R.E.D. Cows can actually be any colour.
For as long as I can remember, farmers and my veterinary colleagues have always considered high producing cows to be more difficult to get in calf, which has translated into high production equals poorer reproduction. Is this really true?
Actually, on average, within any farm system worldwide, the highest producing herds have better reproductive outcomes than lower producing herds. While there are some individual problem herds, high producing herds generally have better nutrition and management which is what supports the higher production in the first place, and hence better reproduction. It is not all about genetics either.
Reproduction is not obligatory for the cow. Getting pregnant when things aren’t going right (nutrition, health, management, comfort etc), represents a threat to the long term survival of the cow. She has mechanisms to combat these various perceived threats or stressors, both chronic and acute, that alter hormones and behaviour, reducing the chances of pregnancy. At its most basic, reproduction and pregnancy is what the cow does with energy left over from everything else she has to fuel. It is the gap between input and need that is critical, of which actual production is only one part. The gap is primarily energy which may be directly or indirectly linked to specific nutrients and is exacerbated when grazed pasture is a major part of the diet.
Where the problem really lies is within herd, individual cow outcomes. This is what each farmer sees and hence is what most influences the belief that high producing cows have poorer fertility. This is where R.E.D plays a significant role. R.E.D stands for Relative Energy Deficit, a term long used in the dairy industry, and now seen increasingly in the human high performance sports arena, with equally negative effects on reproduction.
Basically R.E.D means that even if the actual nutritional or management input is good enough for a very high milk outcome, there is still not enough fuel in the system to have enough left over for successful reproduction. It is all about the ‘relative’ difference, either between herds or amongst cows in the same herd. This may be transitory, even just on a day to day basis or it may be chronic and more severe, lasting for weeks or months.
High production in itself is not a reproductive risk in most instances, but it does increase the challenges. However, R.E.D. cows can occur in any herd at any level of performance.
Genetic selection has enhanced the predisposition to use body tissue, both protein and fat, at an excessive rate in early lactation for production, prolonging and exacerbating the potential for negative energy balance in the transition and fresh periods. This can impede or impair follicular development, and compromise early embryonic survival. Fat (cholesterol) based hormonal precursors may be lacking. Leptin production from adipocytes (fat cells) may be inadequate and the calving to first oestrus period prolonged.
These problems can all be overcome by appropriate transition management and nutrition, reducing NEB risk, improving ovarian function, and ensuring a healthy reproductive tract.
At its most severe. R.E.D. affected cows are genuinely anoestrus, i.e., do not cycle, do not have any normal ovarian function because the gap between need and supply is extreme and/or chronic. Condition loss is also usually greater than normal for the herd. Increased production means greater use of glucose for milk leaving less for other non-essentials. Heat behaviour and mounting behaviour may be considered non-essentials, behind maintenance, health, and production. Consequently, the incidence of NVO’s (non-visible oestrus) or silent heats may increase and/or actual time spent on mounting behaviour etc, decrease. Heat periods are perceived to be weaker and shorter if seen at all. Cows cannot get pregnant if not mated because they are not seen on heat. Electronic monitoring from basic pedometer activity to more complete systems including temperature, and/or ovarian scanning, and/or hormonal measurements confirm that most of these cows are cycling and ovulating, even if not seen on heat. Timed A1 programmes can also be used to overcome some of the above issues of shorter, weaker, or no visible heats. As these are primarily energy based problems it is not surprising that such cows are associated with a lower conception rate, mediated by poorer follicle quality, embryonic loss, and failure by implementation.
Where the R.E.D. issues are transient, NVO may only occur because on the day the cow should have been seen on heat, energy demand for other needs was suddenly higher than usual. This is usually because of bad weather, decreased lying time, etc., but can be because of pasture changes. In the worst cases, those cows may simply be found dead, or go down when asked for extra activity, e.g., walking up hill back to the dairy, even go into convulsions at milking time.
Need is too sudden to stop udder use of glucose so hypoglycaemia occurs and can be rapidly fatal. Cows can’t be mated if not detected on heat (or if dead!).
Within our own client base, those herds where average per cow per day production on pasture based diets exceeds 2.5 kgs MS/cow/day, can expect to have 5 % plus of NVO cows, at least on “problem days”, yet these are rarely truly anoestrus. At averages over 40 Lt or 3.0 kgs MS/cow/day, this can climb to over 10 %. On individual days, depending very much on weather conditions, disrupted lying time, or walking distances, this can be much higher and be zero on good days. Yet all of these cows can be successfully mated if ‘detected on heat’, assuming the equally high risk of metabolic disease can also be avoided.
NB: This is very different to the underfed, under conditioned herd, especially if complicated by undergrown first calving heifers, where cows usually are genuinely anoestrus with no ovarian activity – an unfortunately too common occurrence in NZ.
High production does potentially increase the risk of negative energy balance (N.E.B) and associated metabolic disease. There is a high metabolic load on these cows, and this may inhibit oocyte development and/or depress embryonic survival pre-implantation, and/or depress establishment of a pregnancy post recognition, but these are mostly preventable issues for most cows.
There is a high correlation between embryo quality, milk yield, N.E.B, and/or R.E.D cows within a herd. As a general guide, milk protein % in early lactation may reflect rumen energy efficiency and/or N.E.B itself.
Higher milk yields and lower protein% compared to herd mates is a reproductive risk. Look at your 1st and 2nd herd tests, particularly for cows calved less than 6 weeks, and compare protein % to the group/age average. Within the herd, there is a strong correlation between lower milk protein % at critical times and lower pregnancy rates.
The liver is the most important organ in the body of a high performance cow, responsible for producing most of the glucose needed to ‘fuel’ all activities, including production and reproduction. The high work rates the liver needs to maintain for high glucose production may depress other liver functions, such as detoxifying and excreting the previous cycles oestrogen. This allows accumulation of oestrogen from both the current cycle and the previous one, which ‘flattens’ the cycle and potentially increases the risk of cystic ovaries or anoestrum. NB Feeding the cow extra glucose directly is not a solution as the rumen bacteria will ferment this to something else.
Conversely increased milk production can lead to faster metabolism of progesterone in the liver which lowers progesterone levels and increases the risk of loss of pregnancies, which are also more easily overcome by
endogenous P.G production. This also increases the risk of multiple ovulations.
Recent work by the university of Wisconsin has shown that high production, regardless of breed or age, increases the chance of twins as would be expected if the risk of multiple ovulations is increased.
Twinning increases the risk of the cow having twins again (and again!). This is exactly what we see in our high producing herds in NZ as well, (relative to system and input), with twinning rates exceeding 15% p.a. Having twins as a 1st or 2nd calver may be a negative for milk production in those lactations, largely due to associated prolonged N.E.B over the transition period but having twins in the 3rd plus lactation increases production, provided the sub-clinical and clinical ketosis of the transition and fresh period can be overcome. Where this well managed, twinning is not a negative for subsequent reproductive success. We have recorded some of the highest producing cows in some herds having at least 5 successive sets of twins!
Despite the fact that high production does potentially increase the risk of poorer reproductive performance, on a herd basis, this is not what we see in practice. Some of NZ’s highest producing herds, pasture plus systems, have our best reproductive performance. Six week In Calf Rate, i.e., the percentage of all non-pregnant cows able to be mated that are confirmed pregnant, within 6 weeks of planned start of mating (or within 2 cycles) is our best guide to reproductive success and is also highly correlated with profitability.
Empty rate, or cows not pregnant, is not a good guide, as it is time dependant. Target 6 week I.C.R is greater than 75%, yet the NZ national average for all of this century to date has only been between 60% and 68%, despite interventions. We at DPSL deal with a much higher producing group of herds, across all systems, than the national or regional average, but they have an average 6 week I.C.R. in the high 70%, many over 80%, up to 94%, and with less, or no intervention, than the average.
This is achieved by getting the basics right. Fully Grown First Calving heifers adapted to the lactational regimes well before calving. Body condition score targets being met on time. Rate and degree of condition change controlled and minimised.
Excellent transition management and nutrition. A focus on cow comfort in all areas. Having a healthy capacious fully functioning rumen, no SARA. Maintaining lactational DMI of at least 4% liveweight on average, every day. Meeting all specific nutrient requirements. Optimising pasture quality and intake. Having good systems for reproductive management.
Despite best efforts, many herds still have individual cows that are more difficult to get pregnant. These are the R.E.D cows often described by farmers as cows that never put on condition, another reflection of energy balance and efficiency in that individual. Why does R.E.D occur in an otherwise well fed well maintained herd?
R.E.D is about the gap between energy available and what is actually used, so number one reason is that those cows are not being fed enough. Mostly, we feed rations, in terms of available dry matter and nutrients based in the herd “average” cow which is simply not enough for some cows. Averages assume that some i.e., the smaller younger cows and lower producers eat less than the bigger older or higher producers, but this can still leave some in deficit. Grazing can be a major complication for the high producer who won’t be able to make up needs, as she cannot eat much more grass than the lowest producers or smallest cows.
Common problems include the big Holstein type cows in a herd of mainly smaller cows or Jersey’s, or cows of greater genetic potential than their herd mates. Big cows of highest genetic merit may be at greatest risk. This does not mean high genetic merit cows have lower fertility, they may just need more for the extra production, definitely more than a smaller cow even at the same production level.
A more common problem in NZ is that of cows that have some degree of impaired liver function. Regardless of feed available, the liver is limited in what it can do.
Genetics usually dictates that production needs come first. We see three common problems, the main one being that at some time in its life, the cow has had a significant Facial Eczema sporedesmin toxic challenge. This liver damage is mostly permanent, so glucose production is always limited.
Fatty liver disease problems mostly occurring in carry over or long lactation over fat cows, or cows that have gained anexcessive amount of fat (body condition) over the dry period (usually from excessive feeding of maize silage or fodder beet to dry cows). The associated metabolic problems can be complex due to compromised liver health and function.
Following incidences of subacute or clinical rumen acidosiswith damage to the integrity of the rumen mucosa, bugs and fungi can get into the blood stream and be filtered out by the liver (amongst other places). Micro abscesses in the liver, which can coalesce into bigger abscesses, not surprisingly also reduce liver health and function. Some of these problems may occur in calves with excessive starch (meal) intake in an undeveloped rumen, resulting in some permanent damage including chronic liver abscessation.
Anything that depresses feed conversion efficiency canresult in R.E.D cows. This includes all health issues.
Attitude, competitiveness, and resilience of individual cows is highly varied. Some cows are simply wimps, easily pushed away from feed and water, or dry lying spaces by herd mates, irrespective of size or age. These cows can
still produce to a high level, but actual feed conversion efficiency is not as good as better adjusted herd mates. Their high production genetics are not matched by a competitive enough attitude so regardless of feed offered,
they won’t get enough, or will be bullied away a lot more. On top of not eating their share, they may be more anxious and stressed which further reduces feed efficiency, meaning less energy is available for reproduction and/or disease avoidance or recovery. The R.E.D. is caused by the cow herself.
Poor cow comfort that creates chronic stress or anxiousness has a similar effect. This may be twice a day because cows are not comfortable in the dairy, or they don’t get on with farm staff or don’t have enough personal space etc. As well as depressing feed efficiency, stress disrupts normal progesterone – oestrogen cycles and consequently reproductive success. Too many farmers struggle to recognise the relevant cow signs and outcomes or understand the real impact of poor cow comfort. Death is a worse outcome than not getting pregnant, from an evolutionary point of view, so if energy is limited, survival comes first.
Written by Sue Macky, B V Sc, Dairy Production Services