September 5, 2017 at 3:32 p.m.

Same diet doesn't result in same milk production

By Jim Linn- | Comments: 0 | Leave a comment

I was asked by my nutrition colleague the other day why feeding the same diet on a farm with one herd in a tie stall barn and the other in a free stall resulted in different milk productions. The two herds are located on the same farmstead and managed by the same people, but not intermixed. The tie stall barn herd averages 115 lbs of milk/cow/day while the free stall barn herd is typically 10 lbs/cow/day lower. As we started to discuss possible reasons for the differences, a paper in the Journal of Dairy Science (August 2008) from Spain came to mind. Alex Bach, a former graduate student at the University of Minnesota, and his coworkers looked at nondietary factors related to differences in milk production amongst herds fed the same diet. They surveyed 47 dairy farms feeding the exact same diet. A TMR containing all forages and concentrates was mixed at a local feed cooperative and delivered to farms daily for more than eight months before the survey was conducted. Milk production of the herds ranged from 45 to 74 lbs/cow/day.
The survey collected information on the profile of the owners, information regarding the animals (reproductive performance, incidence of pathology, culling rate, etc.), information on the facilities (number of feeders, waterers, stalls, cleanliness, etc.) and information on management practices (numbers of daily milkings, feed deliveries, feed push-ups, cleaning frequency, etc.). The amount of feed delivered to each herd, daily milk production and milk quality were obtained for each herd. In addition, the chemical quality of drinking water from each dairy enterprise was determined.
What they found was over 50 percent of the milk production differences between farms was attributed to animal management and housing factors. The most important factors related to milk production were heifer rearing, presence of feed refusal in bunks, push up of feed and the number of free stalls available per lactating cow.
The average age heifers were bred was 16.9 months with an age at first calving of 27.7 months. Both management practices had a negative impact on milk production and were beyond current recommendations of calving heifers at 23 to 24 months of age. For every month above 24 months of age at calving, milk production on the farm was lowered by about 1.1 lbs/day.
The amount of TMR dry matter (DM) delivered to the lactating cows on these farms ranged from 36 to 55 lbs/cow/day. As would be expected, the higher producing herds had a larger amount of TMR delivered per day than lower producing herds. All herds were fed once per day and those herds assuring there was some weigh back before the next days feeding averaged 3.5 lbs more milk/cow/day than those with slick bunk management. No estimate on the amount of feed weigh back was given, but a two percent feed weigh back per day would be a good economical target.
Only 10 percent of the herds in the survey did not push up feed at least once per day. Time and labor to push up feed was a good investment as the herds that pushed up feed averaged 8.6 lbs/cow/day more milk than those that didn't. Pushing feed up more than once per day however, did not have any additional positive affect on milk production.
Eighty five percent of the herds in the survey housed cows in free stalls and the others were on a bedded pack. Although herd size was small (averaging 68 lactating cows) compared to our free stall dairies, the findings I believe are applicable to our lactating and fresh cow groups. Milk production was positively correlated with number of stalls and number of milking cows. As cow numbers increased above one cow per stall, milk production declined. They also found stall maintenance was related to milk production with farms having the best maintained stalls having the highest milk production and those with the worst maintained stalls the lowest. The better the stall maintenance and the greater the availability of stalls likely resulted in longer resting times of cows, and thus greater milk production. The survey data support that every cow needs a well maintained stall and her own space for comfort and optimum milk production.
The feed push up and stall/cow points from the survey likely account for some of the milk production difference in my colleague's tie stall and free stall herds. Many of the non-diet factors one would typically associate with differences in herd average milk production such as days in milk, age of cows, genetics, milk components, milk quality, culling, herd health and personnel management are all similar or equal in these two herds. Both herds are milked three times a day. Average dry matter intake of the two herds also is equal at 57 lb/cow/day. The freestall cows, while eating the same about of ration dry matter but milking 10 lb/cow less, also have a slightly lower body condition score than the tie stall barn cows.
The tie stall barn cows each have their own well maintained bed to lie down in when they choose to. Feed is always in front of them and they do not have to leave their stall to eat. They also are milked in their stall. There is no competition for a stall, feed or water as in the free stall barn. Even though the free stalls are not greatly over crowded by some standards at 15 percent, the free stall cows do experience competition for a stall, feed and water. They also are more active in having to walk from their stall any time they want to eat, drink and be milked. Free stall cows also incur disruptions during the day from other cows in heat and moving around that tie stall cows do not. All of the extra activity and standing of cows in free stalls requires more energy than cows standing up or lying down in the same space most of the day.
Does the extra activity of the free stall housed cows equal 10 lb less milk/cow? Yes, and the colder environment of the free stalls this winter required additional energy to stay warm, which probably accounts for the lower body condition. The average activity energy cost is about 20 percent of the maintenance energy requirement or approximately three mega calories for large Holstein cows. Milk production requires about 0.33 mega calories/lb. In this situation where free stall and tie stall cows are eating the same amount of ration dry matter, the energy needed for 10 lb of milk can easily be accounted for in the additional activity of the free stall cows.
The solution to getting the free stall and tie stall barn cows to be equal in milk production is providing more energy to the free stall cows. Cows can either acquire the additional energy by increasing their ration dry matter intake or increasing the energy density of the ration at the current dry matter intake. How to get cows to eat more is a major nutrition challenge with no easy or readily apparent solution. Increasing the energy density of the ration in this case isn't easy either when adequate fiber and other nutrients need to be maintained. Adding high energy feeds like fat can help, but there is a limit on how much can be added. If one adheres to the recommendations and guidelines of the Nutrient Requirements of Dairy Cattle publication, about 90 lb of milk/cow is about all we can really formulate a diet for and meet all of the requirements, especially fiber. High producing cows have high dry matter intakes so I guess we will just ask the cows in the free stalls to eat more feed and spend less time moving around.
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