Protein Degradability and Calcium Salts of Long-Chain Fatty Acids in the Diets of Lactating Dairy Cows: Productive Responses

Abstract

Our objective was to evaluate the effect of excessive intake of ruminally degradable crude protein [11.1 and 15.7% of dietary dry matter (DM)] and supplemental fat (Ca salts of long-chain fatty acids at 0 or 2.2% of dietary DM) on the productive performance of lactating Holstein cows (n = 45) during the first 120 d postpartum. The main N sources were soybean meal and urea in the diets with high concentrations of degradable protein versus a combination of vegetable and animal by-product feedstuffs in the diets with less degradable protein. Cows fed the diets with excess degradable protein had slower rates of increase in DM intake (DMI) and milk production, had lower plasma insulin and greater plasma glucose and urea concentrations, and lost more than twice the body weight of cows fed the diets with less degradable protein. Supplemental fat in the highly degradable protein diet reduced the loss of body condition, stimulated DMI, and reduced concentrations of plasma nonesterified fatty acids early postpartum compared with the highly degradable protein diet without added fat. Without affecting DMI, supplemental fat stimulated milk production (2 kg/d) starting at 3 wk postpartum. During early lactation, DMI and milk production were sensitive to the degree of ruminal degradability of protein and energy supplementation in the form of fat.

Effect of dietary energy source on energy balance, production, metabolic disorders and reproduction in lactating dairy cattle

“…This theory is supported by firstly other studies that found a positive relationship between elevated NEFA, decreased glucose levels and the incidence of fatty liver [58,59,89]; secondly, evidence that indicates the relationship between liver triglyceride content and plasma NEFA concentrations [59]; and thirdly, associations between dietary fat supplementation and elevated plasma NEFA levels [9,63].…”

“…The number of days open are reported to be reduced by glycogenic nutrient supplementation in two out of three studies [77,118]. A few studies (3 out of 10 studies) [62,63,65,67,101,102,105,126] showed a decrease in the number of days open after fat addition to the diet.…”

“…Table I shows reported effects of feeding either extra glycogenic or lipogenic nutrients on plasma NEFA, BHBA, glucose, insulin and growth hormone (GH) levels. Concerning plasma NEFA levels, 13 [9, [60][61][62][63][64][65][66][67][68] out of 15 studies found an increase after feeding extra lipogenic nutrients. In contrast to studies where extra glycogenic nutrients were fed, 13 [60,61,66,[68][69][70][71][72][73] out of 14 reported studies found a decrease in plasma NEFA levels.…”

“…In general, the negative effect of extra lipogenic sources on dry matter intake is higher when the degree of saturation of fatty acids is lower, probably because of the more pronounced negative effects of unsaturated fatty acids on rumen carbohydrate fermentation. As a result, 73% of the studies on feeding extra lipogenic nutrients [15,61,63,65,75,100,101,104,106] and also 73% of the studies on increasing dietary glycogenic nutrients [61,[69][70][71][72]117] obtained a higher net energy (NE) intake in the treatment group compared to the control group, illustrated by Figure 4 shows an overview of studies that reported milk yield and composition after feeding either more glycogenic nutrients or lipogenic nutrients. Both feeding extra lipogenic nutrients or glycogenic nutrients had similar effects on kg of milk produced per day [8, 15, 60-72, 75, 77, 78, 82, 99-104, 106, 107, 110, 111, 115-122] …”

“…In addition, several studies found increased pregnancy rates [15,62,63,122,127], elevated plasma progesterone (P4) level [15,62,63,105], increased diameters of preovulatory follicles [64] and greater follicular populations [127][128][129] after dietary fat supplementation. However, other groups detected a negative relation between dietary fat addition and follicular development [9], pregnancy rates [65,104,125] or plasma P4 concentration [64].…”