Relation of Diet to Rumen Volatile Fatty Acids, Digestibility, Efficiency of Gain and Degree of Unsaturation of Body Fat in Steers

Studies on the properties of New Zealand butterfat: VIII. The fatty acid composition of the milk fat of cows grazing on ryegrass at two stages of maturity and the composition of the ryegrass lipids

The lipid content of short rotation ryegrass at two stages of growth was followed at weekly intervals for several months in two spring-early summer seasons. Short succulent ryegrass consisting entirely of leaf tissue contained more lipid (mean, 8·1% of the dry weight) than mature ryegrass which contained appreciable stalk (mean, 5·1% of the dry weight). The lipid from the new growth contained fatty acids with appreciably higher proportions of linolenic acid, which was balanced mainly by lower proportions of linoleic and palmitic acids.

When monozygotic twin milking cows were grazed on the short rotation ryegrass grown to two stages of maturity, it was found that the fatty acid composition of the milk fat from the two groups was different. The milk fat of cows grazed on the new growth contained higher proportions of oleic acid and other C18acids, whilst the proportions of myristic and palmitic acids were lower. The total proportions of the short-chain fatty acids were not greatly different, although in the group on new growth butyric acid was present in higher proportions and hexanoic and octanoic acids in lower proportions. The higher unsaturation of the fatty acids in the milk fat of this group of cows may be related to the higher levels of unsaturated fatty acids in the young ryegrass diet and to the extent to which these unsaturated fatty acids are hydrogenated in the rumen.

The effect on growth rate and on milk yield and composition of finely grinding the hay and cooking (flaking) the maize in mixed diets for growing and for milking heifers

The volatile fatty acids produced during fermentation in the rumen have been shown to vary in their nutritive properties. Armstrong & Blaxter (1957) found that for lipogenesis in the adult sheep the value of the acids increases with increasing chain length. Rook & Balch (1961) showed that the individual acids have characteristically different effects on the synthesis of the various constituents of milk. In consequence the nature of the end products of fermentation must be one factor affecting the utilization of foods for productive purposes.

Woodpulp fines or corn silage as roughages in complete rations or a pelleted complete ration for young dairy replacements from birth through 18 weeks of age

Holstein calves, 18 females and 12 males, were assigned randomly to 10 blocks of 3 calves each by sex, and within each block were assigned randomly to one of three experimental rations. All calves received sour colostrum from day 1 through day 35. The respective dry rations were offered beginning at day 8. The three rations consisted of (dry basis): 1) 11% woodpulp fines and 89% concentrate; 2) 33.7% corn silage and 66.3% concentrate; and 3) a commercially available pelleted complete ration. From birth through 8 wk, calves fed woodpulp gained more weight than those fed silage and approximately equal weight to calves fed commercial ration. From 8 through 18 wk. calves fed the latter gained more weight than other calves. Dry matter intake followed the same order as weight gain. Blood samples were obtained biweekly beginning with the 2nd wk from the jugular vein of each calf. There were no differences in glucose 2 through 18 wk. Urea nitrogen of plasma was greater in calves fed commercial ration than in other calves in six of the sampling periods. Calves fed silage had more urea nitrogen in plasma than calves fed woodpulp for three of the sampling periods. Rumen tissue from male calves at 18 wk fed woodpulp showed the most normal appearance in papillae color, density, and length. Calves fed silage had rumen tissue showing short, black, nodular papillae. Calves fed commercial ration showed long, branched, necrotic papillae that were keratotic and loosely attached.

THE ADDITION OF BUFFERS TO RUMINANT RATIONS: I. EFFECT ON WEIGHT GAINS, EFFICIENCY OF GAINS AND CONSUMPTION OF RATIONS WITH AND WITHOUT ROUGHAGE

A total of sixty-eight beef steers were used in three feeding trials to determine the effects of adding buffers to ruminant rations. The buffers used in these trials were sodium propionate and mixtures of sodium bicarbonate, potassium carbonate and calcium carbonate (as ground limestone). They were fed at levels varying from 2 to 9 pounds per 100 pounds of the concentrate ration. Data on feed consumption, weight gains and efficiency of feed conversion are presented.The addition of buffers to a ration containing timothy hay fed ad libitum did not prove beneficial. Buffers at the highest level (9 pounds per 100 pounds) were detrimental in the hay-concentrate ration. When the hay was removed from the ration there were highly significant decreases in weight gains and T.D.N. consumption. These decreases were partially offset by the addition of buffers to the all-concentrate rations. The results may have a practical application in the feeding of low-roughage rations.