Around the world, dairy production continues to intensify, with farmers increasing stocking rates, feeding more supplements, and transitioning into fully housed systems. Dairy production in Victoria is no exception and farmers are starting a move towards intensive (i.e. permanently housed) dairy operations. Challenges associated with these transformations have included difficulties, or failure, to obtain planning approval and public concern around the effect of intensive developments on environmental degradation, animal welfare and industry image. We examined current land-use planning provisions, environmental requirements, animal-welfare regulations, industry guidelines and codes of practice for their applicability and suitability to the implementation of intensive dairy-production operations, particularly large-scale ones, in Victoria, Australia. Our aim was to clearly identify factors that have the potential to hinder the growth and expansion of existing dairy-production systems into intensive operations, and the establishment of new intensive dairy enterprises. The majority of legislation examined posed no obstacles to the development of large-scale intensive dairy operations. New definitions for intensive livestock production and the inclusion of an intensive dairy-farm category in the State planning provisions will reduce current confusion across and within planning departments. A standard methodology to determine separation distances is required and a code for intensive dairy farming would greatly assist with the planning-approval process. Many advisory publications fall short when applied to intensive dairy operations as they are currently written for pasture-based farms with limited infrastructure for regularly feeding or housing large herds of >700 cows.

Binding of IgG antibodies to Entodinium spp. in the rumen of sheep (Ovis aries) was investigated by adding IgG, purified from plasma, directly into the rumen. Plasma IgG was sourced from sheep that had or had not been immunized with a vaccine containing whole fixed Entodinium spp. cells. Ruminal fluid was sampled approximately 2 h after each antibody dosing. Binding of protozoa by a specific antibody was detected using an indirect fluorescent antibody test. An antibody titer in the ruminal fluid was determined by ELISA, and the concentration of ruminal fluid ammonia-N and ruminal pH were also determined. Entodinium spp. and total protozoa from IgG-infused sheep were enumerated by microscopic counts. Two-hourly additions of IgG maintained a low antibody titer in the rumen for 12 h and the binding of the antibody to the rumen protozoa was demonstrated. Increased ammonia-N concentrations and altered ruminal fluid pH patterns indicated that additional fermentation of protein was occurring in the rumen after addition of IgG. No reduction in numbers of Entodinium spp. was observed (P > 0.05). Although binding of antibodies to protozoa has been demonstrated in the rumen, it is unclear how much cell death occurred. On the balance of probability, it would appear that the antibody was degraded or partially degraded, and the impact of this on protozoal populations and the measurement of a specific titer is also unclear.

In this experiment 12 rumen-fistulated cows in late lactation, grazing Persian clover (Trifolium resupinatum) at four pasture allowances [9, 16, 32 and 53 kg dry matter (DM)/cow. day], had their entire rumen contents removed and sampled six times over 6 days, with the time of sampling varied between days. These rumen pool size measurements occurred at 0645 hours, 0915 hours, 1045 hours, 1345 hours, 1530 hours and 1900 hours. The cows were offered new allocations of pasture twice daily at 0715 hours and 1530 hours. Herbage intake increased (P < 0.001) from 5.6 to 20.4 kgDMas pasture allowance increased. Pasture allowance had no effects on rumen pool sizes of wet matter (WM) (P = 0.95), DM (P = 0.914), neutral detergent fibre (NDF, P = 0.499) or the DM% of the digesta (P = 0.078). Rumen pool sizes of WM, DM and NDF varied throughout the day. Pool sizes of WM and DM were lowest at 0645 hours and highest at 1900 hours for all allowances (P < 0.001) and along with pool sizes of NDF, were also lower at 0645 hours compared with 0915 hours and at 1530 hours compared with 1900 hours. The lack of increase in rumen pool sizes as pasture allowance increased when cows grazed Persian clover suggests that outflow rates increased with the increasing intakes. The low, and similar, rumination times between allowances also suggests that there is little restriction to the ability of outflow rates to increase when cows graze Persian clover at increasing allowances. The changes in rumen pool sizes over the day were consistent with the twice daily allocation of fresh pasture to the cows. The diurnal rumen pool size information obtained from this experiment will assist with the development of mechanistic rumen models that are capable of simulating the discontinuous intake and varying rumen pool sizes of cows in grazing systems.

Residual feed intake (RFI), as a measure of feed conversion during growth, was estimated for around 2,000 growing Holstein-Friesian heifer calves aged 6 to 9 mo in New Zealand and Australia, and individuals from the most and least efficient deciles (low and high RFI phenotypes) were retained. These animals (78 New Zealand cows, 105 Australian cows) were reevaluated during their first lactation to determine if divergence for RFI observed during growth was maintained during lactation. Mean daily body weight (BW) gain during assessment as calves had been 0.86 and 1.15 kg for the respective countries, and the divergence in RFI between most and least efficient deciles for growth was 21% (1.39 and 1.42 kg of dry matter, for New Zealand and Australia, respectively). At the commencement of evaluation during lactation, the cows were aged 26 to 29 mo. All were fed alfalfa and grass cubes; it was the sole diet in New Zealand, whereas 6 kg of crushed wheat/d was also fed in Australia. Measurements of RFI during lactation occurred for 34 to 37 d with measurements of milk production (daily), milk composition (2 to 3 times per week), BW and BW change (1 to 3 times per week), as well as body condition score (BCS). Daily milk production averaged 13.8 kg for New Zealand cows and 20.0 kg in Australia. No statistically significant differences were observed between calf RFI decile groups for dry matter intake, milk production, BW change, or BCS; however a significant difference was noted between groups for lactating RFI. Residual feed intake was about 3% lower for lactating cows identified as most efficient as growing calves, and no negative effects on production were observed. These results support the hypothesis that calves divergent for RFI during growth are also divergent for RFI when lactating. The causes for this reduced divergence need to be investigated to ensure that genetic selection programs based on low RFI (better efficiency) are robust.

Feed makes up a large proportion of variable costs in dairying. For this reason, selection for traits associated with feed conversion efficiency should lead to greater profitability of dairying. Residual feed intake (RFI) is the difference between actual and predicted feed intakes and is a useful selection criterion for greater feed efficiency. However, measuring individual feed intakes on a large scale is prohibitively expensive. A panel of DNA markers explaining genetic variation in this trait would enable cost-effective genomic selection for this trait. With the aim of enabling genomic selection for RFI, we used data from almost 2,000 heifers measured for growth rate and feed intake in Australia (AU) and New Zealand (NZ) genotyped for 625,000 single nucleotide polymorphism (SNP) markers. Substantial variation in RFI and 250-d body weight (BW250) was demonstrated. Heritabilities of RFI and BW250 estimated using genomic relationships among the heifers were 0.22 and 0.28 in AU heifers and 0.38 and 0.44 in NZ heifers, respectively. Genomic breeding values for RFI and BW250 were derived using genomic BLUP and 2 bayesian methods (BayesA, BayesMulti). The accuracies of genomic breeding values for RFI were evaluated using cross-validation. When 624,930 SNP were used to derive the prediction equation, the accuracies averaged 0.37 and 0.31 for RFI in AU and NZ validation data sets, respectively, and 0.40 and 0.25 for BW250 in AU and NZ, respectively. The greatest advantage of using the full 624,930 SNP over a reduced panel of 36,673 SNP (the widely used BovineSNP50 array) was when the reference population included only animals from either the AU or the NZ experiment. Finally, the bayesian methods were also used for quantitative trait loci detection. On chromosome 14 at around 25 Mb, several SNP closest to PLAG1 (a gene believed to affect stature in humans and cattle) had an effect on BW250 in both AU and NZ populations. In addition, 8 SNP with large effects on RFI were located on chromosome 14 at around 35.7 Mb. These SNP may be associated with the gene NCOA2, which has a role in controlling energy metabolism.

Feed conversion efficiency of dairy cattle is an important component of the profitability of dairying, given that the cost of feed accounts for much of total farm expenses. Residual feed intake (RFI) is a useful measure of feed conversion efficiency, as it can be used to compare individuals with the same or differing levels of production during the period of measurement. If genetic variation exists in RFI among dairy cattle, selection for lower RFI could improve profitability. In this experiment, RFI was defined as the difference between an animal's actual feed intake and its expected feed intake, which was determined by regression of dry matter (DM) intake against mean body weight (BW) and growth rate. Nine hundred and three Holstein-Friesian heifer calves, aged between 5 and 7 mo, were measured for RFI in 3 cohorts of approximately 300 animals. Calves were housed under feedlot style conditions in groups of 15 to 20 for 85 to 95 d and had ad libitum access to a cubed alfalfa hay. Intakes of individual animals were recorded via an electronic feed recording system and BW gain was determined by weighing animals once or twice weekly, over a period of 60 to 70 d. Calves had DM intake (mean ± SD) of 8.3±1.37 kg of DM/d over the measurement period with BW gains of 1.1±0.17 kg/d. In terms of converting feed energy for maintenance and growth, the 10% most efficient calves (lowest RFI) ate 1.7 kg of DM less each day than the 10% least efficient calves (highest RFI) for the same rate of growth. Low-RFI heifers also had a significantly lower rate of intake (g/min) than high-RFI heifers. The heritability estimate of RFI (mean ± SE) was 0.27 (±0.12). These results indicate that substantial genetic variation in RFI exists, and that the magnitude of this variation is large enough to enable this trait to be considered as a candidate trait for future dairy breeding goals. A primary focus of future research should be to ensure that calves that are efficient at converting feed energy for maintenance and growth also become efficient at converting feed energy to milk. Future research will also be necessary to identify the consequences of selection for RFI on other traits (especially fertility and other fitness traits) and if any interactions exist between RFI and feeding level.

Using data from almost 2,000 Holstein-Friesian dairy heifers measured for growth rate and feed intake in both Australia and New Zealand (NZ), we demonstrated substantial variation in residual feed intake (RFI) and 250-day-liveweight (LWT250d). The respective heritabilities of RFI and LWT250d were 0.25 and 0.31 in Australian data and 0.41 and 0.25 in NZ data. Further, using around 630,000 SNP markers, genomic breeding values for RFI and LWT250d could be predicted with a moderate degree of accuracy (RFI: 0.41 and 0.31 in Australian and NZ data respectively; LWT250d: 0.41 and 0.25 in Australian and NZ data respectively).

Studies investigating variation in birth sex ratio indicate that the energy status of the dam prebreeding can influence the sex of the subsequent offspring. The Trivers-Willard hypothesis suggests that dams in good condition would produce more male offspring, whereas dams in poor condition (relative to dams in good condition) would produce more female offspring. However, results testing this hypothesis are associative in nature, with no data available from controlled experiments. Hence, this study tested the hypothesis that feed allowance around the time of conception alters birth sex ratio in lactating dairy cows. Cows (n = 770 on 2 farms) were randomly allocated to 2 treatments before the seasonal breeding period and offered either unrestricted (UnRes; n = 453, across 4 herd replicates) or restricted (Res; n = 317, across 3 herd replicates) allowance of fresh pasture for the first 14 d of breeding. Restricted cows responded by reducing milk yields throughout the treatment period and took 3 to 4 wk to recover. The birth sex ratio of resultant offspring was evaluated for cows that conceived in the first 21 d of breeding (UnRes n = 234; Res n = 142). Birth sex ratio was not different between UnRes and Res treatments. Association analysis, within treatments, identified that cows had a greater odds of producing a male offspring if they had lower milk fat to protein ratio before conception, were in a lower body condition score precalving, and gained condition from calving to the breeding period. No relationship between body condition score prebreeding and birth sex ratio was identified. In the current study, no difference in the birth sex ratio was observed following a short-term feed restriction around the conception. However, alternative indirect measures of energy balance (e.g., milk fat:protein ratio) may be a useful tool when examining the relationships between energy balance in dairy cows and birth sex ratio.

Reproduction and milk production responses were compared between dairy cows offered a high (HPA; n=453 in 4 replicates) or low (LPA; n=317 in 3 replicates) pasture allowance for the first 14 d after the planned start of mating (d 0 of experiment) in 2 seasonal, pasture-based dairy herds. Estimated pasture dry matter intake (DMI) between d -1 and 13 were 14.3+/-2.8 and 8.0+/-1.7kg of DM/cow per day for HPA and LPA cows, respectively. The LPA cows produced 22% less energy-corrected milk during the 14-d feeding treatment period, and milk yield remained less in LPA cows at d 53 despite all cows receiving pasture allowances to support DMI of 16kg of dry matter/cow per day from d 14 onwards. The 3-wk submission rate (percentage of cows inseminated at least once from d 0 to 20) and the 3- and 6-wk pregnancy rates of LPA cows (88, 45, and 71%, respectively) were lower than those of HPA cows (94, 53, and 78%, respectively), but conception rates to first (50%) or second (47%) service and final pregnancy rates (93%) did not differ between treatments. These results quantify the immediate and subsequent responses in reproductive performance and milk production to a severe restriction in DMI at the onset of a seasonal breeding period in pasture-grazed dairy cows.

Failure to gan or actual loss of weight is a common condition in young infants which has been a subjec of disussion for centuries, and m the past there was a tendency to regard wasting as a clinical entity. This conception is entirely wrong (Parsons, 1924); it is but a symptom of some underlying condition and i in this respect comparable wnth odter common symptoms such as vonming, convulions, and diarrhoea, none of which is regarded as a diseae sui generis. The causes of severe wasting may be classified under two main headings, (a) insufficient food, and (b) presence of infection. nsufiient food may be due to quantitative or qualtative defects m the diet or it may be the result of inpaired absorption from the ahmentary tract due to disease or diarrhoea. It may also be due to insuffiEent food reaching the intesine, as in abnormal conditions of the oesophagus or of the stomach, for example, pyloric stenosis. It is dilicult in some cases to separate lack of food from the presence of infection as the cause of wasting, because vomitingand diarrhoea and intolerance of food may be the result of infection and so introduce the starvation factor. Conversely, the infant who is not receiving adequate food is more liable to infection than the one whose nutrition is normal. In treating states of malnutrition it is always xnessary to discover the underlying cause, for unl this is removed, the measures desgned to arrest the progress of wasting will probably fail.

Nylon bags containing Persian clover, perennial ryegrass or perennial pasture hay were incubated for 12-h periods in lactating dairy cows grazing Persian clover pasture. The hypothesis was that the rate of dry matter disappearance over the first 12 h of incubation in the rumen would be lower when bags were inserted at a time when the rumen pH was at its lowest point for the day compared with a time when it was at its highest. It was also hypothesised that the reduction in rate of DM loss over 12 h at the initially low and then fluctuating rumen pH would be lower for Persian clover than for perennial ryegrass and the hay. Rumen fistulated cows grazing at 4 different pasture allowances (9, 16, 32 and 53 kg DM/day; 4 cows per treatment) were used in a completely randomised, split-plot design. The nylon bag incubation periods were 0700 to 1900 hours (period 1) and 1900 to 0700 hours (period 2) and rumen fluid pH was measured every 3 h during these periods. The ruminal fluid pH at the time of insertion of the nylon bags was higher (6.3 v. 5.7; P<0.001) in incubation period 1 than in period 2, and there was an interaction between the effects of incubation period and pasture allowance on the average rumen fluid pH in each period. Rate of DM loss was higher (3.47 v. 3.28%/h; P = 0.019) in incubation period 1 than in incubation period 2, highest (P<0.001) for clover, followed by ryegrass and then hay (5.05 v. 3.15 v. 1.93%/h) and higher (P<0.001) in cows grazing at the low (9 and 16 kg DM/cow) compared with high (32 and 53 kg DM/cow) allowances. There was a significant linear relationship (P<0.05) between DM loss rate calculated over 12 h and rumen fluid pH for grass and hay, but for clover this relationship only occurred in incubation period 2. These results suggest that more than 1 factor is important for determining feed degradation rates in the rumen at any particular time and that only using rates of forage DM loss that are obtained from nylon bags inserted prior to the morning feed, may overestimate the extent of rumen degradation of the feed eaten over the whole day in cows strip-grazing highly digestible pastures.

An experiment was conducted in which cows in early lactation grazed Persian clover (Trifolium resupinatum L.) or perennial ryegrass (Lolium perenne L.)-dominant pastures at low or high pasture allowances in order to determine the effects of pasture type and level of feeding on rumen fermentation patterns. The hypotheses for grazing dairy cows were: (i) the consumption of Persian clover would result in a more rapid rate of degradation and less stable rumen fermentation patterns compared with perennial ryegrass; and (ii) the greater intake of cows grazing at high compared with low pasture allowances would also cause less stable rumen fermentation patterns. Stability of rumen fermentation refers to the level to which rumen fluid pH declines, especially for long periods of a day, indicating that the rumen is not coping with neutralising and/or removing acids. Cows grazing Persian clover had lower (P<0.05) average daily rumen fluid pH (5.7 v. 5.9), molar proportions of acetic acid (68.3 v. 70.6%) and ratios of lipogenic to glucogenic volatile fatty acid (4.6 v. 5.1) in the rumen than those grazing perennial ryegrass. They had higher (P<0.05) rumen fluid ammonia-N (26.3 v. 13.0 mg/100 mL) and total volatile fatty acid (165 v. 134 mmol/L) concentrations and molar proportions of butyric (11.3 v. 10.7%) and propionic (17.2 v. 16.1%) acids than cows grazing perennial ryegrass. Cows grazing at low pasture allowances had a higher (P<0.05) average daily rumen fluid pH (5.9 v. 5.7) and lower rumen fluid ammonia-N (18.6 v. 20.7 mg/100 mL) and total volatile fatty acid (143 v. 156 mmol/L) concentrations than cows grazing at high pasture allowances. Cows given Persian clover at the high allowance had a rumen fluid pH less than 6.0 for the entire day while rumen fluid pH was below 6.0 for at least 15 h of the day on all the other treatments. There was no effect (P>0.05) of pasture allowance on the degradation rate of perennial ryegrass dry matter, but the higher allowance of Persian clover resulted in the highest (P<0.05) rate of degradation of dry matter compared with either ryegrass treatment or the low allowance of Persian clover. The effective dry matter degradability of Persian clover was greater (P<0.05) than that of perennial ryegrass, and the effective dry matter degradability of herbage in cows grazing at low allowances was greater (P<0.05) than at higher allowances. However, future research should consider neutral detergent fibre degradation in grazing dairy cows with low rumen fluid pH levels.

An experiment was conducted to investigate the hypothesis that increasing the intake of Persian clover (Trifolium resupinatum L.) would decrease rumen fluid pH and the rate of loss of neutral detergent fibre from nylon bags. It was further hypothesised that the reduction in the rate of disappearance of neutral detergent fibre with increased intake would be less in highly digestible clover than in highly digestible ryegrass or pasture hay. Sixteen rumen fistulated cows, in late lactation, were used in a completely randomised, split-plot design for 33 days. There were 4 pasture allowance treatments (9, 16, 32 and 53 kg dry matter (DM)/cow.day of Persian clover) with 4 cows per treatment. Cows grazed in individual plots, pasture intakes were measured, and rumen fluid and in sacco measurements were undertaken. Pasture DM intake increased asymptotically as pasture allowance increased from 9 to 53 kg DM. Cows grazing at the 9 kg pasture allowance spent less time grazing than cows at higher allowances (294 v. 368, 421 and 414 min, P<0.05). Cows grazing at the 2 lower allowances spent less time grazing at night than cows at the 2 higher allowances. There was no effect (P>0.05) of pasture allowance on time spent ruminating, which averaged 236 min. Estimated rates of intake increased (P<0.05) with pasture allowance. Average daily rumen fluid pH decreased linearly (P<0.05) with pasture intake, with the averages for the pasture allowance treatments being 6.03, 5.95, 5.83 and 5.79 as pasture allowance increased. The patterns of rumen fluid pH over 24 h indicated that it was only late in the night that treatment differences were detected, with the lower pasture allowance treatments recording higher rumen fluid pH values than the higher pasture allowance treatments. There was no effect of pasture allowance on average daily rumen fluid ammonia-N concentrations (25 mg/100 mL). Total volatile fatty acids concentrations averaged 139, 152, 163 and 168 mmol/L as pasture allowance increased from 9 to 53 kg DM/cow.day. The proportion of acetate in total volatile fatty acids generally declined (71.4, 70.4, 67.4 and 69.2%; s.e.d. = 1.14) and the proportion of propionate generally increased (15.2, 15.5, 17.6 and 17.0%; s.e.d. = 0.77) as pasture allowance increased from 9 to 53 kg DM/cow, respectively. Rate of neutral detergent fibre loss from nylon bags was highest in clover, and lowest in hay, and was higher in cows grazing at 9 and 16 kg allowances compared with cows at 32 and 53 kg (P<0.05). There was a linear relationship (P<0.05) between rate of neutral detergent fibre loss and rumen fluid pH for clover and ryegrass, but not hay (P>0.05). There were no differences (P>0.05) in total rumen contents (75.6 kg; s.e.d. = 6.95), or DM (7.3 kg; s.e.d. = 0.73) and neutral detergent fibre (2.7 kg; s.e.d. = 0.32) pools, of cows grazing at different allowances. Offering cows increasing allowances of Persian clover pasture reduced rumen digesta retention times, as rumen pool sizes did not change. Average daily pH fell with increasing allowance due to differences in daily intake and pH patterns, and increasing pasture allowance decreased the rate of disappearance of neutral detergent fibre. It is suggested that increased outflow rates, driven by differences in daily pH patterns and changes in substrate composition, were responsible for the decline in disappearance of neutral detergent fibre from nylon bags, but the effects of the factors cannot be separated.

Cows grazing highly digestible pasture in early spring can have very low rumen fluid pH that can negatively impact on the efficiency of microbial digestion. In this experiment, cows in early lactation grazed perennial ryegrass (Lolium perenne L.)-based pasture alone at low or high allowances, or at a low allowance supplemented with either a cereal grain pellet, a chopped hay cube or a cube containing cereal grain and chopped hay to determine the effects of the addition of neutral detergent fibre as hay on chewing behaviour and stability of rumen fermentation. The hypotheses tested were that: (i) supplementing high digestibility ryegrass pasture with pelleted cereal grain would increase the proportion of the day that the pH of rumen fluid was below 6.0 and would decrease the rate of degradation of neutral detergent fibre in pasture and hay; and (ii) the inclusion of chopped hay with the cereal grain supplement in cubes would reduce the proportion of the day that the rumen fluid pH was below 6.0 and restore the rate of degradation of neutral detergent fibre in pasture and hay to that in unsupplemented cows. Rumen fluid pH was highest (P<0.05) in cows fed a chopped hay cube and lowest (P<0.05) in cows fed a cube containing cereal grain and chopped hay, with no significant (P>0.05) difference between those fed pasture only or cereal grain pellets. The introduction of grain, with or without hay, did not substantially alter the pattern or magnitude of changes in rumen fluid pH, but did reduce (P<0.05) the rate of degradation of neutral detergent fibre in pasture (5.3 v. 7.6%/h) and hay (2.7 v. 5.0%/h) in the rumen. Rumen degradation rates of pasture dry matter and neutral detergent fibre were not improved by adding chopped hay. Total volatile fatty acid concentrations in rumen fluid were highest (P<0.05) on the high pasture allowance treatment and lowest (P<0.05) on the low pasture allowance and the chopped hay cube treatments. Supplementation with grain reduced (P<0.05) the proportion of acetate and increased (P<0.05) the proportion of propionate in total volatile fatty acids. There were no significant (P>0.05) effects of dietary treatment on time spent grazing or on rate of biting while grazing. Cows in treatments receiving grain supplements (532 min) and those in the high pasture allowance treatment (566 min) spent more (P<0.05) time ruminating than those in the low pasture allowance (415 min) and chopped hay cube (465 min) treatments. The relative contributions of low pH and of starch to the reduction in rates of dry matter and neutral detergent fibre degradation in the rumen cannot be determined from this experiment, however, it is likely that both factors contribute to a relative increase in the metabolic activity of non-cellulolytic microorganisms.

Control, acid or buffer solution was infused intraruminally into cows eating highly digestible grassbased pasture and the rates of neutral detergent fibre (NDF) degradation of 4 highly digestible ryegrasses were determined using the nylon bag technique. The control solution was water, the acid solution was a mixture of acetic and hydrochloric acids and the buffer solution contained sodium hydrogen carbonate and disodium hydrogen orthophosphate. The average daily ruminal fluid pH of cows receiving acid infusion was lower, and the diurnal variation in ruminal fluid pH was greater, than that of cows receiving the control or buffer infusion. Cows receiving acid or buffer infusion had a slower rate of NDF degradation than cows receiving the control infusion. The rate of NDF degradation did not decrease as the proportion of NDF in the grass increased. The composition and structural arrangement of NDF was likely to have differed between pasture sources. The cellulolytic pH threshold for highly digestible pasture in grazing cows remains poorly defined because variations in pH are likely to be as, or more, important than a mean value.