Wednesday, July 4, 2012

When Too Much of a Good Thing is Really Too Much.

I wrapped up herd check and was chit-chatting with the herdsman when the calf feeder approached me with a serious concern.  In the past week, 3 calves around 2 weeks of age have suddenly died after having a normal appetite the feeding 12 hours prior to death.  The announcement of “Sudden Death” immediately sounded the alarm bells, but for sake of completeness, we reviewed our pre-weaning calf management protocols.  No management changes had been made.  Colostrum management checked out fine – a gallon within 2-4 hours of birth.  Pre-fresh and maternity pens were clean and not overcrowded.  Calf housing was clean, dry and well-bedded.    All equipment was visually clean.  Collection, mixing, and feeding equipment are rinsed out with warm water, sanitized with dish soap, rinsed with hot water and allowed to dry.  Multiple members of the family feed the calves, so I wanted to make sure all feeders are on the same page.  They were.  The farm feeds 3 quarts of milk replacer per feeding in order to maintain an adequate caloric intake on a 22:20 all-milk replacer and to meet our growth and body condition expectations at weaning.  As long as the milk replacer has been mixed according to instructions, the mix should be at the optimal concentration.  Free-choice water and calf-starter are provided, however, I needed to re-check mixing procedures.  In the meantime, a calf was sent to the state veterinary diagnostic lab for necropsy and cultures.


Why was I concerned about milk replacer concentration?  The alarm bells mentioned earlier were screaming Clostridium perfringens, a bacterium which loves to proliferate when exposed to high levels of carbohydrates in the intestines.   Clostridium perfringens is a normal inhabitant of the intestines, but when exposed to high levels of carbohydrates, Clostridium perfringens proliferates rapidly, sporulates, and then releases toxins causing an enterotoxemia and the classical “Sudden Death.” 

How can we prevent overloading the intestines with an excessive level of carbohydrates?  You have to watch the osmolality of your solution.  Osmolality is a fancy term for concentration.  As the osmolality of your solution increases, the calf’s stomach empties quicker, leading to a rapid increase of carbohydrates in the intestine.  Osmolality increases as you add more powder over the labeled amount and as you add more additives, like probiotics, electrolytes, colostrum supplements mixed in colostrum, “Foo-foo dust,” etc.  To avoid excessive osmolality, you should avoid adding extra milk replacer and placing additives in the solution.  Feed electrolytes and colostrum supplements in a separate mix. 

My client was mixing a large batch of milk replacer.  Instead of using the cup that came with the milk replacer bag, he was using a large scoop.  In place of using weight for measurement, he was essentially using volume (It took this many cups to fill a scoop).  However, powder in the larger scoop compacts as you shove it into the bag.  After weighing the amount of powder per scoop, we figured, the batch was receiving one large scoop too many.  The osmolality of the mix was too high.  Since making the adjustment to the mix, “Sudden Deaths” have disappeared.  Necropsy culture results confirmed our suspicion.

This case is timely, because soon you will be feeding more milk replacer to cold stressed calves.  Calves are most comfortable when environmental temperatures are between 50-70F.  To maintain body temperature in extreme temperatures, body tissue (fat, muscle) is utilized.  Calves will die from starvation if not properly managed.  Therefore, calves need more energy (calories) during cold stress periods.  Calves should receive 30% more milk or milk replacer (20% fat minimum) by mixing 30% more replacer per feeding or by increasing feeding frequency (3x instead of 2x).  In order to prevent Clostridium perfringens entertoxemia and “Sudden Death,” you should mix the milk replacer according to labeled instructions and feed 30% more of the correctly mixed batch rather than adding 30% more milk replacer powder to 2 quarts of mix which increases osmolality.  Accelerated growth milk replacers are an alternative to conventional milk replacer, but it is even more important to closely monitor mixing instructions because of the increased risk of  Clostridium perfringens entertoxemia and death over conventional milk replacer.  As the calf grows, consistently increase milk so proper body condition is maintained.  Calves require free choice grain and water.  Hay or forages should be avoided in pre-weaned calves to allow adequate grain intakes and rumenal development.  Furthermore, calves should be allowed to “nest” in deeply bedded straw that covers the extremities when the calf lies down, effectively creating greater insulation.  Finally, keep the hutches well ventilated even in the coldest temperatures.  With proper nutrition, adequate bedding, and a short windbreak that prevents drafts while the calves are lying down, hutches can remain open. 

With “Old Man Winter” coming, avoid Clostridium perfringens-related Sudden Death by mixing milk replacer according to labeled instructions and by preventing the urge to place additives in your milk, colostrum, or milk replacer.

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