Fat in Lactation Rations : Review

Abstract

Recent research has demonstrated the effectiveness of added fat in diets to maintain milk production and fat percent. Much of the earlier work which indicated that fat affects digestion negatively may not be applicable because of great differences in the nature of diets and fats fed and especially in total feed intake. Nevertheless, much remains to be learned about interactions of fat, fiber, calcium, and rumen microorganisms if feeding of fat is to be maximized. The uniquely high acidity in the duodenum combined with detergent action of bile acids, lysolecithin, and fatty acids causes saturated fatty acids to be more digestible in ruminants than in nonruminants. Large quantities of added dietary fat increase concentrations in plasma of very low density lipoprotein triglyceride which increases their uptake by the mammary gland with inhibition of short chain fatty acid synthesis and consequent changes in milk fatty acid composition. In some cases, secretion of milk fat is increased. Current research and practice demonstrate that 3 to 5% fat may be added to diets for lactation to increase energy intake of high-producing cows and/or to reduce starch feeding, thereby increasing the ratio of forage to concentrate to prevent depression of milk fat.

Desempenho e características da carcaça de cordeiros confinados alimentados com grãos de soja

“…No entanto, dependendo do teor ou fonte de gordura utilizados, o desempenho do animal pode ser comprometido, pois ácidos graxos polinsaturados de cadeia longa livres são potencialmente tóxicos aos microrganismos ruminais, particularmente aos protozoários e bactérias celulolíticas (Palmquist & Jenkins, 1980), contribuindo para a redução na atividade microbiana e subseqüente digestão (Gibb et al, 2005). Não houve diferença entre os tratamentos para RCQ, RCF e QR, cujas médias observadas foram de 48,9, 47,7 e 2,4%, respectivamente (Tabela 3).…”

Effects of Different Fat Sources on Fermentative Characteristics and Microbial Efficiency in the Rumen, and Nutrients Digestibility of Dairy Cows

“…In addition, A:P ratio was also highest in OIL and lowest in MEG(P < 0.05). Palmquist and Jenkins(1980) observed that A : P ratio in the rumen was reduced by fat supplementation. Generally, characteristic of ruminal fermentation in cows have not been altered by supplementation of as much as 6% of dietary fat (Schauff and Clark, 1989;Klusmeyer et al, 1991;Drackley and Elliott, 1993).…”

“…However, dietary fat supplements are known to cause negative modification to fermentation and nutrient digestion in the rumen. Reductions have been demonstrated in fibre and organic matter digestion, methanogenesis, ammonia concentrations and acetate:propionate value (Devendra and Lewis, 1974;Palmquist and Jenkins, 1980). Therefore, various methods such as formaldehyde-treated emulsions of fat in proteins (Scott et al, 1971), calcium soaps (Jenkins and Palmquist, 1982), heat treatment (Tice et al, 1994), fatty acyl amides (Fotouhi and Jenkins, 1992), the crystalline hydrogenated fat (Elliott et al, 1994) and feeding whole oilseeds (Scollan et al, 2001) for protecting fat sources from rumen metabolism, which offers the possibility that fat sources fed in such a form may interfere less with rumen metabolism.…”

Consumo de forragem e desempenho de novilhas de corte recebendo suplementos em pastagem de azevém

“…O consumo de pasto pelas novilhas que recebiam gordura provavelmente visou a saciar a sua demanda energética, pois a ingestão de dietas com gordura pode fazer com que os animais em pastejo tenham essa demanda atendida mesmo ingerindo uma quantidade menor de pasto (GAGLIOSTRO & CHILLIARD, 1992). A quantidade ingerida de gordura, 3% na MS da dieta, foi inferior ao limite de 5 a 6% na MS da dieta (PALMQUIST & JENKIS, 1980). Conforme esses autores, valores maiores de gordura podem afetar a fermentação ruminal, pela formação de uma camada gordurosa em torno das partículas de fibra, dificultando a ação das bactérias celulolíticas no rúmen.…”