F.P. O’Mara

Effects of different transition diets on energy balance, blood metabolites and reproductive performance in dairy cows

The objective of this study was to evaluate the effect of diets differing in energy density (ED) in the last 4 weeks of the dry period and in the first 8 weeks of lactation on energy balance (EB), blood metabolites and reproductive performance. Three diets (grass silage:straw 75:25 on a dry matter basis (SS), grass silage (S) and grass silage+3 kg/day of concentrates (C)) pre-calving and two diets (4 kg (LC) or 8 kg/day of concentrates (HC)+grass silage ad libitum) post-calving were combined in a 3×2 factorial design. Sixty second-lactation Holstein–Friesian cows were blocked according to expected calving date and body condition score into groups of six and were then allocated at random to the treatments. Individual feeding started on average 34 days prior to parturition and measurements were made until the end of the 8th week of lactation. Net energy (NE) intake increased (5.6, 6.5 and 9.0 UFL/cow per day; (standard error of the difference (S.E.D.)=0.22) and EB improved pre-calving as the ED of the diet increased. Post-calving, milk energy output was significantly different between pre-calving treatments at 10.5, 11.6 and 12.7 UFL/day (S.E.D.=0.48) for SS, S and C respectively. Cows on the highest ED diet pre-calving (C) had a greater degree of negative energy balance (NEB) than cows on the lowest ED diet pre-calving (SS) for 7 of the first 8 weeks of lactation. At calving, cows on C had a lower plasma urea concentration than those on S and cows on SS had a lower plasma bile acid concentration than those on S. At week 2 post-calving, C had a higher plasma β-hydroxybutyrate concentration than SS and a higher plasma protein concentration than SS or S. Post-calving, cows receiving HC had higher NE intakes averaged over the first 8 weeks of lactation and lower NEB in each of the first 8 weeks of lactation than those on LC. Plasma glucose and bile acid concentrations were higher on HC compared to LC at week 2 post-calving. Plasma urea concentrations were lower (P<0.05) on HC compared to LC.

The nutritive value of palm kernel meal measured in vivo and using rumen fluid and enzymatic techniques

Abstract The objectives of this experiment were to determine the in vivo digestibility of solvent extracted and expeller palm kernel meal (PKM) and to establish how well this was predicted by laboratory techniques. Eight samples of expeller PKM and four samples of solvent extracted PKM were collected over 4 years. Their in vivo digestibility was measured by total faecal collection using four wethers per sample. The laboratory methods for predicting digestibility were the in vitro rumen fluid (RF), neutral detergent cellulase with gammanase (NCG), and pepsin cellulase with gammanase (PCG) methods. Gammanase has been added to the latter two methods specifically to improve the prediction of digestibility of PKM. The solvent extracted samples had higher organic matter digestibility (691 vs. 653 g/kg, sed 15.7) and crude protein digestibility (727 vs. 597 g/kg, sed 36.6). However, the expeller samples had higher ( P =0.12) contents of digestible energy (13.4 vs. 12.5 MJ/kg DM, sed 0.48) due to their higher gross energies (20.6 vs. 19.1 MJ/kg DM). None of the laboratory digestibility tests predicted digestibility satisfactorily. The residual standard deviation was 29, 32 and 31 g/kg for the RF, NCG and PCG methods, respectively. In particular, two expeller samples and two solvent extracted samples were grossly underpredicted by the laboratory methods. These results indicate that PKM is a medium quality energy feed for ruminants and that enzymatic procedures including gammanase or the in vitro rumen fluid method do not accurately predict its digestibility.

The effect of dietary protein content and hay intake level on the true and apparent digestibility of hay

The digestibility of concentrate feeds has been determined by difference using hay as a basal forage in many institutions. The objective of this experiment was to examine the effect of hay intake level and dietary crude protein (CP) content on hay digestibility. Groups of wether lambs (1 year old) were fed three levels (600, 700 and 800 g/day) of hay each at two CP contents (103 and 182 g CP/kg DM), achieved by using a urea solution. An extra group of lambs were fed hay unsupplemented with urea (42 g CP/kg DM) at a level of 800 g/day. The true organic matter digestibility (True OMD, calculated using two methods: True OMD 1 and 2) and apparent OMD of all treatments fed the 182 g CP/kg DM diets were significantly higher (P<0.05) than treatments fed the 103 g CP/kg DM diet (OMD: 632.8 g/kg vs. 604.2 g/kg; True OMD 1: 720.6 vs. 694.1 g/kg; True OMD 2: 711.8 vs. 681.0 g/kg). Apparent and true digestibility also increased as hay allowance increased and a significant linear effect was observed for GED. For the three groups fed 800 g/day of hay, significant differences in digestibility due to CP content only occurred between the 182 and the 42 g CP/kg DM diets (with the exception of CP digestibility). Although the effect of CP content was significant in some cases, the magnitude of the observed digestibility response is of little consequence for concentrate feed evaluation.

Intake, digestibility, milk production and kinetics of digestion and passage for diets based on maize or grass silage fed to late lactation dairy cows

Abstract This experiment compares maize and grass silage in relation to dry matter (DM) intake, milk production and the kinetics of digestion and passage for both forages. Twenty-two multiparous late lactation dairy cows were fed diets based on maize or grass silage (diets MS and GS, respectively) for a period of 7 weeks. Milk production was determined over 4 weeks ( n =11 per treatment) with total diet digestibility, forage DM intake and rumen outflow rate being determined in tie stalls ( n =7 per treatment). Forage degradability characteristics were determined using three fistulated steers. The difference in forage DM intake between treatments was highly significant ( P P >0.05). However, cows fed the MS diet had a significantly higher milk fat and milk protein content and milk fat yield ( P

The relationship between feeding level, rumen particulate and fluid turnover rate and the digestibility of soya hulls in cattle and sheep (including a comparison of Cr-mordanted soya hulls and Cr2O3 as particulate markers in cattle)

Abstract The aim of this work was to investigate the inter-relationships between feeding level, digestibility and rumen particulate and fluid turnover rate (k1p and k1f: % per hour) for high concentrate diets in cattle and sheep. In Experiment 1, four fistulated steers were used in a 4×4 Latin square experiment to determine k1p at high (12.45 kg/d) and low (6.48 kg/d) intakes using either Cr-mordanted soya hulls or Cr 2 O 3 as particulate markers. In the second and last period of this experiment, soya hulls digestibility and k1f were determined for each intake level. In Experiment 2, seven 1 year old wether sheep were used to determine the digestibility of soya hulls, k1p and k1f at high (907 g/d; n =3) and low (703 g/d; n =4) intakes. Increasing feeding level depressed DM, OM and GE digestibility ( P P P P P >0.10). For the pooled data set, linear relationships ( P P >0.05). These results indicate that depressions in digestibility at high feeding levels are associated with higher rumen turnover rates and that much of the variation in concentrate digestibility can be explained by changes in rumen turnover rate in both species.

Effect of DL-malic acid supplementation on feed intake, methane emissions, and performance of lactating dairy cows at pasture.

The objective of this study was to determine the effect of dietary dl-malic acid (MA) supplementation on feed intake, methane (CH(4)) emissions, and performance of mid lactation Holstein-Friesian cows at pasture. Twenty-four (6 primiparous and 18 multiparous) mid- to late-lactation cows (206 +/- 65 d in milk) grazing a mixed-species grass sward were blocked on parity, days in milk, and pretrial milk yield, and randomly allocated within block to 1 of 2 dietary treatments offered twice daily at milking in 2 equal portions (6 kg/d in total): a control concentrate (0 g/d of MA) and a concentrate supplemented with MA (480 g/d of MA) over a 6-wk period. Cows were allowed a 3-wk acclimation period followed by a 5-d CH(4) measurement period. Enteric CH(4) emissions were estimated using the sulfur hexafluoride tracer gas technique, and herbage intake was measured using the n-alkane technique. Dietary supplementation with MA did not affect voluntary intake of herbage or total dry matter intake, body weight gain, milk yield, fat-corrected milk yield, or daily CH(4) production. These results suggest that there is little benefit to be gained from the dietary supplementation of dairy cows at pasture with MA at least within the inclusion rates used in this study.

An investigation of feeding level effects on digestibility in cattle for diets based on grass silage and high fibre concentrates at two forage: concentrate ratios

This experiment investigated the effect of feeding level on diet digestibility at two forage:concentrate ratios for diets containing grass silage. Four rumen fistulated Holstein–Friesian steers were used in a latin square experiment comprising a 2×2 factorial arrangement of treatments. Treatments were maintenance and 1.6×maintenance feeding level and 500 or 850 g of soya hulls/kg DM. Digestibility was determined by total collection, with fractional soya hulls (k1p) and fractional solute outflow rate (k1f) determined for the rumen using Cr-mordanted soya hulls and Co-EDTA, respectively. Rate of digestion was determined in-sacco. Increasing feeding level and soya hulls inclusion decreased diet DM, OM, CP, NDF, ADF and GE digestibility (P<0.01). The depression due to feeding level was greater for 850 g/kg DM soya hulls diets for GE (P<0.05), DM (P=0.06) and OM (P=0.06) digestibility. Rate of slowly degradable soya hulls DM and NDF digestion was lower (P<0.05 and P=0.07) for 850 g/kg DM soya hulls diets. Soya hulls k1p and k1f increased with feeding level but only the increase in k1f was significant (P<0.01). Diet OM, NDF and GE digestibility were positively related to rumen pH 6 h after feeding (P<0.01; R2=0.50 to 0.69). These results suggest that lower rumen pH values may be an important component of the larger digestibility depressions often observed for high concentrate diets.