Dr ML van der Leek
Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria.
On the face of it, most veterinary interventions and/or recommendations are justified. In isolation they might be both executable and profitable, yet all of the consequences may not have been considered. Knowledge and understanding thereof might explain the reluctance of a client to embrace what seems ‘no-brainer’ advice. Sadly, we are less skilled in appreciating what happens after we get into our vehicle and leave the farm.
With some pertinent examples we will examine the world of unintended consequences in dairy consulting and the need to consider the totality of the dairy enterprise especially when such consequences are delayed. A broader view may lead to less frustration for the veterinarian and better acceptance of our advice by the dairyman.
The following will be used to demonstrate implications not necessarily obvious at the time of the consultation:
- Lowering Calf Mortality.
- The Law of Diminishing Returns.
- Nutrition – What Not to Do.
- Incentive Programs.
- Marginal Thinking.
We as veterinarians need to look beyond our immediate areas of expertise and consider and prioritize our advice in the context of the dairy enterprise in its entirety. We need to remain cognizant of all consequences, positive and negative, that may result from our interventions and recommendations.
It is the tendency of both the dairymen and the veterinarian to feel an acute and immediate need to intervene when things start to go wrong. A brief ‘wait and see’ attitude might be warranted in some cases as the risks of any early intervention may outweigh a brief time period given to allow the situation to develop.
Lowering Calf Mortality
Saving sick calves is a favourite pastime of many a veterinarian, but we may fail to appreciate that every calf saved has to be raised. And that the treatment of sick calves may take up a significant amount of time and resources.
In a replacement rearing program, expenses are incurred whilst no income is being generated prior to calving at 22 months-of-age at best. The cost of raising a heifer is the third highest expense following feed and labour. Average cost to raise a heifer calf ranges from R10 000 to R14 000 and R7 500 to R10 000 for Holsteins and Jerseys, respectively. It generally takes 2.2 lactations to recover this cost (see figure below).
Heifers gaining 700 vs 220 g per day increase their first lactation milk yield by 750 to 1 500 L. Or, for every 450 g gained above 450 g first lactation heifers produce 450 L more milk. This improved growth implies a higher cost for feeding with the result that the struggling dairy may suffer both from pressure on their cash flow to purchase feed as well as raise inferior heifers through limit feeding or poor quality feed.
Instead resolving a relatively minor cow health issue may increase milk and cash flow and do more for the dairies long term viability. It is sometimes best for the struggling dairymen to sell their calves. Ideally, calves are sold to a knowledgeable, local calf raiser, thus allowing the dairyman to buy their heifers back at a later stage. This is also a prudent strategy during a start-up.
The Law of Diminishing Returns (a.k.a the KISS principle)
As veterinarians we have a tendency to recommend ‘gold standard’ interventions modifying or adding to existing standard operating procedures (SOPs). As do cows, employees also have time budgets and only so many hours in the day. We need to be aware of their current work load and the amount of time that they have available for expanded or new responsabilities. A new intervention embraced by an owner may result in a shift in attention from a basic task and create a new and bigger problem than was to be solved.
Fresh cow management
It is typical that fresh cows receive extra attention and may be brought to the crush on a daily basis. Intensive fresh cow programs include the daily taking of rectal temperatures and rectal examinations to ascertain uterine involution and the presence/absence of uterine infections.
When transition cow problems are prevalent the intensity of fresh cow management program just increases. Retained placentas, milk fevers, LDAs and ketosis might precipitate instituting additional treatment and/or preventive programs (these may include injectable antibiotics, drenches, propylene glycol, calcium). It is important to consider that at some point such programs become counter-productive, especially with unskilled/untrained employees.
They do so because employees have to divert time to the activity and because cows are denied the opportunity to rest and eat when DMI is so very important. Fresh cows should be worked for no more than 30 minutes. In larger dairies it may take a couple of hours to treat and drench cows and a vicious cycle may develop. More sick cows, more treatments, less eating and resting, and then even more sick cows! Although seemingly counterintuitive there comes a point where it may be prudent to minimize animal handling even at the potential risk of losing a cow. It is here where the value of a skilled employee pays back many times over. One who by observation alone can detect, pull and treat cows that are in trouble. Stanchions/headlocks are also a valuable tool to restrain cows with little effort.
Amaral-Phillips, 2014; Goff, 2001; Overton, 2010; Scholnik, Budine & Jonkman, 2011; Schroeder, 2012.
Synchronisation programs rely on the successful completion of multiple steps, including injections and/or the insertion and removal of CIDRs. The more the steps in the protocol, the greater the risk of failure as missing a single step negates the entire program. Even on the best of dairies, it may take considerable effort to find all the cows on a list. Secondly, few of these programs use a 7-day interval for part of the program and may include steps at intervals other than 12 or 24 hrs. Any attempt to facilitate the routine execution of such programs might be useful and a program with lower efficacy might be justifiable to increase compliance.
Calf Diarrhoea Outbreaks
A good example where a unconventional approach might be indicated is during a calf diarrhoea outbreak. This may be approached in one or both of two ways. Although antibiotics are usually not indicated for the treatment of calf diarrhoea, the dairymen, and sometimes more so the employees, feel an intense need to treat. As an alternative to antibiotic use, the author has recommended that sick calves be treated with Vitamin B Complex. It causes no harm, is cheap and satisfies the need to do something. The more difficult recommendation is that diarrhoea calves not be treated at all. Clearly such recommendation will depend on the agent and the severity of the diarrhoea.
If the treatment option is elected a single person should be assigned to treating calves and that this person should remain outside of the hutch. Multiple employees doing treatments and climbing in and out of hutches can rapidly escalate a calf diarrhoea outbreak.
Moving Transition Cows
It’s only recently that we’ve begun so appreciate the consequences of cow moves and how to minimize the negative effects. Typical cow and pen moves during the transition period might include:
Dry → Steam-up → CALVING → Fresh
Dry → Steam-up → Maternity → CALVING → Fresh
The second is often recommended or preferred where there are issues with calving difficulty and/or stillbirths. This may be counter-productive.
At issue is both the timing of a move as well as the number of cows being moved. Typically steam-up moves are made once a week with a group of cows being moved. In contrast, maternity pen moves are made on a daily basis, usually only with individual cows. This is very disruptive and should be avoided (see figure below). Ideally cows can be moved to a maternity pen 12 to 24 hrs prior to calving but this is almost impossible, especially given that the normal range for calving dates is ± 10 days. If an intervention is needed it is the recommendation that steam-up cows only be moved to a maternity area when they are visibly in labour. Alternatively, small groups of cows are moved to individual maternity pens.
It is a fallacy that extended lactations are profitable. Over the lifetime of a cow shorter lactations and therefore more frequent peaks is more profitable than fewer, longer lactations. If an extended lactation policy is being followed there will also be more cows that are later in lactation with a negative effect on profitability. This effect is illustrated with the figure below, showing that when considered over an entire lactation, there is a profit period, a breakeven period but also a portion when there is a loss.
It is estimated for every one-day increase in average DIM, you will lose 0.08 kg of milk per cow, which means a herd at 180 DIM will produce 0.80 kg milk per cow per day less in comparison with a herd at 170 DIM.
Jones, 2013; Stevenson, 2009.
Nutrition – Fresh cows, Low Producers and Ration Processing.
It is very common for dairymen to feed a fresh cow ration. The intent of a fresh cow ration is to stimulate dry matter intake (DMI) and combine sufficient NDF and carbohydrate, feeding a more energy dense ration.
Formulated fresh cow diets are often adjusted during times of transition cow problems. Typically the ration is made ‘safer’ through the addition of hay in the total mixed ration (TMR) and/or the provision of free-choice hay outside of the TMR. With a high energy demand, cows are left not having this need met affecting not only future milk production but especially the immune system. Subclinical hypocalcaemia is another risk. An alternative is the high fibre steam-up (and possibly dry) ration that promotes DMI and rumen fill. Post calving this rumen fill moderates the diet transition and cows can go straight to a high cow ration.
Amaral-Phillips, 2014; Goff, 2001; Overton, 2010.
Feeding by production group is widely practiced making it appear logical. It is however rarely justifiable to feed low cow rations (see marginal thinking below). Any event that detracts from the dilution of maintenance or a cow consuming additional feed is undesirable. Such may occur either through limit feeding or the removal of essential feed ingredients from the ration. Individulal cow lactation curves can be telling with a dip in milk production occurring following a move from a high to a low producing group.
Eicker, Fetrow & Stewart, 2006.
Rations (TMR) processing
Ration sorting is universally considered an evil that should be corrected. In herds where there are associated cow health problems, specifically sub-acute rumen acidosis (SARA), this is indeed the case. However, where there are no serious health problems this should be addressed with care. The sorted ration might indeed be providing the nutrients to support the milk production. Processing the forage will mean dilution of the ration and decreased milk production.
Labour accounts for 15 to 20% of total costs and incentive programs are often touted as a way to motivate employees and improve SOP compliance. On the face of it they seem an obvious way to achieve such and are often recommended by consultants, including veterinarians. However they are not always easy to design and implement and there needs to be an awareness of the complexities and pitfalls.
The author prefers the use of random cash bonuses. These cannot be anticipated, give immediate recognition for a job well done, don’t become routine and all employees are eligible.
Somatic Cell Count (SCC)
A classic incentive program involves bonuses being paid to milkers given the reduction of and/or maintenance of a target SCC. There are several issues of importance to recognize, some also applicable to other incentive programs.
Firstly, the SCC is multifactorial, including the cleanliness of the cow environment, rainy weather (especially where the cows are housed outside), the failure to maintain equipment and/or the lack of adequate training. The actions of an individual milker might sabotage the results of the group.
It becomes a tough decision whether to pay a bonus when such factors are at play. The value of an incentive program is also questionable once an SCC target is reached. Maintaining the SCC means that the bonus really becomes a routine monthly part of the salary and loses its value as an incentive (‘incentive fatigue’). Receiving the bonus month after month and then losing it during a rainy month does not endear one to your milkers. Other issues germane to SCC incentive programs include: removing too many cows from the milking herd and unnecessarily increasing the hospital group size; increasing the number of days spent in the hospital group and the rapid culling of cows with a high SCC.
It is also inherently unfair that incentive programs only be offered to employees where they are easy to implement. Wages remain a major motivation for all dairy employees.
There is often a misplaced emphasis on conception rate (CR) when evaluating breeding programs and individual breeders. It does not take long for an astute breeder to figure out that the selective breeding of cows will increase their CR. As a consequence the number of pregnant cows and pregnancy rate (PR) might suffer. Overzealous heat detection may have a similar consequence as ineligible cows are being bred that don’t conceive.
The success of a breeding program is best measured by PR:
Pregnancy rate = heat detection rate x conception rate
This is evaluated in cohorts of 21-day cycles and different combinations for each of CR and PR can result in the same number of pregnant cows:
There are many idiosyncrasies in culling programs. We are sometimes aghast at a client’s reluctance to cull a cow for what seems to be an obvious reason. Yet we may not appreciate the importance of cash flow and marginal milk (see below).
Further, and sometimes counterintuitive, high cull rates are not necessarily a bad thing. The higher the PR, the more heifers are available to replace underperforming cows. The sooner that cows are replaced the greater the odds that some cows be sold as productive milk cows instead of for slaughter. As cull cow prices increase it increasingly becomes an option to consider the sale of underperforming cows. A herd the author worked with in the USA had a stable herd size of 3 000 milking cows with an average of 38 kg of milk. With a PR in the mid-twenties cows were placed on a cull list when their milk production dropped below 23 kg.
Although culling can be assessed mathematically in one of several ways, most all called cull rate, the preferred method is:
Herd turnover rate = Number of culls for the period / Average inventory for the period
There is value distinguishing the reasons for cows being culled but this data may be difficult to log consistently. The distinction between forced (biological) vs economic instead of voluntary vs involuntary is preferred. Assigning a culling reason can be difficult due to inadequate culling definitions and the fact that there often are multiple reasons that might have precipitated in a culling decision.
Remember too that more aggressive culling reduces replacement cost:
(Cost of replacement – Cull cow
income) / Unit of milk sold
Culling also creates an opportunity to improve herd health and lower death rates. Pertinent examples include the removal of cows with chronic mastitis and poor breeders. Cutting cull rates in herds with average production has a greater impact than in herds with high production. Culling has a strong relationship to profits, but it is not direct relationship and there is statistically significant relationship between profit level and cull rate.
Some questions worthy of consideration when considering culling are:
- Is the facility filled to capacity with milk cows? A facility should always be filled to capacity as all additional cows contribute marginal milk.
- On an individual cow basis is a cow producing income or need she be replaced? A cow might be disruptive to cow flow (lame or slow milker) or the value of her milk production might not exceed the cost of her feed intake.
- What is the overall cull rate? A cull rate can only be sustained if there are sufficient animals to replace those being culled either through internal growth and/or purchases.
Bond, 2013; Brett, 2011; Fetrow, Nordlund & Norman, 2004; Karszes, 1997; Nennich, 2006; Salfer, 2015; St-Pierre, 2013; Socha, Defrain & Tomlinson, 2008; Wardynski, 2012.
This refers to both to the available stalls and the available feed bunk space (with less than 0.6 m deemed too little). It has always been assumed that any degree of overstocking was detrimental. In contrast it is quite common for dairymen to overstock their pens there being a financial incentive to spread fixed costs over a greater number of cows without expanding facilities. Recent work has shed light on this issue and affirms the risks of overcrowding. Submissive cows are affected more.
A unit change in the stalls to cow ratio increased milk production by 7.5 kg, but there was considerable variation in the response. There was no relationship between stall availability and milk production where the stocking density was ≤ 100%, i.e. there is no benefit to understocking.
Effect on lying/resting: At the William H. Miner Agricultural Research Institute they found that each additional hour in resting time resulted in a milk production gain of 1.7 kg. Lying time takes preference over feeding time and the latency to lying down was reduced. This might incorrectly be interpreted as an increase in cow comfort, cows wanting to lie down as soon as possible. Cows would rather wait for a stall than eat and often skip eating after milking instead finding a stall. Lying time consequences include: standing on concrete and subsequent lameness; a stress response with suppression of immune function; and decreased milk flow to the udder and foetus.
Effect on feeding: Increasing bunk space from 51 cm to 102 cm resulted in fewer aggressive interactions and increased the percentage of cows feeding. Comparing headlocks/stanchions to post and rail there were fewer aggressive interactions with headlocks. It is preferable that all cows eat at the same time to ensure that they are consuming the same unsorted ration.
Higher stocking rates result in cows eating fewer meals and eating faster (up to 25%) with consequences for rumen health. Cows prefer synchronous group behaviour e.g. eating as a group when fresh feed is delivered. Cows in a 6-row barn and therefore limited bunk space are unable to feed at the same time.
Effect on reproduction: For every 1% increase in stocking rate, the conception rate decreased by 0.1%. As bunk space decreased from 61 cm to 30.5 cm, cows pregnant by 150 days decreased from 70 to 35 %.
Effect on milk quality: Not always statistically significant but overcrowding may result in a decreased milk butterfat, an increased SCC and an increase in the incidence of clinical mastitis.
Effect on rumination: No consistent measurable effect, but likely reflected in the lower milk butterfat seen with overcrowding.
Several indeces can be used to evaluating the extent of overcrowding with SUI being the preference:
Cow comfort index (CCI) = cows lying in a stall / total number of cows
Stall use index (SUI) = cows lying in a stall / total number of cows available to lie down (excludes cows eating) = cows in a stall/cows wasting time (not eating or lying)
Stall standing index (SSI) = portion of cows standing in a stall
Overcrowding needs to be examined in the light of a cow’s time budget and how this changes from normal:
However, some measure of overstocking might not be detrimental given the specific conditions on a a particular farm, such as group size and 4 vs. 6-row barns. Overstocking results in increased competition affecting natural behaviours but some overstocking may be possible without affecting these behaviours.
Thumb rules would be to not exceed 120% in milk cow pens in a 4-row barn vs. 100% in a 6-row barn.
In contrast, for steam-up groups stocking density should not exceed 80% of bunk space especially in a 6-row barn. Being less costly 6-row barns are workable for milk cows but not recommended for steam-up cows. For dry lots ensure 56 square meters per lactating cow and 4.5 square meters of resting space and shade. In bedded packs ensure 11 square meters per steam-up cows and 7.5 square meters for lactating cows.
Barmore, 2015; Botheras, 2006; Durst, 2013; Krawczel & Grant, 2013; Moore, 2010; Grant, 2012.
The maintenance cost of a cow is diluted at higher levels of milk production. Maintenance cost is the feed cost associated with the cow being able to maintain normal body functions. This amount of feed needed for maintenance does not change regardless of the level of milk production. A typical Holstein cow requires 10 Megacalories (MCal) of Net Energy of Lactation (NEL) per day just to maintain normal body functions. If her diet on a Dry Matter (DM) basis contains 0.76 MCal/lb of NEL, she must eat 13 lb (5.9 kg) of feed DM to meet maintenance requirements.
If a cow produces 13.6 kg/day of milk, she needs an additional 10 MCal of NEL. Therefore, she must consume 11.8 kg of feed DM or twice as much feed as needed for maintenance and is 50% of her diet for maintenance. If she produces 27.7 kg/day of milk, she needs to consume a total of 30 MCal/day of NEL or 17.7 kg of feed DM and now 33% of her diet is being used for maintenance.
The more milk a cow produces, the more her maintenance cost is diluted to a smaller percentage of the total feed cost per day. At about 54.5 kg of milk, only 20% of feed NEL goes toward maintenance and 80% into the bulk tank. Feed efficiency increases as a cow produces more milk up to a certain point; probably somewhere between 45.5 and 68.0 kg of milk daily.
Although feed efficiency is closely related to profitability, the relationship is not absolute. As the cow produces more milk and eats more feed she will eventually be limited by not being able to consume more feed and diets must become more nutrient dense to offset the decrease in additional Dry Matter Intake (DMI). Increasing the nutrient density of the diet requires adding ingredients that are more expensive.
The extra 10 lb of milk in the above example would be worth $1.50 and it only cost $1.00 to get the extra 10 lb of milk. This would be considered marginal milk which is defined as the additional amount of milk that is produced from increasing feed intake or nutrient intake over and above the amount of feed and nutrients required to cover the total maintenance cost of the cow. The marginal milk cost in this case would be $1.00 for the extra 10 lb of milk produced per cow. This still amounts to an extra $0.50 per cow per day of potential profit for cows producing 90 lb of milk even over cows that are producing 80 lbs of milk.
Two numbers are then needed to calculate marginal potential: average maintenance cost per cow per day and additional feed cost per unit of milk. For convenience the maintenance cost approximates the cost of the dry cow ration so that this can be used.
Economic estimates that involve increased milk production need to account for the increased food costs (marginal feed costs), not average feed costs. Maintenance feed cost is included in the average feed cost and therefore does not reflect the marginal cost.
Decisions must be based on the marginal impact and not the average performance. In nearly all cases, the most profitable unit of physical production is the last one, viewed from a marginal thinking perspective.
Block, 2011; Eicker, Fetrow & Stewart, 2006; Hutchison, 2012.
The dairy veterinarian is equipped with an incredible technical skillset that can be leveraged when adopting a consulting role. Unfortunately our training and understanding of the dairy enterprise in its totality is lacking.
Consequently we are not always aware of the implications of our advice. What might seem obviously advantageous may appear less so when reviewed in the full context or some time in the future. Awareness of the issues raised in this paper allows the consulting veterinarian to critically valuate and tailor their advice.