Although there can be a feed savings, producers need to consider special nutrition and management requirements
At one time dairy cows were kicked out of the barn to graze green pastures in the spring and were only brought inside at milking time. Times have sure changed — the trend for more milk produced by individual cows consuming great quantities of ensiled and dried roughages moved most productive lactating dairy cows indoors. But in the face of modern, intense dairying, some producers are returning their lactating cows to pastures as a way of making milk.
Wisdom says grazing dairy cattle in Western Canada will not be an all-year affair. However, dairy producers might be able to let cows effectively graze fields for four to five months starting in mid-May and then return them to more conventional dairy-feeding programs in early autumn. Some dairy specialists say providing good quality and quantity of pasture legumes and grasses could technically provide from 25-100 per cent of their nutrient requirements, depending on milk-production goals.
Dr. Mike Hutjens from the University of Illinois estimates good-quality pasture, without grain or protein supplements, should produce 25 kg of milk in mid-lactation dairy cows. Therefore, he expends dairy producers could increase milk yields to about 30-35 kg of milk per cow per day if 50 per cent of the cow herd’s dry matter intake was supplied by good-quality pasture, with the remaining 50 per cent filled by a special well-balanced partial mixed ration (PMR).
Partial Mixed Ration
This PMR would complement the nutrition of the existing pasture and should contain silage or long-stem dry hay to help meet “effective fibre” requirements, which is usually deficient in sprouting lush pastures early in the growing season. A PMR might also contain a high level of undegradable or bypass proteins such as distillers grains or brewers mash to offset large quantities of highly soluble protein commonly found in legumes. Furthermore, many PMRs have a proportionally higher concentrate or grain: forage ratio compared to their barnyard TMR counterparts because they function as a source of highly available energy for milk production. Finally a mineral-vitamin pack rounds out most PMRs.
Advocates of PMR/pasture feeding lactating cows often promote several advantages such as improved general health and better conception rates among cows due to exercise, as well as more efficient use of land not suitable for anything else other than grazing. Frequently, they say there is a significant reduction in overall feed costs.
Dairy producers who take notice of these pasture attributes, especially when the subject of saving feed costs comes up, should first figure out the actual net economics. For example, during a four-month grazing period for 100 milking cows; if the overall feed cost savings were 25 per cent of the average feed costs of $6/head/day, then the gross feed savings would be: 25 per cent x $6 x 100 cows x 120 days = $18,000.
And the cons
Such gross savings are offset by a potential loss or inconsistent milk production from pasture-fed cows due to possible lower overall dry matter intake of the lactation herd, early-lactation cows failing to meet demanding energy requirements and the cows’ preference for plants that are not high quality or lack quality uniformity.
In addition, any investment needed to support dairy cows on pasture such as extra waterers, additional fences and even a new back-rubber to control flies should be subtracted from the original feed-cost savings.
No economic spreadsheet will show lactating dairy cows reared on pasture also require special management compared to an enclosed dairy barn system. Consequently, it is very important to estimate the number of cows per acre that should be allowed to graze at any one time — high-quality paddocks may support from one cow per 1.5 to two acres, and as pasture quality decreases, so should the stocking rate (fewer cows per acre).
Some intensely managed rotational grazing systems move cattle every day or every few days to stimulate pasture regrowth and ensure good pasture quality. Their herd managers also realize that pasture intake by dairy cows is related to the time cows spend grazing; dairy cattle are highly selective ruminants and typically graze for only six to nine hours per day. Overall forage consumption is also influenced by the amount of grassland trampled, defecated upon or simply wasted.
Even if forage consumption by dairy cows of the best pasture is deemed adequate, we must always consider the effect of season upon pasture quality, because pasture energy and protein are typically higher in the spring and lower during the summer and onwards. As pasture grasses mature, digestibility by rumen microbes also significantly decrease, because total plant fibre content (as well as indigestible fibres) increase. More supplemental feeds (re: which might lower our initial feed cost savings) may be required as the season progresses.
Coupled with aging seasonal pastures, we must be aware heat stress will likely hit the Prairies for several weeks during mid- and late summer and could have a significant negative effect upon milking dairy cows’ feed intake. Heat-stressed dairy cows have little interest in grazing and tend to lie in shade or hang around waterers (double or triple their normal water consumption). Furthermore, these miserable cows not only eat less during hot weather, but they tend to divert essential nutrients away from milk production and toward basic organ maintenance.
Such challenges are often a matter of routine when using pasture for dairy cows. Grazing dairy cattle takes special nutrition and management, which encompasses homework, a strategy to handle challenges and hard work. The payoff can be potentially lower feed costs, while maintaining good milk revenue and higher profits. †