Effects of PMRs on rumen and milk production

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With the increase of robot milking systems, this study may lend some insight as to feeding strategies that may be most effective for stabilizing rumen environment. The study was done on pasture-based cattle, but did compare rations where ingredients are fed separately or in a partial mix situation with less additional supplementation in milking parlor.

In this trial all cows had a forage base of perennial ryegrass. They were then split into groups and fed three ways:

 1. The control group was fed crushed wheat grain twice a day in the milking parlor and ryegrass at pasture.

2. A ration similar to the control in ingredients and nutrient density but mixed and fed on a feed pad twice a day, this was called a partial mixed ration (PMR).

3. This ration was mixed and had additional canola added to increase metabolizable protein, (PMR+canola).

Within each of the feeding groups there were smaller groups of cows fed (top-dressed) additional protein and energy supplements.

The cows fed the PMR had the lowest incidence of ruminal acidosis. Acidosis increased as supplement was increased. Milk fat yield was highest in the PMR+canola cows fed the higher levels of supplement, next was PMR cows and lowest was the control grazing cows. Milk protein yield was also the highest for the PMR+canola cows with higher supplementation. In all groups milk, energy-corrected milk, and protein yields increased in groups fed a partial mixed ration with additional supplementation. Milk fat percentage decreased as supplement levels increased.

This study also looked closely at ruminal bacteria populations. Despite large among and within group variation in bacterial community composition, distinct bacterial communities occurred among feeding strategies, supplement amounts.

The conclusion was feeding supplement in a PMR scenario reduced the amount of ruminal acidosis and altered ruminal bacterial communities, regardless of the amount fed. However, this feeding strategy did not lead to a measurable difference in milk production when compared to the control component fed cows.

 

Link to abstract



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