12 CIRCULAR 870 ; U. S. DEPARTMENT OF AGRICULTURE 



pastures, except for 2 years when end of the period was estimated from 

 climatic records: 1935, the year before pastures were stocked, and 1937, 

 when cattle were placed in them about 6 weeks too early. 



The starting date for this period, for all 14 years of study, averaged 

 October 24, but differed considerably from year to year. The interval 

 between germination of seed and restriction of plant growth by low 

 temperatures averaged about 3 weeks but varied from to 76 days. 

 Green forage produced during this interval was not sufficient in any year 

 to maintain satisfactory cattle gains during the entire fall-winter period. 



In some years, however, forage growth after early rains was sufficient 

 to produce gains of cattle early in the fall. For example, in 1939 — the 

 year with earliest effective rainfall — there was a good start of forage 

 growth after a total of 1.97 inches of rainfall between September 25 and 

 October 7, and the unsupplemented yearling heifers gained in weight. 

 Later, during a drought that extended into January, plant growth was 

 stopped and many plants died. The unsupplemented heifers stopped 

 gaining in weight, but they ended the fall-winter period with a net gain 

 of about 40 pounds each. 



There was considerable variation in plant growth and cattle gains 

 in other years, but the poorest fall growth of forage occurred during the 

 1937-38 and 1943-44 seasons when the first effective rains occurred late 

 in the fall, after mean daily temperatures were below 50°. In these two 

 seasons the unsupplemented heifers lost about 20 to 25 pounds each 

 during the period of inadequate green forage. 



Poor growth of forage in the fall also means that green forage will not 

 be adequate in amount until late in the winter. For example, in the 

 1937-38 and 1943-44 seasons, feeding of supplements was needed until 

 late February or early March. 



Even when good growth of forage occurs in early fall, the end of supple- 

 mental feeding cannot be predicted with certainty. Cold weather during 

 the winter, often coincident with dry weather, may halt plant growth 

 before the green forage is adequate in amount. Also, part of the avail- 

 able forage may be frozen back after being judged adequate, making it 

 advisable to resume feeding. This happened in two of the five years 

 when feeding was terminated before January 15. However, there seems 

 to be little likelihood of prolonged forage scarcity when supplemental 

 feeding is terminated in February. 



DEPENDABLE GREEN FORAGE IN SPRING 



The period of most dependable forage is approximately 4 months long, 

 from January or February into June. During this period the vegetation 

 develops from early-leaf stage through seedstalk, flower, and mature- 

 fruit stages. In these stages of plant development the mixed cover of 

 many plant species provides an adequate amount of well-balanced cattle 

 forage. 



Several signs can be used in late winter to judge when green forage is 

 adequate in amount. The grasses average 2 to 3 inches high but are 

 considerably taller under trees or in other areas where conditions have 

 been favorable for plant growth. Some plants of early-growing species 

 such as slender oat may be 6 inches high or taller. Filaree is 1.5 to 2.0 

 inches high on the average and considerably taller on small spots. Young 

 animals usually wall have started to gain in weight when the forage has 



