Heat Stress in Dairy Calves

Penn State Extension has a well-written resource on this topic. This is a brief summary.

For a comprehensive review on heat stress in dairy calves use your phone or computer to enter this URL https://extension.psu.edu/heat-stress-in-dairy-calves or if you are reading this on one of those just click HERE. This Penn State resource has this outline:

·         Introduction

·         How hot is too  hot?

·         Strategies to help calves beat the heat

o   Provide shade

o   Move more air

o   Offer plenty of water

o   Keep grain fresh

o   Consider inorganic bedding

o   Work calves in the morning

o   Consider feeding more milk replacer

Consider feeding more milk replacer! [Sam's commentary on this strategy]

If you are currently feeding two quarts of either milk or milk replacer twice daily your calves are being shortchanged! Dealing with heat stress uses up lots of energy. We do not have hard numbers to tell us exactly how much more to milk/milk replacer to feed.

Nevertheless, boosting their energy intake through milk/milk replacer can be a workable way to get more groceries into young calves. Practical ways to do this include:

·         Increasing volume of whole milk fed – move up 1 quart per feeding is an example.

·         For milk replacer, increase volume fed OR

·         For milk replacer, move up from 8 ounces of powder makes 2 quarts (12% solids) to 10 ounces makes 2 quarts (15% solids)

If, however, every time you try to increase the volume fed you observe an increase in treatable scours, then you need to check out this resource in our calf management resource library – “Feeding more milk without scours.” Click HERE if you are reading this on your phone or computer or enter this URL http://atticacows.com/library/newsletters/FeedingMoreMilkwithoutScoursR1845.pdf

Weaning Readiness: Is it the daily calf starter intake level or the total amount of calf starter consumed?

A research team measured efficiency of digestion of calf starter grain (CSG) post-weaning. Efficiency of digestion was used as a measure of weaning readiness. Daily calf starter intakes as well as total amounts of starter consumed up to weaning were recorded.

The calves varied widely on daily calf starter intake levels beginning at three weeks of age - this was related directly to the volume of milk replacer (MR) consumed - one-half of the calves received about 1.5 lbs. of replacer powder daily while the other half was fed 2.4 lbs. daily.

These two different milk replacer feeding rates resulted in the moderate MR calves averaging 1.8# daily calf starter eaten and high MR calves consuming only 0.5#/day at day 42 when their milk replacer rations were cut in half. Then, they were both weaned at 49 days regardless of daily calf stater intake level.

By day 56 calf starter intakes accelerated up to 4.2#/day and 3.5#/day respectively for moderate MR and high MR feeding groups.

So, what did the efficiency of digestion numbers look like?

Calves that began eating calf starter grain (CSG) at a younger age and ate more total CSG had slightly higher levels of digestive efficiency at 8 weeks of age. [CSG was in pelleted form]

As I read the data reported in the research article it looks like both length of time eating CSG and total volume consumed contribute to desirable feed conversion rates in our weaned calves.

In practical terms, if larger volumes of milk/milk replacer are fed extra care needs to be taken to ease these calves into 100% dependence on CSG at weaning time. A good three weeks of at least 0.5#/day CSG may be a workable rule of thumb to observe before withdrawing all milk. Cutting the milk ration in half around 35 days nearly always results in an accelerated rate of CSG intake. These data suggest a full week at 3.5 - 4.5#/day CSG consumption is desirable at the time of full milk withdrawal.

Just a note from a recent experience, be sure to check that CSG contains some kind of coccidiostat - saving money by leaving it out of a CSG is ill advised. Weaning is always a stressful time and coccidia always take advantage of stress events to hammer our transition heifers.

Remember, also, at weaning to introduce hay slowly over a period of 2 or more weeks in order to allow time for the rumen microbial population to multiply enough to effectively digest this fiber. Abrupt introduction of "free-choice" hay is associated with weight loss, pneumonia outbreaks and coccidiosis.

Reference: Quigley, J.D. and Others, " Effects of feeding milk replacer at 2 rates with pelleted, low starch or texturized, high-starch starters on calf performance and digestion." Journal of Dairy Science 101:5937-5948. June 2018.

Colostrum: Yet another Update

The July issue of the calf management newsletter is now on-line. The URL is http://atticacows.com/library/newsletters/CEJuly2018.pdf or just click HERE.

The summary points are:

• How our management choices shortchange our calves
• Role of colostrum on gastrointestinal tract development
• Role of colostrum on immunity
• Take home ideas for strengthening colostrum management

Enjoy.

Is it Okay to Draw Blood After Day 2?

Drawing blood to check on the effectiveness of the colostrum management program is an increasing common best calf management practice. But, when should the blood sample be taken? A small research project drew blood samples daily for up to 10 days to answer that question.

1. Blood samples drawn up to 9 days of age will provide reasonably reliable estimates of passive transfer immunity.

2. Blood samples drawn 24 to 48 after first colostrum feeding do result in slightly more reliable blood serum total protein (BSTP) estimates than those at 8 and 9 days of age.  

3. But, for management purposes the variation between 2 and 9 day samples is small enough so that we should not hesitate to blood sample the older calves.

I recognize that not every dairy will find it possible to draw blood on all their calves between 24 and 48 hours like I did with my calves. These data support the practice of weekly blood sampling if daily blood draws are not practical. 

Alternatively, with a small herd with monthly or quarterly assessment of colostrum management blood sampling between days 2 and 9 may allow including enough heifer calves to give useful information. 

Just for Reminders:

A. Remember that blood samples are fragile - careful handling will result in fewer broken red blood cells and more accurate estimates.
B. Keep a supply of distilled water at hand all the time - it only takes a minute or two to calibrate your refractometer; reliable readings depend on calibrated instruments.
C. Lab practice suggests that blood samples that have been held more than one day may require some extra time in the centrifuge to get full separation of blood serum.
D. If using gravity method of separation, undisturbed samples held at room temperature for approximately 24 hours will have the closest match with samples spun with a centrifuge (i.e., between 95 and 98 percent agreement).

Reference: Wilm, Jensine and Others, "Technical Note: Serum total protein and immunoglobulin G concentration in neonatal dairy calves over the first 10 days of age." Journal of Dairy Science 101:6430-6436 June 2018

Exploring Low Colostrum Yields

Colostrum yield data were collected from Jersey cows in a Texas herd. There were 1,143 first-lactation cows and 752 second-lactation cows and 1,003 cows of third lactation and greater (total records = 2,988)

Fact #1. Huge variation in colostrum volume among cows of all lactations

     1st lactation varied from 0 to 30.6 lbs. [17.5kg] (est. 18 quarts)

     2nd lactation varied from 0 to 53.2 lbs. [24.2kg] (est. 25 quarts)

     3rd & greater lactation varied from 0 to 58.5 lbs. [26.6kg] (est. 27 quarts)

Fact #2. No colostrum at all

     1st lactation - 3 out of 1,143 had no colostrum (0.3%)

     2nd and greater lactation - 105 out of 1,755 had no colostrum (6%)

Fact #3. Strong seasonal influence - December being the lowest volume month. Research  team suggests maybe a photoperiod influence. June-July yields were the highest.

Fact #4. Factors influencing volume but only a small amount included calving age, gender of calf, previous lactation 305ME, dry period length. Environmental factors (e.g., THI) and predigree had minor influence on volume. Note that this was only one herd in a Texas environment (2,988 Jersey cows).

TAKE HOME?

1. Expect and prepare for wide variations among animals. Don't beat yourself up over the small percentage of cows with zero yields - they are going to happen. Adopt best management practices for calm and gentle animal handling to promote optimum let-down at first milking. 

2. Be prepared to take advantage of high-yielding cows - adopt best management practices for collection and storage of colostrum in excess of immediate needs. 

3. Remember that we continue to get the biggest bang for our buck when we feed enough high quality CLEAN colostrum ASAP after birth. When available and practical, second and third small feedings of colostrum in the first 24 hours do boost blood IgG levels.

4. If practical, calves benefit from feeding transition milk (that is, 2nd, 3rd and 4th milkings) - this milk can help us avoid treatments with antibiotics during the critical first two weeks of life.

Reference: Gavin, K. and Others, " Low colostrum yield in Jersey cattle and potential risk factors."
Journal of Dairy Science 101:6388-6398 June 2018.

Good Colostrum Quality from 2nd Milking

Is  it worth your time to check second milking from mature cows for antibody concentration? YES.

Dr. Noelia Silva-del-Rio, UC Davis Veterinary Medicine Extension specialist in Tulare CA, measured first and second milking from third or greater lactation Jersey cows. She had 134 first-milking samples and 68 second-milking samples.

43% of the second-milking samples contained IgG concentrations of 50g/L  (the industry standard for acceptable quality for first feeding).  

Given a shortage of first milking colostrum, Dr. Silva-del-Rio encourages producers to collect and test 2nd milking. 

I agree. These data suggest that nearly one-half of the time the 2nd milking will be suitable for the first feeding of newborn calves. 

Reference: California Dairy Magazine, May 2018, p16.

Feeding Hay with Calf Starter Grain

The June 2018 issue of the calf management newsletter, "Feeding Hay with Calf Starter Grain," is now available at 

http://atticacows.com/library/newsletters/CEJune2018.pdf or click HERE.

The summary bullet points are:

• Achieve better outcomes feeding a mix of grain and hay compared to grain only.
• If a “little” is good, would “more” be better? No!
• Practical alternatives for including 5 percent chopped hay.
• What if no chopped hay?

Enjoy!