N. Lopez-Villalobos

Effects of stocking rate, supplementation, genotype and their interactions on grazing dairy systems: a review

Abstract The main effects of, and the interactions between, stocking rate (SR), supplementation and genotype on dry matter (DM) intake, herbage utilisation, milk production and profitability of grazing dairy systems have been reviewed. The SR determines the average herbage allowance (HA) per cow and therefore has a major effect on herbage intake (HI) and on the productivity of grazing dairy systems. In this review, the effect of HA on HI is presented separately for two groups of studies: those that measured allowance at ground level and those that measured allowance at a cutting height of 3–5 cm above ground level. HI and milk yield per hectare usually increase as SR increases. However, there is generally an associated reduction in HI and milk yield per cow because of the decrease in average HA at a higher SR. The dual objectives of adequate level of feeding per cow and high herbage utilisation per hectare can be achieved through the inclusion of supplements. The milk response to supplements depends mainly on the size of the relative energy deficit between potential energy demand and actual energy supply. The relative energy deficit determines both energy partitioning within the cow and substitution rate. The relative energy deficit is increased by either a high demand for energy within the cow or by a deficit of dietary energy available to meet the demand. Cows of different genotype differ in their potential for milk yield. Cows with high genetic potential for milk yield undergo higher relative energy deficits under grazing dairy systems, resulting in lower substitution rates, higher milk responses to supplements, but also lower body condition score, which, in turn, leads to lower reproductive performance. Whole-farm experiments in many countries have demonstrated that the inclusion of supplements, with a concomitant increase in SR, can have synergistic effects in improving the productivity of grazing dairy systems. Overall, the level of supplementation required per cow and the optimum SR depend on the genetic potential of the cow, the size of the responses to supplement, the value of milk and the costs of feeding supplements.

Neonatal mortality in New Zealand sea lions (Phocarctos hookeri) at sandy bay, enderby island, auckland islands from 1998 to 2005

As part of a health survey of New Zealand sea lions (Phocarctos hookeri) on Enderby Island, Auckland Islands (50°30′S, 166°17′E), neonatal mortality was closely monitored at the Sandy Bay colony for seven consecutive years. Throughout the breeding seasons 1998–99 to 2004–05, more than 400 postmortem examinations were performed on pups found dead at this site. The primary causes of death were categorized as trauma (35%), bacterial infections (24%), hookworm infection (13%), starvation (13%), and stillbirth (4%). For most pups, more than one diagnosis was recorded. Every year, two distinct peaks of trauma were observed: the first associated with mature bulls fighting within the harem and the second with subadult males abducting pups. In 2001–02 and 2002–03, epidemics caused by Klebsiella pneumoniae increased mortality by three times the mean in nonepidemic years (10.2%). The increased mortality was attributed directly to acute suppurative infection due to the bacterium and also to an increase in traumatic deaths of debilitated pups. Parasitic infection with the hookworm Uncinaria spp. was a common finding in all pups older than three weeks of age and debilitation by the parasite may have contributed to increased susceptibility to other pathogens such as Klebsiella sp. or Salmonella sp. This study provides valuable quantitative data on the natural causes of neonatal mortality in New Zealand sea lions that can be used in demographic models for management of threatened species.

Effects of ewe size and nutrition on fetal mammary gland development and lactational performance of offspring at their first lactation

Many environmental factors applied postnatally are known to affect milk production of the dam, but to date, the effects of different fetal environments on subsequent first lactational performance of the offspring have not been reported. Four hundred fifty heavy (H; 60.8 kg +/- 0.18) and 450 light (L; 42.5 kg +/- 0.17) dams were randomly allocated to ad libitum (A) or maintenance (M) nutritional regimens from d 21 until d 140 of pregnancy, under pastoral grazing conditions (HA, n = 151; HM, n = 153; LA, n = 155; LM, n = 153). At d 100 of pregnancy, a sub-group of twin-bearing dams was killed and fetal mammary glands collected. From 1 wk before lambing, all remaining dams were fed ad libitum until weaning. After weaning, female progeny were managed and fed under pastoral conditions as 1 group. At 2 yr of age, 72 twin-rearing ewe offspring were milked once a week for 7 wk. Fetuses from M-dams had heavier mammary glands (P = 0.03) compared with A-fetuses. Fetuses from H-dams had greater (P = 0.0008) mammary duct area compared with L-fetuses. At 2 yr of age, M-offspring had greater milk yields at d 7 (P = 0.02) and d 28 (P = 0.09) of lactation and tended to have greater accumulated milk yields (P = 0.11) compared with A-offspring. Ewes born to M-dams showed greater lactose percentage at d 14 (P = 0.002), d 21 (P = 0.06), and d 28 (P = 0.07) of lactation and greater (P = 0.049) accumulated lactose yields and CP (P = 0.06) yields compared with A-offspring. Ewes born to H-dams displayed greater milk yields at d 14 (P = 0.08) and d 21 (P = 0.02) and had greater accumulated milk yield (P = 0.08) and lactose yield (P = 0.04) compared with L-offspring. Lambs born to M-offspring were heavier at birth (P = 0.02) and grew faster until weaning (P = 0.02), matching the milk yield and composition data, compared with their ad libitum counterparts. Birth weight was not affected (P > 0.10) by grand dam size; however, lambs born to H-offspring grew faster from birth until d 49 of age (P = 0.03). In conclusion, dam nutrition during pregnancy affected the resulting milk production of the offspring and composition and growth of their lambs. In addition, dam size affected the milk production of the offspring, lactose yield, and growth of their lambs. These findings are important for furthering our understanding of how the environment to which the female fetus is exposed can affect her subsequent development and her ability to nourish the next generation.

Within- and between-animal variance in methane emissions in non-lactating dairy cows

Several studies on methane (CH4) emissions have focussed on selecting high and low CH4-emitting animals. One challenge faced by this work is the lack of consistency, or repeatability, in animal rankings over time. Repeatability for individual animals over time needs to be high to reliably detect high and low CH4-emitting animals. A possible explanation for the lack of repeatability is a relatively high within-animal variation in daily CH4 emissions, meaning that animals could then change their ranking when compared at different points in time. An experiment was undertaken with four non-lactating dairy cattle to assess the within- and between-animal variation in CH4 emissions over time when measured using the sulfur hexafluoride (SF6) tracer technique. Two contrasting diets were fed to the cattle at maintenance energy levels: lucerne silage (diet 1) and a cereal + lucerne + straw mixed ration diet (diet 2). Daily CH4 measurements were undertaken for 23 days on diet 1 and 30 days on diet 2. There was a significant (P < 0.001) difference between diet 1 and diet 2 in daily CH4 production, with mean (±s.e.) production of 124.3 (11.1) g CH4/day from diet 1 and 169.8 (±11.0) g CH4/day from diet 2. Lower CH4 yield (g CH4/kg dry matter intake) was recorded on diet 1 (22.8 ± 2.0) than diet 2 (32.0 ± 2.0). Cows differed significantly (P < 0.05) from one another in daily CH4 yield (diet 1: cow 1 = 19.4 ± 0.6, cow 2 = 22.2 ± 0.8, cow 3 = 23.2 ± 0.7, cow 4 = 25.4 ± 0.6; diet 2: cow 1 = 26.0 ± 0.7, cow 2 = 36.4 ± 0.7, cow 3 = 29.3 ± 0.7, cow 4 = 36.6 ± 0.7). Variances for daily CH4 yield were smaller for diet 1 (within animal = 6.91, between animals = 6.23) than for diet 2 (within animal = 10.09, between animals = 27.79). Estimates of repeatability (variation between animals/total variation) for daily CH4 yield were 47 and 73% in diet 1 and 2, respectively. Coefficients of variation in average daily CH4 emissions in this experiment ranged from 8 to 18% despite the fact that each animal received the same quantity and quality of feed each day. While further research is required, the high within-animal variability in CH4 emissions measured using the SF6 tracer technique may explain why there has been difficulty in obtaining consistent rankings in CH4 yields when animals are measured on multiple occasions. The results also suggest that the SF6 tracer technique may exaggerate apparent between animal differences in CH4 emissions.

Controlling the onset of natural cryptosporidiosis in calves with paromomycin sulphate

A prospective, controlled-blind field trial was conducted to evaluate the efficacy and safety of paromomycin sulphate, given for 10 days from birth, in preventing natural cryptosporidiosis in calves. In the untreated control group, oocyst shedding and diarrhoea followed the pattern that had occurred on the farm before the trial, consistent with a perinatal infection, whereas in the treated group, the prepatent period was significantly longer than in the control group (P<0.01) and oocyst shedding and diarrhoea started only after the drug was withdrawn. However, the regimen did not reduce the incidence of disease in the treated group.

Development and application of a processing model for the Irish dairy industry

A processing-sector model was developed that simulates (i) milk collection, (ii) standardization, and (iii) product manufacture. The model estimates the product yield, net milk value, and component values of milk based on milk quantity, composition, product portfolio, and product values. Product specifications of cheese, butter, skim and whole milk powders, liquid milk, and casein are met through milk separation followed by reconstitution in appropriate proportions. Excess cream or skim milk are used in other product manufacture. Volume-related costs, including milk collection, standardization, and processing costs, and product-related costs, including processing costs per tonne, packaging, storage, distribution, and marketing, are quantified. Operating costs, incurred irrespective of milk received and processing activities, are included in the model on a fixed-rate basis. The net milk value is estimated as sale value less total costs. The component values of fat and protein were estimated from net milk value using the marginal rate of technical substitution. Two product portfolio scenarios were examined: scenario 1 was representative of the Irish product mix in 2000, in which 27, 39, 13, and 21% of the milk pool was processed into cheese (€ 3,291.33/t), butter (€ 2,766.33/t), whole milk powder (€ 2,453.33/t), and skim milk powder (€ 2,017.00/t), respectively, and scenario 2 was representative of the 2008 product mix, in which 43, 30, 14, and 13% was processed into cheese, butter, whole milk powder, and skim milk powder, respectively, and sold at the same market prices. Within both scenarios 3 milk compositions were considered, which were representative of (i) typical Irish Holstein-Friesian, (ii) Jersey, and (iii) the New Zealand strain of Holstein-Friesian, each of which had differing milk constituents. The effect each milk composition had on product yield, processing costs, total revenue, component values of milk, and the net value of milk was examined. The value per liter of milk in scenario 1 was 24.8, 30.8, and 27.4 cents for Irish Holstein-Friesian, Jersey, and New Zealand strain of Holstein-Friesian milk, respectively. In scenario 2 the value per liter of milk was 26.1, 32.6, and 28.9 cents for Irish Holstein-Friesian, Jersey, and New Zealand strain of Holstein-Friesian milk, respectively.

Use of crossbreeding with beef bulls in dairy herds: effect on age, body weight, price, and market value of calves sold at livestock auctions.

The aim of this study was to investigate the effect of different breeds and breed crosses on age (AC, d), BW (kg), price (PR,

Dystocia in beef heifers: A review of genetic and nutritional influences

/kg), and market value (MV,

Quantifying the effect of thermal environment on production traits in three breeds of dairy cattle in New Zealand

/calf) of purebred and crossbred calves sold for veal and beef production. The Kovieh wholesale cattle organization (Bolzano, Italy) grouped calves from several dairy herds located in the Trentino-Südtirol region in Italy and sold them by public auctions. Data on AC, BW, PR, and MV from 96,458 calves were recorded from January 2003 to December 2007 and consisted of 4 pure breeds [2 dairy, Brown Swiss (BS) and Holstein-Friesian (HF); and 2 dual-purpose, Simmental (SI) and Alpine Grey (AG)], and 8 crossbreds by crosses of Limousin (LI) and Belgian Blue (BB) with the 4 dam breeds. Least squares means for AC, BW, PR, and MV were calculated for breeds and breed crosses with a model that included fixed effects of herd of birth, age (except for AC), sex, and breed of the calf, year and season of auction, and interactions between the main effects. The coefficients of determination of the models were 0.41, 0.51, 0.84, and 0.82 for AC, BW, PR, and MV, respectively. Sex, age, and breed were the most relevant sources of variation for BW (P < 0.001), whereas breed and sex were the most important sources of variation for AC, PR, and MV (P < 0.001). Also, PR and MV were significantly influenced (P < 0.01) by all the effects included in the model, except for season x age interaction in the case of MV. Market value of male was greater (P < 0.001) than that of female calves, with the exception of BS (-

Effect of nutrition from mid to late pregnancy on the performance of twin- and triplet-bearing ewes and their lambs

28.76/calf) and HF (-