It is well accept- ed that sup- plemental ru- men-protected fat benefits herd reproductive performance by minimising body weight loss and accelerating body weight gain after calving.


Effects on digestibility of nutrients There was no effect of supplementation of protected fat on the digestibility of most of the feed nutrients, but the digesti- bility of Ether Extract (EE) increased significantly from 73% to 85.5% when protected fat was supplemented in the diet of the dairy animals. The increase in the digestibility of the fat indicates that added fat is more digestible than the basal diet fat or fat supplementation dilutes the endogenous lipid se- cretions, resulting in a more accurate estimate of the true lipid digestibility. Protein digestibility also increases with pro- tected fat supplementation, but in other cases no increase in protein digestibility was noted. Fibre digestibility varied with the level of protected fat supplementation in the diet and was not affected at the low level of supplementation.


Reproduction It is well accepted that supplemental rumen-protected fat benefits herd reproductive performance by minimising body weight loss and accelerating body weight gain after calving. In addition, research strongly suggests that unsaturated veg- etable fatty acids could have additive effects on reproductive parameters in the cow, including follicular size and hormone patterns. Linoleic acid has been identified as one of the es- sential fatty acids that may have direct effects on reproduc- tive function. The higher linoleic acid level is the basis for at least one rumen-protected fat product that is promoted with- in the feed industry for its supposed ability to improve reproductive performance.


Milk production According to many reports, a significant increase of 5.5– 24.0% in the milk yield of dairy animals was observed when fed supplemented bypass fat. The stage of lactation influenc- es the supplemental effect of the bypass fat on milk yield and


26 ▶ DAIRY GLOBAL | Volume 8, No. 3, 2021


Fat Corrected Milk (FCM) yield which is generally increased in early and peak lactation, probably due to the higher energy intake, more efficient use of fat by the mammary gland and enhancement of tissue mobilisation before peak production. It was reported that the FCM yield of lactating cows was increased when Ca-LCFA was supplemented at up to 6% of the dietary DM but decreased at 9% of the dietary DM. Sup- plementation of bypass fat adversely affects the milk protein percentage (-0.12 percentage unit) due to the dilution of milk protein as higher milk volume synthesised is not synchro- nised with the uptake of amino acids by the mammary gland.


Effects on heat-stressed animals It makes sense that enhancing ration energy density by utilis- ing fats could be particularly beneficial during hot weather. However, research on the effects of feeding high-fat rations during hot weather has yielded inconsistent results. This is probably because it is very easy to overfeed unprotected fat sources, such as whole oilseeds, when the cow’s feed intake is significantly reduced due to heat stress. If fat is overfed, then the negative effects of the fat on fibre digestibility will negate any possible gains with increased ration density. Because bypass fats do not affect rumen fermentation, they should probably make up a greater percentage of the total fat included in the ration during hot weather.


Economic benefits Feeding of protected fat to dairy animals has been shown to give a profit of US$ 1.3 per cow per day, apart from the im- provement in reproductive performance and health of animals. An additional profit of US$ 0.6 per animal per day can be made when feeding bypass protein together with the protected fat.


References are available from the author upon request.


PHOTO: H. HACH | PIXABAY


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