PSII-5 Effect of progressive limit feeding in feedlot steers: A pilot study

The objective was to analyze the effect of progressive limit feeding on growth and performance during the finishing phase in feedlot steers. Thirty-nine steers (BW = 469 ± 31 kg) were divided into three blocks by weight. In each block, five steers were randomly assigned to a pen to be progressively limit fed (PLF), while the remaining eight steers were fed a common finishing diet ad libitum in a control (CON) pen. Progressive limit feeding refers to maintaining a previously growing animal at constant size by reducing the amount of feed offered by 3.29% daily for 14 consecutive days. Thus, on d 14, PLF steers were consuming 63% of original dry matter intake (DMI). All steers were fed ad libitum from d 15 until slaughter (d 106). Steers were fed a finishing diet, consisting primarily of dry-rolled corn, corn silage, and modified wet distillers grains. Data were analyzed using the MIXED procedure of SAS 9.4. Final BW was not affected (P = 0.82) by treatment; PLF and CON steers were 665 and 669 kg, respectively. Treatment did not affect overall ADG (P = 0.73); however, treatment did affect (P = 0.01) d 15–83 ADG as PLF steers gained 2.28 kg/d compared with 1.90 kg/d for CON steers. Overall DMI of PLF steers was 9% less (P = 0.02) than for CON steers (9.9 and 10.9 kg/d, respectively). Treatment did not affect (P = 0.10) DMI from d 15–106. Overall gain:feed (0.183 and 0.173 for PLF and CON steers, respectively) was not affected (P = 0.46) by treatment. Carcass characteristics were not affected (P ≥ 0.24) by treatment. A similar overall growth performance and reduced DMI for PLF steers suggests that progressive limit feeding may be a cost-effective approach to finishing feedlot steers.

Thirst interneurons that promote water seeking and limit feeding behavior in Drosophila

Thirst is a motivational state that drives behaviors to obtain water for fluid homeostasis. We identified two types of central brain interneurons that regulate thirsty water seeking in Drosophila, that we term the Janu neurons. Janu-GABA, a local interneuron in the subesophageal zone, is activated by water deprivation and is specific to thirsty seeking. Janu-AstA projects from the subesophageal zone to the superior medial protocerebrum, a higher order processing area. Janu-AstA signals with the neuropeptide Allatostatin A to promote water seeking and to inhibit feeding behavior. NPF (Drosophila NPY) neurons are postsynaptic to Janu-AstA for water seeking and feeding through the AstA-R2 galanin-like receptor. NPF neurons use NPF to regulate thirst and hunger behaviors. Flies choose Janu neuron activation, suggesting that thirsty seeking up a humidity gradient is rewarding. These findings identify novel central brain circuit elements that coordinate internal state drives to selectively control motivated seeking behavior.

75 Management of the Young Calf When Dams Are Limit-fed in Confinement

Limit-feeding cows in confinement can lower feed costs; however, calves have limited time to access feed. This study was designed to evaluate management options to economically improve calf performance. Calves (n = 54) were stratified by age (105 ± 16 DOA) and assigned randomly to one of nine groups, then each group assigned randomly to one of three treatments: 1) kept with dam with access to cow diet only (PAIRS) 2) early-weaned (EW) or 3) kept with dam with access to creep (CREEP). The cow diet was 54% wet distillers grains (WDGS), 37% straw, and 8% corn. This diet was fed to meet dry cow requirements (7.7 kg DM/d) for EW, lactation requirements (10.9 kg DM/d) in CREEP, and lactation requirements plus allow for some calf intake (14.8 kg DM/d) in PAIRS. The calf diet consisted of 51% alfalfa hay, 25% WDGS, and 22% corn. Calves in the EW had greater (P < 0.01) intake (5.0 kg DM/d) than CREEP (4.1 kg DM/d) from 105 to 203 DOA. Calf ADG differed (P < 0.01) among treatments from 105 to 203 DOA, with CREEP (1.29 kg/d) being greater (P = 0.02) than EW (1.01 kg/d) and both being greater (P ≤ 0.02) than PAIRS (0.74 kg/d). At ~203 DOA, PAIRS and CREEP were weaned and all calves were fed a growing diet. Calf intakes during the growing phase (223 to 314 DOA) did not differ (P = 0.39). However, calf ADG tended (P < 0.06) to differ. The ADG of PAIRS (1.13 kg/d) and EW (1.10 kg/d) did not differ (P = 0.67) but were greater (P ≤ 0.05) than CREEP (0.92 kg/d). However, when calf value and total feed costs were considered, creep resulted in the most return over feed costs at weaning as well as at the end of growing.

Effect of feeding method on nutrient utilization and cow performance in limit-fed cow-calf systems

Delivery of limit-fed, complete rations requires significant capital investment and creates logistical challenges for producers. Deconstruction and separate delivery of roughage and concentrate portions of diets may decrease feeding cost. Two experiments were conducted to evaluate the potential of separately limit-feeding roughage and concentrate. In Experiment 1, 4 ruminally cannulated steers (371 ± 12 kg BW) were used in a 4 × 4 Latin square to evaluate the effects of time of concentrate delivery in deconstructed diets. Intake was restricted to 80% of predicted NEm requirements of a diet consisting of wheat straw (35%), cracked corn (29%), and distillers’ grains (27%) formulated to contain 1.58 Mcal NEm/kg. Treatments were: concentrate fed 2 h prior to wheat straw (-2S), concentrate and wheat straw fed as total mixed ration (TMR), concentrate fed 2 h after wheat straw (+2S), and concentrate fed 12 h after wheat straw (+12S). In Experiment 2, 95 mid- to late-gestation cows (503 ± 151 kg) were used in a 112-d trial to evaluate feeding system on cow performance. Cows were assigned to 1 of 12 pens. Treatments were limit-fed the complete diet from Experiment 1 (TMR), fed roughage and concentrate portions of the deconstructed TMR 12 h apart (SEP), and ad libitum bermudagrass hay (HAY). Body weight, BCS, and back fat measures were collected every 28 d. In Experiment 1, treatment did not affect DM or OM digestion (P ≥ 0.88), rate of particulate passage (P ≥ 0.55), or ruminal DM fill (P ≥ 0.19). Fill averaged 3.8 kg DM. Nadir of ruminal pH occurred 4 to 8 h after concentrate was delivered, but mean ruminal pH was not different among treatments (P = 0.22) ranging from 6.4 to 6.6 for +2S and 12S, respectively. In Experiment 2, treatment did not affect final BW (518 kg; P = 0.72) or final BCS (5.6; P = 0.67), but limit-fed strategies tended (P = 0.06) to have greater final RE (137.1, 98.9 and -14.6 Mcal for TMR, SEP, and HAY, respectively). Delivering forage and concentrate separately did not change digestion, and timing of concentrate delivery had only minor effects on ruminal fermentation. Limit-feeding a TMR or separate delivery of roughage and concentrate sustained cow performance compared to ad libitum hay consumption.

133 Supplementing xylanase increased the digestibility of non-starch polysaccharides, particularly arabinoxylan, in diets high in insoluble corn fiber fed to swine with a 36-d dietary adaptation period

Xylanase should increase arabinoxylan digestibility in swine, but the responses in corn-based diets are inconsistent. The experimental objective was to investigate xylanase efficacy in growing pigs fed a diet high in insoluble corn fiber and afforded a longer adaptation period than typically reported in the literature. Sixty gilts (25.4 ± 0.9 kg BW; L337 × Camborough), were blocked by weight, housed individually, and randomly assigned to one of four dietary treatments: a low-fiber control [LF; 6.9% non-starch polysaccharides (NSP)], a 30% corn bran high-fiber control (HF; 17.6% NSP), HF + 100 mg xylanase/kg (HF+XY; Econase XT 25P; AB Vista, Marlborough, UK), and HF + 50 mg arabinoxylan-oligosaccharide/kg (HF+AX; 3-7 degrees of polymerization). Diets contained 0.5% CrO3. Gilts were fed ad libitum for 36 d, followed by 10-d of limit feeding (80% of average ad libitum intake) and were housed in metabolism crates. On d 46, pigs were necropsied and ileal, cecal, and colonic digesta were collected; ileal digesta was pooled within replicate for NSP analysis (n=6 per treatment). Data were analyzed as a linear mixed model using replicate and block as random effects, and treatment as a fixed effect. Compared to LF, the HF diet reduced (P< 0.01) apparent ileal digestibility (AID) of total NSP (32.7 vs. 16.3%), insoluble NSP (50.0 vs. 21.5%), and insoluble arabinoxylan (29.8 vs. 15.4%). Xylanase (HF+XY vs. HF) increased (P< 0.01) AID of total NSP by 39.8% (27.1 vs. 16.3%) and insoluble NSP by 34.0%. This may be attributed to xylanase increasing AID of total arabinoxylan by 54.5% over HF, 44.5% over LF, and 56.9% over HF+AX (33.0, 15.1, 18.3, and 14.2%, respectively; P=0.02). In conclusion, increasing insoluble fiber reduces NSP digestibility, but xylanase can increase AID of arabinoxylan and NSP. Supplementing an arabinoxylan-oligosaccharide, a potential release product of the xylanase, did not increase NSP digestibility.

Effects of monensin inclusion and level of intake in limit-feeding strategies for beef cows1

A study was conducted to evaluate the effects of intake management and ionophore inclusion on diet utilization under managed intake conditions in beef cattle. Two experiments utilized common diets fed at 120% (H) or 80% (L) of maintenance with either 0 or 200 mg/d monensin in a factorial arrangement. Forty cows were fed for 56 d (Exp. 1) to evaluate effects on diet utilization and energy retention; diets were fed to 16 ruminally cannulated steers (Exp. 2) to determine effects on digestion, energy value, and ruminal fermentation. Cows fed H had greater body weight (BW) gain (P < 0.01) and retained energy (RE; P < 0.01), although estimated heat production was also greater (P < 0.01). Monensin had limited effects on overall BW gain (P = 0.97). Monensin had no effect on RE (P = 0.94) or calculated heat energy (HE; P = 0.53) despite effects on diet utilization observed in steers. In steers, L increased (P < 0.01) digestion of dry matter, organic matter, acid detergent fiber, and gross energy (GE) and reduced (P < 0.01) passage rate; monensin did not affect digestion (P > 0.15) but did reduce passage rate (P < 0.03). Monensin lowered (P < 0.01) acetate:propionate ratio and increased (P < 0.05) ruminal pH. Monensin did not alter feed required for maintenance; however, limit-feeding reduced apparent daily maintenance requirement to 62.85 kcal/kg BW0.75, a 26% reduction from model-predicted values.

Growth performance and apparent total tract nutrient digestibility of limit-fed diets containing wet brewer’s grains to Holstein heifers

The objective of this study was to evaluate the growth performance and apparent total tract nutrient digestibility of Holstein heifers limit-fed diets containing different amounts of wet brewer’s grains (WBG). A 12-wk randomized complete block study was conducted using 30 yearling Holstein heifers [378 ± 27 d of age, and body weight (BW) of 357.8 ± 27.6 kg (mean ± SD)]. Treatments were 0%, 10% and 20% of WBG on a dry matter (DM) basis and diets were formulated to be limit-fed for dry matter intake (DMI) at 2.35% of BW and provided 15% crude protein (CP) and 2.27 Mcal metabolizable energy/kg of DM. Dry matter intake was recorded daily, while BW and skeletal measurements were measured every 2 wk. During week 12, fecal samples were collected directly from the rectum over four consecutive days and composited by heifer to determine apparent total tract nutrient digestibility using acid detergent insoluble ash as a marker. Data were analyzed using the MIXED procedure of SAS. Dry matter intakes, BW, and average daily gain were not different among treatments (P = 0.2, P = 0.4, and P = 0.6, respectively). Dry matter intakes ranged from 8.6 to 9.0 kg/d. Average BW were 404.4, 411.5, and 409.3 kg for heifers fed the 0%, 10%, and 20% WBG diets, respectively. Average daily gains were 1.03, 1.04, and 0.96 kg/d for heifers fed the 0%, 10%, and 20% WBG diets respectively. Skeletal measurements and body condition scores (BCS) were not different among treatments except for the change in heart girth (P < 0.01) and initial BCS (P < 0.01). Apparent total tract digestibilities of DM, organic matter, CP, fat, and hemicellulose were greater or tended to be greater in heifers fed 0% and 20% WBG treatments than heifers fed 10 % WBG (P = 0.04, P = 0.04, P = 0.06, P = 0.06, and P = 0.01, respectively). Neutral detergent fiber, acid detergent fiber, and fat digestibilities were similar among treatments (P = 0.2, P = 0.3, and P = 0.3, respectively). During the digestibility phase, DMI tended to be greater (P = 0.08) for the 10% WBG treatment. These results demonstrate that limit-feeding heifers with diets containing up to 20% WBG could replace soybean- and corn-based concentrates in diets without adverse consequences to the heifer growth performance.