662. The comparative efficiency of some methods of estimating the live weight of dairy cows

SummaryThirty-six lactating cows were used in a 3×2 factorial design experiment to study the effects of level of energy and fibre intake on milk yield and composition over an 8-week experimental period. Three levels of fibre intake — 1g of crude fibre per 25, 17·5 and 10 kcal of estimated metabolizable energy (ME) requirements — were given in diets supplying both 80 and 100% of energy requirements. The level of energy intake significantly affected milk yield, milk energy output and the percentage solids-not-fat (SNF) and protein in the milk. The effects of fibre intake on both milk yield and milk energy output were marked but not significant. Fibre intake had a significant curvilinear effect on both the SNF and protein in the milk with the highest fibre intake resulting in a significant decrease in both fractions. A significant linear decrease was obtained in the lactose fraction as the fibre intake increased.The total volatile fatty acid (VFA) level in the rumen was significantly affected by both energy and fibre intake. The level of energy intake only significantly affected the proportion of propionic acid. Fibre intake significantly affected the proportion of both acetic and butyric acids resulting in mean proportions of acetic acid of 66, 70 and 72 at the low, medium and high fibre intakes. The correlations between the rumen acids and lactation efficiencies are also presented.Multiple regression analysis within each fibre level has been used to partition the ME available for production between that used for milk energy output and liveweight change. The results showed efficiencies of utilization of ME for milk output of 66, 65 and 56 on the low, medium and high fibre diets respectively.Nitrogen balance data are presented.

Section: Effect Of Energy Intake On Milk Yield and Compositionsupporting

confidence: 92%

Section: Effect Of Energy Intake On Milk Yield and Compositionsupporting

confidence: 92%

Effect of fibre level in the diet of the dairy cow on milk yield and composition

Gordon¹,

Forbes²

1971

“…It is generally accepted (Burt, 1957) that level of feeding, with the exception of marked underfeeding, has little effect on the lactose content of milk, and the results presented here are in agreement. The changes in lactose percentage with grazing were small: the mean increase was greater for the 'low-energy' than for the 'highenergy' groups in each test-period, but did not reach significance.…”

Section: Lactosesupporting

confidence: 89%

The effect of the plane of energy nutrition of the cow during the late winter-feeding period on the changes in the solids-not-fat content of milk during the spring-grazing period

Rook¹,

Rowland²

1960

Three groups of eight Friesian cows, four of high and four of low milk yield, were given during the last month of the winter-feeding period rations that provided respectively low, normal and high planes of energy nutrition, at approximately 75,100 and 130% of the Woodman standards for starch equivalent (s.E.). They were then all changed to the grazing of good, spring pasture, without supplementary food. The changes with grazing in solids-not-fat (S.N.F.) content and yield of milk were markedly influenced by the previous level of winter feeding. After 15-18 days of grazing the mean changes in S.N.F. percentage were +0-33, +0-11 and -0-12 for the low, normal and high energy groups, and the corresponding changes in milk yield were +7-70, +2-13 and -0-68 lb per cow per day.

“…On at least three occasions(i,2,]9), the S.N.F. percentage in the milk of cows has been increased by extra feeding; Burt (3,20), however, recorded a variable effect in a group of broadly similar experiments conducted at various centres.…”

Section: Discussionmentioning

confidence: 96%

724. Levels of feeding of concentrates for dairy heifers before and after calving

Broster

Ridler

Foot

1958

1. Two levels of steaming-up and two levels of concentrates feeding during the first 84 days of lactation have been compared in a 2 x 2 factorial experiment over three winter seasons, using fifty-two Shorthorn and thirty-six Friesian heifers. The levels of steaming up were 2 cwt. and ½ cwt. of concentrates fed over the last 21 and 14 days of pregnancy, respectively. The levels of concentrates during lactation were 5 and 3 lb. per 10 lb. milk per day. Roughages were fed for maintenance. After the 84th day of lactation all animals were given the same treatment for the remainder of the lactation. Milk yield, milk composition and live weight were measured throughout the lactation.2. The treatments were annotated as HH, HL, LH and LL, the first letter indicating level of steaming-up and the second the level of concentrates feeding in the first 12 weeks of lactation.3. Mean milk yields were as follows:4. The LH treatment reqiuird 3 cwt. more concentrates than HL to produce the same amount of milk.5. The response to additioal concentrates on the LH treatment after calving was l lb. additional milk per l lb. additional starch equivalent.6. Butterfat percentages were higher (3·69%) in both groups on low-lactation feeding than in the two groups on high-lactation feeding (3·43%). The HL group (i.e. the group that received high steaming-up and low-lactation feeding) combined high milk yield with a higher butterfat percentage, and at current milk and feedingstuff prices and under the conditions of the trials, this group showed a greater cash return than the groups on the other three treatments.