Influence of source and amount of dietary protein on performance, blood metabolites, and reproductive function of primiparous beef cows.
Forty Angus x Hereford 2-yr-old primiparous cows (358 kg) were used to determine the effects of source and amount of CP on performance, reproductive function, and metabolic status of suckled primiparous cows. A 2 x 2 factorial treatment arrangement was used; cows received either 100 or 150% of NRC recommendations for CP in diets that contained either soybean meal (low escape = L) or corn gluten meal/blood meal (high escape = H) as the principal supplemental protein source. Resulting treatments were 100-L, 100-H, 150-L, and 150-H. Cows were individually fed diets for 100 d or until they were observed to be in standing estrus. Diets were isoenergetic and limit-fed to meet NRC recommendations for NE, Ca, and P for 364-kg, 2-yr-old primiparous cows producing 4.5 kg of milk daily and gaining .23 kg/d. Increased CP tended (P = .09) to increase ADG in cows, but body condition score was unaffected. Increased CP and use of a CP source with higher potential for ruminal escape increased ADG in calves from d 0 to 97 (P = .002 and .04, respectively), which corresponded with numerical changes in milk production. Feeding high escape CP sources decreased plasma glucose and urea N (P = .04 and .0001, respectively). Increased CP tended (P = .12) to increase plasma glucose and increased (P = .0001) plasma urea N. Treatment had no effect on profiles of LH or progesterone. Although numerical differences in conception rate seemed large for 100-L compared with the remaining treatments, statistical significance was not detected.(ABSTRACT TRUNCATED AT 250 WORDS)
Rusche
W C
WC
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-0201.
Cochran
R C
RC
Corah
L R
LR
Stevenson
J S
JS
Harmon
D L
DL
Brandt
R T
RT
Minton
J E
JE
D000821:Animal Feed; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000097:blood / Q000254:growth & development / Q000502:physiology*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D005298:Fertility; D007774:Lactation / Q000097:blood / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood; D010298:Parity; D049590:Postpartum Period / Q000097:blood / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood / Q000502:physiology*; D011897:Random Allocation; D015430:Weight Gain
D001786:Blood Glucose; D004044:Dietary Proteins; D007986:Luteinizing Hormone