Effect of zinc sources and experimental conditions on zinc balance in growing wethers

Three experiments were conducted with growing wethers to evaluate apparent excretion and retention of Zn from various sources. In Exp. 1 and 2, Zn-ethylene diamine (ZE), Zn hydroxychloride (ZHYD), Zn-lysine/glutamate (ZAA), and Zn-glycinate (ZG) were used and ZnSO4 (ZS), Zn hydroxychloride (ZHYD), Zn-lysine/glutamate (ZAA), and Zn-glycinate (ZG) were used in Exp. 3. In Exp. 1, 8 wethers were used in a replicated 4 × 4 Latin Square design. In Exp. 2 and 3, 40 wethers were used in a randomized block design. In Exp. 1, each period (total 4 periods) consisted of 14-day diet adaptation and 4 days of total collection of feces and urine. In Exp. 2 and 3, wethers received a basal diet for 14 days and received experimental diets for 9 days (diet adaptation), followed by 4 days of total collection of feces and urine. Total collection was conducted in wooden metabolic cages. All data were analyzed using the MIXED procedure of SAS as a Latin square design for Exp. 1 and a completed randomized block design for Exp. 2 and 3. In all experiments, dry matter intake did not differ among treatments except that it tended to be different in Exp. 2. In Exp. 1, no difference in Zn excretion (88%) and retention (11%) as proportion of Zn intake was observed among Zn sources. In Exp. 2, total tract digestibility of crude protein was greater (P < 0.01) for ZAA than ZE and ZG (82.0 vs. 79.1 and 77.8%, respectively) and greater (P < 0.01) for ZHYD than ZG (80.2 vs. 77.8%). However, total tract digestibility of neutral detergent fiber was low (on average 16%) for all treatments with no difference among treatments in Exp. 2. Apparent excretion and retention of Zn as proportion of Zn intake did not differ among treatments, and Zn retention (~1.4% of Zn intake) was very low for all treatments. In Exp. 3, ZHYD and ZAA had greater retention of Zn (17.8 vs. 1.5%; P = 0.01) than ZG. Fecal Zn excretion was greater (97.3 vs. 81.2%; P = 0.01) for ZG vs. ZHYD and ZAA, and Zn retention for ZG was only 1.5% of Zn intake. In conclusion, potential increases in Zn absorption and retention were observed for ZHYD and ZAA compared with ZS and ZG in Exp. 3 and these differences were not found in Exp. 1 and 2. Experiment 1 used a Latin square design and Exp. 2 used a diet containing largely undigestible fiber. These experimental conditions may have affected Zn metabolism in wethers. Inconsistent results on Zn balance for ZG among the experiments warrant further studies regarding its bioavailability.

EFECTO DE LA SUPLEMENTACIÓN ENZIMÁTICA EN PARÁMETROS PRODUCTIVOS DE CUYES (LÍNEA SINTÉTICA P 0.625)

The aim of this study was to evaluate the effect of the supplementation of an enzymatic complex in integral diets for guinea pigs in the growing phase on productive performance. In total, 54 male guinea pigs (Synthetic line P 0.625) were used and submitted to a diet free of the enzyme complex (T1), and two experimental ones, one with 0.1% (T2) and the other with 0.2% (T3) of enzyme complex evaluated between two weeks of age (weaning) and after rearing (nine weeks old). It was statically evaluated and there were found no significant difference between treatments in relation to final body weight, weight gain, feed intake and feed conversion; and it was reported the weekly average of percentage of dairy dry matter intake by body weight.

Comparisons between intake values observed and predicted by nutritional systems for confined nellore cattle

This study compared the dry matter intake (DMI) of Nellore heifers and bulls in the feedlot, predicted by the BR-Corte (2010 and 2016) and NRC (2000) nutritional systems. Hence, two experiments were conducted in a completely randomized design. The first one used 47 Nellore bulls, not castrated, with an average initial weight of 413 kg, and 19 months of age. The second experiment used 24 Nellore heifers with an average initial weight of 300 kg and 23 months of age. The accuracy and approximation of the DMI estimates by the nutritional systems were adjusted with the simple linear regression model and the root mean square error of prediction (RMSEP). The DMI was 8.06 kg day-1 for Nellore heifers and 11.54 kg day-1 for bulls, which are higher than the values ​​ predicted by the nutritional systems. The NRC (2000) and BR-Corte (2010 and 2016) underestimated DMI in 20.84, 20.09, and 19.35% for heifers and 28.07, 16.20, and 11.78% for bulls, respectively. It was concluded that the BR-Corte 2010 and 2016 were the most suitable models to estimate the DMI of Nellore heifers and bulls for higher precision and accuracy.

Individual Feed Efficiency Monitoring of Charolaise Candidate Young Bulls in Relation to Feeding Behavior and Self-Performance Test Results

This study evaluated the effect of differences in residual feed intake (RFI) of Charolaise candidate young bulls on feeding behavior and self-performance test results. Bulls were classified into high and low RFI (H-RFI, L-RFI) groups. Bulls were fed in a HOKOFARM system to measure individual animal intake and behavior. L-RFI bulls had significantly lower feed intakes (p = 0.002) and higher gain to feed ratio (p = 0.001), lower intake per day/kg DM (dry matter) (p = 0.002) and lower intake g/body weight/day (p < 0.001). L-RFI animals had lower visits number per day (p = 0.02), but spent longer time per visit (p = 0.02), and tended to have higher intake g/visit (p = 0.06) on feeders. The correlation between RFI and DMI (dry matter intake)/bodyweight/day as well as intake per day/kg were large and positive. Back-loin length and rump length, and moreover muzzle width and frame, showed negative correlations with RFI value. However, bulls with better RFI values associated with lower legs score. Results reveal that RFI was shown beneficial correlations with economically relevant self-performance traits. Further investigations are needed to seek additional indicator traits that are predictive for RFI.

The Effects of Non-Fiber Carbohydrate Content and Forage Type on Rumen Microbiome of Dairy Cows

The main objective of our current study was evaluating the effects of NFC supplementation and forage type on rumen microbiota and metabolism, by comparing microbial structures and composition among samples collected from cows fed AH (alfalfa-based diet), H-NFC (CS-based diet with high NFC) and L-NFC (CS-based diet with low NFC) diets. Our results show that microbial communities were structurally different but functionally similar among groups. When compared with L-HFC, NFC increased the population of Treponema, Ruminobacter, Selenomonas and Succinimonas that were negatively correlated with ruminal NH3-N, and urea nitrogen in blood, milk and urine, as well as significantly increasing the number of genes involved in amino acid biosynthesis. However, when compared to the AH group, H-NFC showed a higher abundance of bacteria relating to starch degradation and lactate production, but a lower abundance of bacteria utilizing pectin and other soluble fibers. This may lead to a slower proliferation of lignocellulose bacteria, such as Ruminococcus, Marvinbryantia and Syntrophococcus. Lower fibrolytic capacity in the rumen may reduce rumen rotation rate and may limit dry matter intake and milk yield in cows fed H-NFC. The enzyme activity assays further confirmed that cellulase and xylanase activity in AH were significantly higher than H-NFC. In addition, the lower cobalt content in Gramineae plants compared to legumes, might have led to the significantly down-regulated microbial genes involved in vitamin B12 biosynthesis in H-NFC compared to AH. A lower dietary supply with vitamin B12 may restrict the synthesis of milk lactose, one of the key factors influencing milk yield. In conclusion, supplementation of a CS-based diet with additional NFC was beneficial for nitrogen conversion by increasing the activity of amino acid biosynthesis in rumen microbiota in dairy cattle. However, lower levels of fibrolytic capacity may limit dry matter intake of cows fed H-NFC and may prevent increased milk yield.

Effects of forage inclusion and cattle breed on apparent digestibility and ruminal pH of steers fed a whole shelled corn-based diet

Objectives were to evaluate the effects of cattle breed, Holstein or Angus, and forage inclusion on total tract digestibility and ruminal pH in cattle fed a whole shelled corn (WSC) based diet. Six Holstein and 6 Angus steers, were assigned to a 2 × 3 factorial arrangement of treatments. Factors included breed, Holstein or Angus, and forage inclusion at 0, 8, or 16% forage (dry matter (DM) basis). Steers were fed in a replicated 3 × 3 Latin square, split-plot design. Each period consisted of 14 d diet adaptation followed by 7 d of sample collection. Data were analyzed using the MIXED procedures in SAS (v9.4 SAS Inst. Inc., Cary, NC). Repeated measures were used to analyze changes in ruminal pH over time. There was no interaction of breed × diet (P ≥ 0.19) on dry matter intake (DMI) or digestibility; however, Holstein steers had greater (P = 0.03) DMI than Angus steers. Despite the impact of breed on intake, there was no effect (P ≥ 0.33) of breed on diet digestibility. Digestibility of DM increased (linear; P &lt; 0.01) as forage was removed from the diet, but there were no differences (P ≥ 0.32) in NDF and starch digestibility. However, due to the change in diet, NDF intake digested on a grams per day basis increased (P ≤ 0.01) and starch intake digested (g/d) decreased (P = 0.01) as forage inclusion increased. There was a tendency for breed × diet interaction (P = 0.08) on ruminal pH. Holstein steers fed 8% or 16% forage had greater ruminal pH than Holstein steers fed 0% forage; but, ruminal pH of Angus steers was not altered by diet.