M. Spanghero

Laboratory variation of 24 h in vitro gas production and estimated metabolizable energy values of ruminant feeds

Intra- and inter-laboratory variation of in vitro gas production and calculated metabolizable energy (ME, MJ/kg DM) values were studied using 16 test feeds in 7 laboratories. Intra-laboratory variation was low, with six of the seven laboratories having very high relationships in gas production between runs (R 2 ≥ 0.96) and slopes that did not differ from unity. Inter-laboratory differences were higher with highly significant ( P< 0.001) differences among laboratories in both gas production and calculated ME values. Three of the six test laboratories generated predicted ME values that did not differ from the seventh (reference) laboratory. Combining intra-laboratory variation in gas production and inter-laboratory variation in predicted ME values, three of the six test laboratories were judged acceptable overall. ME values predicted by the gas production technique by laboratories in different parts of the world cannot be considered absolute.

Nitrogen balance and partitioning of some nitrogen catabolites in milk and urine of lactating cows

After calving, two groups of four cows were fed fescue hay (10 kg/d) and a concentrate (8 kg/d) containing 0 or 20 g kg−1 urea in order to induce different rumen microbial growth: the partition between the urine and milk excretion of allantoin, uric acid, creatinine and urea was examined. After 21 d of lactation, individual feed intakes, total faeces and urine output and milk yield were recorded for five consecutive days and these measurements were repeated three times at 21-d intervals. In comparison with the control, the urea-supplemented diet had higher apparent digestibility of DM (697 vs. 662 g kg−1, P < 0.05), OM (718 vs. 681 g kg−1, P < 0.05), NDF (600 vs. 542 g kg−1, P < 0.01) and crude protein (631 vs. 497 g kg−1, P < 0.01). The urea-supplemented diet caused higher (P < 0.01) outputs of N in the milk (91 vs. 75 g d−1) and urine (72 vs. 34 g d−1) and a moderate amount was retained (+24 g d−1), while in the control diet the N balance was negative (−3 g d−1). The inclusion of urea caused a significantly (P < 0.01) higher urinary output of allantoin (11.3 vs. 9.3 g N d−1) and urea (44.1 vs. 4.7 g N d−1), while no dietary effects were detected for uric acid or creatinine. The allantoin and uric acid excretion in milk was not significantly higher for the cows receiving urea, which had higher outputs of creatinine (90 vs. 71 mg Nd−1, P < 0.05) and urea (1559 vs. 507 mg N d−1, P < 0.01). The ratio between the quantitative excretion in urine and milk of allantoin, uric acid and creatinine (10.7, 10.2 and 68.7, respectively) did not differ between dietary treatments, while the urine/milk urea excretion ratio had a significant interaction between dietary treatments and periods.

Digestibility and allantoin excretion in cows fed diets differing in nitrogen content

Eight lactating cows were offered 20 kg d−1 hay and 8 kg d−1 concentrate; four of the cows received concentrate containing 20 g kg−1 urea. After 21 d in lactation, individual feed intakes, total faeces and urine output and milk production were recorded for 5 consecutive days and these measurements were repeated 3 times at 21 day intervals. There was no significant difference in DM intake between dietary treatments. Dietary DM in the diet containing urea was significantly more digestible (697 vs. 662 g.kg−1 DM, P < 0.05). About 47% of the additional NPN intake was lost in the urine and the remainder was partitioned between milk (20%) and body retention (33%). These latter two fractions indicate that the additional dietary N was partially captured by rumen microorganisms and metabolised by the host. Allantoin output was significantly (P < 0.01) higher in the cows receiving dietary urea. In conclusion, more urinary allantoin was excreted by cows receiving the diet that was expected to induce higher microbial synthesis.

Rumen fermentation characteristics and digestibility of cattle diets containing different whey:maize ratios

Three experimental diets were formulated to contain the same amount of fescue hay (560 g kg−1 dry matter (DM) Festuca arundinacea) and differing condensed rennet whey:maize meal ratios (0:100, 50:50 and 100:0 on a DM basis, diets M, MW and W, respectively). The diets were fed during two experimental periods to six rumen fistulated, non lactating Simmental cows (average level of intake: 77 g DM kg−1 LW0.75, four cows per treatment). Whey used alone caused a lower rumen pH at 1.5 and 3.0 h after the morning meal (P < 0.01) in comparison with the other two diets, while after 4.5 h rumen acidity values were similar between diets. After feeding, the inclusion of whey led to regular increases (P < 0.05) in the concentrations of propionic acid at 1.5 h (12.4 mmol, 18.3 mmol and 23.8 mmol l−1, respectively for M, MW and W diets), while at 3.0 h the W diet remained significantly higher than the other two (22.1 mmol vs. 14–14.2 mmol l−1, P < 0.01). This was also the case for butyric acid where higher (P < 0.01, 1.5 h) levels were observed for diets containing whey (11.6 and 13.3 mmol vs. 7.9 mmol l−1). The dry and organic matter in the W and MW diets were 3 percentage points (P < 0.05) more digestible than the M diet. The soluble cell content fraction digestibility regularly and significantly increased (P < 0.05) as whey substituted maize (from 749 to 814 g kg−1). The inclusion of whey caused an increase in rumen liquid turnover rate (from 7.1 to 13.4–12.3% h−1, P = 0.058) and enhanced levels of urinary volume which almost doubled in diets containing whey (from 78 to 132–138 mg kg−1 LW0.75, P < 0.05). Urinary allantoin output did not differ between dietary treatments while higher urinary outputs of uric acid were found for cows fed diets containing whey (2.39–2.58 g vs. 1.36 g day−1, P < 0.05).

N losses, purine N derivatives excretion and intestinal digestible protein requirements of cows at maintenance

Three rumen fistulated Simmental cows were fed 4 diets (in 4 experimental periods) obtained by substituting part of the basal fescue hay diet (8 kg/d/cow) with extracted soyabean meal (0, 50, 100 and 150 g/kg hay). Including the soyabean meal gave a range of nitrogen (N) intake from 508 to 1448 mg/kg LW0.75/d and of intestinal digestible protein (PDI) from 2.2 to 6.0 g/kg LW0.75/d. The regression of the apparently digested N (y) with the dietary N content (x) was highly significant (r=0.99; P <0.001) and the intercept obtained (−4.25 g N/kg DM) represents the theoretical metabolic loss with zero dietary N. The intercept of the regression between N balance (y) and ingested N (x) (−311 mg N/kg LW0.75/d; r=0.68; P< 0.05) represents an estimate of total endogenous N losses (urinary and faecal). The maintenance requirement for PDI estimated at N equilibrium (3.88 g PDI/kg LW0.75) was slightly higher than the value adopted by INRA (1988). Urinary purine derivatives N excretion was highly correlated (r=0.85; P< 0.001) with the estimated rumen microbial digestible true protein.

Digestibility and metabolic utilization of diets containing whole-ear corn silage and their effects on growth and slaughter traits of heavy pigs

The aim was to evaluate 2 levels of dietary inclusion of chopped whole-ear corn silage (WECS) on energy and nutrient utilization, growth, and slaughter performances of heavy pigs. Two in vivo experiments were conducted to determine digestibility and metabolic utilization of WECS using 18 barrows weighing 118 ± 8 kg BW on average, metabolic cages and respiration chambers (Exp. 1), and the effect of WECS on the growth performance and carcass traits on 42 barrows from 90 to 170 kg BW (Exp. 2). In both experiments, pigs were fed 3 experimental diets: a control diet (CON) containing cereal meals, extracted soybean meal, and wheat bran (80%, 9%, and 8% of DM, respectively) and 2 diets containing 15% (15WECS) or 30% WECS (30WECS) on a DM basis in place of wheat bran and corn meal. The diets were prepared daily by mixing the WECS to a suitable compound feed. Feed intake was always restricted to allow a daily DMI of 7.2% BW(0.75) in Exp. 1 and from 8.0% to 6.5% BW(0.75) in Exp. 2. Diets had similar NDF contents (15.2% to 15.8% of DM), and WECS inclusion resulted in a slight reduction in CP content (from 14.0% to 13.6% of DM) and a considerable decrease in P content (from 0.47% to 0.30% of DM). Digestibility of OM, CP, and fat was similar among diets, whereas P digestibility was lower (P < 0.05) for the 30WECS diet (33.5%) in comparison with the CON and 15WECS diets (45.5% and 44.1%, respectively). Nitrogen lost in feces and urine and N retained were not different among diets, whereas P retained decreased with the increase of WECS (5.4, 3.7, and 2.2 g/d for the CON, 15WECS, and 30WECS diets, respectively; P < 0.05). No difference among diets was observed for energy balance. The WECS contained 13.48 MJ ME and 9.39 MJ NE/kg DM. In Exp. 2, feed intake was not depressed by WECS inclusion, and the ADG for the whole experiment was not different among dietary treatments (from 737 to 774 g/d). Fecal pH was lower (P < 0.05) for the WECS diets than the control diet (7.10 and 7.00 vs. 7.40) and for the sampling at 150 kg BW than that at 130 and 110 kg BW (6.96 vs. 7.29 and 7.24). At slaughter, lean percentage in the carcass was lower in the 30WECS diet than those of the other 2 diets (46.8% vs. 48.3% and 48.6%, P = 0.05). The overall experimental data obtained in both trials indicate that substitution of wheat bran and corn meal for WECS (up to 30% of DM) does not affect, with the exception of P utilization and carcass leanness, energy and nutrient utilization and performance of heavy pigs in the last phase of growing.

Performance of lactating simmental cows fed two diets differing in the content of digestible intestinal protein (PDI)

In each of two trials, two diets differing in intestinal digestible protein (PDI) content (LP: low protein, 70 g kg−1 dry matter; HP: high protein, 120 g kg−1 dry matter) were given to multiparous Simmental cows in early lactation. Effective rumen degradabilities of nitrogen and non-protein dry matter of feed ingredients, estimated by the nylon-bag technique, were used to calculate PDI contents of diets. In trial 1, two groups of six cows were fed, in two successive periods of 7 weeks each, the diets LP and HP allocated according to energy requirements (LPR and HPR). In trial 2, the diets LP and HP were fed in two periods of 6 weeks each to 24 cows (six cows/group) according to energy requirements (LPR and HPR) or ad libitum (LPL and HPL). In trial 1, total and energy-corrected milk (ECM) yields were significantly higher (P < 0.01) for cows receiving diet HPR (20.7 and 19.2 vs. 18.9 and 17.4 kg day−1), while milk fat and protein contents were similar. Live weight changes were different between groups (−126 and +39 g day−1 respectively, for LPR and HPR diets) but this difference was not significant. In trial 2, cows fed HPL diets had significantly higher milk yields compared with the LPL and LPR diets (20.0 vs. 17.7 and 17.4 kg day−1, respectively, P < 0.05), but not with the HPR diet (19.0 kg day−1). ECM yield was higher (P < 0.05) for cows receiving more protein both between restricted groups (18.4 vs. 16.4 kg day−1, respectively for HPR and LPR groups) and between ad-libitum groups (18.8 vs. 17.0 kg day−1, respectively for HPL and LPL groups). Milk composition was not affected by dietary treatments. Diets fed according to requirements caused negative, but differing, live weight changes (−783 and −44 day−1 respectively for LPR and HPR diets, P < 0.05). For ad-libitum treatments, LPL cows lost live weight while HPL cows gained live weight (−221 vs. 433 day−1, respectively, P < 0.05). In the present experiments, increasing the supply of dietary PDI improved milk production even if the recycled nitrogen and live weight change could have contributed to protein requirements.

Effect of dietary inclusion of whole ear corn silage on stomach development and gastric mucosa integrity of heavy pigs at slaughter.

The effect of dietary inclusion of whole ear corn silage on stomach development and on the incidence of gastric lesions was studied in heavy pigs. Three groups of 14 castrated male pigs were fed a control cereal-based diet and two diets containing whole ear corn silage (15% or 30% DM) from 90 kg bodyweight to slaughter at 170 kg. The diets with whole ear corn silage increased the amount of neutral detergent fibre in the stomach contents, the weight of the organs and the area of the pyloric region. Follicular gastritis was significantly lower and gastritis less severe in pigs fed the whole ear corn silage diets than pigs fed the control diet. The inclusion of whole ear corn silage in the diet influenced the development of the stomach and reduced the incidence of gastritis in heavy pigs.

Repeatability and reproducibility of the Cornell Net Carbohydrate and Protein System analytical determinations

Abstract The increasing use in Italy of the Cornell Net Carbohydrate and Protein System (CNCPS) led researchers of five Italian universities to carry out a collaborative study to evaluate the precision of the CNCPS chemical analysis and derivate fractions. Each laboratory conducted in duplicate the chemical analyses according to the Weende (dry matter; crude protein; ether extract; crude fibre; ash), Van Soest (neutral and acid detergent fibre, NDF and ADF; acid detergent lignin; ADL) and CNCPS (soluble proteins, SP; non-protein nitrogen, NPN; neutral and acid detergent insoluble protein, NDIP and ADIP; starch, ST) schemes on the same five feeds (barley meal, wheat straw, maize silage, dried lucerne and field beans). Anomalous analytical data were identified and corrected by the “box-plot” graphic tool before the calculation of the CNCPS protein (B1, B2 and B3) and carbohydrate (A, B2 and C) fractions. Finally, repeatability (chemical analysis) and reproducibility (chemical analysis and fractions) were calculated and expressed as relative values (repeatability and reproducibility standard deviation as percentage of the corresponding mean, RSDr and RSDr, respectively). Chemical analyses of the Weende scheme, together with NDF, ADF and ST analyses, have satisfactory repeatability (0.3-6.2%) and reproducibility (0.3-11.2%) values. On the contrary the ADL, NPN, NDIP and ADIP analyses showed high variability, both within and between laboratories (RSDr and RSDr between 20 and 45%). The SP analysis had an intermediate value of precision (RSDr=10.6%; RSDr=16.4%). Finally, since different combinations of several chemical analyses with scarce (ADL, NPN, NDIP, ADIP, SP) or average precision (e.g. NDF and starch) are used to calculate CNCPS fractions (excluding B2 protein fraction), also the reproducibilities of these fractions are poor and range from 10 to 20%.

Impact of NDF degradability of corn silage on the milk yield potential of dairy cows.

Abstract The neutral detergent fibre (NDF) degradability of corn silage samples, measured in vitro (ivNDFd) by a filter bag system, was used to examine (i) the relationship between the ivNDFd and that calculated from acid detergent lignin (L) content (NDFd) and (ii) the impact of ivNDFd variations on the predicted milk yield (MY) of dairy cows fed corn silage based diets. A total of 173 samples of corn silage were collected during a period of three years (2001-03) in different dairy farms of the Po Valley (Northern Italy). Each sample was analysed for chemical composition and was also tested in triplicate for the ivNDFd using the DaisyII incubator (Ankom, Tech. Co., Fairport, NY, USA) with incubation time of 48hs. Moreover, the NDFd of samples was calculated from the L contents, while the measured ivNDFd values were used to estimate the NEl, the potential dry matter intakes (DMI) and to predict the MY of cows. Corn silage samples of the three years were similar for NDF and starch contents (44.2 and 30.7% DM, on average, respectively) while samples from 2003, in comparison with 2001 and 2002, had lower crude protein (6.9 vs 8.3-8.4% DM, P<0.01) and L contents (3.3 vs 3.6-3.9% DM, P<0.01) and higher ivNDFd values (53.3 vs 45.6-47.8%, P<0.01). The relationship between ivNDFd and NDFd was weak (R2=0.09, not significant). The MY predicted from the NEl content and DMI of corn silage (5.5 MJ/kg DM and 8.9 kg/d) minus the maintenance energy costs, was 11.5 kg/d on average (coefficient of variation 20%). Our simulations indicate that a variation of ivNDFd by +1.0% changes the NEl of corn silage to have an expected variation in milk yield of +0.15 kg/d. If the ivNDFd is also used to predict the corn silage DMI then a +1.0% variation in ivNDFd of corn silage produces an overall +0.23 kg/d MY variation. The present results indicate that ivNDFd is highly variable in corn silage populations and differences in this nutritional parameter have an appreciable impact on the predicted milk yield from dairy cows.