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Effects of Photoperiod and Pair-Feeding on Lactation of Cows Fed Corn or Barley Grain in Total Mixed Rations¹

Laval University, Québec, Québec, Canada G1K 7P4

D. Petitclerc², N. St. Pierre and G. Pelletier

Agriculture Canada Research Station, Lennoxville, Québec, Canada, J1M 1Z3

G. J. St. Laurent

Laval University, Québec, Québec, Canada G1K 7P4

ABSTRACT

Effects of photoperiod and type of grain were assessed using 47 cows (wk 1; 59.5 d of lactation) exposed daily to 16 h of light (long day) and fed randomly one of two diets containing an equal amount of cracked corn or rolled barley. During wk 5, cows were assigned within each diet to long day and ad libitum feeding, short day (8 h of light: 2 h of dark: 2 h of light: 12 h of dark) and ad libitum feeding, or long day and ad libitum feeding (wk 5 to 8) followed by pair feeding with short day cows between wk 9 and 16. Milk composition was not affected by treatments. Between wk 9 and 16, long day cows fed for ad libitum consumption or pair fed produced 5 to 11% more milk than cows exposed to short day; feed intake of long day cows fed for ad libitum consumption was greater than short day and long day pair fed cows. Milk yield and total feed intake were not affected by type of grain in the diet. In conclusion, long day photoperiod increased milk yield and feed intake. Feeding cows from peak of lactation with barley or corn in total mixed rations did not affect milk production.

¹ Lennoxville Research Station Contribution No. 266.

² Reprint requests should be addressed to: Denis Petit-clerc, Agriculture Canada, Research Station, PO Box 90, Lennoxville, Quebec J1M 1Z3.

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