Assessment of cyclopropenoic acid levels in commercially available Australian whole cottonseeds and cottonseed meals

Summary

Carcases having hard fat at boning temperatures are a significant problem for the Australian beef industry and attempts to minimise the problem by modifying temperature cycles can have an adverse effect on meat quality. Feeding of whole cottonseed to cattle has been implicated in contributing to increased fat hardness through the presence of cyclopropenoic fatty acids (CPFA) present in the oil. It was the aim of this study to determine the CPFA contents of the major varieties of cottonseeds used for cotton production in Australia and to determine if differences occurred between varieties. These values were compared with published values for whole cottonseeds from other countries.

Twenty-five varieties of commercial Australian cottonseeds were analysed for their oil contents, fatty acid compositions and for their CPFA contents. Whole cottonseeds were obtained from four locations ranging from central NSW to central Queensland and some varieties were obtained from two seasons. The total oil content of linted whole cottonseed did not significantly differ between varieties and accounted for about 21% of the weight. Seeds of unknown origins obtained from feedlots were highly variable in oil contents and had a mean value of about 17%. The oil content of cottonseed meal, a crushed de-fatted product, was about 3%. The fatty acid composition of the extracted oils was remarkably constant across varieties, locations and seasons (yields from 2 years). The major fatty acids present in cottonseed oils were linoleic acid (56.7 - 1.61%), palmitic acid (23.0 - 1.09%), oleic acid (15.0 - 1.11%) and stearic acid (2.29 - 0.11%) and these values are fairly similar to those previously reported for different varieties. The fatty acid compositions of the varieties containing the INGARD gene were not significantly different from the standard varieties. The content of total CPFA was generally below 0.8% of the total fatty acids with malvalic acid being the major CPFA (0.38%) followed by sterculic acid (0.19%).

Overall, values for all varieties were fairly constant ranging from means of 0.38 to 0.75% but most falling between 0.5-0.6% of the total fatty acids. The lowest value for CPFA was obtained with the variety Pima S-7. On the other hand, individual values of CPFA for some varieties approached 0.8% (variety CS8S) with malvalic acid being 0.5%. INGARD varieties were not different from the standard. Analysis of single varieties grown in several locations, some from two seasons, did not show any significant variation. The off-grade varieties of seeds appeared to have a significantly higher content of CPFA compared with those product-grade varieties obtained at the same time. Thus, given several exceptions, it would appear that the content of CPFA in extracted oils from most varieties of cottonseeds is quite similar.

Furthermore, their contents are similar to and not higher than those reported for the US and other countries. On the basis of these findings, there would appear to be little advantage in selecting particular varieties of cottonseeds for use as feeds for feedlot cattle. Whilst Pima S-7 does have somewhat lower CPFA contents, its use as a feed ingredient would be limited as it is not widely available. The requirement for evaluation of a field method for assessing the CPFA contents in oils of whole cottonseed and meals was not necessary in view of the outcome of this study. However, a literature search was undertaken to find, or develop, a rapid, safe and easy to use field method. All methods found and reported here were unsuitable for this purpose because of their complexity, equipment needs or requiring use of hazardous chemicals.