Browsing by Author "Breytenbach, Stephan"

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    Effect of forage type and cottonseed supplementation on the production of dairy cows
    (Stellenbosch : Stellenbosch University, 1997) Breytenbach, Stephan; Coetzee, J.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: The type of forage seems to influence the production response of dairy cows receiving supplements of whole cottonseed. Literature indicated that supplementation of whole cottonseed in diets with maize silage as the only dietary forage resulted in improved milk yields but depressions in the milk fat content. It was also indicated in the literature that milk fat depression was alleviated when 10 to 20% of the maize silage were substituted with luceme hay. Oat silage is the main source of forage for large numbers of lactating dairy cattle in the Western Cape. The question that needs to be answered is whether this depression in milk fat is a property of maize silage, or also of oat silage. Diets containing approximately 7% fat (DM), mainly from whole cottonseed, and approximately 3% fat (DM) were used to evaluate the in sacco degradability of oat silage, maize silage and luceme hay. The degradability of the samples in the rumen was fitted on the exponential equation p =a+ b(l - e-ct). Effective degradation ofDM, OM, NDF and ADF was calculated for each treatment by introducing fractional outflow rates of 0.02, 0.05 and 0.08/h. There was no difference in the degradability of the three forages within the same diet. Effective degradability of DM, OM and ADF did not differ in effective degradability between the two diets. The effective NDF degradability was lower (p < 0.05) in the cottonseed supplemented diet at an outflow rate of 0.08/h. The oat silage in six commercial diets was substituted at different rates by luceme hay. Diets contained either whole cottonseed supplemented at 18% of DM or no inclusion of cottonseed. Twelve lactating dairy cows were used in a change-over experimental design. The inclusion of whole cottonseed did not affect milk yield, improved (p < 0.05) milk fat percentage from 3.09 to 3.33% and decreased (p < 0.05) milk protein percentage from 2.84 to 2.75%. Dry matter intake was significantly lower (p < 0.05) on the whole cottonseed diets (17.8 vs. 18.2 kg/cow/day). As expected, the inclusion of whole cottonseed shifted the fatty acid composition of milk fat from short chain fatty acids to more longer chain fatty acids. It was difficult to quantify this change in fatty acid composition due to interactions between the levels of forage and the cottonseed inclusion. The inclusion levels of oat silage and luceme hay were compliments of each other. Significant differences could therefore be due to the increasing levels of luceme hay or the decreasing levels of oat silage. An increase in the amount of luceme included in the diets led to significant differences in almost all the production responses measured Milk fat percentage being the only exception. Even milk fat percentage showed an increase, although not significant. Whole cottonseed can be included in diets with oat silage as the only dietary forage. The price of whole cottonseed, the milk price structure of the milk buyer and the genetic potential of the cows will determine the economic viability of whole cottonseed inclusion.