The adoption of good practices of handling improves dairy calves welfare: Case study

The aim of this study was to assess the effect of the adoption of a set of good practices of handling on dairy calves welfare. Data were retrieved from the records of a commercial farm, considering three periods: Conventional handling (CH, 12 mo.), transitional period (TP, 4 mo.), and good practices handling (GPH, 12 mo.). During CH calves were kept in individual pens, milk-fed in open pails and subjected to abrupt weaning; while during TP and GPH they were kept in groups, milk-fed in nipple-pails, brushed for 5 min. once a day, and subjected to progressive weaning. TP was assumed as a training period necessary for GPH implementation. The percentages of calves treated with antibiotics and numbers of deaths per month were used as indicators of calves welfare. Statistical analysis was performed using a logistic regression model to compare the number of deaths per month between CH and the other periods. Chi-square test was used to compare the percentage of animals treated with antibiotics per month. Results showed that CH had a higher risk of calf's death then TP and GPH, as well as a higher percentage of animals treated with antibiotics. In conclusion, the adoption of good practices of handling improved dairy calves welfare.

Such variations have been explained by the effect of breed or genetic groups (Davis, Norberg, & Fogh, 2020) and meteorological conditions (Stull et al., 2008, Roland, Drillich, Klein-Jöbstl, & Iwersen, 2016, as well as by the differences in raising and handling conditions (Botteon, Botteon, Santos Júnior, Pinna, & Lóss, 2008;Moran, 2011;Walker et al., 2012;Barry et al., 2019). For example, in a study carried out by Abuelo, Havrlant, Wood, and Hernandez-Jover (2019) in Australian dairy farms, only 19.5% of the colostrum samples analysed (n = 221) meet the standards of satisfactory IgG concentration (>50 g L -1 ) and microbiological quality (total bacteria and total coliform counts lower than 100,000 and 10,000 cfu mL -1 , respectively); and the results of Stull et al. (2008) showed that calf mortality increases when the average daily temperature are less than 14 o C and higher than 24 o C, and that, under the meteorological condition in which the study was carried out, rain was not an important predictor of mortality.
Infectious diseases, particularly diarrhoea and pneumonia, are characterized as the main causes of dairy calf morbidity and mortality (Gulliksen et al., 2009;Beaver, Meagher, von Keyserlink, & Weary, 2018;McConnel et al., 2019). However, there is little information on the prevalence of these diseases in Brazilian dairy cattle herds. In one of the few studies published on the subject, Botteon et al. (2008) (Cruz et al., 2011) showed high prevalence of diarrhoea (mean 23.7%) and pneumonia (mean 16.8%) in dairy calves. Additionally, Fruscalso, Olmos Antillon, and Hötzel (2020) reported that the main cause of calf mortality was diarrhoea, being responsible for more than 40% of deaths.
One strategy used to reduce spreading infectious diseases among dairy calves is to maintain them in individual pens, without any possibility of physical contact (McGuirk, 2008;Gulliksen et al., 2009). This is a common practice in Brazilian dairy farms, where small outdoor shelters, commonly called "casinhas tropicais", are used to keep a calf isolated from each other (Vinholis, Tupy, Pedroso, Primavesi, & Bernardi, 2006). However, according to Costa, von Keyserlingk, and Weary (2016) the social isolation has a negative impact on dairy calves welfare; being suggested by the authors that the best way to deal with the higher risk of spreading infections, when keeping dairy calves in group housing, is by the adoption of appropriated management, instead isolating them.
It should also take into consideration that using open-pails to milk-feed dairy calves increases the risk of harming their welfare, since they are not able to express proper suckling behaviour, which lead to motivational and physiological disturbances, characterized by the expression of cross-suckling abnormal behaviour (de Passillé, 2001) and by precluding oesophageal groove to close, which is essential for proper milk digestion (Martín-Alonso, Cal-Pereyra, Fernández-Caso, & Gonzáles-Montaña, 2019).
To the best of our knowledge, no studies have been conducted assessing the effects of adopting a set of good handling practices on the welfare of dairy calves. Thus, the aim of this study was to evaluate the effects of adopting of a set of good practices of handling (control of the colostrum ingestion, group housing, milkfeeding in nipple-pails, brushing during suckling, and progressive weaning) on the welfare of dairy calves raised under a commercial dairy farm in Brazil.

Material and methods
This study was approved by the Committee of Ethical Use of Animals of the Faculty of Agricultural and Veterinary Sciences, UNESP, Jaboticabal, São Paulo State, Brazil (Protocol number 17310/15).
The study was conducted with the data file of a commercial dairy farm located in the municipality of Taiaçu, São Paulo, Brazil (21º08'40" S and 48º30'45'' W, average altitude of 565 m above sea level), by considering the frequencies of treatments with antibiotics and calves losses during a period of 2 years and 4 months, comprising data from before (12 mo., n = 511), during (4 mo., n = 128) and after (12 mo., n = 420) the adoption of good practices of calves handling as a routine. Months within periods were assumed as replications.
During the first 12 months of data records calves were handled in a conventional way (conventional handling, CH), staying with their mothers during the first 24 hours of life, suckling colostrum directly from them (without any control of the quality and amount of colostrum ingested); and navels were treated within the first 12 hours after birth by immersion in 10% iodine solution. From the 2 nd to the 30 th day of life calves were housed in individual pens (1.5 m² calf -1 , with 10 cm of sawdust or straw as bed) installed in a shed; during the first 2 days of this period, they received colostrum (ad libitum) in bottle; and from the 4 th day old, they were fed with a commercial milk replacer (Sprayfo Violet®) in open-pails, receiving 4 L of milk replacer per day (divided in two meals) until weaning. On the 31 st day of life, calves were moved to outside and housed in "casinhas tropicais" (installed under the shade of coconut palms and on a sand bed), being tied to them with a 1.2 m. Weaning was carried out in an abrupt way, when they were around 70 days old. Handling procedures were carried out with few interactions with calves.
During the following 4 months of the study period (transitional period, TP), farm staff was trained to adopt a set of good practices of handling, when the following handling procedures started to be adopted: Calves remained with their mothers during the first 24 hours of life, but an additional offer of high quality colostrum (tested using a colostrometer) were supplied in bottles, assuring the ingestion of 2 L of colostrum up to 6 hours after birth, plus 2 L up to 12 hours. The navels were treated within the first six hours after birth, also with total immersion in a 10% iodine solution; and from the 2 nd to the 30 th day of life, the calves were housed in larger individual pens (3.0 m² calf -1 ), besides having access to a paddock between feed meals (except on rainy days), where they were able to socialize and play. From the 4 th day of life, the calves were milk-fed with the same milk replacer and the same amount but, in this case, using nipple-pails, allowing the calves to suckle. Calves were brushed for five minutes during morning milk-feed and, from the 31 st day of life, they were moved into paddocks (Cynodon spp.) with free access to water and shade, where they stayed in groups of 6 to 8 animals until weaning. Calves were weaned gradually (see Table 1 for details), completing weaning when Acta Scientiarum. Animal Sciences, v. 43, e53327, 2021 reaching 70 days of life and 70 kg of body weight (when a calf did not reach the minimum body weight, it continued receiving 1 L of milk day -1 until reaching it).
We assumed that after the TP, the adoption of the good practices of handling was already integrated in the farm handling routine; then, the following 12 months of the data records was assumed as a new period (good practices of handling, GPH). In all periods (CH, TP, and GPG) calves had free access to hay and concentrate (with 18% crude protein) throughout milk-feeding period. Table 1. Protocols adopted for milk-feeding dairy calves from birth to weaning according to the handling procedure: conventional handling (CH) and good practices of handling (GPH).
Calf age (

Statistical analysis
To control the effect of seasonal influences, comparisons between CH and GPH were conducted for the same months of the year.
The fixed effects of handling procedures (CH, TP, and GPH) on the likelihoods of calf death were analysed using restricted maximum likelihood (REML). A logistic regression model with the probit link function (for an adjacent normal distribution) and with a binomial distribution of the response variables was applied by using the GENMOD procedure in SAS (SAS Institute Inc., Cary, NC), CH was set as the reference class. The Chi-Square test was used to compare the relative frequencies of antibiotic use between CH, TP, and GPH.

Results and discussion
The mortality rate per month from birth to weaning was extremely high (18.79%) before the adoption of the good practices of handling (CH), reducing expressively after their adoption, dropping to 7.81% (58.4% reduction) during TP (when the good practices of handling was still being implemented) and to 5.24% when GPH were already implemented in the farm routine (72.1% reduction). The results of the statistical analysis sustained these reductions with high probability, showing that the risk of calf mortality was significantly lower (p < 0.005) after the adoption of good practices of handling (TP and GPH), when the odds ratio for calves death, which were reduced to less than half when compared to the value estimated in CH (reference class), as shown in Table 2. The same tendency was observed when considering the percentage of calves treated with antibiotics, dropping from 68.1% per month in CH, to 45.7% in TP and 34.2% in GPH (p < 0.001 for both), indicating a reduction of 32.9% and 49.8%, respectively, after the adoption of the good practices of handling. No statistically difference was observed between the percentages of calves treated with antibiotics in TP and GPH (Figure 1).
The big standard errors found in this study were due to uncontrolled environmental factors, e.g., the birth season, which has effects on the quality of the colostrum and the prevalence of diarrhoea and pneumonia (Gulliksen et al., 2009), and survival of dairy calves (Zhang et al., 2019). Thus, for both indicators, CH showed the worst situation, indicating that the adoption of the set of good practices of handling evaluated in this study contributes to the reduction of calf losses and health problems in dairy herds, reducing the costs with veterinary care and the financial loss with calves deaths, which have an expressive impact on the dairy farms economic performance (Demir, Aydin, & Ayvazoğlu, 2019). These results challenge the expectation that just keeping dairy calves in individual pens is sufficient to reduce the risk of infectious disease transmission, making clear that there is a need for more investment and attention to define the proper handling procedures for dairy calves. For example, as reported by von Keyserlingk and Weary (2011) it is difficult to maintain a good standard of hygiene in collective facilities when compared to individual pens, but it is likely that the adoption of GPH implemented in this study would facilitate this, by allowing the calves to spend a period of time outside, in paddocks, mostly from 30 days of age, when they stayed all time on pasture.
It also should be taken into account that, despite of being acknowledged as essential to assure proper passive immunity through colostrum ingestion (Hulbert & Moisá, 2016), the calf's first meal was not under the control of calves' caretakers before the adoption of GPH procedures. Thus, there is a high probability that the action of offering an adequate amount of good quality colostrum in the first six hours after birth in bottles was crucial to reduce the number or severity of health problems and, consequently, the number of calves deaths, as previously reported by Swensson, Lundborg, Emanuelson, and Olsson (2003).
Despite of the importance of early identification of diseases to ensure good welfare for dairy calves (Mahendran et al., 2017), it is well known that it is not an easy task for dairy farmers (Whay, Main, Green, & Webster, 2003). This limitation may have been overcome after the adoption of GPH procedures, since it promoted a closer contact between handlers and calves, mainly when carrying on the tactile stimulation. This is because the closeness would facilitate the recognition of subtle changes in respiratory rate, stool consistency, and behaviour (e.g., signs of apathy and loss of appetite), which are signals of health problems, enabling handlers to adopt early care or treatments to solve them. In addition, it should be also taken into account that tactile stimulation can have a positive effect on calves' immune responses, as reported for rats (Solomon, Levine, & Kraft, 1968) and human infants (Ang et al., 2012). Therefore, our results oppose the notion that promoting physical isolation of dairy calves is sufficient to maintain them in good health, suggesting that the promotion of a closer contact with their caretakers is a better strategy to prevent or minimize disease severity.
Results from previous studies also indicated that the use of open-pails to milk-feed of dairy calves increase the risk of harming their welfare, since under such conditions calves are not able to express proper suckling behaviour, resulting in motivational and physiological disturbances, characterized by the expression of crosssuckling (abnormal) behaviour (de Passillé, 2001) and when the oesophageal groove close incompletely (Martín-Alonso et al., 2018). Thus, it is likely that using nipple-pails after the GPH adoption has contributed to reduce calves frustration (de Passillé, 2001), and to improve milk digestion, either by preventing milk from being fermented in the rumen (Kaba, Abera, & Kass, 2018) or by enhancing the production of digestive enzymes (stimulated by suckling), which reduce the risk of osmotic diarrhoea caused by milk fermentation in the intestines (Quigley lll, Drewry, Murray, & Ivey, 1997).
Similar approach can be used when assessing the effect of gradual weaning. Previous results (Khan et al., 2007;Steele et al., 2017) indicated that its (singly) adoption leads to less stress and better calves performance; then, it can be assumed that it had also an important role in the promotion of calves welfare after the adoption of GPH procedures.
It is clear that we were not able to identify which one of the GPH procedures adopted in this study had the greatest positive impact on calf health and welfare, but we can hypothesize that the proximity between calves and their caretakers (which included physical contact), played an important role in reducing health problems and calves' deaths. Therefore, in a moment that the automation of livestock husbandry is replacing stockpeople work, further research is needed to check the importance of the close contact between humans and dairy calves on animal welfare and performance.

Conclusion
We conclude that the adoption of a set of good practices of handling (by combining the control of colostrum ingestion control, use nipple-pails, tactile stimulation, group housing, and progressive weaning) improved dairy calves' health and survival, resulting in a direct positive economic impact for milk producers due to the significant reduction in the costs of veterinary care and economic losses related to calf mortality.
The results also allow to conclude that isolating dairy calves, by raising them in individual pens, is not enough to ensure good health and survival if a set of good practices handling is not jointly adopted.