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Title: Milk production responses of beef cows in a drylot system

item SPENCER, COURTNEY - Oklahoma State University
item BAYLIFF, CORBIT - Oklahoma State University
item REDDEN, MILES - Oklahoma State University
item MCGEE, ADAM - Oklahoma State University
item REUTER, RYAN - Oklahoma State University
item HORN, GERALD - Oklahoma State University
item Moffet, Corey
item LALMAN, DAVID - Oklahoma State University

Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Breed association genetic trends indicate that the genetic potential for milk yield in several popular breeds has dramatically increased over the past 25 years. However, little data is available characterizing the dynamic relationship of milk yield, milk composition and calf performance to energy intake. Therefore, the objective of this experiment was to determine the milk yield and milk composition responses of lactating beef cows over a range of feed energy intake. Two experiments were conducted in consecutive yr using a total of 80 beef cow/calf pairs (40 per yr). Each yr, 8 cow/calf pairs were assigned to one of 5 energy intake levels (135, 159, 176, 200, and 223 kcal NEm·kg BW-0.75·d-1 for 111 d until weaning in yr one and 142, 159, 177, 193, and 212 kcal NEm·kg BW-0.75·d-1 for 125 d until weaning in yr two). Each pen of 8 cows and their calves were managed together as contemporaries and group fed. The range of feed energy intakes was accomplished by varying the amount of feed provided to the cows, while the calves had ad libitum access to the same diet in a creep area. Calves did not have access to the cows’ feed. Cow body weight, body condition, milk yield and composition, and calf BW gain and creep feed intake were measured. Dependent variables were regressed on linear and quadratic terms of energy intake. The mixed model included year as a random effect and treatment energy level as a fixed effect. Quadratic regression models were not significant (P > 0.05). Milk yield (P = 0.004), milk fat percentage (P = 0.017), milk urea nitrogen (P = 0.028), milk protein percentage (P = 0.005), and solids non-fat (P = 0.002) increased linearly with increasing cow energy intake. Each additional kcal of NEm·kg BW-0.75·d-1 resulted in 0.41 g of additional milk yield ·kg BW-0.75·d-1. Efficiency of conversion of cow energy intake to milk energy production was 0.36. Under these conditions, increasing cow energy intake to increase milk energy production was not efficient.