Manger Space Can Be Restricted With TMR
Many older dairy barns, as well as three and six row free stall barns have limited manger space. Not all the animals can eat at the same time. Many experts have held the view that this reduces feed intake, lowers milk production in cows and restricts growth rate of heifers.
A Pennsylvania State University study, reported in the January 1999 Journal of Dairy Science sheds valuable light on the question of how much manger space is needed for growing heifers fed total mixed ration (TMR). Other studies reported in recent years have addressed the same issues for milking cows.
In the heifer study, researchers J. I. Longenbach, A. J. Heinrichs, and R. E. Graves, restricted the manger space of dairy heifers of various ages. In the initial trial, 4-month-old calves were given either 6 or 12 inches of manger space. Either two-thirds or all the calves could eat at the same time. A fairly high-energy total mixed ration was limit fed to support a growth rate suitable for calving at two years. Although the heifers with limited bunk space ate faster, and ate more meals of shorter duration, their growth rates were the same as the group that could eat all the time.
In a second trial, 11 to 15 month heifers limit fed TMR rations were provided with 6, 12 or 18 inches of manger space. Out of 9 heifers per group, 5, 8, or 9 respectively were able to eat at once. As in the first trial, heifers with restricted bunk space ate faster in smaller meals. Although average rates of growth were the same, variation in growth rate among the heifers was slightly greater in the group with the least bunk space.
In the third trial, 17 to 21 month old heifers were given the same space as younger heifers in trial two. Only 4, 7 or 8 could eat at once, but growth rate and variation among heifers was the same.
The authors concluded that manger space allotments of 6" at 4 to 7 months, 12" at 11 to 15 months and 18" at 17 to 21 months were adequate to support rapid growth and early calving, when heifers were limit fed a TMR. When the space provided was less, eating behaviour changed but there was virtually no affect on growth.
Findings of a field study of two high-producing herds in six-row free stall barns show similar conclusions apply to milking cows. Both herds had high production groups of about 90 cows, averaging 40 litres of milk per day on 3X milking.
Each herd in the study, conducted by William Menzi and Larry Chase and reported at an International Housing Conference in 1994, averaged 10,700 kg milk. Cows were fed a TMR 2 or 3 times daily, and feed was also pushed up 2 times daily.
Manger space per cow was 15 and 16 inches. This is 33% less than the 24 inches needed for all cows to eat at once.
Available space at the feed bunk was monitored by time lapse video. The video revealed that space at the manger was less than 50% occupied most of the day and periods of "no space at the manger" were rare and brief when they occurred. Although this study did not compare production and manger space, the fact that there was nearly always space available, suggests that manger space was not causing stress or reduced feed intake.
It should be emphasized that both these trials involved TMR rations and good feeding management. Diets were provided in amounts adequate to meet requirements in the heifer trial and were fed free choice in the milking herds. Fresh feed was provided twice daily and feed was pushed up at other times. Based on these results it would appear that three and six row free stall barns provide more than adequate access to feed.
Issues such as the use of self-locking headgates, ventilation and crowding in the barn still need to be addressed better than in a 4 row barn. But these studies suggest that competition for feed bunk space itself is not a concern with good feeding management.
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