One of my friends Tim called in April of last year. “Marc,” he said, “One of my dairy clients, might be interested in working with us over the summer on a reproduction project – would you like to help?”
Tim is a dairy consultant in the Bosque River valley of Texas and keeps a tight rein on his clients. He is quite protective of his relationships with them. Jared Froetschner, who works as an area manager for us, and I jumped at the chance. Pregnancy rates in the Bosque River area often range in the single digits during the hot summer, and Marc’s herd was no exception.
For the cost of donating to the dairyman’s ration some beta-carotene (a precursor to vitamin A), we’d get a chance to work with Tim and Marc over the summer in Marc’s 1,250-cow herd.
Our objectives during this unique opportunity were to get a baseline serum beta-carotene measurement from cows in various stages of lactation and evaluate whether supplementing the entire herd during this time would improve Marc’s pregnancy rates during August through October of 2008.
So we drew up a plan. We decided to supplement the entire herd (lactating, dry and transition cows) with 400 mg of beta-carotene premix from July 15 for 100 days through October of 2008. We would sample cows initially for beta-carotene blood levels and evaluate reproduction after obtaining complete DairyComp 305 records through October. We had no way to divide the herd, so our repro comparisons would be made versus historical data from 2006 and 2007.
Here were the results for our two objectives.
1. We found that cows in Marc’s and other Southwest herds were very low in beta-carotene blood levels; well below the recommended 2-3 ug/ml of serum. (See Table 1*.) This was surprising because they feed a lot of forage, and normally forage is considered a good source of beta-carotene. (Remember why your mom told you to eat carrots?) Supplementation with the vitamin brought up blood levels, but we learned we can’t count on forage to provide enough beta-carotene to meet ideal requirements. (See Table 2*.)
Marc’s response was typical of many dairy producers. “So what? How is this affecting my cows?” That’s where the repro analysis via DairyComp 305 came in.
2. Tim used the program to compare herd reproduction performance in August, September and October in 2008 (the test year) versus the same time period in 2006 and 2007. Figures 1 and 2 show the improvements seen in pregnancy rates in first-lactation heifers (Figure 1) and in multiparous cows (Figure 2) compared with previous years. The first four breeding cycles after 50 days in milk were used to compute the averages, which to Marc seemed like the most realistic way to think about his repro program and which uses heat detection and a 50-day voluntary waiting period.
Is this scientific research? Hardly – a demonstration at best, since we weren’t able to compare untreated (control) cows with treated (beta-carotene) cows during the same time frame. In statistical terms, we had no degrees of freedom.
Lots of things affect dairy cow reproduction, and vitamin status is just one of them. Nonetheless, we all concluded that the supplementation did some good, and we made some plans to fine-tune the program in the summer doldrums of 2009. Since that conversation, guess what happened to Marc’s milk price (and his appetite for new input costs)? I’m sure you can guess.
What did the dairyman gain from this exercise? If nothing else, he gained some knowledge about both his feeding and breeding programs and a few more sets of eyes and ears to bounce ideas off of. PD
*Tables and figures omitted but are available upon request to editor@progressivedairy.com
Mark Engstrom
Technical Services DSM
Nutritional Products
mengstrom@dsm.com
