Timing of supplementation alters grazing behavior and milk production response in dairy cows

Abstract

Offering feed supplements to grazing dairy cows results in substitution of pasture; however, previous data indicate that the time at which concentrate supplements are offered might affect the level of substitution. These data indicated that cows grazed more intensely presunset, regardless of the amount of supplement offered. It was, therefore, hypothesized that substitution rate would be less, and response to supplement greater if cows received their supplement at the p.m. rather than the a.m. milking. Forty-eight multiparous, nonpregnant, Holstein-Friesian cows, approximately 60 d in milk, were randomly allocated to 1 of 3 treatments in an incomplete crossover arrangement. Treatments were pasture only, pasture + 3 kg of concentrate supplement dry matter (DM) offered during the a.m. milking (AM-SUP), and pasture + 3 kg of concentrate supplement DM offered during the p.m. milking (PM-SUP). Time spent grazing and calculated pasture DM intake did not differ between the AM-SUP and PM-SUP cows. However, a tendency (0.18 kg of milk/kg of concentrate DM) was observed for an increased marginal milk response (kg of milk/kg of DM supplement) for the AM-SUP cows when compared with PM-SUP cows. Irrespective of when supplements were offered, supplementation reduced total grazing time by a similar amount, and the reduction in time spent grazing was evident throughout the day. Cows in the PM-SUP group ruminated for longer and cows in the AM-SUP group spent more time idle compared with the pasture only groups. Cows in the AM-SUP group grazed for less time during the major a.m. grazing bout following a.m. milking compared with PM-SUP cows; in comparison, the major p.m. grazing bout following p.m. milking was unaffected by supplementation. The results indicated possible improvements in marginal milk response to supplements from altering the timing of delivery.

Factors associated with the financial performance of spring-calving, pasture-based dairy farms

“…Neuroendocrine factors are secreted from various tissues to inform the brain of the energy status of the cow . When cows consume a supplement, satiety signals cause the cows to graze for less time (12 min/kg of DM concentrate consumed; Bargo et al, 2003;Sheahan et al, 2011) and consume fewer bites/min (i.e., a lower bite rate; Sheahan et al, 2013). Nevertheless, the estimated substitution rate in the present study is high relative to that reported in the literature for well-managed grazing systems (Stockdale, 2000;Linnane et al, 2004;Sheahan et al, 2011).…”

Effect of increased concentrate allotment before evening grazing on herbage intake, nitrogen utilization and rumen fermentation in dairy cows grazed on perennial ryegrass pasture

“…Sheahan et al . () observed a tendency for an increased marginal milk production response (kg of milk/kg of supplement) in cows supplemented in the morning rather than the evening. This is contrary to Trevaskis et al .…”

“…As the silage mixture contained corn silage and grass silage which was made from more maturated grass than pasture grass, total contents of rumen digesta before evening grazing in our study could be greater compared to the cows studied by Sheahan et al . (). Physical rumen distention is another important factor constraining forage intake (Allen ).…”

“…Sheahan et al . () reported that full‐day grazing dairy cows supplemented with concentrate (3 kg DM/day) during the morning milking reduced grazing time during the major morning grazing bout compared to cows supplemented during the evening milking, but grazing time during the major pre‐sunset grazing bout did not differ between them. Their results are contrary to our results of grazing time and herbage DM intake responses to the increased concentrate level before evening grazing.…”

“…Subsequently, Sheahan et al . () tested the effect of concentrate supplementation time on grazing behavior in dairy cows and reported that morning supplementation reduced grazing time during the major morning grazing bout compared to evening supplementation, but supplementation time did not affect grazing time during the major pre‐sunset grazing bout. These results imply that the evening herbage intake, which is the major portion of daily intake (Taweel et al .…”