Effects of supplement feeding order on lactation, diurnal variation of ruminal ammonia and urea in the blood and milk of dairy cows

Effect of the timing of sodium acetate infusion on the daily rhythms of milk synthesis and plasma metabolites and hormones in Holstein cows

Dairy cows have a daily pattern of feed intake which influences ruminal fermentation and nutrient absorption. Milk synthesis also exhibits a daily rhythm and is altered by the timing of feed availability. Nutrients can regulate physiological rhythms, but it is unclear which specific nutrients affect the rhythms of milk synthesis in the cow. The objective of this study was to determine the effect of the timing of acetate infusion on the daily rhythms of feed intake, milk synthesis, milk fatty acids, plasma insulin and metabolites, and core body temperature. Ten lactating ruminally cannulated Holstein cows (127 ± 24.6 d in milk; mean ± standard deviation) were arranged in a 3 × 3 Latin square design. Treatments were ruminal infusions of 600 g/d of acetate either continuously throughout the day (CON) or over 8 h/d during the day (day treatment, DT; 0900 to 1700 h) or the night (night treatment, NT; 2100 to 0500 h). Experimental periods were 14 d with a 7-d washout between periods. Cows were milked every 6 h during the final 7 d of each experimental period to determine the daily pattern of milk synthesis. Blood samples were taken to represent every 4 h across the day and plasma glucose, insulin, β-hydroxybutyrate, urea nitrogen, and acetate concentration were measured. An intravaginal temperature logger was used to measure core body temperature. Data were analyzed with cosinor-based rhythmometry to test the fit of a cosine function with a period of 24 h and to determine the acrophase (time at peak) and amplitude (peak to mean) of each rhythm. Milk yield fit a daily rhythm for all treatments and DT and NT phase-delayed the rhythm and DT increased the robustness of the rhythm. Milk protein concentration fit a daily rhythm for all treatments and DT increased robustness, whereas NT phase-delayed the rhythm. Plasma acetate concentration also fit a daily rhythm in all treatments. Plasma acetate peaked at ∼1600 h in CON and DT and at 0053 h in NT, reflecting the timing of treatment infusions. There was a daily rhythm in plasma β-hydroxybutyrate that reflected the plasma acetate rhythm. Core body temperature fit a rhythm for all treatments, but the amplitude of the rhythm was smaller than previously observed. In conclusion, the timing of acetate infusion influences peripheral rhythms of milk synthesis and plasma metabolites.

Determination of nitrogen balance in goats fed a meal produced from hydrolyzed spent hen hard tissues

To provide an economically viable and environmentally sound method for disposing of spent laying hens, we manufactured a proteinaceous meal from the hard tissue fraction of mechanically deboned laying hens (primarily feathers, bones, and connective tissue). We hydrolyzed the hard tissue and coextruded it with soybean hulls to create a novel feather and bone meal (FBM) containing 94.2% DM, 23.1% CP, 54.5% NDF, and 7.3% fat (DM basis). We evaluated the FBM in supplements for meat goats in which it provided 0, 20, 40, or 60% of the N added to the supplement compared with a negative control supplement with no added N source. The remainder of the N was contributed by soybean meal (SBM). Supplementation of N resulted in greater DMI than the negative control (P = 0.005), and DMI changed quadratically (P = 0.11) as FBM increased in the supplement. Digestibility of DM was similar in all diets, including the negative control (P > 0.10). Fiber digestibility increased linearly as dietary inclusion of FBM increased (P = 0.04 for NDF, P = 0.05 for ADF), probably as a result of the soybean hulls in the FBM. Nitrogen digestibility declined linearly from 60.5% with 0% FBM to 55.6% with 60% FBM (P = 0.07), but N retention changed by a quadratic function as FBM replaced SBM (P = 0.06). Negative control goats had less N digestibility (P < 0.001) and N retention (P = 0.008) than N-supplemented goats. Feather and bone meal had a greater proportion of ruminally undegradable B(3) protein than SBM (23.1 vs. 0.3% of CP, respectively). Ruminal VFA and pH were unaffected by replacing SBM with FBM, but supplying no source of N in the concentrate resulted in reduced total VFA in ruminal fluid (P = 0.04). Ruminal ammonia concentration increased quadratically (P = 0.07) as FBM increased, reflecting increased intake, and it was much less in unsupplemented goats (P < 0.001). Serum urea had less variation between 0 and 4 h after feeding in goats receiving 40 or 60% of added N as FBM in comparison with those receiving only SBM or 20% FBM. Feather and bone meal promoted a more stable rumen environment, possibly because of reduced rates of protein degradation within the rumen. A palatable by-product meal for ruminants can be made from spent laying hen hard tissue, one that supports N metabolism similar to that of traditional protein sources.

Evaluation of secondary protein nutrients as a substitute for soybean meal in diets for beef steers and meat goats

Finding appropriate disposal techniques for waste products is one of many challenges facing the poultry-processing industry. One waste generated in significant quantities is dissolved air floatation sludge, a product of wastewater treatment. Converting dissolved air floatation sludge into a dry feed product (meal) for incorporation into livestock feed appears to be a viable solution. This meal, called secondary protein nutrients (SPN), is high in protein (45% CP), fat (28% crude fat), and minerals. The protein consists of 85% B(2) and B(3) fractions, which are moderately to slowly degradable in the rumen, and therefore may potentially escape ruminal degradation and be available for digestion in the lower gastrointestinal tract. The goal of this research was to evaluate SPN as an alternative to traditional protein sources for ruminants by substituting it on an equivalent N basis for soybean meal in cattle and meat goat diets (0, 25, 50, 75, and 100% for cattle; 0, 20, and 40% for goats). When included in corn silage-based steer diets, increasing SPN resulted in linear and quadratic declines in both DMI and ADG (P < 0.001). Dry matter intake diminished with inclusion rates above 50%, and ADG were reduced after inclusion of SPN reached 25% of added N. Feed efficiency (the reciprocal of the efficiency of gain, which is represented by G:F) declined linearly (P < 0.001) with each incremental increase in SPN. Addition of up to 40% added N as SPN in goat diets caused no change in DMI, digestibility of DM or fiber, or N retention. Ruminal VFA concentrations showed little variation in either species. Increasing the proportion of SPN in the feed caused linear declines in ruminal NH(3) in steers (P < 0.001). Increasing SPN in goat diets, however, resulted in only a trend toward reductions of this parameter (P = 0.14). The decreases observed may have resulted from decreasing ruminal protein degradability or increasing fat caused by increasing the proportion of SPN in the feed. Urinary urea N as a percentage of urinary N showed significant declines in cattle, but not in goats, over the ranges of SPN offered. These results indicate that SPN can be included in diets for ruminants to supply up to 40% of supplemental N with little negative impact on animal performance.