Symposium review: Re-evaluation of National Research Council energy estimates in calf starters

Abstract

Provision of nutrients in appropriate amounts to meet nutrient requirements for growth, production, and reproduction is the basis for modern animal nutrition. Ration formulation systems predict nutrient requirements based on numerous inputs and then predict nutrient supply based on predicted intake and nutrient content of feeds. Energy systems are used to predict energy supply based on gross caloric content of feeds followed by adjustments for digestion and metabolism of ingested energy. Many models of energy supply use static coefficients of digestibility based on nutrient composition of feed. Other models partition digestion dynamically between ruminal and postruminal digestion but use static estimates of intestinal digestibility to predict energy supplied to the animal. In young calves, both ruminal fermentation and intestinal digestion are underdeveloped; therefore, existing models of energy supply might overestimate the energy available before complete gastrointestinal maturation. In a series of experiments, we reported that total-tract digestion of nutrients changes with advancing age and nutrient intake. Total-tract digestion was measured in calves from 3 to 16 wk of age when fed different amounts and types of milk replacers. Calves were also fed different types of calf starter for ad libitum consumption. Total-tract digestibility of protein, fat, neutral detergent fiber, and nonfiber carbohydrate (NFC) was used to calculate the metabolizable energy (ME) in starter. We used nonlinear regression to estimate the contribution of protein and fat from starter and milk replacer before weaning. Early in life, calculated ME of starter was low and increased with increasing intake of NFC. Cumulative intake of NFC was more highly correlated with changing ME values than other indices, including age, intake of milk replacer, or intake of other nutrients in starter. When calves consumed at least of 15 kg of NFC, ME calculated from digestibility measurements was similar to the ME calculated using National Research Council equations and indicated maturation of gastrointestinal digestion. Our data suggest that intake of NFC is critical to gastrointestinal maturation and the calf's ability to extract energy from calf starter.

Calf starter containing a blend of essential oils and prebiotics affects the growth performance of Holstein calves

“…Thus, different EO can exert different effects on nutrient digestibility. These digestibility coefficients are within the ranges and similar to those recently published by Quigley (2019).…”

Early feeding strategies in lambs affect rumen development and growth performance, with advantages persisting for two weeks after the transition to fattening diets

“…Previous studies have suggested that a comparatively low number of amino acids and peptides may be absorbed and metabolized by the rumen tissue ( 88 ). However, the development of the rumen epithelium requires increased cell and protein turnover ( 25 , 89 ). In the present study, many upregulated DEGs in the ES + EW group were annotated in pathways related to amino acid metabolism, including biosynthesis of amino acids, cysteine and methionine metabolism, arginine and proline metabolism, valine, leucine, and isoleucine degradation; glycine, serine, and threonine metabolism; and lysine degradation.…”

Models to predict dry feed intake in Holstein calves to 4 months of age

“…Increasing forage in rations reduced total DFI, as indicated by the negative coefficient for PctForage in both nonlinear and linear models. Reduced DFI with increasing forage in the diet has been reported (Hill et al, 2008;2010b, 2019, although others reported increasing DFI with forage in the diet (Coverdale et al, 2004;Khan et al, 2011b). Measurement of long forage intake is often difficult and may increase error associated with DFI measurements.…”

“…For example, the 2001 Dairy NRC model assumes that DFI is the amount of feed required to provide ME to achieve a target rate of ADG (NRC, 2001). Because it has been shown recently that the ME in CS is not a fixed value (Quigley, 2019;Quigley et al, 2019a,b), prediction of the contribution of ME from dry feed may be difficult, thereby confounding prediction of DFI.…”