Internal herd growth has enormous potential for increasing farm
Areas that affect rate of internal herd growth are; ratio of heifer calves, number of stillborn calves, calf and heifer mortality rates, and all factors influencing culling rates on a herd
Several easily implemented tactics for improving numbers of live heifer calves are discussed
Why promote internal herd growth (IHG)? Simple – financial consultants have found it to be the most consistent factor to sustained profitability on dairy farms. Rates of IHG of 8-12% are readily achievable, with some dairies growing at whopping rates of greater than 15%. A few points of clarification are in order: First, IHG is for everyone, from 40 to 10,000 cow dairies. Extra animals are the same as cash if a dairy does not want to milk any more cows. Sale of excess animals helps many small dairies maintain profitability. Obviously, dairies wanting to grow can do so with IHG. This relatively slower rate of expansion is easier for some managers to adapt to than doubling the herd size overnight. However, even in herds wanting to expand rapidly, IHG reduces the number of replacements that must be purchased. Financially, IHG is like an unlimited IRA – you don’t pay tax on the additional assets until they are sold. The power of compounding interest is in effect in herds with sustained IHG – this is what really increases herd numbers over time. Finally, increased animal numbers also increase a dairy’s borrowing capacity, allowing for more ease in financial capital extensions.
Factors influencing IHG
The many areas on the dairy that influence the rate of IHG are:
- Ratio of heifer calves born
- Stillborns or dead on arrivals (DOA)
- Calf mortality
- Heifer completion rate
- Factors influencing herd turnover rate
a. Transition cow health
IHG: Making it happen
Ratio of heifer calves born: No, the moon doesn’t have any effect on the sex of the calf. The most consistent way to increase heifer calf numbers is with sexed semen. Companies are just starting to offer this product. Semen costs are typically in the $45-64/unit range. Conception rates will be lower than those achieved with conventional semen, although the results really vary by bull. Conception rates in heifers typically decrease from around 60-65% to 40-45% with sexed semen. An additional negative has been the value of healthy, large bull calves; these animals are often worth more than $150. On the positive side, sexed semen can allow for rapid expansion in a biosecure manner. The economics can also be favored if the DOA rate on the dairy is historically lower for heifer than bull calves.
Reducing stillborns: Stillborns, or DOA, are defined as calves that are born dead or die within a few minutes of birth. An achievable goal is a DOA rate of <4%. Stillborns increase with over-conditioned heifers, inadequate attention to the prefresh group, and fetal – maternal mismatches (calves are too big).
Often sires are identified as the main culprit behind high DOA in heifers. However, the average percent of difficult births in heifers for all sires is 8.3%, with approximately 95% of sires falling between 6 and 11 %DBH (2004 National Association of Animal Breeders). Sires do have an effect on calving difficulty, but it is not as great as many think.
The average temperature during the winter has been related to calf size, with larger calves being born following colder temperatures (Deutscher et al, 1999). Over-conditioned heifers are more likely to have difficult births simply because the pelvic canal is reduced in size by adipose tissue. Energy levels need to be substantially reduced after pregnancy occurs to minimize this from occurring.
The main factor I have seen used to successfully reduce DOA is increased monitoring of the freshening cow. Freshening pens should be checked on a half-hour basis. The identification of animals that have started to calve, and a reference point to gauge progression of calving, should be noted (e.g. ID# 1132, feet out 2” at 12:45). Calving normally takes about 30-45 minutes to complete in cows (from rupture of chorioallantois or “waterbag” to birth of calf), and less than 2 hours in heifers. Any animal that is not making progress should be evaluated rectally or with a hygienic vaginal examination. Some fat heifers will simply quit calving – I think they’re exhausted. Again, lack of progress would be a sign to evaluate these animals. The main concern with aggressively monitoring freshening cows is that people will pull calves before the dam is adequately dilated, and the dam will be damaged in the process. This will not happen if people are properly trained in assisting calvings. Herd managers should work with their veterinarian in developing these intervention procedures. Also, hygiene of equipment and of the cow must be emphasized and taught to those that will be assisting in the calving process.
Table 1. Calf Report for 01/19/04 – 01/18/05 (DairyComp305)
The above report is from a dairy that averaged 15% DOA the previous year. They made an intervention strategy at the end of February that reduced the DOA to a 4% annual rate. The “strategy” was to have some training sessions on proper assistance at calving, and to put a clipboard in the maternity area to be initialed when the pen is checked on an hourly basis. This table is available in DC305 by typing Events, and then choosing Calf Table. Specific lactation groups can also be evaluated (e.g. Events for lact=1).
Keep calf mortality low: An achievable goal for calf mortality during the first 60 days of life is <1%. I know it’s achievable because I see dairies accomplishing this. As with DOA, first, you need to know what the number is in a given herd. The percentage can sneak up on a producer and be higher than expected. For example, a 100 cow herd will have about 110 freshenings/year, ending up with about 50 live heifer calves. Losing one calf every other month, or having two streaks of problems throughout the year where 2-3 calves are lost each time, will result in a 10% calf mortality rate, which is about the industry average (8.7% according to NAHMS, 2002).
Table 2. EVENTS FOR LACT=0 AGE <3/BIS FOR 02/19/04 – 02/18/05 (DC305)
This dairy lost 40 calves from February 2004 to February 2005 out of 482 live heifer births (8.3% mortality rate). Note how the deaths are grouped in the summer months and March. The herd had a Salmonella outbreak during the summer that led to the spike of deaths during that time period.
The key to low calf mortality rates and perhaps most of the other areas we will be discussing is consistently getting procedures done correctly. Most calves that die succumb from scours, with pneumonia a distant second. Ulcers, bloat, and acute clostridial deaths often occur in streaks. Areas to consider in herds with calf mortality problems include: dam vaccinations; degree of over-crowding and heat stress in prefresh cows; calving area hygiene; colostrum quantity, quality, and timing; calf nutrition program; housing type; and detection and therapy of calf scours and pneumonia.
Heifer completion rate: Weaned heifers don’t always make it to the milking string. Reproduction problems, pneumonia, and freak deaths will take a few percent; an achievable goal is to try to keep it less than 3% of weaned heifer calves, although I have seen an 800 cow dairy that only lost 1% of these animals over a year’s time.
It shouldn’t be too difficult to get heifers pregnant. Heat detection and conception rates should both exceed 60%, with pregnancy rates above 25%. Herds should try to have animals calve in a tight Age at First Calving pattern; animals calving much younger than the goal may be too small, while those calving much older are more likely to be fat. Generally prostaglandin given at 14 day intervals works well in heifer reproduction programs.
Factors influencing herd turnover rate: Cull rate has a huge effect on IHG. The point here is not to keep cows simply because they are alive, but to minimize the problems cows may experience (mastitis, poor reproduction, sick, low milk, bad feet, etc.) so that they don’t have to be sold. Obviously, it is way beyond the scope of this paper to comprehensively cover each of these areas. I just want to hit on what I have seen recently as some of the “high points” that can influence cow health in the following areas:
Transition Cow Health
- Minimize over-crowding of prefresh and fresh areas
- Feed high-fiber prefresh rations and use Rumensin to regulate the ruminal ecosystem
- Be wary of too many group changes during the transition period
- Monitor fresh cows closely, but don’t interfere with their desire to be cows
- Have milking SOP, and review them every other month
- Promote teat dipping or foam applicators as compared to spraying
- Do what needs to be done to have stall surfaces clean and dry
- Culture clinical cases, and any purchased animals (include Mycoplasma culture)
- Trim all cows twice per year, and whenever lame
- Use footbaths as much as it takes to control externally caused foot problems
- Maintain appropriate fiver levels for a given herd to minimize rumen acidosis
- Promote a comfortable cow environment, with short holding area times, so cows get off their feet.
- If using synchronization programs, make certain that they are being implemented correctly
- If using heat detection, make certain that it is being aggressively done
- Use the Presynch and Resynch programs
- Injuries are a leading cause of culling on some dairies. Cows are exposed to the “causative factor” multiple times per day, increasing their risk of eventually becoming injured. Main causes for injuries include slippery floors (holding area, cross-overs, walkways, area near water troughs, surface of manure slats,…) and metal obstacles (gate latches, bolts).
- Johne’s is usually the main problem; control procedures should be in place on all dairies
- BVD, respiratory pathogens, Salmonella, and BLV should also be considered
- Deaths are a leading cause of culling on many dairies; an average for larger dairies is NY would be about 8%. An achievable (although not easily) goal is <4%.
- Necropsies should be performed id the cause of death is uncertain
Normand St-Pierre of The Ohio State University (Columbus, OH, USA) created a spreadsheet that does a good job of estimating IHG based on a dairy’s relative success in the areas discussed. It is very helpful to demonstrate to producers the effect that changes in various factors influencing herd growth will have on the dairy over time.
Internal herd growth is a very powerful way for herds to improve their profitability. Analyze herds to determine which areas influencing IHG they are weakest in, and then work to address these opportunity areas.