Foraging Skills of Dairy Animals: Is foraging an acquired or innate skill? Science sheds some light on the matter.

When a group of dairy producers discuss pasture management, it does not take a lot of time for the discussion to diverge to foraging skills of dairy cows. There is a belief that animals should be exposed to pasture at an early age in order to gain experience that will be beneficial later in their productive life.

In fact, there are grounds for this belief. According to early work on foraging skills, researchers reported that ruminants exposed to pasture remember previous experiences. They learn to select specific forages and will select the same specific forages later in life.

Other studies conducted in the nineties reported that experiences obtained as a young animal affected diet selection, grazing behaviour and, animal productivity months or years later both in sheep and cattle. Furthermore, it was shown that ruminants exposed to pasture acquired their foraging skills at an early age and grazed more efficiently than animals that were not exposed to pasture. However, much of this research work was conducted in extensive, unimproved grazing systems, where animals were exposed to toxic plants as well as pasture that varied greatly in nutritional value. In North America, grazing dairy cattle pastures typically contain high-quality grasses and legumes. Investigating how early grazing experiences affect grazing behaviour or milk yield of dairy cows under these particular conditions was needed.

Furthermore, little was known on how long it takes for lactating dairy cows with no previous grazing experience as heifers to adapt to pasture under intensive rotational management systems.

To answer these questions, a three year project was conducted and came to an end recently. This study evaluated the carryover effects of dairy heifer grazing experience on behaviour and first-lactation performance as dairy cows. Holstein and Holstein X Jersey crosses were used for the experiment and were divided amongst 4 different treatments: 1-Heifers assigned to pasture as weaned calves as well as yearlings; 2-Heifers assigned to pasture as weaned calves but then housed in confinement as yearlings; 3- Heifers housed in confinement as weaned calves and then assigned to pasture as yearlings; 4- Heifers housed in confinement as weaned calves and as yearlings. During the third year of the project, all animals were assigned to summer pasture as lactating cows.

Several parameters were recorded including: dry matter intake, animal behaviour and activity using global positioning technology.

The first year of the experiment was simply to expose 2 groups of heifers to a grazing environment for 41 days. The other 2 groups of heifers were housed continuously in confinement.

During the second year, it was possible to evaluate the carryover effects of the grazing experience on current heifer grazing behaviour. The experienced heifers that grazed during the first year spent more time grazing on the first day than inexperienced heifers. This suggested that heifers with previous grazing experience remembered how to graze, because these heifers started grazing immediately upon exposure to the pasture during the second year. In contrast, heifers with no previous grazing experience exhibited a clear reluctance to graze on the first day. However, after only a few days, both groups behaved similarly.

On the third summer of the project, the animals were now lactating. Once again, it was possible to evaluate the carryover effects of the grazing experience on cow grazing behaviour. Cows that were previously exposed to pasture, either as a calf or yearling spent more time grazing on the first day than cows with no previous experience. Once again however, after 5 days on pasture, inexperienced cows showed the same grazing patterns as experienced cows.

In terms of milk production, on the first day on pasture, cows that had not grazed as heifers during the second year produced less milk than cows that had grazing experience as heifers during the second year. This was most likely caused by the lower percentage of the time spent grazing. However, average daily milk production during the whole study did not differ.

Results from this study show that experience early in the life of dairy heifers grazing high quality pasture does affect grazing behaviour and milk production but only during the first few days of exposure to pasture. However, cows with no previous grazing experience adapt relatively quickly to grazing and milk production recovers within a few days after first exposure to pasture.

Reference:

Assessment of heifer grazing experience on short-term adaptation to pasture and performance as lactating cows. F. Lopes , W. Coblentz, P. C. Hoffman, and D. K. Combs. Journal of Dairy Science. 96 :3138-3152 (2013)


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