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No description available.

No description available.

No description available.

No description available.

No description available.

Two experiments were conducted to determine the effects of grazing stockpiled perennial forage in field paddocks relative to feeding similar quality round bale hay in drylot pens on rumen degradation characteristics of forage; beef cow performance, cow reproductive efficiency, estimated dry matter intake and forage utilization, forage yield and quality, soil nutrients and system costs. Winter feeding systems were (i) stockpiled perennial forage (TDN = 58.9%; CP = 8.5%) grazing (SPF) and (ii) drylot feeding (DL) of round bale hay (TDN = 57.9%; CP = 8.4%). Experiment I was an in situ study, where five Hereford heifers (398 ± 14 kg) fitted with rumen cannulae were fed a grass hay (DM = 93.2%; TDN = 50.8%; CP = 9.8%; NDF = 66.2%) diet. In situ degradability of both stockpiled forage (SPF) and round bale hay (BH) samples collected at start (October) and end (December) of the field study were determined. The soluble fraction (S) of DM was greater (P = 0.01) in SPF October forage compared to SPF December, BH October and BH December forages. The potentially degradable fraction (D) of CP was lowest (P = 0.04) in BH December forage than in SPF October, SPF December and BH October forages suggesting that hay quality declined more rapidly than stockpiled forage and method of preservation may have affected overall hay quality. Furthermore, D fraction of both ADF and NDF was higher in SPF samples suggesting stockpiled forage may be more digestible than hay. However, the D fraction of NDF in both SPF and BH forages declined with later sampling date possibly due to effect of weathering and leaf loss. In Experiment II, 6, 4-ha paddocks consisting of meadow bromegrass (Bromus riparius Rehm) and alfalfa (Medicago sativa), were randomly assigned to 1 of 2 replicated (n = 3) winter feeding systems. In this study 58 dry pregnant (120 ± 16 d) Angus cows (675 kg ± 51 kg), stratified by body weight (BW; corrected for conceptus gain), were allocated to either the SPF or DL systems. Cows in winter feeding systems were provided additional energy supplement (rolled barley) (TDN = 86.4%; CP = 12.4%) depending on environmental conditions to maintain body condition, with no weight gain above that of conceptus growth. Dry matter intake (DMI) and forage utilization were estimated using the herbage weight disappearance method. The effects of winter feeding systems on soil nutrients were determined the following spring after winter grazing. Forage yield in DL (4683 ± 495 kg ha-1) and SPF (4032 ± 495 kg ha-1) systems was not different (P = 0.18) between treatments. However, forage utilization was lower (P < 0.01) in SPF (83.5%) than the DL (94.4%) system, signifying lower accessibility to stockpiled forage due to snow depth, lower temperatures, freezing rain and wind. Cows in the SPF system had higher forage DMI (P = 0.04) and supplementation intake (P < 0.01) compared to cows in drylot pens likely a combined effect of effective ambient temperatures below the lower critical temperature (LCT) during the grazing period and the higher potentially digestible fraction of neutral detergent fiber in stockpiled forage than hay. Cow BW change, average daily gain, rib fat change and rump fat change were not different (P > 0.05) between winter feeding systems. Reproductive performance of beef cows was not affected (P > 0.05) by either winter feeding methods as cows in both systems maintained body condition score (BCS) at 2.5 to 3.0 throughout the study. Average total production cost was 19% lower in SPF system compared to DL system. In conclusion, the rumen degradation characteristics of stockpiled perennial forages focused in this study support the utilization these forages in a winter feeding system to meet the nutrient requirements of dry beef cows in early to mid-gestation. It may be cost effective to manage beef cows in field grazing of stockpiled perennial forages in western Canada, without any negative impact on beef cow performance or reproductive efficiency.

Calving is an essential event in dairy production, as lactation only begins after calving and cows must give birth at regular intervals in order to maintain milk production. Careful management is important during the weeks around calving as this is when dairy cows most frequently experience health problems. Experienced stockmen use judgements based on physical and behavioural changes in order to recognise when cows may be about to calve, and subsequently be available to offer assistance when required. With increasing herd sizes and large numbers of cows per stockman, individual attention is often difficult. An automated system that monitors behavioural or physiological changes before calving could potentially be used to predict the time of calving, and help improve supervision by farm staff. Data comprising two years of records from Langhill Farm were used to identify any variables which could be used for calving prediction or as risk factors for various calving problems. Records kept by stockmen detailing the signs of calving and time of observation were compared with quantitative behavioural data. Observations from video recordings were used to identify any consistent behavioural changes occurring the day before calving that could be used to predict the onset of calving. The frequencies of lying and tail raises proved to be the most useful indicators, as they showed consistent changes in the final six hours before calving. Differences between heifers and cows, and between those experiencing calving difficulties and those which did not, were also investigated. Differences between heifers and cows were shown which should be taken into account when predicting calving times. However, no early-warning signs of difficulties were identified for cows and heifers assisted with a calving jack. Cows were also fitted with collars containing accelerometers to investigate if features in tri-axial accelerometer data could be shown to correspond to specific behaviours. Some success was achieved in identifying eating behaviour and postural changes, demonstrating that there is potential for monitoring behaviour using this method. Weekly heart rate recordings were also taken to establish if there was a change in the heart rate or heart rate variability during the final six weeks of gestation. Changes were found but, although they were statistically significant, they were considered too subtle for any practical application. Consistent changes in behaviour were observed in the six hours before calving, some of which could be measured using accelerometers. These changes have the potential to be used as the basis of an automated monitoring system to predict calving.

Dairy cattle make a significant contribution to global methane emissions. Milking cows in the UK make up about a fifth of the total cattle population, with Holstein-Friesian cows being the most common breed. Investigating ways to minimise methane, a potent greenhouse gas (GHG) produced by dairy cows from enteric fermentation and manure, has gained importance in recent years due its role in climate change. Currently, GHG emissions from UK dairy farming are predicted using the Intergovernmental Panel on Climate Change (IPCC) Tier II methodology. The IPCC Tier II methodology and statistical prediction equations from the literature were evaluated for their ability to reliably model methane output using data from the Langhill Holstein-Friesian experimental herd. The Langhill dairy herd is on a long-term breeding and feeding systems experiment, and cows are on average 88% North American Holstein genes. The production systems within the herd represent a range of dairy systems that may be found commercially. Therefore, production values were assumed to be representative of those that could be found in the commercial Holstein-Friesian population, so factors affecting system methane emissions and appropriate mitigation options could be investigated. Prediction equations using dry matter (DM) intake and gross energy intake as input values were the most appropriate equations for reliably estimating daily enteric methane output. However, if DM intake values are not available, the IPCC Tier II method was found to provide a suitable prediction of methane emissions over a cow‘s lactation and lifetime. This study found that GHG emissions from enteric fermentation and manure, expressed as carbon dioxide equivalents (CO2-eq.), account for about 66% of dairy system CO2-eq. emissions, with enteric methane output being the main contributor (34% of system CO2-eq. emissions). Breeding for increased kilograms of milk fat plus protein production was shown to help reduce dairy system methane emissions. Cows of predominantly North American Holstein genes in this study produced more milk when fed a diet with a low proportion of forage and had lower GHG emissions and land requirement per kilogram energy corrected milk than similar cows fed a diet with a higher proportion of forage. Strategies to mitigate GHG emissions (including methane) and the environmental impact of dairy systems should seek to select animals that better utilise their feed intake to meet their genetic potential for milk production.

Imprecise control of bovine oestrus and ovulation and the highly variable nature of the superovulatory response impedes use of reproductive technologies. The use of GnRH to control antral follicle development and, hence, the oestrous cycle was investigated using 40 maiden heifers. Two GnRH agonist sources (Fertagyl; Receptal) were tested at two frequencies (24; 48 hour) and luteinising hormone release profile; and pattern of antral follicle and luteal development were monitored. Post cessation of GnRH treatment gonadotrophin was given at either a fixed or variable time relative to oestrus and superovulatory response assessed. Basal LH values were unaffected by treatment. Treatment at 24, but not 48 hour intervals resulted in reduced LH response values. Fertagyl 24 hour treatment stimulated increased numbers of follicles to grow to 3-5 mm and 6-9 mm but inhibited growth to 10 mm, maturation and ovulation. Four waves of follicular development occurred in GnRH agonist, but not control, animals. Luteolysis and oestrus was delayed in a proportion of animals challenged with prostaglandin during GnRH agonist treatment. Exogenous gonadotrophin given at fixed time (day 10 1 where oestrus = day 0) post cessation of treatment, elicited a greater superovulatory response than when given at variable time. There was a positive relationship between number of ovulations and viable embryos; and a negative relationship between body weight and progesterone concentration and consequently superovulatory response. High superovulatory responses were observed when gonadotrophin treatment was initiated in the presence of an active corpus luteum and the absence of a dominant follicle. It was concluded that GnRH agonist given every 24 hours depleted LH reserves; allowed selection and dominance of antral follicles, but not maturation and ovulation; precluded prostaglandin induced luteolysis in some animals; and increased ovulations and embryos when gonadotrophin treatment was at a fixed time.