The U.S. National Research Council

An experiment was conducted on two dairy farms in Puerto Rico (Gurabo and Cidra) from September 1998 to July 1999 with the objective of quantifying chloride (Cl-) concentrations and uptake in grazed forage, Aif plots were fertilized with the equivalent amount of 330,110, and 220 kg/ha/yr (N, P205, K20) and the treatments consisted of four Cl- levels (0, 82,164, and 328 kg/ha/yr) split in four applications. Forage was harvested every 28 days during the seven-month experiment. Plant Cl- concentrations were determined by means of a potentiometric titration in the laboratory. Yields (fresh and dry weight) were not significantly affected by Cl- levels, which suggests that background soil concentrations were sufficiently high so as not to limit plant growth. Mean monthly Cl- concentrations in forage tissue were significantly affected by Cl- levels, increasing from 0.79 to 0.82% in Cidra and from 0.68 to 0.96% in Gurabo. Cumulative Cl- uptake by forage in the sevenmonth study period for the highest Cl- treatment was 124 and 161 kg/ha in Cidra and Gurabo, respectively. Our data suggest that excess Cl- in milk does not necessarily originate from Cl-containing fertilizer. Estimated CI consumption by dairy cows consuming tropical forages and concentrate is higher than that suggested by the U.S. National Research Council.

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PERFORMANCE OF BEEF STEER CALVES DURING WINTER AND ON PASTURE AS AFFECTED BY FEEDING A WINTERING RATION AT DIFFERENT LEVELS WITH AND WITHOUT ADDED FAT

Canadian Journal of Animal Science ◽

10.4141/cjas68-052 ◽

1968 ◽

Vol 48 (3) ◽

pp. 397-402

Author(s):

C. D. T. Cameron

Keyword(s):

Research Council ◽

National Research Council ◽

Feed Utilization ◽

Feed Conversion ◽

Fiber Digestion ◽

Grazing Period ◽

Beef Steer ◽

Different Levels ◽

The U.S ◽

Total Digestible Nutrient

Gains by Hereford and Angus steer calves overwintered at a total digestible nutrient (TDN) level of intake 14% above the U.S. National Research Council standard were still greater at the end of a 100-day grazing period than those by comparable calves wintered on approximately 2, 8, 14, or 22% lower levels of intake. There was little difference in gains at the end of the grazing period between the calves fed at the two lower feeding levels. The TDN:gain ratio for the calves fed at the lowest level of intake (1.13 kg TDN daily/100 kg body weight) was significantly (P < 0.01) greater than those for the calves on higher levels of intake.Mean gains by the calves fed added fat were greater during the winter and the subsequent grazing period than those by calves on corresponding rations without added fat. Calves fed added fat were significantly (P < 0.01) more efficient in feed utilization than those that did not receive added fat in their diets.Within the relatively narrow intake ranges studied, apparent digestibility of ration components other than crude fiber were not affected by level of intake. Fiber digestion coefficients by the calves fed at the higher levels of intake were greater (P < 0.05) than those by the calves on the lowest feeding level.Winter and summer gains were greater (P < 0.05 and P < 0.01, respectively) and efficiency of feed conversion was higher (P < 0.01) for Hereford than for Angus calves.

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