title: Effects of differences in starch content of diets with whole cottonseed or rice bran on milk casein.
abstract: Forty lactating Holstein cows in early to midlactation were used in a randomized complete block design to measure the effects of the following diets on milk casein. Treatments were four complete rations fed for ad libitum intake consisting of 1) 60% concentrate, 10% alfalfa hay, and 30% corn silage; 2) 45% concentrate, 10% alfalfa hay, 30% corn silage, and 15% whole cottonseed; 3) 60% concentrate, 5% alfalfa hay, 20% corn silage, and 15% whole cottonseed; and 4) 45% concentrate, 10% alfalfa hay, 30% corn silage, and 15% rice bran. Least squares means for daily DM intake all were significantly different and were 3.51, 3.90, 3.28, and 3.74% BW, respectively. Cows fed diet 3 had higher arterial glucose and insulin and venous insulin. Least squares means were significantly different for milk yield, 30.1, 31.4, 28.4, and 31.6 kg/d; for milk protein, 3.30, 3.13, 3.48, and 3.12%; and for casein N, .376, .358, 3.73, and .330, respectively. However, milk protein and casein N yields were similar for all cows. The diet that contained the highest percentage of starch did not result in a significantly higher percentage of casein N in the milk but had the lowest milk production. Both whole cottonseed and rice bran, substituted for concentrate, depressed milk protein percentage.
authors.affiliation: Department of Animal Science, Texas A&M University, College Station 77843.
authors.forename: D L
authors.initials: DL
authors.lastname: Wilks
authors.forename: C E
authors.initials: CE
authors.lastname: Coppock
authors.forename: K N
authors.initials: KN
authors.lastname: Brooks
authors.forename: C E
authors.initials: CE
authors.lastname: Gates
mesh_terms: D000821:Animal Feed; D000818:Animals; D002364:Caseins / Q000096:biosynthesis*; D002417:Cattle / Q000502:physiology*; D003369:Cottonseed Oil; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004435:Eating; D005260:Female; D007774:Lactation / Q000502:physiology*; D016018:Least-Squares Analysis; D008892:Milk / Q000737:chemistry* / Q000378:metabolism; D012275:Oryza; D011897:Random Allocation; D013213:Starch / Q000378:metabolism
chemical_list: D002364:Caseins; D003369:Cottonseed Oil; D004040:Dietary Carbohydrates; D013213:Starch