DHI Notes...

September 2006 | TMR’s suffer heat stress, too | Bennet Cassell

State DHI averages for important management areas in August 2006

Management area	August 2006	Change from last year
Rolling herd average milk	21764	+925 lbs.
Peak yield in heifers	76	1 lbs.
Days to first breeding	96	+2 days
Days open	166	+7 days
Net Merit of proven service sires	$297	*
Herd turnover less dairy sales (%)	29%	0%
Monthly average SCS	3.4	0.0
Feed cost per cwt. (milking cows)	$5.62	-$0.18
Milk blend price	$13.19	-$2.08

Summer in Virginia always seems to have its way with dairy cows. Production for milking cows on test in Virginia averaged 68.9 lbs in June. By July, the average dropped to 66.2, and fell even further in August to 64.2 lbs. The decline happened in spite of a decrease in days in milk from 212 to 201 days, and fresh heifers were not responsible. Somatic cell counts increased through the summer, from 3.0 in June to 3.4 in August. There are no numbers yet on pregnancy rates for July and August, but there is little reason to expect any good news on that front, if history repeats itself. Late summer is a tough time to get cows bred in this state. These performance indicators show classic signs of summer heat stress, and perhaps because of changes in rations that some producers have made in response to low milk prices. I suspect that, on many farms, feed quality has suffered because of high temperatures as well. The feed was harvested and stored well before the July and August heat and humidity, but TRM’s don’t remain palatable very long in hot weather, regardless of initial forage quality. The best remedies are simple: practice good bunk face management at the silo and deliver freshly mixed feeds “several” times a day. Think about how the cow may view feed that has been in the mixer wagon or the feed bunk for the better part of a day – heated, dried out, and well explored by herdmates. This note will appear in print about the same time that frost coats the bottom lands and clear, crisp fall days remind us what a wonderful place Virginia is to call home. Summer heat stress will be a fading memory, but the lessons of that heat and humidity should still affect feeding programs. Feed your cows as you would like to be fed when you go to a restaurant – with fresh, appetizing dishes with eye appeal delivered on time in a pleasant setting. Let’s not go into portion size in this comparison. Cows should eat to appetite. Most of us, and I’m clearly in that category, shouldn’t!

Bennet Cassell
Genetics and Management