of earlier calving cows. Some restriction on heifer nutrition pre-calving is usually carried out to try to prevent dystocia although, heifers in a fit condition at calving seldom experience dystocia problems. Good post-calving nutrition of heifers is even more critical than in adult cows as heifers are more difficult to get back in calf. The choice of sire for first calving heifers is an important issue, with calving ease being the major determinant.

Mating heifers first at 15 months should be considered on properties where two year heifer mating weights are in excess of 360 kg, as not only should these heifers be at critical mating weight at 13 months of age but heifers heavier than 360 kg can in fact be expected to have a significantly depressed pregnancy rate when mated as two year olds. The use of techniques to synchronise oestrus has potential in the management of the first calving heifer and may result in more heifers being mated at 13-15 months. In one trial where "two cycles" of mating were used the duration of mating in the synchronised and subsequent mating was only 23 days. Thus synchronisation clearly shortens the mating period.

(4) Mineral Deficiencies

Knowledge of the district is important in assessing trace element requirement for breeding cows. Many properties in the Taihape district have confirmed copper deficiencies and the majority of cows receive a copper treatment (injection) in the late winter period. A few properties with marked selenium deficiencies use selenium injection pre-calving. Rock salt or salt blocks are commonly used in the spring period. While sodium deficiency has been diagnosed in the Taihape area, the benefits of salt supplementation are unknown. Phosphorous deficiency has rarely been diagnosed and milk fever, which is a condition related to calcium deficiency (and nutrition and body condition) occasionally occurs in beef cows. The main mineral deficiency encountered with cows is magnesium, but this deficiency is so interrelated with nutrition it was discussed in that section. Certain farms and soil types do seem more prone to this problem. It appears the application of fertiliser, particularly potassium will exacerbate a hypomagnesaemia problem. As with all advice on cow management, mineral supplementation is specific to the individual property and farming system.

(5) Culling Policies

The first priority in culling is to identify dry cows. Pregnancy testing is a relatively low cost input. It has been argued by farmers that the management programme outlined above is so successful, with low wintering costs and high pregnancy rates, that pregnancy testing is unnecessary - all dry cows can be culled at calf marking. However, pregnancy testing also ensures management targets have been met and, in most autumns a dry cow can be sold and an in-calf one purchased at similar values. A dry cow simply competes for winter feed with more profitable classes of stock. Cows not rearing a calf should still be identified at calf marking and either culled or permanently identified with a small ear tag. Re-offending cows can then be culled.

Identifying cows rearing poor calves can also be achieved and these cows are also a priority for culling in a well performing herd. This can be easily achieved by holding the poor calves in the yards next to the paddock where the rest of the mob is released. Within a few hours, cows with calves in the yard will be back at the yard calling for them. The best long term gains are gained by using this practice on first calvers. Cows need not be culled for age unless they are over 10 years and have significantly below average condition in the autumn. Individual cows have performed well to 16 years of age under hard hill country conditions. Unsound cows (including lame etc.) should be culled, prior to winter. By identifying that small percentage of poor performers, a sound culling policy will aid in the goal of the herd annually weaning in excess of 90% (cows mated) of well grown, even weaners. With the national average weaning percentage stuck around 82% there is obviously room for improvement.

Further Reading

Montgomery, G.W. 1984. Factors influencing reproductive performance in the cow. In Beef Cattle Reproduction - Animal Industries Workshop, Lincoln College Publication.

McCall, D. G., Scott, M. C. and Dow, B. W. 1988. Calf Weaning and Summer Grazing Strategies for Efficient Beef Cow Use on Hill Country. Proceedings New Zealand Society Animal Production 48:237-242.

McMillan W. H. and McCall, D. G. 1991. The beef breeding herd: options for using winter feed most productively. Proceeding New Zealand Grassland Association 53: 141-144.

Nicoll, G. B. 1979. Influence of pre- and post-calving pasture allowance on hill country beef cow and calf performance. New Zealand Journal of Agricultural research 22:417-424

Nicol A. M. and Nicoll, G. B. 1987. Pastures for beef cattle. In Livestock Feeding on Pasture. New Zealand Society of Animal Production Occasional Publication 10:119-132.

Peachey, B.M. and Morris, S.T. 1998. Effect of sward height during lactation on heifer and calf performance. Proceedings of the New Zealand Grasslands 60:225-228.

Pleasants, A. B., Barton, R. A. and McCall, D.G. 1994. Nutritional buffering: Do we make the best use of this phenomena in the breeding cow. Proceedings of New Zealand Society of Animal Production 54: 329-331.

Grace, N. D. 1983. The Mineral Requirements of Grazing Ruminants. New Zealand Society of Animal Production Occasional Publication .