Consistency in Forage Quality Control Needed
The upcoming transition to new-crop corn silage might be a good time for nutritionists to revisit the importance of forage feeding consistency with dairy producers and, perhaps even more so, their feeders.
A high standard of consistency and quality control is expected from suppliers of purchased concentrates and specialty ingredients.
The challenge on many dairies is that managing quality control for high-moisture grains and forages falls under the purview of each individual dairy.
This column reviews recent research on the effects ration consistency can have on dry matter intake (DMI), production and the time it takes cows to recover from lapses in forage and/or total mixed ration consistency.
Forage dry matter
Dairy ration options decrease as milk production increases. This is due to the cow's high nutrient demand and minimum requirements for effective fiber (Mertens and Berzaghi, 2009).
Researchers at the U.S. Dairy Forage Research Center have been running a series of experiments focusing on the effects of abrupt changes in forage dry matter and feed allowance on milk production.
The first experiment (Mertens and Berzaghi, 2009) investigated the effect of a single-day abrupt change in forage dry matter. Forty-eight cows that were 138 days in milk were assigned to one of six treatments where either forage or ration dry matter was reduced 8-16% with the addition of water, similar to what would occur with heavy rainfall on bunker silo faces or when feeding imprecise rations based on as-fed ratios of ingredients.
Their conclusion was that single-day variation in forage dry matter (and ration fiber composition) had an immediate effect on DMI. Every 2.2 lb. of DMI decline led to 1.7 lb. of milk lost in each of the following two days.
On-farm, rapid methods of forage analysis based on rugged near-infrared instrumentation, integrated with feed mixing software, were proposed as a solution to help manage this variation.
The second experiment (Boyd and Mertens, 2010) was designed to quantify the effects of longer periods - one, two or three days - of changes in forage dry matter. The trial tried to mimic realistic responses of most dairy feeders by investigating the effect of offering cows more feed if they cleaned up the feed bunk (because less ration dry matter was offered).
Diets consisting of 18% alfalfa and 36% corn silage were fed as control (no water added) and treatment (water added to decrease forage dry matter by eight percentage units) to cows that were 65 days in milk and milking an average of 95 lb. Each period consisted of a three-day pre-treatment phase, a one-day, two-day or three-day treatment phase and a three-day post-treatment phase.
Similar to the first experiment, DMI on day 1 was significantly reduced by 3.2 lb. when averaged across all treatments. DMI did recover during the following one to three days even during treatment phases. Although daily milk decreased slightly on day 1, the average decrease for all three treatments was largest (4.3 lb.) on day 2.
It was concluded that abrupt changes in forage dry matter cause economically significant reductions in milk yield; however, the duration of the change (one, two or three days) does not worsen the loss if adequate ration amounts are provided.
The third experiment, which has not been published, is intended to look at the response to changing forage dry matter in late-lactation cows.
This trial was designed in response to producers claiming that early-lactation cows seem more resilient to ration changes compared to late-lactation cows, which have more difficulty rebounding from bouts of ration inconsistency (Mertens, 2010).
Its interesting to compare the Dairy Forage Research Center findings with abrupt changes in forage dry matter to more progressive responses in a recent Pennsylvania State University study (Rico and Harvatine, 2010) that investigated the recovery time from diet-induced milk fat depression (dMFD).
A control diet with 32% neutral detergent fiber (NDF) was fed during control and recovery periods. A low-fiber (27% NDF) and high-oil (3% soybean oil) ration was fed during the dMFD period. Treatment periods were 21 days in length.
In this trial, DMI progressively decreased when cows were switched to the dMFD ration, achieving significantly lowered intakes after day 6. Intakes fully recovered after 15 days into the recovery period. Milk protein percent was actually elevated (6%) on the dMFD treatment, while milk yield (averaging 71.5 lb.) was not significantly affected by treatment.
In contrast, milk fat percent and milk fat yield decreased progressively from day 1 and were statistically lower than the control by day 3 and day 7, respectively. After switching to the recovery diet, milk fat percent and milk fat yield increased progressively, recovering to the same level as the control group on days 19 and 11, respectively.
It was concluded that recovery from dMFD occurs progressively, with a very short lag, when dietary NDF and polyunsaturated fatty acid concentrations are corrected.
The Bottom Line
Thinking about these studies, I am reminded by nutritionists, almost on a daily basis, that much of the country seems to be battling milk fat depression. I wonder how much of this problem may be related to variation in forages and the effect that has on NDF intake, rumination and spiraling episodes of "off feed followed by gorging."
Many of the milk fat depression problems associated with variation in fat content in wet distillers grains from plants with marginal quality control have now been recognized and solved. Perhaps the next area of focus needs to be on implementing technology and protocols to better manage the variation that exists in individual dairy farm forage bunkers.
Boyd, J., and D.R. Mertens. 2010. Abrupt changes in forage dry matter of one to three days affect intake and milk yield in early lactation cows. J. Dairy Sci. 93 (E_Suppl. 1):562 (abstr.).
Mertens, D.R. 2010. Personal communication.
Mertens, D.R., and P. Berzaghi. 2009. Adjusting for forage variability via on-farm analysis. Proceedings of Getting More From Forages Conference. Madison, Wis. July 29. Accessed at: www.ars.usda. gov/sp2UserFiles/Place/36553000/presentations/ Getting_More_from_Forages /Mertens.pdf.
Rico, D.E., and K.J. Harvatine. 2010. Time course of recovery from diet induced milk fat depression in dairy cows. J. Dairy Sci. 93 (E_Suppl. 1):740 (abstr.).
This article was originally published in the October 2010 Feedstuffs issue, and is reproduced with their permission.